When I was hooking the signal generator gnd to the chassis, I drew a small spark. Where is the proper place to groung the signal generator when aligning?
I know I got the cart before the horse by trying to check out the IF frequency before I had recapped the set. But is it chassis gnd I'm after or B-?
I found big capacitor problems since then. The 40uf/10uf on the schematic is actually 40uf/20uf reading on the electrolytic. I have to replace it anyway, it's way toast, but what should I go by, the schematic or the part designation? Also, a 20uf was toast too. Maybe that accounts for the spark.
Looking forward to communication on this project, thanks as always...Neal
If the 20-uF cap appears original, then I'd go with that size. If not, then I'd try to follow the schematic. Either 10- or 20-uF might be OK.
Re: signal generator, I would feed the signal through a small cap, maybe .001uF. That will block any DC. The negative lead should go to B-.
If you don't have a manual for your generator, get one from BAMA or use the one for an EICO 315 as a go-by.
Lots of times, if your generator is just in the same room as the radio, you can pick up the modulated signal through the antenna or the IF stages. So, I sometimes wonder why all the persnickity hook-up instructions are necessary.
Doug
:Hi all,
:
:When I was hooking the signal generator gnd to the chassis, I drew a small spark. Where is the proper place to groung the signal generator when aligning?
:
:I know I got the cart before the horse by trying to check out the IF frequency before I had recapped the set. But is it chassis gnd I'm after or B-?
:
:I found big capacitor problems since then. The 40uf/10uf on the schematic is actually 40uf/20uf reading on the electrolytic. I have to replace it anyway, it's way toast, but what should I go by, the schematic or the part designation? Also, a 20uf was toast too. Maybe that accounts for the spark.
:
:Looking forward to communication on this project, thanks as always...Neal
But, more importantly, I modified my generator by adding a .01-uF cap at the RF ouput jack (inside the cabinet). I don't know why such a cap wasn't installed by Eico.
I also changed the RF jack to BNC (the original jack used the now-obsolete Amphenol mic jack).
Doug
:Neal: As far as the e-caps are concerned, I would replace them all automatically whether they are good, bad, or indifferent.
:
:If the 20-uF cap appears original, then I'd go with that size. If not, then I'd try to follow the schematic. Either 10- or 20-uF might be OK.
:
:Re: signal generator, I would feed the signal through a small cap, maybe .001uF. That will block any DC. The negative lead should go to B-.
:
:If you don't have a manual for your generator, get one from BAMA or use the one for an EICO 315 as a go-by.
:
:Lots of times, if your generator is just in the same room as the radio, you can pick up the modulated signal through the antenna or the IF stages. So, I sometimes wonder why all the persnickity hook-up instructions are necessary.
:Doug
:
I've recapped everything. There is a .2uf cap in there with a wire wrapped around it. From the other thread they talked about eliminating that because it was used for war time frequencys or something. I have it out and it had more leads on the bottom than I expected and I lost track of which went where. Can I just leave it out? Or does it provide biasing for something?
Before I recapped I had a loud noise output. But now with the bad 40/20uf back in I have nothing. Could it be the wirewound capacitor that is out. I had it in (right or not I don't know) and still nothing so I took it back out...Neal
:Neal: As far as the e-caps are concerned, I would replace them all automatically whether they are good, bad, or indifferent.
:
:If the 20-uF cap appears original, then I'd go with that size. If not, then I'd try to follow the schematic. Either 10- or 20-uF might be OK.
:
:Re: signal generator, I would feed the signal through a small cap, maybe .001uF. That will block any DC. The negative lead should go to B-.
:
:If you don't have a manual for your generator, get one from BAMA or use the one for an EICO 315 as a go-by.
:
:Lots of times, if your generator is just in the same room as the radio, you can pick up the modulated signal through the antenna or the IF stages. So, I sometimes wonder why all the persnickity hook-up instructions are necessary.
:Doug
:
::Hi all,
::
::When I was hooking the signal generator gnd to the chassis, I drew a small spark. Where is the proper place to groung the signal generator when aligning?
::
::I know I got the cart before the horse by trying to check out the IF frequency before I had recapped the set. But is it chassis gnd I'm after or B-?
::
::I found big capacitor problems since then. The 40uf/10uf on the schematic is actually 40uf/20uf reading on the electrolytic. I have to replace it anyway, it's way toast, but what should I go by, the schematic or the part designation? Also, a 20uf was toast too. Maybe that accounts for the spark.
::
::Looking forward to communication on this project, thanks as always...Neal
From what you've described, I suspect that during your recapping, you introduced one or more wiring errors (which is easy to do). I suggest that you pull out the schematic and, with colored pencils, verify everthing.
My normal approach is to troubleshoot a radio, and get it working, after a fashion, before recapping. Then, I check the operation after each cap is replaced. I know that this suggestion is too late, at least for this set.
Alignment is the last step in the repair process. You really can't align a set that isn't working.
:Thanks Doug...A 20uf for the 40/10 and hook to B- through a .001uf cap for alignment.
:
:I've recapped everything. There is a .2uf cap in there with a wire wrapped around it. From the other thread they talked about eliminating that because it was used for war time frequencys or something. I have it out and it had more leads on the bottom than I expected and I lost track of which went where. Can I just leave it out? Or does it provide biasing for something?
:
:Before I recapped I had a loud noise output. But now with the bad 40/20uf back in I have nothing. Could it be the wirewound capacitor that is out. I had it in (right or not I don't know) and still nothing so I took it back out...Neal
:
It's a .22uf and it's c18. Terry tells me that he left his out and it worked aok.
