Hi, all: I have a philco 37-620. It's been in my family for years and I know that no one has tampered with it. My problem is the case of the missing compensators. The schematic and drawings of the chassis from the Rider manual shows sets of three adjustable capacitors for the ant, rf, and osc sections. However, my radio has only one for ant and rf. The osc section looks like the drawing. Otherwise, my set seems identical to what is shown on the schematic. I'm guessing that perhaps there might have been some sort of change that the company made mid-way in the model year and then didn't print a revised schematic. I should also mention that the model number is on a label inside the cabinet, but the chassis does not have any label with the model number on it (possibly fell off?). I don't have any reason to believe that someone swapped the original chassis with this one as it all appears to go together well. Anyone got an idea about this? Thanks. Mark

Hi, Mark. Here's the schematic: http://www.nostalgiaair.org/PagesByModel/212/M0013212.pdf

It's hard to say why the shortwave ant and RF trimmers are missing. Could very well have been an undocumented circuit change during production. Those trimmers could have been considered expendable since SW alignment wouldn't have been too critical. I wouldn't worry about it.

:Hi, all: I have a philco 37-620. It's been in my family for years and I know that no one has tampered with it. My problem is the case of the missing compensators. The schematic and drawings of the chassis from the Rider manual shows sets of three adjustable capacitors for the ant, rf, and osc sections. However, my radio has only one for ant and rf. The osc section looks like the drawing. Otherwise, my set seems identical to what is shown on the schematic. I'm guessing that perhaps there might have been some sort of change that the company made mid-way in the model year and then didn't print a revised schematic. I should also mention that the model number is on a label inside the cabinet, but the chassis does not have any label with the model number on it (possibly fell off?). I don't have any reason to believe that someone swapped the original chassis with this one as it all appears to go together well. Anyone got an idea about this? Thanks. Mark

Doug, thanks for your reply. It turns out that the missing trimmers are actually for the standard and police bands. Part of my reasoning for posting this was that I wondered if there was another schematic out there that is more accurate. I am working on the radio, mainly replacing caps and checking everything else. I have a couple of problems: Reception starts off okay,but then becomes less sensitive after a couple of minutes. Local stations continue to come in fairly well, but weaker stations almost disappear. I also have some crackling noise on standard broadcast band. I don't have IF transformers with the silver mica capacitors, so no silver mica disease. If anyone has any suggestions, please pass them on to me. Thanks. Mark
:Hi, Mark. Here's the schematic: http://www.nostalgiaair.org/PagesByModel/212/M0013212.pdf
:
:It's hard to say why the shortwave ant and RF trimmers are missing. Could very well have been an undocumented circuit change during production. Those trimmers could have been considered expendable since SW alignment wouldn't have been too critical. I wouldn't worry about it.
:
:
::Hi, all: I have a philco 37-620. It's been in my family for years and I know that no one has tampered with it. My problem is the case of the missing compensators. The schematic and drawings of the chassis from the Rider manual shows sets of three adjustable capacitors for the ant, rf, and osc sections. However, my radio has only one for ant and rf. The osc section looks like the drawing. Otherwise, my set seems identical to what is shown on the schematic. I'm guessing that perhaps there might have been some sort of change that the company made mid-way in the model year and then didn't print a revised schematic. I should also mention that the model number is on a label inside the cabinet, but the chassis does not have any label with the model number on it (possibly fell off?). I don't have any reason to believe that someone swapped the original chassis with this one as it all appears to go together well. Anyone got an idea about this? Thanks. Mark

Hi Mark,
I recommend http://www.philcorepairbench.com/ and get his service data. It's well worth it. The 37-620 production runs I know of, not about cause I don't have, are 121, 122, 125, and 126. There's some differences! I did have a Philco, can't remember which one where one of the condenser was removed in a later production run.

