Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Closed
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: 1 Guest(s)
[-]
Recent Posts
HiFi (Chifi) tube amp build - but my own design.
Well, maybe - maybe not  :lol: It's been an interesting project so far! Something so simple, yet so cranky. The 1st one ...TV MAN — 05:12 PM
1949 Motorola 5A9M
Haven't thought of Burgess batteres in a while  https://www.radionostalgia.ca/lib/Images/battery/us/burgess1D.jpgi ...Vlad95 — 03:50 PM
Philco Model 16 wiring question
Measure the voltages first, just in case.morzh — 02:19 PM
1949 Motorola 5A9M
Haven't thought of Burgess batteries in a while Mr. Fixer. Boston Edison always used Burgess in their Bright Star yellow...Paul Philco322 — 02:17 PM
1949 Motorola 5A9M
Thanks Sam. I'll let you know. I can probably scare some up from the local radio club.klondike98 — 02:07 PM
Philco 89 Code 123 Osc Coil
Hello,  I thought I would post my findings on my bad oscillator tickler coil. There were 27 turns on the outer coil b...dconant — 12:38 PM
Philco Model 16 wiring question
Thanks Morzh. So it appears I did wire it incorrectly and I have to switch the wires between pins 2 and 4.bobclausen — 09:24 AM
Philco 46-1209 strange behavior
No, it's not a problem, just during certain condition it could show up. Yes, an internal tube short could do that too. ...morzh — 09:13 AM
HiFi (Chifi) tube amp build - but my own design.
You sound guys are never satisfied. :crazy: :clap:RodB — 09:10 AM
HiFi (Chifi) tube amp build - but my own design.
I got some new ceramic octal tube sockets installed and also tried some different coupling caps.  The results:  The go...TV MAN — 08:42 AM

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

>