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

37-650 buzzing
#12

AAAARRRRRGGGGGHHHHH!!!!! Icon_redface

D**n it, that's what I get for having too many things going on at once...

Wil (Bill), I gave you incorrect information. I apologize.

I completely forgot that the 37-650 uses a "trick" audio circuit. To avoid using an audio interstage transformer, audio is fed from the 1st audio tube (6K5G) to the control grid of one of the 6F6G output tubes. Then, to achieve the phase inversion necessary in a push-pull audio output circuit, an out of phase signal is taken from this same 6F6G and fed to the control grid of the other 6F6G tube.

So, if you happened to remove the first 6F6G, you would have no sound. But if you pulled the other 6F6G while leaving the first one in place, you would still hear sound.

Therefore my original advice applies, which was:

Quote:Other possibilities: bad ground connection(s), heater-cathode short in a tube, poor solder connections, miswiring/a component mistakenly soldered to the wrong place.

When you replaced the electrolytics, did you connect the negative leads of (57) and (59A) to B- (center tap of the power transformer, and the ungrounded end of resistor (58) )?

Electrolytic (59) is drawn backwards in the schematic, also. The positive lead of this electrolytic (10 uF, 50 volts) should be connected to ground (chassis). The negative lead goes to B-. In other words, the opposite of how it is shown in the schematic.

Try those thoughts, take two aspirin and call me in the morning. I've got a migraine already. Icon_crazy

--
Ron Ramirez
Ferdinand IN


Messages In This Thread
37-650 buzzing - by wil - 01-23-2011, 12:15 PM
Re: 37-650 buzzing - by Ron Ramirez - 01-23-2011, 10:07 PM
Re: 37-650 buzzing - by wil - 01-24-2011, 01:14 PM
Re: 37-650 buzzing - by Ron Ramirez - 01-24-2011, 05:21 PM
Re: 37-650 buzzing - by philcoradio1234 - 01-24-2011, 07:32 PM
Re: 37-650 buzzing - by Ron Ramirez - 01-24-2011, 08:03 PM
Re: 37-650 buzzing - by wil - 01-25-2011, 11:04 AM
Re: 37-650 buzzing - by Ron Ramirez - 01-25-2011, 11:24 AM
Re: 37-650 buzzing - by wil - 01-25-2011, 05:08 PM
Re: 37-650 buzzing - by Ron Ramirez - 01-25-2011, 05:20 PM
Re: 37-650 buzzing - by wil - 01-26-2011, 03:16 PM
Re: 37-650 buzzing - by Ron Ramirez - 01-26-2011, 07:46 PM
Re: 37-650 buzzing - by wil - 01-27-2011, 06:56 PM
Re: 37-650 buzzing - by Ron Ramirez - 01-27-2011, 09:00 PM
Re: 37-650 buzzing - by wil - 02-03-2011, 04:14 PM
Re: 37-650 buzzing - by Ron Ramirez - 02-03-2011, 08:06 PM
Re: 37-650 buzzing - by wil - 02-05-2011, 01:05 PM
Re: 37-650 buzzing - by Ron Ramirez - 02-06-2011, 01:42 AM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Zenith H725
Ed; One thing that I will say about these is that Brand Z was considerate enough to make these mica caps easily acces...Arran — 02:34 PM
Philco 610B oscillator wiring
Do you know what run # your chassis is? It took me a while to find what you were basing updates/modification on as I did...Radioroslyn — 07:34 AM
Need to purchase some accessories for restoration of my Old Philco Radio
COLLEAGUES, Thank you all for such good and important suggestions as how to find good replacement parts. I will go fo...palonso — 07:05 AM
Zenith H725
Here's what the inside of AM IFT2 looked like, and the other pic shows the discs I made to take place of the mica and ke...EdHolland — 07:40 PM
Zenith H725
IF2 will need replacement caps. The arcing was severe enough that the mica is pitted and holed where the HT flashed over...EdHolland — 04:04 PM
My Philco 37-116 Restore
Measuring from center tap like the tube voltages show. Cap 127 is isolated from ground. Cap 127 shown in upper left of p...dconant — 08:05 AM
My Philco 37-116 Restore
Are you measuring relative to the centertap or the GND?morzh — 11:57 PM
Philco 610B oscillator wiring
Still not clear on the wiring interface between the 6A7 and oscillator. After refering to the available schematics and s...Tubester — 07:18 PM
Refinishing Ideas
My 37-116 code 121 is the best sounding radio i have...a daily driver. Since we are talking about "changes". ...poulsbobill — 07:18 PM
My Philco 37-116 Restore
Hello, I finally got brave enough to take the cans off the Expander Unit. Got the grid cap wires replaced and back toget...dconant — 06:50 PM

[-]
Who's Online
There are currently 1187 online users. [Complete List]
» 3 Member(s) | 1184 Guest(s)
AvatarAvatarAvatar

>