Bill VA

Doug, thanks for your reply. It turns out that the missing trimmers are actually for the standard and police bands. Part of my reasoning for posting this was that I wondered if there was another schematic out there that is more accurate. I am working on the radio, mainly replacing caps and checking everything else. I have a couple of problems: Reception starts off okay,but then becomes less sensitive after a couple of minutes. Local stations continue to come in fairly well, but weaker stations almost disappear. I also have some crackling noise on standard broadcast band. I don't have IF transformers with the silver mica capacitors, so no silver mica disease. If anyone has any suggestions, please pass them on to me. Thanks. Mark
::Hi, Mark. Here's the schematic: http://www.nostalgiaair.org/PagesByModel/212/M0013212.pdf
::
::It's hard to say why the shortwave ant and RF trimmers are missing. Could very well have been an undocumented circuit change during production. Those trimmers could have been considered expendable since SW alignment wouldn't have been too critical. I wouldn't worry about it.
::
::
:::Hi, all: I have a philco 37-620. It's been in my family for years and I know that no one has tampered with it. My problem is the case of the missing compensators. The schematic and drawings of the chassis from the Rider manual shows sets of three adjustable capacitors for the ant, rf, and osc sections. However, my radio has only one for ant and rf. The osc section looks like the drawing. Otherwise, my set seems identical to what is shown on the schematic. I'm guessing that perhaps there might have been some sort of change that the company made mid-way in the model year and then didn't print a revised schematic. I should also mention that the model number is on a label inside the cabinet, but the chassis does not have any label with the model number on it (possibly fell off?). I don't have any reason to believe that someone swapped the original chassis with this one as it all appears to go together well. Anyone got an idea about this? Thanks. Mark

Bill and Doug: Thanks for your suggestions. I did go to the website below and ordered the service data. There were some very significant changes in this model year and the info I received is very helpful. I never would have figured it out on my own. So far, I have completed the recap and found a bad tube that was causing some of the noise and the decreasing sensitivity. I still am not done. SW reception is extremely poor now (less of a concern to me)and I will eventually look into that. Main concern is volume. Radio has to be played with volume at least halfway up or better. I'll keep at it. I hate how difficult it is to get at some of the parts in this radio chassis, especially the ant, rf, and osc section. Mark

:Hi Mark,
:I recommend http://www.philcorepairbench.com/ and get his service data. It's well worth it. The 37-620 production runs I know of, not about cause I don't have, are 121, 122, 125, and 126. There's some differences! I did have a Philco, can't remember which one where one of the condenser was removed in a later production run.
:
:Bill VA
:
:
:Doug, thanks for your reply. It turns out that the missing trimmers are actually for the standard and police bands. Part of my reasoning for posting this was that I wondered if there was another schematic out there that is more accurate. I am working on the radio, mainly replacing caps and checking everything else. I have a couple of problems: Reception starts off okay,but then becomes less sensitive after a couple of minutes. Local stations continue to come in fairly well, but weaker stations almost disappear. I also have some crackling noise on standard broadcast band. I don't have IF transformers with the silver mica capacitors, so no silver mica disease. If anyone has any suggestions, please pass them on to me. Thanks. Mark
:::Hi, Mark. Here's the schematic: http://www.nostalgiaair.org/PagesByModel/212/M0013212.pdf
:::
:::It's hard to say why the shortwave ant and RF trimmers are missing. Could very well have been an undocumented circuit change during production. Those trimmers could have been considered expendable since SW alignment wouldn't have been too critical. I wouldn't worry about it.
:::
:::
::::Hi, all: I have a philco 37-620. It's been in my family for years and I know that no one has tampered with it. My problem is the case of the missing compensators. The schematic and drawings of the chassis from the Rider manual shows sets of three adjustable capacitors for the ant, rf, and osc sections. However, my radio has only one for ant and rf. The osc section looks like the drawing. Otherwise, my set seems identical to what is shown on the schematic. I'm guessing that perhaps there might have been some sort of change that the company made mid-way in the model year and then didn't print a revised schematic. I should also mention that the model number is on a label inside the cabinet, but the chassis does not have any label with the model number on it (possibly fell off?). I don't have any reason to believe that someone swapped the original chassis with this one as it all appears to go together well. Anyone got an idea about this? Thanks. Mark

Very interesting mmakazoo.I have a 37-610 that has been completely recapped and almost all of the resistors replaced as well.This radio displays the very same symptoms as yours.It will start with good volume and then after a few minutes it will drop and get rather noisy.All three bands will play.However,like you said,you have to crank up the volume.I noticed today that to listen on the highest band on weaker stations,the volume needs to be almost all the way up.Strangely,I found by accident, that if I connect a jumper lead to the antenna wire and momentarily touch the headphone jack on my c.b. base station,the volume will jump back to normal!Which tube did you replace by the way?My tester says all my tubes are okay,but I'm sure a tube(6A8?) is causing my problem.Please post your findings,you may solve the riddle for us both.Thanx.

