Anyone know why a Philco Jr., model 80 cathedral would only tune a narrow range of frequency at the low frequency end of the b'dcast band?

Thanks
Lou

:Anyone know why a Philco Jr., model 80 cathedral would only tune a narrow range of frequency at the low frequency end of the b'dcast band?
:
:Thanks
:Lou

Sure sounds like the oscillator. Lazy weak tube? Check around the oscillator section of your tuning cap for shorting gangs. Maybe a cap in the oscillator coil circuit? That's a start anyway.

Yeah - interesting

It picks up a local station at the low frequency end of the band, and then the noise floor sloly fades away as I tune up in frequency. I agree could be a lazy tube.I am using #36s in it.

Lou

::Anyone know why a Philco Jr., model 80 cathedral would only tune a narrow range of frequency at the low frequency end of the b'dcast band?
::
::Thanks
::Lou
:
:Sure sounds like the oscillator. Lazy weak tube? Check around the oscillator section of your tuning cap for shorting gangs. Maybe a cap in the oscillator coil circuit? That's a start anyway.

:Yeah - interesting
:
:It picks up a local station at the low frequency end of the band, and then the noise floor sloly fades away as I tune up in frequency. I agree could be a lazy tube.I am using #36s in it.
:
:Lou
:
:::Anyone know why a Philco Jr., model 80 cathedral would only tune a narrow range of frequency at the low frequency end of the b'dcast band?
:::
:::Thanks
:::Lou
::
::Sure sounds like the oscillator. Lazy weak tube? Check around the oscillator section of your tuning cap for shorting gangs. Maybe a cap in the oscillator coil circuit? That's a start anyway.

Lou, you could try changing the 36 tube, but a common problem with these early Philcos is moisture in the oscillator coil. Remove the coil and bake it in the oven for about 20 minutes at 200 degrees. Then spray a coat of lacquer. Steve

Well, I did a little test last nite.

I took a pocket radio down to the "lab" , turned the Philco 80 on, and then tuned around the band while looking for the local oscillator on the pocket radio.
NoGo!! That means that the set is acting like a TRF without the LO and picking up the local station.

I have fixed one of these before. It is pobably and open local oscillator coil. I had to rewind one on the last set I fixed. After I did that, it worked like a champ.

Lou

::Yeah - interesting
::
::It picks up a local station at the low frequency end of the band, and then the noise floor sloly fades away as I tune up in frequency. I agree could be a lazy tube.I am using #36s in it.
::
::Lou
::
::::Anyone know why a Philco Jr., model 80 cathedral would only tune a narrow range of frequency at the low frequency end of the b'dcast band?
::::
::::Thanks
::::Lou
:::
:::Sure sounds like the oscillator. Lazy weak tube? Check around the oscillator section of your tuning cap for shorting gangs. Maybe a cap in the oscillator coil circuit? That's a start anyway.
:
:Lou, you could try changing the 36 tube, but a common problem with these early Philcos is moisture in the oscillator coil. Remove the coil and bake it in the oven for about 20 minutes at 200 degrees. Then spray a coat of lacquer. Steve

:Well, I did a little test last nite.
:
:I took a pocket radio down to the "lab" , turned the Philco 80 on, and then tuned around the band while looking for the local oscillator on the pocket radio.
:NoGo!! That means that the set is acting like a TRF without the LO and picking up the local station.
:
:I have fixed one of these before. It is pobably and open local oscillator coil. I had to rewind one on the last set I fixed. After I did that, it worked like a champ.
:
:Lou
:
:::Yeah - interesting
:::
:::It picks up a local station at the low frequency end of the band, and then the noise floor sloly fades away as I tune up in frequency. I agree could be a lazy tube.I am using #36s in it.
:::
:::Lou
:::
:::::Anyone know why a Philco Jr., model 80 cathedral would only tune a narrow range of frequency at the low frequency end of the b'dcast band?
:::::
:::::Thanks
:::::Lou
::::
::::Sure sounds like the oscillator. Lazy weak tube? Check around the oscillator section of your tuning cap for shorting gangs. Maybe a cap in the oscillator coil circuit? That's a start anyway.
::
::Lou, you could try changing the 36 tube, but a common problem with these early Philcos is moisture in the oscillator coil. Remove the coil and bake it in the oven for about 20 minutes at 200 degrees. Then spray a coat of lacquer. Steve

It could be the Green dot thing. Here is a Philco antenna coil, but seems same thing happens to the Osc. coil. Some other tips here as well.

http://www.oldradiosrus.com/build.html

Well, I found the answer to this one. Staring me right in the face!!

