01-08-2011, 08:20 PM
Hello.
I'm restoring a 37-620 Chairside.
It belongs to the father of a friend of mine. Supposedly it worked within the last 20 years or so.
I've replaced all the capacitors (a total PITA due to the sub-chassis) and it will now power up and produce a small hum. But that is all...
Adjusting the tone control appears to filter the hum. If I touch (or even come close to touching) the grid cap of detector 2 (the 6Q7G) I get a very very loud 60hz hum in the speaker. If I tune my little grundig M400 am radio to 1070khz and tune the philco to 625ish khz I can hear the oscillator in the grundig speaker. The tuning capacitor moves the oscillator around as I would expect (you can hear it on the grundig and also see it on the scope if I look at the grid cap on that tube). The frequency changes as i would expect when moving between the three bands.
Apart from that I get nothing. The volume control doesn't do anything that I can tell. There is no fuzz anywhere on any of the bands.
The "socket voltages" listed in the rider pages mostly line up. However the voltages labeled 70V show up more around 90V. I'm unsure what those actually are, though?
All of the tubes check out on my (admittedly crappy Radio City Products 802N) tube tester.
So now I'm stumped.
This is the second radio I have attempted restoration on. My Philco 112 Lowboy pretty much worked great from the moment I powered it up after the re-capping. Apparently I got lucky on that one.
Does anyone have any hints on what I should look at next?
I'm restoring a 37-620 Chairside.
It belongs to the father of a friend of mine. Supposedly it worked within the last 20 years or so.
I've replaced all the capacitors (a total PITA due to the sub-chassis) and it will now power up and produce a small hum. But that is all...
Adjusting the tone control appears to filter the hum. If I touch (or even come close to touching) the grid cap of detector 2 (the 6Q7G) I get a very very loud 60hz hum in the speaker. If I tune my little grundig M400 am radio to 1070khz and tune the philco to 625ish khz I can hear the oscillator in the grundig speaker. The tuning capacitor moves the oscillator around as I would expect (you can hear it on the grundig and also see it on the scope if I look at the grid cap on that tube). The frequency changes as i would expect when moving between the three bands.
Apart from that I get nothing. The volume control doesn't do anything that I can tell. There is no fuzz anywhere on any of the bands.
The "socket voltages" listed in the rider pages mostly line up. However the voltages labeled 70V show up more around 90V. I'm unsure what those actually are, though?
All of the tubes check out on my (admittedly crappy Radio City Products 802N) tube tester.
So now I'm stumped.
This is the second radio I have attempted restoration on. My Philco 112 Lowboy pretty much worked great from the moment I powered it up after the re-capping. Apparently I got lucky on that one.
Does anyone have any hints on what I should look at next?
