My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?

Hi Brett

This radio uses a selenium rectifier. Have you checked voltage to be sure it's good? On the schematic it shows a voltage of 140, above SE1. If this voltage is low replace the selenium rectifier with a silicon diode. 1N4004 - 1N4007 will work and only costs a few cents.

Other parts, such as caps, should be replaced in a radio of this age.

Norm

http://www.nostalgiaair.org/PagesByModel/565/M0025565.pdf

:My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?

:My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?

Hi Brett,
I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.

I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.

By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.

When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.

Best Regards,

Bill Grimm

::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
:
:Hi Brett,
: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
:
: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
:
: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
:
: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
:
:Best Regards,
:
:Bill Grimm

:::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
::
::Hi Brett,
:: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
:: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
::
:: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
:: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
:: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
::
:: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
::
:: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
::
::Best Regards,
::
::Bill Grimm
Norm and Bill,
WOW, I’ll try and digest all this. This is all new to me. I love old radios and have about a dozen. I recapped this one, replaced the dial cord and polished the Bakelite. But I’m new at this and I don’t know what any of this stuff is. I bought a couple of books but the terminology makes my head spin. I really appreciate your help and I’ll try to figure this out. I wish there was a class I could take. Do you have any suggestions on how to start learning? Thanks again, Brett.

::::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
:::
:::Hi Brett,
::: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
::: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
:::
::: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
::: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
::: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
:::
::: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
:::
::: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
:::
:::Best Regards,
:::
:::Bill Grimm
:Norm and Bill,
:WOW, I’ll try and digest all this. This is all new to me. I love old radios and have about a dozen. I recapped this one, replaced the dial cord and polished the Bakelite. But I’m new at this and I don’t know what any of this stuff is. I bought a couple of books but the terminology makes my head spin. I really appreciate your help and I’ll try to figure this out. I wish there was a class I could take. Do you have any suggestions on how to start learning? Thanks again, Brett.
:
Hi Brett,
Sorry, I didn't mean to scare you. You mentioned that you recapped the set. Have you tested the tubes?

Once the tubes are OK, then check the sockets. I have found socket failure on many of these sets. The 19T8 is most often affected.

After those checks, Silver Mica Disease is the most common problem. To get a handle on silver Mica disease, I have found a capacitor analyzer indespensable. Do you have one?

One thing in your favor is that AM when it is on seems to be clear. Classic Silver Mica disease sounds like someone is in the audio booth with the radio announcer constantly crumpling up a newspaper.

Best Regards,

Bill Grimm

:::::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
::::
::::Hi Brett,
:::: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
:::: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
::::
:::: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
:::: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
:::: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
::::
:::: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
::::
:::: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
::::
::::Best Regards,
::::
::::Bill Grimm
::Norm and Bill,
::WOW, I’ll try and digest all this. This is all new to me. I love old radios and have about a dozen. I recapped this one, replaced the dial cord and polished the Bakelite. But I’m new at this and I don’t know what any of this stuff is. I bought a couple of books but the terminology makes my head spin. I really appreciate your help and I’ll try to figure this out. I wish there was a class I could take. Do you have any suggestions on how to start learning? Thanks again, Brett.
::
:Hi Brett,
: Sorry, I didn't mean to scare you. You mentioned that you recapped the set. Have you tested the tubes?
:
: Once the tubes are OK, then check the sockets. I have found socket failure on many of these sets. The 19T8 is most often affected.
:
: After those checks, Silver Mica Disease is the most common problem. To get a handle on silver Mica disease, I have found a capacitor analyzer indespensable. Do you have one?
:
: One thing in your favor is that AM when it is on seems to be clear. Classic Silver Mica disease sounds like someone is in the audio booth with the radio announcer constantly crumpling up a newspaper.
:
:Best Regards,
:
:Bill Grimm
Bill,
No, I have not checked the tubes. I'm looking for a tester, but I'm not sure what to get. The AM sounds great, until it fades. I'm 30 miles East of Cleveland and I pull in Boston and Chicago like they're down the street. All I get on FM is a soft consistant hum. I have a multi tester but no capacitor analyzer.But I'll pick one up. I did notice there are a lot of Mica capacitor in these radios. I'll replace the selenium rectifier with a silicon diode too. As soon as I figure out what it is. I read what they do but I don't know what it looks like. It seems like the power supply has to go right into it. I have to order a tube for another set I'll just go ahead and get a 19T8 as well. I’m serious about learning this stuff. Thanks, Brett