Make sure that your AVC resistor is on value. Make sure that all other resistors are on value as well. Make absolutely sure that none of the condensers are leaky at all. Make sure that your oscillator tube is in good condition. The schematic is rather complicated, so I may study it at some other time if I have the time. Hopefully someone else will come up with a good suggestion, first. The above, though is very important. When resistors are drifted or condensers are leaky by even the slightest amount (millions of ohms), circuits get sloppy and unreliable.

Thomas

And when all is said and done, change out that 6A8 with other ones regardless of how each tests. See if that will help.

Bill VA

:Make sure that your AVC resistor is on value. Make sure that all other resistors are on value as well. Make absolutely sure that none of the condensers are leaky at all. Make sure that your oscillator tube is in good condition. The schematic is rather complicated, so I may study it at some other time if I have the time. Hopefully someone else will come up with a good suggestion, first. The above, though is very important. When resistors are drifted or condensers are leaky by even the slightest amount (millions of ohms), circuits get sloppy and unreliable.
:
:Thomas

The tube I changed was a 6k7g. There are two in this radio, it happened to be the one in the rf section. I actually swapped it with one from my zenith and now the zenith exhibits the same problems. It tested okay, but I heard something inside "clinking" and grew suspicious. I will change the 6a8, too. Will check the resistors again in the avc circuit. Thanks again for everyone's input. Mark

:And when all is said and done, change out that 6A8 with other ones regardless of how each tests. See if that will help.
:
:Bill VA
:
::Make sure that your AVC resistor is on value. Make sure that all other resistors are on value as well. Make absolutely sure that none of the condensers are leaky at all. Make sure that your oscillator tube is in good condition. The schematic is rather complicated, so I may study it at some other time if I have the time. Hopefully someone else will come up with a good suggestion, first. The above, though is very important. When resistors are drifted or condensers are leaky by even the slightest amount (millions of ohms), circuits get sloppy and unreliable.
::
::Thomas

Well, I think I have it solved. Thanks to Thomas about checking the resistors. It was the one in the AVC circuit. I was careless and had not checked before and it was way off. Just finished up putting the chassis back in the cabinet and it's playing very well. SW is working good, too. Mark

:The tube I changed was a 6k7g. There are two in this radio, it happened to be the one in the rf section. I actually swapped it with one from my zenith and now the zenith exhibits the same problems. It tested okay, but I heard something inside "clinking" and grew suspicious. I will change the 6a8, too. Will check the resistors again in the avc circuit. Thanks again for everyone's input. Mark
:
::And when all is said and done, change out that 6A8 with other ones regardless of how each tests. See if that will help.
::
::Bill VA
::
:::Make sure that your AVC resistor is on value. Make sure that all other resistors are on value as well. Make absolutely sure that none of the condensers are leaky at all. Make sure that your oscillator tube is in good condition. The schematic is rather complicated, so I may study it at some other time if I have the time. Hopefully someone else will come up with a good suggestion, first. The above, though is very important. When resistors are drifted or condensers are leaky by even the slightest amount (millions of ohms), circuits get sloppy and unreliable.
:::
:::Thomas

Good to hear it. If the AVC resistor is drifted, the circuit will be so loose that it'll do whatever it feels like doing. Stray charges and radiations and whatever electrons that happen to collect on the grids of the various tubes will randomly mess around with the AVC circuit. More often than not electrons will slowly build up on the grids of the RF tubes, and reception will get quieter and quieter until "pop," it just goes dead.

T.