I checked the feedback coils in the set, and they were continuous. Hmm - no local oscillator. So , it dawned on me. Take the two #36 tubes in the set ( Det /Osc and Second Detector ) and swap them. Voila!! Obviously, one of the tubes did not have enough transconductance to oscillate. Now, the set runs beautifully.

Amazing that you can do so much with three tubes and a rectifier!!

Thanks
Lou

::Well, I did a little test last nite.
::
::I took a pocket radio down to the "lab" , turned the Philco 80 on, and then tuned around the band while looking for the local oscillator on the pocket radio.
::NoGo!! That means that the set is acting like a TRF without the LO and picking up the local station.
::
::I have fixed one of these before. It is pobably and open local oscillator coil. I had to rewind one on the last set I fixed. After I did that, it worked like a champ.
::
::Lou
::
::::Yeah - interesting
::::
::::It picks up a local station at the low frequency end of the band, and then the noise floor sloly fades away as I tune up in frequency. I agree could be a lazy tube.I am using #36s in it.
::::
::::Lou
::::
::::::Anyone know why a Philco Jr., model 80 cathedral would only tune a narrow range of frequency at the low frequency end of the b'dcast band?
::::::
::::::Thanks
::::::Lou
:::::
:::::Sure sounds like the oscillator. Lazy weak tube? Check around the oscillator section of your tuning cap for shorting gangs. Maybe a cap in the oscillator coil circuit? That's a start anyway.
:::
:::Lou, you could try changing the 36 tube, but a common problem with these early Philcos is moisture in the oscillator coil. Remove the coil and bake it in the oven for about 20 minutes at 200 degrees. Then spray a coat of lacquer. Steve
:
:
:It could be the Green dot thing. Here is a Philco antenna coil, but seems same thing happens to the Osc. coil. Some other tips here as well.
:
:http://www.oldradiosrus.com/build.html
:
:

PS

You guys did say I may have a weak tube but I had to prove it for myself!!

Thanks
Lou

:Well, I found the answer to this one. Staring me right in the face!!
:
:I checked the feedback coils in the set, and they were continuous. Hmm - no local oscillator. So , it dawned on me. Take the two #36 tubes in the set ( Det /Osc and Second Detector ) and swap them. Voila!! Obviously, one of the tubes did not have enough transconductance to oscillate. Now, the set runs beautifully.
:
:Amazing that you can do so much with three tubes and a rectifier!!
:
:Thanks
:Lou
:
:
:
:::Well, I did a little test last nite.
:::
:::I took a pocket radio down to the "lab" , turned the Philco 80 on, and then tuned around the band while looking for the local oscillator on the pocket radio.
:::NoGo!! That means that the set is acting like a TRF without the LO and picking up the local station.
:::
:::I have fixed one of these before. It is pobably and open local oscillator coil. I had to rewind one on the last set I fixed. After I did that, it worked like a champ.
:::
:::Lou
:::
:::::Yeah - interesting
:::::
:::::It picks up a local station at the low frequency end of the band, and then the noise floor sloly fades away as I tune up in frequency. I agree could be a lazy tube.I am using #36s in it.
:::::
:::::Lou
:::::
:::::::Anyone know why a Philco Jr., model 80 cathedral would only tune a narrow range of frequency at the low frequency end of the b'dcast band?
:::::::
:::::::Thanks
:::::::Lou
::::::
::::::Sure sounds like the oscillator. Lazy weak tube? Check around the oscillator section of your tuning cap for shorting gangs. Maybe a cap in the oscillator coil circuit? That's a start anyway.
::::
::::Lou, you could try changing the 36 tube, but a common problem with these early Philcos is moisture in the oscillator coil. Remove the coil and bake it in the oven for about 20 minutes at 200 degrees. Then spray a coat of lacquer. Steve
::
::
::It could be the Green dot thing. Here is a Philco antenna coil, but seems same thing happens to the Osc. coil. Some other tips here as well.
::
::http://www.oldradiosrus.com/build.html
::
::

Well, I also noticed....

SOMEONE had put the wrong cap value ( electrolytic) on one side of the speaker field coil ( too small a value - 0.5 uF - perhaps he read it as 5 uF?).

After putting the correct value in , I now have absolutely NO hum. This is the quietest radio with the best fidelity I have had to date - with four tubes!!