::::::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
:::::
:::::Hi Brett,
::::: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
::::: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
:::::
::::: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
::::: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
::::: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
:::::
::::: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
:::::
::::: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
:::::
:::::Best Regards,
:::::
:::::Bill Grimm
:::Norm and Bill,
:::WOW, I’ll try and digest all this. This is all new to me. I love old radios and have about a dozen. I recapped this one, replaced the dial cord and polished the Bakelite. But I’m new at this and I don’t know what any of this stuff is. I bought a couple of books but the terminology makes my head spin. I really appreciate your help and I’ll try to figure this out. I wish there was a class I could take. Do you have any suggestions on how to start learning? Thanks again, Brett.
:::
::Hi Brett,
:: Sorry, I didn't mean to scare you. You mentioned that you recapped the set. Have you tested the tubes?
::
:: Once the tubes are OK, then check the sockets. I have found socket failure on many of these sets. The 19T8 is most often affected.
::
:: After those checks, Silver Mica Disease is the most common problem. To get a handle on silver Mica disease, I have found a capacitor analyzer indespensable. Do you have one?
::
:: One thing in your favor is that AM when it is on seems to be clear. Classic Silver Mica disease sounds like someone is in the audio booth with the radio announcer constantly crumpling up a newspaper.
::
::Best Regards,
::
::Bill Grimm
:Bill,
: No, I have not checked the tubes. I'm looking for a tester, but I'm not sure what to get. The AM sounds great, until it fades. I'm 30 miles East of Cleveland and I pull in Boston and Chicago like they're down the street. All I get on FM is a soft consistant hum. I have a multi tester but no capacitor analyzer.But I'll pick one up. I did notice there are a lot of Mica capacitor in these radios. I'll replace the selenium rectifier with a silicon diode too. As soon as I figure out what it is. I read what they do but I don't know what it looks like. It seems like the power supply has to go right into it. I have to order a tube for another set I'll just go ahead and get a 19T8 as well. I’m serious about learning this stuff. Thanks, Brett

Brett,

If you would like to see a picture of a selenium rectifer, check out:

http://www.theodoregray.com/PeriodicTable/Elements/034/

It is down about the middle of the page or so.

Radiodoc
**********

:::::::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
::::::
::::::Hi Brett,
:::::: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
:::::: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
::::::
:::::: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
:::::: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
:::::: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
::::::
:::::: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
::::::
:::::: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
::::::
::::::Best Regards,
::::::
::::::Bill Grimm
::::Norm and Bill,
::::WOW, I’ll try and digest all this. This is all new to me. I love old radios and have about a dozen. I recapped this one, replaced the dial cord and polished the Bakelite. But I’m new at this and I don’t know what any of this stuff is. I bought a couple of books but the terminology makes my head spin. I really appreciate your help and I’ll try to figure this out. I wish there was a class I could take. Do you have any suggestions on how to start learning? Thanks again, Brett.
::::
:::Hi Brett,
::: Sorry, I didn't mean to scare you. You mentioned that you recapped the set. Have you tested the tubes?
:::
::: Once the tubes are OK, then check the sockets. I have found socket failure on many of these sets. The 19T8 is most often affected.
:::
::: After those checks, Silver Mica Disease is the most common problem. To get a handle on silver Mica disease, I have found a capacitor analyzer indespensable. Do you have one?
:::
::: One thing in your favor is that AM when it is on seems to be clear. Classic Silver Mica disease sounds like someone is in the audio booth with the radio announcer constantly crumpling up a newspaper.
:::
:::Best Regards,
:::
:::Bill Grimm
::Bill,
:: No, I have not checked the tubes. I'm looking for a tester, but I'm not sure what to get. The AM sounds great, until it fades. I'm 30 miles East of Cleveland and I pull in Boston and Chicago like they're down the street. All I get on FM is a soft consistant hum. I have a multi tester but no capacitor analyzer.But I'll pick one up. I did notice there are a lot of Mica capacitor in these radios. I'll replace the selenium rectifier with a silicon diode too. As soon as I figure out what it is. I read what they do but I don't know what it looks like. It seems like the power supply has to go right into it. I have to order a tube for another set I'll just go ahead and get a 19T8 as well. I’m serious about learning this stuff. Thanks, Brett
:
:Brett,
:
:If you would like to see a picture of a selenium rectifer, check out:
:
:http://www.theodoregray.com/PeriodicTable/Elements/034/
:
:It is down about the middle of the page or so.
:
:Radiodoc

Hey Doc, Thanks, It does help. I also got the Zenith part# 212-7-SE1. I'll order the diode and resistor and change them out.
:**********
:

::::::::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
:::::::
:::::::Hi Brett,
::::::: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
::::::: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
:::::::
::::::: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
::::::: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
::::::: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
:::::::
::::::: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
:::::::
::::::: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
:::::::
:::::::Best Regards,
:::::::
:::::::Bill Grimm
:::::Norm and Bill,
:::::WOW, I’ll try and digest all this. This is all new to me. I love old radios and have about a dozen. I recapped this one, replaced the dial cord and polished the Bakelite. But I’m new at this and I don’t know what any of this stuff is. I bought a couple of books but the terminology makes my head spin. I really appreciate your help and I’ll try to figure this out. I wish there was a class I could take. Do you have any suggestions on how to start learning? Thanks again, Brett.
:::::
::::Hi Brett,
:::: Sorry, I didn't mean to scare you. You mentioned that you recapped the set. Have you tested the tubes?
::::
:::: Once the tubes are OK, then check the sockets. I have found socket failure on many of these sets. The 19T8 is most often affected.
::::
:::: After those checks, Silver Mica Disease is the most common problem. To get a handle on silver Mica disease, I have found a capacitor analyzer indespensable. Do you have one?
::::
:::: One thing in your favor is that AM when it is on seems to be clear. Classic Silver Mica disease sounds like someone is in the audio booth with the radio announcer constantly crumpling up a newspaper.
::::
::::Best Regards,
::::
::::Bill Grimm
:::Bill,
::: No, I have not checked the tubes. I'm looking for a tester, but I'm not sure what to get. The AM sounds great, until it fades. I'm 30 miles East of Cleveland and I pull in Boston and Chicago like they're down the street. All I get on FM is a soft consistant hum. I have a multi tester but no capacitor analyzer.But I'll pick one up. I did notice there are a lot of Mica capacitor in these radios. I'll replace the selenium rectifier with a silicon diode too. As soon as I figure out what it is. I read what they do but I don't know what it looks like. It seems like the power supply has to go right into it. I have to order a tube for another set I'll just go ahead and get a 19T8 as well. I’m serious about learning this stuff. Thanks, Brett
::
::Brett,
::
::If you would like to see a picture of a selenium rectifer, check out:
::
::http://www.theodoregray.com/PeriodicTable/Elements/034/
::
::It is down about the middle of the page or so.
::
::Radiodoc
:
:Hey Doc, Thanks, It does help. I also got the Zenith part# 212-7-SE1. I'll order the diode and resistor and change them out.
::**********
::

