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

Replaced the capacitors but all I get is a hum
#40

Andy


1. Measure the voltages across all tubes, compare with the Voltage chart. Report it here. Pay most attention not to some discrepancies but to drastic ones. Like voltages on plates being 0V or close instead of say 100+ Volts like they should be.

2. In case most turn out OK,
What you should do first is to try to do the "grid cap touch" test.
You have to be VERY careful as I understand you are not well familiarized with things yet.

You can use a screwdriver with an insulated handle for that. Most of us use our hands but for you I'd recommend starting with the screwdriver.

Unfortunately In your case there are no grid caps so it makes it a bit more challenging.

Start touching with the screwdriver the grids of the tubes going away from the audio like the G1 in this tube.

http://www.radiomuseum.org/tubes/tube_7v7.html

Listen if the buzz is there when you touch.
See when it stops.

then start checking the continuity of the interstage RF transformers after the tube where it stopped.

3. Overall continuity check on all inductances (RF transformers mostly what they are) should be done.


Messages In This Thread
RE: Replaced the capacitors but all I get is a hum - by morzh - 11-08-2013, 10:18 AM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Philco Model 38-7: what caps & resistors do fail typically?
Since you stated earlier, you have a console 38-7XX.  They also had a 38-7T (table), and 38-7CS (chairside).  A very nic...GarySP — 01:18 PM
Part numbers to model cross
That I wouldn't know, but sometimes the radio document itself shows one, same as the capacitor cans' etc pinouts.morzh — 12:46 PM
Part numbers to model cross
Thank you morzh, that is exactly what I was looking for. Now , is there some where that shows pinouts for Philco power ...Jim Dutridge — 11:37 AM
Restoration of the Canadian General Electric A-87
Thanks for your help Michael. In fact, this video is only an intermediate result. Later I had to apply another tinting l...RadioSvit — 09:01 AM
Restoration of the Canadian General Electric A-87
Great job on the cabinet. PS. In the US notation, "kenotron" refers to specific type of tubes; we call re...morzh — 08:24 AM
Part numbers to model cross
This document has at least some tables of models and parts used. Example: Choke 32-7572, used in 604 radio. Search f...morzh — 08:19 AM
Restoration of the Canadian General Electric A-87
I also checked all the radio tubes on my Hickok 530 tube tester. The 5Z3 kenotron turned out to be faulty, all the other...RadioSvit — 08:02 AM
Restoration of the Canadian General Electric A-87
Well... While the varnish is drying up, I started repairing the chassis... Of course I started by replacing the pa...RadioSvit — 07:12 AM
Philco Model 38-7: what caps & resistors do fail typically?
Hello Martin, Welcome aboard our little community what great Model 38-7 Sincerely Richardradiorich — 12:30 AM
Philco Model 38-7: what caps & resistors do fail typically?
Welcome to the Phorum Martin. I count about 9 paper caps, the 3 electrolytic caps and 2-Y2 safety caps to replace th...RodB — 09:44 PM

[-]
Who's Online
There are currently 1440 online users. [Complete List]
» 1 Member(s) | 1439 Guest(s)
Avatar

>