Neal: I looked at the schematic, and didn't see a 0.2-uF cap - but maybe I missed it.
:
:From what you've described, I suspect that during your recapping, you introduced one or more wiring errors (which is easy to do). I suggest that you pull out the schematic and, with colored pencils, verify everthing.
:
:My normal approach is to troubleshoot a radio, and get it working, after a fashion, before recapping. Then, I check the operation after each cap is replaced. I know that this suggestion is too late, at least for this set.
:
:Alignment is the last step in the repair process. You really can't align a set that isn't working.
:
::Thanks Doug...A 20uf for the 40/10 and hook to B- through a .001uf cap for alignment.
::
::I've recapped everything. There is a .2uf cap in there with a wire wrapped around it. From the other thread they talked about eliminating that because it was used for war time frequencys or something. I have it out and it had more leads on the bottom than I expected and I lost track of which went where. Can I just leave it out? Or does it provide biasing for something?
::
::Before I recapped I had a loud noise output. But now with the bad 40/20uf back in I have nothing. Could it be the wirewound capacitor that is out. I had it in (right or not I don't know) and still nothing so I took it back out...Neal
::
:
Let me know.
Terry F
BTW, I didn't have to align my radio when I finished it so put this on the back burner.
Thanks for letting me know that you left yours out and it still worked. That takes a load off my mind. It looks like I've a wiring error to find, while waiting for my 40uf and my 20uf to arrive.
Did your set have a 40/10 or a 40/20 in it. Mine had a 40/20 in it. It was way toast. No capacitance at all in one of them and like 6uf in the other...Neal
:I left the wire wound .2 mfd cap out when I did mine. What are your audio output tube voltages? This is a good place to start. Make sure the negative lead of your meter is on the B-. I used pin #5 of the 7C7 as a reference point. This is also the point where I connected the negative lead of the duo 10-40mfd cap. FYI
:
:Let me know.
:
:Terry F
:
:BTW, I didn't have to align my radio when I finished it so put this on the back burner.
:Terry,
:
:Thanks for letting me know that you left yours out and it still worked. That takes a load off my mind. It looks like I've a wiring error to find, while waiting for my 40uf and my 20uf to arrive.
:
:Did your set have a 40/10 or a 40/20 in it. Mine had a 40/20 in it. It was way toast. No capacitance at all in one of them and like 6uf in the other...Neal
:
::I left the wire wound .2 mfd cap out when I did mine. What are your audio output tube voltages? This is a good place to start. Make sure the negative lead of your meter is on the B-. I used pin #5 of the 7C7 as a reference point. This is also the point where I connected the negative lead of the duo 10-40mfd cap. FYI
::
::Let me know.
::
::Terry F
::
::BTW, I didn't have to align my radio when I finished it so put this on the back burner.
Terry F
It's really loud just by turning on the set, but the volume control does make it even louder, including distortion, by turning it up...Neal
:Does the volume control affect the hum level (up/down)?
:
:Terry F
Terry F
In answer to your question, the loudness of the humm follows the volume control.
I think I have discovered my problem. I will verify when I get back to my set. I replaced what I thought to be a candohm resistor with a 50W wirewound resistor. Turns out this thing I thought was a resistor turned out to be a choke. L1, 500 ohms.
I just read where if you do such a deed you can expect it to cause an output hummm. So when I get back to my set I will verify. I might have a bad choke however, we'll see when I do the old switcheroo. Thanks for your responses. I'll get back to you after 'smoke test'...Neal
:OK, how about turning it down? Does this reduce the hum/buzz?
:
:Terry F
It wasn't the choke either. I finally found that in clipping out the .2uf with the wire wrapped around it, I had inadvertantly clipped the filament wire between 7b7 and 7c6. They were nubbed off within a quarter of an inch of the sockets and very difficult to see. The wire had embedded itslef in the wax bottom of the .2uf capacitor and it looked like it had two extra leads coming out of it. If you would recall, I think I mentioned that it had more leads than I expected. Well, two of the leads were actually the filament wire traveling from tube to tube embedded in the end wax of the .2uf.
The set is working great now, I'm just trying to find the right crystal for the phonograph. All is well that ends well.
Problems like that are always so simple once you've found them...Neal
HI Terry,
:
:In answer to your question, the loudness of the humm follows the volume control.
:
:I think I have discovered my problem. I will verify when I get back to my set. I replaced what I thought to be a candohm resistor with a 50W wirewound resistor. Turns out this thing I thought was a resistor turned out to be a choke. L1, 500 ohms.
:
:I just read where if you do such a deed you can expect it to cause an output hummm. So when I get back to my set I will verify. I might have a bad choke however, we'll see when I do the old switcheroo. Thanks for your responses. I'll get back to you after 'smoke test'...Neal
:
::OK, how about turning it down? Does this reduce the hum/buzz?
::
::Terry F
You might try West Tech Services for a phono cartridge (or a rebuild). Google them and send an e-mail. The guy who replied to me was Gary Epling, I believe, but I didn't need a cartridge or a needle.
At any rate, they are a service shop where you can start.
Again, good luck on the total restoration.
Terry F
:Great! I am glad the radio is working.
:
:You might try West Tech Services for a phono cartridge (or a rebuild). Google them and send an e-mail. The guy who replied to me was Gary Epling, I believe, but I didn't need a cartridge or a needle.
:
:At any rate, they are a service shop where you can start.
:
:Again, good luck on the total restoration.
:
:Terry F