Hi Brett,
Two ideas on your fading AM. First, fading is of course normal on distant stations on AM at night. Second, if the fade happens on local stations also, look to see if the filaments of the tubes fade also. If so you have a tube with an intermittant filament.
On your dead FM, try checking the voltages at the the pin and the lug of the socket. I have often found bad tube sockets on these.
If your bad FM is caused by a tube, the bad tube is most likely the 19T8. You can order a 19C8. They work fine and cost less.
Another test is to momentariy swap the 12AU6 and one of the 12BA6. If you lose the AM, then the 12AU6 is bad.
Another test is to check the voltage on pin 1 of the 12AU6 when in FM position. It needs to be negative on the order of -0.4 volts. If it is zero or positive, then you have a bad IF transformer.

For the replacement diode, I use 1N4004 or 1N4007. They are cheap and common. Since it is an H723, not an H724, you will have plenty of tie points for mounting the diode, resistor, and new filters.

All the Best,

Bill Grimm

:::::::::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
::::::::
::::::::Hi Brett,
:::::::: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
:::::::: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
::::::::
:::::::: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
:::::::: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
:::::::: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
::::::::
:::::::: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
::::::::
:::::::: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
::::::::
::::::::Best Regards,
::::::::
::::::::Bill Grimm
::::::Norm and Bill,
::::::WOW, I’ll try and digest all this. This is all new to me. I love old radios and have about a dozen. I recapped this one, replaced the dial cord and polished the Bakelite. But I’m new at this and I don’t know what any of this stuff is. I bought a couple of books but the terminology makes my head spin. I really appreciate your help and I’ll try to figure this out. I wish there was a class I could take. Do you have any suggestions on how to start learning? Thanks again, Brett.
::::::
:::::Hi Brett,
::::: Sorry, I didn't mean to scare you. You mentioned that you recapped the set. Have you tested the tubes?
:::::
::::: Once the tubes are OK, then check the sockets. I have found socket failure on many of these sets. The 19T8 is most often affected.
:::::
::::: After those checks, Silver Mica Disease is the most common problem. To get a handle on silver Mica disease, I have found a capacitor analyzer indespensable. Do you have one?
:::::
::::: One thing in your favor is that AM when it is on seems to be clear. Classic Silver Mica disease sounds like someone is in the audio booth with the radio announcer constantly crumpling up a newspaper.
:::::
:::::Best Regards,
:::::
:::::Bill Grimm
::::Bill,
:::: No, I have not checked the tubes. I'm looking for a tester, but I'm not sure what to get. The AM sounds great, until it fades. I'm 30 miles East of Cleveland and I pull in Boston and Chicago like they're down the street. All I get on FM is a soft consistant hum. I have a multi tester but no capacitor analyzer.But I'll pick one up. I did notice there are a lot of Mica capacitor in these radios. I'll replace the selenium rectifier with a silicon diode too. As soon as I figure out what it is. I read what they do but I don't know what it looks like. It seems like the power supply has to go right into it. I have to order a tube for another set I'll just go ahead and get a 19T8 as well. I’m serious about learning this stuff. Thanks, Brett
:::
:::Brett,
:::
:::If you would like to see a picture of a selenium rectifer, check out:
:::
:::http://www.theodoregray.com/PeriodicTable/Elements/034/
:::
:::It is down about the middle of the page or so.
:::
:::Radiodoc
::
::Hey Doc, Thanks, It does help. I also got the Zenith part# 212-7-SE1. I'll order the diode and resistor and change them out.
:::**********
:::
:
:Hi Brett,
: Two ideas on your fading AM. First, fading is of course normal on distant stations on AM at night. Second, if the fade happens on local stations also, look to see if the filaments of the tubes fade also. If so you have a tube with an intermittant filament.
: On your dead FM, try checking the voltages at the the pin and the lug of the socket. I have often found bad tube sockets on these.
: If your bad FM is caused by a tube, the bad tube is most likely the 19T8. You can order a 19C8. They work fine and cost less.
: Another test is to momentariy swap the 12AU6 and one of the 12BA6. If you lose the AM, then the 12AU6 is bad.
: Another test is to check the voltage on pin 1 of the 12AU6 when in FM position. It needs to be negative on the order of -0.4 volts. If it is zero or positive, then you have a bad IF transformer.
:
: For the replacement diode, I use 1N4004 or 1N4007. They are cheap and common. Since it is an H723, not an H724, you will have plenty of tie points for mounting the diode, resistor, and new filters.
:
:All the Best,
:
:Bill Grimm
Bill,
Thanks, good stuff. A few quick questions, how long is momentarily on the 12AU6 and the 12BA6 switch? It can take up to five minutes to warm up and cut out. Also, on the resistor, where I’ve been buying my supplies, list 51 & 68 Ohm 2 Watt Metal Oxide or 5 Watt Power Resistors. Will one of these do, or do I need to go elsewhere? Now I haven’t opened the radio back up yet, so I just desolder the rectifier and leave it in place and solder the diode in its stead. Then find the resistor and replace it. Right?
Thanks again, Brett