Lou

:PS
:
:You guys did say I may have a weak tube but I had to prove it for myself!!
:
:Thanks
:Lou
:
::Well, I found the answer to this one. Staring me right in the face!!
::
::I checked the feedback coils in the set, and they were continuous. Hmm - no local oscillator. So , it dawned on me. Take the two #36 tubes in the set ( Det /Osc and Second Detector ) and swap them. Voila!! Obviously, one of the tubes did not have enough transconductance to oscillate. Now, the set runs beautifully.
::
::Amazing that you can do so much with three tubes and a rectifier!!
::
::Thanks
::Lou
::
::
::
::::Well, I did a little test last nite.
::::
::::I took a pocket radio down to the "lab" , turned the Philco 80 on, and then tuned around the band while looking for the local oscillator on the pocket radio.
::::NoGo!! That means that the set is acting like a TRF without the LO and picking up the local station.
::::
::::I have fixed one of these before. It is pobably and open local oscillator coil. I had to rewind one on the last set I fixed. After I did that, it worked like a champ.
::::
::::Lou
::::
::::::Yeah - interesting
::::::
::::::It picks up a local station at the low frequency end of the band, and then the noise floor sloly fades away as I tune up in frequency. I agree could be a lazy tube.I am using #36s in it.
::::::
::::::Lou
::::::
::::::::Anyone know why a Philco Jr., model 80 cathedral would only tune a narrow range of frequency at the low frequency end of the b'dcast band?
::::::::
::::::::Thanks
::::::::Lou
:::::::
:::::::Sure sounds like the oscillator. Lazy weak tube? Check around the oscillator section of your tuning cap for shorting gangs. Maybe a cap in the oscillator coil circuit? That's a start anyway.
:::::
:::::Lou, you could try changing the 36 tube, but a common problem with these early Philcos is moisture in the oscillator coil. Remove the coil and bake it in the oven for about 20 minutes at 200 degrees. Then spray a coat of lacquer. Steve
:::
:::
:::It could be the Green dot thing. Here is a Philco antenna coil, but seems same thing happens to the Osc. coil. Some other tips here as well.
:::
:::http://www.oldradiosrus.com/build.html
:::
:::

Yeah, those radios don't hum much at all. The filter appears to be tuned, with the .01 MFD cap across the field, but I'm not certain. My Philco 60 actually doesn't have the parallel field cap, and it still is hum-free.

The Philco 8o uses a regenerative IF stage. That is why it is so powerful. Though the IF is only one frequency, sometimes the feedback circuit can work irratically, though your trouble is more likely the local oscillator, like you seem to have found. The reason why there is no user regeneration control is because the IF only operates at one frequency, and so regeneration rarely needs to be re-tuned. The set is a superheterodyne with regenerative IF and detection (same stage). Very good idea, except that those kinds of detectors don't sound too good at low volumes. The audio gets kinda grainy due to the square law effect--working in the curve instead of the straight area of the tube's conduction.

A superregenerative superheterodyne makes for a simple and very nice FM radio. Your detector is no superregenerative, but rather simply regenerative. A superregenerative detector goes into and out of regeneration at ultrasonic frequencies (inaudible). Maximum efficiency occurs right before regeneration, so if the detector is swung in and out of regeneration at a really quick rate, it will automatically detect the signal with maximum strength.

T.

I was looking through some old radio publications I have. Have not gown through this for a number of years.
Found an almost " lost Art " about early power supply designs. Seems the power designers back then really knew there stuff about tuned chokes and filters. Gave a lot of the math that goes with this. The basic of it is to tune the power circuit with small capacitors across the the field chokes, and at both ends. The precision of this gives a smooth almost pure DC output. ( such as in that Clairion 60 ) You did correct me on. Only radios of the high quality seem to use this, as the cost factor again figures in. Glad to hear that some of this forgotten art still lives.

Well, brute force is better at all line frequencies then available. Once larger value electrolytics became available in compact sizes, the manufacturers went with those instead (the brute force method). The tuned filter was specific to a certain line frequency (which, today, thankfully, is 60 all over the country). The tuned method of filtering was popular before large value electrolytics became practical. However, as we've seen, the tuned power supplies can work remarkably well with very small capacitances.

T.

Thanks all for all the great info on the power supplies.

As I said before, you would never know the radio was turned on initially ( absolutely NO hum). I have never really run across this.

Well, I am going to finish the restoration. This is definitely a keeper for me!!.

Lou

:Well, brute force is better at all line frequencies then available. Once larger value electrolytics became available in compact sizes, the manufacturers went with those instead (the brute force method). The tuned filter was specific to a certain line frequency (which, today, thankfully, is 60 all over the country). The tuned method of filtering was popular before large value electrolytics became practical. However, as we've seen, the tuned power supplies can work remarkably well with very small capacitances.
:
:T.