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

Philco Model 20 escessive hum
#9

(03-25-2015, 08:02 PM)Mondial Wrote:  Tubes, you might try exchanging the 1.5 uF film cap you already have with the input 10 uf cap after the rectifier. Connect the 1.5 uF to the side of the choke connected to the 80 filament, the 10 uF to the other side of the choke as it is now, and the remaining 10 uF to the output of the field coil where you had the 1.5 uF. The last 10 uf would then be from the B+ side of the audio transformer primary to B-. This would give you additional filtering at the 27 audio amp stage, where you need it the most.

This should act to reduce the B+ voltage and bring it down close to the level it was originally. Then you can proceed to track down the hum problem.

This sounds like the best solution to me and would quickly let me know if the problem of loading is being caused by the first 10uf capacitor and I agree, it would add needed filtering to the audio amp. Other people have told me that they have always used 4.7uf caps for the first two filters and never had a problem with a model 20 doing that. Another old timer told me that the audio bias always needs more filtering than originally supplied by Philco. Your solution would verify this. Thanks


Messages In This Thread
Philco Model 20 escessive hum - by Tubesforme - 03-25-2015, 04:52 PM
RE: Philco Model 20 escessive hum - by klondike98 - 03-25-2015, 05:17 PM
RE: Philco Model 20 escessive hum - by Mondial - 03-25-2015, 05:34 PM
RE: Philco Model 20 escessive hum - by Warren - 03-25-2015, 07:00 PM
RE: Philco Model 20 escessive hum - by Tubesforme - 03-25-2015, 07:15 PM
RE: Philco Model 20 escessive hum - by Warren - 03-25-2015, 07:24 PM
RE: Philco Model 20 escessive hum - by Mondial - 03-25-2015, 08:02 PM
RE: Philco Model 20 escessive hum - by Tubesforme - 03-25-2015, 10:09 PM
RE: Philco Model 20 escessive hum - by Arran - 03-27-2015, 01:01 AM
RE: Philco Model 20 escessive hum - by Tubesforme - 03-30-2015, 01:11 PM
RE: Philco Model 20 escessive hum - by morzh - 03-27-2015, 09:52 AM
RE: Philco Model 20 escessive hum - by Tubesforme - 03-27-2015, 04:25 PM
RE: Philco Model 20 escessive hum - by Mondial - 03-27-2015, 04:36 PM
RE: Philco Model 20 escessive hum - by morzh - 03-27-2015, 04:51 PM
RE: Philco Model 20 escessive hum - by radiohenry - 03-28-2015, 09:16 AM
RE: Philco Model 20 escessive hum - by morzh - 03-28-2015, 10:02 AM
RE: Philco Model 20 escessive hum - by radiohenry - 03-28-2015, 04:35 PM
RE: Philco Model 20 escessive hum - by klondike98 - 03-28-2015, 08:47 PM
RE: Philco Model 20 escessive hum - by Tubesforme - 03-30-2015, 01:17 PM
RE: Philco Model 20 escessive hum - by radiohenry - 03-28-2015, 10:17 PM
RE: Philco Model 20 escessive hum - by morzh - 03-30-2015, 01:27 PM
RE: Philco Model 20 escessive hum - by Tubesforme - 03-30-2015, 01:37 PM
RE: Philco Model 20 escessive hum - by morzh - 03-30-2015, 01:41 PM
RE: Philco Model 20 escessive hum - by morzh - 03-30-2015, 01:48 PM
RE: Philco Model 20 escessive hum - by codefox1 - 03-30-2015, 03:21 PM
RE: Philco Model 20 escessive hum - by Tubesforme - 03-31-2015, 03:14 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
An attempt to remove the Field Coil from a G speaker
Hi Morzh, May be a good idea to remove the cone to prevent damage. You may have to do so anyway to remove the pole ...MrFixr55 — 08:44 PM
Philco 91 Restore Code ??
I think that Danaher, the company that owns Beckman-Coulter (the company that I worked for 41 years) owns Fluke. They a...MrFixr55 — 08:35 PM
Philco 91 Restore Code ??
Rod I wish... :lol: I am not sure I'd buy the Fluke, had it not fell in my lap for free. $500 to $800...it's a lot...morzh — 08:09 PM
Philco 91 Restore Code ??
Mike, ...you get a commission?RodB — 07:52 PM
New member
Hi. I specialize in refurbishing Predictas, but I'm in Chicago. If you can get it to me, I'd be happy to go over it. ...Bob Andersen — 06:43 PM
An attempt to remove the Field Coil from a G speaker
I have 3 G speaker, all with open Field coils. Today I pull one of the shelf and decided to try to remove the FC (spo...morzh — 06:07 PM
Philco 91 Restore Code ??
Thanks Mike. I will check them out.dconant — 05:52 PM
Philco 91 Restore Code ??
There is no such thing as bad Fluke. This said, they are expensive. A Fluke is easily 10x the price of comparable CCC...morzh — 05:45 PM
Philco 91 Restore Code ??
Hello Mike, Yes, I have 3 Fluke meters one being my first Fluke 77 and other being Fluke 87. My third is Fluke clamp -...radiorich — 05:04 PM
Philco 91 Restore Code ??
I knew that Fluke was the Cadillac so with that in mind what Fluke would you recommend I get?dconant — 03:53 PM

[-]
Who's Online
There are currently 4447 online users. [Complete List]
» 1 Member(s) | 4446 Guest(s)
Avatar

>