::::::::::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
:::::::::
:::::::::Hi Brett,
::::::::: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
::::::::: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
:::::::::
::::::::: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
::::::::: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
::::::::: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
:::::::::
::::::::: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
:::::::::
::::::::: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
:::::::::
:::::::::Best Regards,
:::::::::
:::::::::Bill Grimm
:::::::Norm and Bill,
:::::::WOW, I’ll try and digest all this. This is all new to me. I love old radios and have about a dozen. I recapped this one, replaced the dial cord and polished the Bakelite. But I’m new at this and I don’t know what any of this stuff is. I bought a couple of books but the terminology makes my head spin. I really appreciate your help and I’ll try to figure this out. I wish there was a class I could take. Do you have any suggestions on how to start learning? Thanks again, Brett.
:::::::
::::::Hi Brett,
:::::: Sorry, I didn't mean to scare you. You mentioned that you recapped the set. Have you tested the tubes?
::::::
:::::: Once the tubes are OK, then check the sockets. I have found socket failure on many of these sets. The 19T8 is most often affected.
::::::
:::::: After those checks, Silver Mica Disease is the most common problem. To get a handle on silver Mica disease, I have found a capacitor analyzer indespensable. Do you have one?
::::::
:::::: One thing in your favor is that AM when it is on seems to be clear. Classic Silver Mica disease sounds like someone is in the audio booth with the radio announcer constantly crumpling up a newspaper.
::::::
::::::Best Regards,
::::::
::::::Bill Grimm
:::::Bill,
::::: No, I have not checked the tubes. I'm looking for a tester, but I'm not sure what to get. The AM sounds great, until it fades. I'm 30 miles East of Cleveland and I pull in Boston and Chicago like they're down the street. All I get on FM is a soft consistant hum. I have a multi tester but no capacitor analyzer.But I'll pick one up. I did notice there are a lot of Mica capacitor in these radios. I'll replace the selenium rectifier with a silicon diode too. As soon as I figure out what it is. I read what they do but I don't know what it looks like. It seems like the power supply has to go right into it. I have to order a tube for another set I'll just go ahead and get a 19T8 as well. I’m serious about learning this stuff. Thanks, Brett
::::
::::Brett,
::::
::::If you would like to see a picture of a selenium rectifer, check out:
::::
::::http://www.theodoregray.com/PeriodicTable/Elements/034/
::::
::::It is down about the middle of the page or so.
::::
::::Radiodoc
:::
:::Hey Doc, Thanks, It does help. I also got the Zenith part# 212-7-SE1. I'll order the diode and resistor and change them out.
::::**********
::::
::
::Hi Brett,
:: Two ideas on your fading AM. First, fading is of course normal on distant stations on AM at night. Second, if the fade happens on local stations also, look to see if the filaments of the tubes fade also. If so you have a tube with an intermittant filament.
:: On your dead FM, try checking the voltages at the the pin and the lug of the socket. I have often found bad tube sockets on these.
:: If your bad FM is caused by a tube, the bad tube is most likely the 19T8. You can order a 19C8. They work fine and cost less.
:: Another test is to momentariy swap the 12AU6 and one of the 12BA6. If you lose the AM, then the 12AU6 is bad.
:: Another test is to check the voltage on pin 1 of the 12AU6 when in FM position. It needs to be negative on the order of -0.4 volts. If it is zero or positive, then you have a bad IF transformer.
::
:: For the replacement diode, I use 1N4004 or 1N4007. They are cheap and common. Since it is an H723, not an H724, you will have plenty of tie points for mounting the diode, resistor, and new filters.
::
::All the Best,
::
::Bill Grimm
:Bill,
: Thanks, good stuff. A few quick questions, how long is momentarily on the 12AU6 and the 12BA6 switch? It can take up to five minutes to warm up and cut out. Also, on the resistor, where I’ve been buying my supplies, list 51 & 68 Ohm 2 Watt Metal Oxide or 5 Watt Power Resistors. Will one of these do, or do I need to go elsewhere? Now I haven’t opened the radio back up yet, so I just desolder the rectifier and leave it in place and solder the diode in its stead. Then find the resistor and replace it. Right?
:Thanks again, Brett
:
Hi Brett,
You can leave the 12AU6 and 12BA6 swapped basically indefinitely. They are adequate replacements for each other. I only swap them back because that is the way the radio was designed. One is remote cut off, the other is sharp cut off pentode. I only have a vague understanding of what that is.
I get my 60 ohm resistors by getting a 69 ohm 3 watt(which I happen to have a whole bunch) and putting a 470, 1.4 watt in parallel.

