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

41-258 B+ Problem
#1

Hi folks. I have just finished recapping, replacing all resistors, and completely rewiring a Philco 41-258. The set plays well, except for some problems with "motorboating" in the upper part of the AM band. I ran a check on the B+ voltage, coming off of the filter caps, and it's way too hot. I am getting about 106 VDC. I tried turning down the line voltage to about 90 VAC with my variac, and the problem went away. So, I installed a 10K dropping resistor on the line right after the last filter cap. I got the voltage drop I was looking for. But, the set now has all kinds of whistles and motorboating on the entire AM band.

I have noticed that this set's oscillator seems to be very sensitive to even minor changes in the power side of the radio. Is there another location, or strategy, that I can use to drop the B+ voltage? Here is the schematic, over at Nostalgia Air:
http://www.nostalgiaair.org/PagesByModel...013411.pdf


Messages In This Thread
41-258 B+ Problem - by Guest - 03-06-2009, 03:23 PM
Re: 41-258 B+ Problem - by codefox1 - 03-07-2009, 12:48 PM
Re: 41-258 B+ Problem - by rghines1 - 03-07-2009, 06:04 PM
Re: 41-258 B+ Problem - by Guest - 03-10-2009, 12:09 AM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
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
Part numbers to model cross
Jim, We have this index put together by Dale Cook but I don't think that is quite what you are looking for. The Parts...klondike98 — 09:37 PM

[-]
Who's Online
There are currently 1509 online users. [Complete List]
» 2 Member(s) | 1507 Guest(s)
AvatarAvatar

>