Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Nothing but slight hum from 37-620
#1

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. Icon_smile

Does anyone have any hints on what I should look at next?


Messages In This Thread
Nothing but slight hum from 37-620 - by audin - 01-08-2011, 09:20 PM
Re: Nothing but slight hum from 37-620 - by audin - 01-09-2011, 12:30 AM
Re: Nothing but slight hum from 37-620 - by audin - 01-09-2011, 09:21 PM



Users browsing this thread: 3 Guest(s)
[-]
Recent Posts
trying to identify this wire type
Thanks to all for the feedback. As Arran said, it is probably an older replacement and yes it has a grid cap so I will ...georgetownjohn — 09:32 PM
trying to identify this wire type
It's possible that the red wire, actually a grid cap lead, is a very old replacement, I can't remember seeing a pre 1939...Arran — 09:18 PM
Gilfillan Brothers Car Radio?
Hi everyone,  Special thanks to Joe Rossi for tracking down this obscure radio and thanks to others who took up the hun...Antipodal — 08:15 PM
trying to identify this wire type
Here's one source for your wire of many. Take care and BE HEALTHY! Gary P.S. Can't get the right color you need? I ...GarySP — 06:40 PM
trying to identify this wire type
...and modern wire of the appropriate gauges and insulation V-rating (300V minimum, usually shown right on the wire) is ...morzh — 05:47 PM
1930s Stromberg-Carlson Tombstone Radio need help identifying model number
I have a question about this radio, is there anyone that has access to this radio that has an intact unmolested speaker ...captainclock1988 — 04:28 PM
1930s Stromberg-Carlson Tombstone Radio need help identifying model number
Well what makes me confuse all of those companies is that all three of those companies (Setchell-Carlson, Stromberg-Carl...captainclock1988 — 04:21 PM
trying to identify this wire type
The red wire is rubber covered wire. The others are cotton braid over rubber often in colors or a tracer, also strand...Chas — 02:43 PM
trying to identify this wire type
Greetings Phorum members, Hope you can help me identify this type of wire in the photo I have attached.  I am not sure ...georgetownjohn — 01:53 PM
Philco 60 Squealing
All correct shields must be in place, all tubes correct no subs of any kind. Check any soldered, riveted ground conne...Chas — 01:24 PM

[-]
Who's Online
There are currently no members online.

>