All the Best,

Bill

::::::::::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
:::::::::
:::::::::Hi Brett,
::::::::: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
::::::::: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
:::::::::
::::::::: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
::::::::: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
::::::::: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
:::::::::
::::::::: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
:::::::::
::::::::: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
:::::::::
:::::::::Best Regards,
:::::::::
:::::::::Bill Grimm
:::::::Norm and Bill,
:::::::WOW, I’ll try and digest all this. This is all new to me. I love old radios and have about a dozen. I recapped this one, replaced the dial cord and polished the Bakelite. But I’m new at this and I don’t know what any of this stuff is. I bought a couple of books but the terminology makes my head spin. I really appreciate your help and I’ll try to figure this out. I wish there was a class I could take. Do you have any suggestions on how to start learning? Thanks again, Brett.
:::::::
::::::Hi Brett,
:::::: Sorry, I didn't mean to scare you. You mentioned that you recapped the set. Have you tested the tubes?
::::::
:::::: Once the tubes are OK, then check the sockets. I have found socket failure on many of these sets. The 19T8 is most often affected.
::::::
:::::: After those checks, Silver Mica Disease is the most common problem. To get a handle on silver Mica disease, I have found a capacitor analyzer indespensable. Do you have one?
::::::
:::::: One thing in your favor is that AM when it is on seems to be clear. Classic Silver Mica disease sounds like someone is in the audio booth with the radio announcer constantly crumpling up a newspaper.
::::::
::::::Best Regards,
::::::
::::::Bill Grimm
:::::Bill,
::::: No, I have not checked the tubes. I'm looking for a tester, but I'm not sure what to get. The AM sounds great, until it fades. I'm 30 miles East of Cleveland and I pull in Boston and Chicago like they're down the street. All I get on FM is a soft consistant hum. I have a multi tester but no capacitor analyzer.But I'll pick one up. I did notice there are a lot of Mica capacitor in these radios. I'll replace the selenium rectifier with a silicon diode too. As soon as I figure out what it is. I read what they do but I don't know what it looks like. It seems like the power supply has to go right into it. I have to order a tube for another set I'll just go ahead and get a 19T8 as well. I’m serious about learning this stuff. Thanks, Brett
::::
::::Brett,
::::
::::If you would like to see a picture of a selenium rectifer, check out:
::::
::::http://www.theodoregray.com/PeriodicTable/Elements/034/
::::
::::It is down about the middle of the page or so.
::::
::::Radiodoc
:::
:::Hey Doc, Thanks, It does help. I also got the Zenith part# 212-7-SE1. I'll order the diode and resistor and change them out.
::::**********
::::
::
::Hi Brett,
:: Two ideas on your fading AM. First, fading is of course normal on distant stations on AM at night. Second, if the fade happens on local stations also, look to see if the filaments of the tubes fade also. If so you have a tube with an intermittant filament.
:: On your dead FM, try checking the voltages at the the pin and the lug of the socket. I have often found bad tube sockets on these.
:: If your bad FM is caused by a tube, the bad tube is most likely the 19T8. You can order a 19C8. They work fine and cost less.
:: Another test is to momentariy swap the 12AU6 and one of the 12BA6. If you lose the AM, then the 12AU6 is bad.
:: Another test is to check the voltage on pin 1 of the 12AU6 when in FM position. It needs to be negative on the order of -0.4 volts. If it is zero or positive, then you have a bad IF transformer.
::
:: For the replacement diode, I use 1N4004 or 1N4007. They are cheap and common. Since it is an H723, not an H724, you will have plenty of tie points for mounting the diode, resistor, and new filters.
::
::All the Best,
::
::Bill Grimm
:Bill,
: Thanks, good stuff. A few quick questions, how long is momentarily on the 12AU6 and the 12BA6 switch? It can take up to five minutes to warm up and cut out. Also, on the resistor, where I’ve been buying my supplies, list 51 & 68 Ohm 2 Watt Metal Oxide or 5 Watt Power Resistors. Will one of these do, or do I need to go elsewhere? Now I haven’t opened the radio back up yet, so I just desolder the rectifier and leave it in place and solder the diode in its stead. Then find the resistor and replace it. Right?
:Thanks again, Brett
:
Hi Brett,
You can leave the 12AU6 and 12BA6 swapped basically indefinitely. They are adequate replacements for each other. I only swap them back because that is the way the radio was designed. One is remote cut off, the other is sharp cut off pentode. I only have a vague understanding of what that is.
I get my 60 ohm resistors by getting a 69 ohm 3 watt(which I happen to have a whole bunch) and putting a 470, 1.4 watt in parallel.

All the Best,

Bill

:::::::::::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
::::::::::
::::::::::Hi Brett,
:::::::::: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
:::::::::: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
::::::::::
:::::::::: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
:::::::::: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
:::::::::: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
::::::::::
:::::::::: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
::::::::::
:::::::::: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
::::::::::
::::::::::Best Regards,
::::::::::
::::::::::Bill Grimm
::::::::Norm and Bill,
::::::::WOW, I’ll try and digest all this. This is all new to me. I love old radios and have about a dozen. I recapped this one, replaced the dial cord and polished the Bakelite. But I’m new at this and I don’t know what any of this stuff is. I bought a couple of books but the terminology makes my head spin. I really appreciate your help and I’ll try to figure this out. I wish there was a class I could take. Do you have any suggestions on how to start learning? Thanks again, Brett.
::::::::
:::::::Hi Brett,
::::::: Sorry, I didn't mean to scare you. You mentioned that you recapped the set. Have you tested the tubes?
:::::::
::::::: Once the tubes are OK, then check the sockets. I have found socket failure on many of these sets. The 19T8 is most often affected.
:::::::
::::::: After those checks, Silver Mica Disease is the most common problem. To get a handle on silver Mica disease, I have found a capacitor analyzer indespensable. Do you have one?
:::::::
::::::: One thing in your favor is that AM when it is on seems to be clear. Classic Silver Mica disease sounds like someone is in the audio booth with the radio announcer constantly crumpling up a newspaper.
:::::::
:::::::Best Regards,
:::::::
:::::::Bill Grimm
::::::Bill,
:::::: No, I have not checked the tubes. I'm looking for a tester, but I'm not sure what to get. The AM sounds great, until it fades. I'm 30 miles East of Cleveland and I pull in Boston and Chicago like they're down the street. All I get on FM is a soft consistant hum. I have a multi tester but no capacitor analyzer.But I'll pick one up. I did notice there are a lot of Mica capacitor in these radios. I'll replace the selenium rectifier with a silicon diode too. As soon as I figure out what it is. I read what they do but I don't know what it looks like. It seems like the power supply has to go right into it. I have to order a tube for another set I'll just go ahead and get a 19T8 as well. I’m serious about learning this stuff. Thanks, Brett
:::::
:::::Brett,
:::::
:::::If you would like to see a picture of a selenium rectifer, check out:
:::::
:::::http://www.theodoregray.com/PeriodicTable/Elements/034/
:::::
:::::It is down about the middle of the page or so.
:::::
:::::Radiodoc
::::
::::Hey Doc, Thanks, It does help. I also got the Zenith part# 212-7-SE1. I'll order the diode and resistor and change them out.
:::::**********
:::::
:::
:::Hi Brett,
::: Two ideas on your fading AM. First, fading is of course normal on distant stations on AM at night. Second, if the fade happens on local stations also, look to see if the filaments of the tubes fade also. If so you have a tube with an intermittant filament.
::: On your dead FM, try checking the voltages at the the pin and the lug of the socket. I have often found bad tube sockets on these.
::: If your bad FM is caused by a tube, the bad tube is most likely the 19T8. You can order a 19C8. They work fine and cost less.
::: Another test is to momentariy swap the 12AU6 and one of the 12BA6. If you lose the AM, then the 12AU6 is bad.
::: Another test is to check the voltage on pin 1 of the 12AU6 when in FM position. It needs to be negative on the order of -0.4 volts. If it is zero or positive, then you have a bad IF transformer.
:::
::: For the replacement diode, I use 1N4004 or 1N4007. They are cheap and common. Since it is an H723, not an H724, you will have plenty of tie points for mounting the diode, resistor, and new filters.
:::
:::All the Best,
:::
:::Bill Grimm
::Bill,
:: Thanks, good stuff. A few quick questions, how long is momentarily on the 12AU6 and the 12BA6 switch? It can take up to five minutes to warm up and cut out. Also, on the resistor, where I’ve been buying my supplies, list 51 & 68 Ohm 2 Watt Metal Oxide or 5 Watt Power Resistors. Will one of these do, or do I need to go elsewhere? Now I haven’t opened the radio back up yet, so I just desolder the rectifier and leave it in place and solder the diode in its stead. Then find the resistor and replace it. Right?
::Thanks again, Brett
::
:Hi Brett,
: You can leave the 12AU6 and 12BA6 swapped basically indefinitely. They are adequate replacements for each other. I only swap them back because that is the way the radio was designed. One is remote cut off, the other is sharp cut off pentode. I only have a vague understanding of what that is.
: I get my 60 ohm resistors by getting a 69 ohm 3 watt(which I happen to have a whole bunch) and putting a 470, 1.4 watt in parallel.
:
:All the Best,
:
:Bill
O. K., I’m back to being a little confused. If I took a 51 Ohm 2 Watt and a 9 Ohm 1 Watt in series, I would have the 60 Ohm, but would I have the 3 Watts I need?

::::::::::::My H723 picks up AM great but fades to nothing then comes in stong for awhile then fades again and so on and so on. Is it a tube? wich one? Also FM doesn't come in at all. Any help out there?
:::::::::::
:::::::::::Hi Brett,
::::::::::: I have become a bit of a specialist on this kind of radio. I have a complete one on eBay now.
::::::::::: These radios are notorious for Silver Mica disease. It usually hits the descriminator IF first and also often hits the combination IF in the middle.
:::::::::::
::::::::::: I test the transformers for leakage just like I test capacitors for leakage on a capacitor analyzer. Leakage on a transformer will be between primary to secondary. This is caused by silver migraiton in the silver mica wafers in the base of the transformers. This allows plate voltage from a previous stage to leak into the grid circuit of the next stage, disrupting its bias.
::::::::::: A more feindish form of silver mica disease causes the silver mica capacitors to open, making the transformer untunable, and sometimes intermittant.
::::::::::: That is the most likely cause of the FM problem. Your particular AM problem resembles something I have heard on two radios recently of this type. AM fades out then spontaneously comes back. I had one that was dead for three days, then AM came back and it played for months with no problem. I have another one now that seems to fade after some time of playing. I am working on it now.
:::::::::::
::::::::::: By the way I agree with Norm's comments on the Selenium rectifyers. I recommend that after you replace the Selenium, also replace the 22 ohm with a 6o ohm 3 watt resistor. The new diode has less voltage drop, and the 60 ohms is needed to put the voltages right.
:::::::::::
::::::::::: When they get going they sound great. I have one in the bedroom that has worked fine for four years. The nice thing is that they get FM. These are one of the most challenging radios for restoration, from an electronics stand point.
:::::::::::
:::::::::::Best Regards,
:::::::::::
:::::::::::Bill Grimm
:::::::::Norm and Bill,
:::::::::WOW, I’ll try and digest all this. This is all new to me. I love old radios and have about a dozen. I recapped this one, replaced the dial cord and polished the Bakelite. But I’m new at this and I don’t know what any of this stuff is. I bought a couple of books but the terminology makes my head spin. I really appreciate your help and I’ll try to figure this out. I wish there was a class I could take. Do you have any suggestions on how to start learning? Thanks again, Brett.
:::::::::
::::::::Hi Brett,
:::::::: Sorry, I didn't mean to scare you. You mentioned that you recapped the set. Have you tested the tubes?
::::::::
:::::::: Once the tubes are OK, then check the sockets. I have found socket failure on many of these sets. The 19T8 is most often affected.
::::::::
:::::::: After those checks, Silver Mica Disease is the most common problem. To get a handle on silver Mica disease, I have found a capacitor analyzer indespensable. Do you have one?
::::::::
:::::::: One thing in your favor is that AM when it is on seems to be clear. Classic Silver Mica disease sounds like someone is in the audio booth with the radio announcer constantly crumpling up a newspaper.
::::::::
::::::::Best Regards,
::::::::
::::::::Bill Grimm
:::::::Bill,
::::::: No, I have not checked the tubes. I'm looking for a tester, but I'm not sure what to get. The AM sounds great, until it fades. I'm 30 miles East of Cleveland and I pull in Boston and Chicago like they're down the street. All I get on FM is a soft consistant hum. I have a multi tester but no capacitor analyzer.But I'll pick one up. I did notice there are a lot of Mica capacitor in these radios. I'll replace the selenium rectifier with a silicon diode too. As soon as I figure out what it is. I read what they do but I don't know what it looks like. It seems like the power supply has to go right into it. I have to order a tube for another set I'll just go ahead and get a 19T8 as well. I’m serious about learning this stuff. Thanks, Brett
::::::
::::::Brett,
::::::
::::::If you would like to see a picture of a selenium rectifer, check out:
::::::
::::::http://www.theodoregray.com/PeriodicTable/Elements/034/
::::::
::::::It is down about the middle of the page or so.
::::::
::::::Radiodoc
:::::
:::::Hey Doc, Thanks, It does help. I also got the Zenith part# 212-7-SE1. I'll order the diode and resistor and change them out.
::::::**********
::::::
::::
::::Hi Brett,
:::: Two ideas on your fading AM. First, fading is of course normal on distant stations on AM at night. Second, if the fade happens on local stations also, look to see if the filaments of the tubes fade also. If so you have a tube with an intermittant filament.
:::: On your dead FM, try checking the voltages at the the pin and the lug of the socket. I have often found bad tube sockets on these.
:::: If your bad FM is caused by a tube, the bad tube is most likely the 19T8. You can order a 19C8. They work fine and cost less.
:::: Another test is to momentariy swap the 12AU6 and one of the 12BA6. If you lose the AM, then the 12AU6 is bad.
:::: Another test is to check the voltage on pin 1 of the 12AU6 when in FM position. It needs to be negative on the order of -0.4 volts. If it is zero or positive, then you have a bad IF transformer.
::::
:::: For the replacement diode, I use 1N4004 or 1N4007. They are cheap and common. Since it is an H723, not an H724, you will have plenty of tie points for mounting the diode, resistor, and new filters.
::::
::::All the Best,
::::
::::Bill Grimm
:::Bill,
::: Thanks, good stuff. A few quick questions, how long is momentarily on the 12AU6 and the 12BA6 switch? It can take up to five minutes to warm up and cut out. Also, on the resistor, where I’ve been buying my supplies, list 51 & 68 Ohm 2 Watt Metal Oxide or 5 Watt Power Resistors. Will one of these do, or do I need to go elsewhere? Now I haven’t opened the radio back up yet, so I just desolder the rectifier and leave it in place and solder the diode in its stead. Then find the resistor and replace it. Right?
:::Thanks again, Brett
:::
::Hi Brett,
:: You can leave the 12AU6 and 12BA6 swapped basically indefinitely. They are adequate replacements for each other. I only swap them back because that is the way the radio was designed. One is remote cut off, the other is sharp cut off pentode. I only have a vague understanding of what that is.
:: I get my 60 ohm resistors by getting a 69 ohm 3 watt(which I happen to have a whole bunch) and putting a 470, 1.4 watt in parallel.
::
::All the Best,
::
::Bill
:O. K., I’m back to being a little confused. If I took a 51 Ohm 2 Watt and a 9 Ohm 1 Watt in series, I would have the 60 Ohm, but would I have the 3 Watts I need?

Hi Brett,
I calculated about 0.2 amp going through the resistor. This means the 51 ohm will dissipate a full 2 watts, perhaps a little bit more. It should be OK. The 9 ohm will dissipate 0.4 watts no problem there.

Best Regards,

Bill

O. K., I’m back to being a little confused. If I took a 51 Ohm 2 Watt and a 9 Ohm 1 Watt in series, I would have the 60 Ohm, but would I have the 3 Watts I need?

One more thing. Make sure the end of the new diode that has the line connected to the radio circuitry. The other end, the anode, connects toward the mains. The resistor(s) can go on either end.

All the Best,

Bill Grimm

Bill, they both have to be 3watts.

:O. K., I’m back to being a little confused. If I took a 51 Ohm 2 Watt and a 9 Ohm 1 Watt in series, I would have the 60 Ohm, but would I have the 3 Watts I need?
:
:One more thing. Make sure the end of the new diode that has the line connected to the radio circuitry. The other end, the anode, connects toward the mains. The resistor(s) can go on either end.
:
:All the Best,
:
:Bill Grimm

: Bill, they both have to be 3watts.
:
:
::O. K., I’m back to being a little confused. If I took a 51 Ohm 2 Watt and a 9 Ohm 1 Watt in series, I would have the 60 Ohm, but would I have the 3 Watts I need?
::
::One more thing. Make sure the end of the new diode that has the line connected to the radio circuitry. The other end, the anode, connects toward the mains. The resistor(s) can go on either end.
::
::All the Best,
::
::Bill Grimm

Hi Planigan,
I did the calculations a while ago, and got 0.2 amps of current draw.
Using ohms law, P = I * I * R, power dissipated by the 9 ohm resistor is 0.36 watts. A 1/2 watt will work fine here. Brett's resistor is 2 watts. The 51 ohm is a little iffy. I get 2.04 watts. I would want a 3 watt there.

Best Regards,

Bill

:: Bill, they both have to be 3watts.
::
::
:::O. K., I’m back to being a little confused. If I took a 51 Ohm 2 Watt and a 9 Ohm 1 Watt in series, I would have the 60 Ohm, but would I have the 3 Watts I need?
:::
:::One more thing. Make sure the end of the new diode that has the line connected to the radio circuitry. The other end, the anode, connects toward the mains. The resistor(s) can go on either end.
:::
:::All the Best,
:::
:::Bill Grimm
:
:Hi Planigan,
: I did the calculations a while ago, and got 0.2 amps of current draw.
: Using ohms law, P = I * I * R, power dissipated by the 9 ohm resistor is 0.36 watts. A 1/2 watt will work fine here. Brett's resistor is 2 watts. The 51 ohm is a little iffy. I get 2.04 watts. I would want a 3 watt there.
:
:Best Regards,
:
:Bill
Can they be more? Like say two 30 Ohm 5 watt?

::: Bill, they both have to be 3watts.
:::
:::
::::O. K., I’m back to being a little confused. If I took a 51 Ohm 2 Watt and a 9 Ohm 1 Watt in series, I would have the 60 Ohm, but would I have the 3 Watts I need?
::::
::::One more thing. Make sure the end of the new diode that has the line connected to the radio circuitry. The other end, the anode, connects toward the mains. The resistor(s) can go on either end.
::::
::::All the Best,
::::
::::Bill Grimm
::
::Hi Planigan,
:: I did the calculations a while ago, and got 0.2 amps of current draw.
:: Using ohms law, P = I * I * R, power dissipated by the 9 ohm resistor is 0.36 watts. A 1/2 watt will work fine here. Brett's resistor is 2 watts. The 51 ohm is a little iffy. I get 2.04 watts. I would want a 3 watt there.
::
::Best Regards,
::
::Bill
:Can they be more? Like say two 30 Ohm 5 watt?

Hi Brett,
More is always OK electrically. Physical space considerations are then the limiting factor. A 20 watt would work well electrically, but woudn't fit in the case.

Best Regards,

Bill

:::: Bill, they both have to be 3watts.
::::
::::
:::::O. K., I’m back to being a little confused. If I took a 51 Ohm 2 Watt and a 9 Ohm 1 Watt in series, I would have the 60 Ohm, but would I have the 3 Watts I need?
:::::
:::::One more thing. Make sure the end of the new diode that has the line connected to the radio circuitry. The other end, the anode, connects toward the mains. The resistor(s) can go on either end.
:::::
:::::All the Best,
:::::
:::::Bill Grimm
:::
:::Hi Planigan,
::: I did the calculations a while ago, and got 0.2 amps of current draw.
::: Using ohms law, P = I * I * R, power dissipated by the 9 ohm resistor is 0.36 watts. A 1/2 watt will work fine here. Brett's resistor is 2 watts. The 51 ohm is a little iffy. I get 2.04 watts. I would want a 3 watt there.
:::
:::Best Regards,
:::
:::Bill
::Can they be more? Like say two 30 Ohm 5 watt?
:
:Hi Brett,
: More is always OK electrically. Physical space considerations are then the limiting factor. A 20 watt would work well electrically, but woudn't fit in the case.
:
:Best Regards,
:
:Bill
Hi Bill,
Well I finally got back to this radio. I bought a tube tester and checked out the tubes. The 19T8 was bad and two of the 12BA6’s had 6BJ6’s instead. I took care of the tubes. The radio played for hours without fading. I’m ready to replace the rectifier and resistor. Does this resistor resemble a flat capacitor with two red dots? I never saw one like this, but if I’m reading everything right, it should be it. Thanks, Brett.
Oh, and also still no FM, but I still have to run the other tests.

: Bill, they both have to be 3watts.
:
:
::O. K., I’m back to being a little confused. If I took a 51 Ohm 2 Watt and a 9 Ohm 1 Watt in series, I would have the 60 Ohm, but would I have the 3 Watts I need?
::
::One more thing. Make sure the end of the new diode that has the line connected to the radio circuitry. The other end, the anode, connects toward the mains. The resistor(s) can go on either end.
::
::All the Best,
::
::Bill Grimm
Can they be more? Like say two 30 Ohm 5 watt?