Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

42-350 Burned Resistor
#9

I think I've made some progress in the power supply, but I'm not listening to the radio yet.

Basically, after I replaced the bad rectifier and oscillator tubes that had internal shorts, I still had too much current through the 1800 ohm resistor I was using to substitute for the field coil. I suspected I had wired the speaker cable wrong, but I found it confusing to trace it down because the tracers were so faded, so I finally decided to replace with new colored wires.

Once that was done, I set the variac at 117 VAC. The DC voltage at the rectifier and B+ at the output tube plate seemed right, and the current was a steady 43 milliamps through the resistor, so I decided to reconnect the speaker. Now I have some AC hum and static noises in the speaker, but no signal. Tuning through the dial makes no difference, but I get a little pop in the speaker when I touch each plate in the signal path with the meter, but not the oscillator.

B+ readings at each plate were all close to right (5 to 10 volts low or high) EXCEPT the oscillator, which was 51 volts instead of 75. Oddly, the high side of resistor #41 (33K ohm) is about 170 volts, which is close to what I think it should be, but the drop across that resistor is much higher than seems right. That makes me think the oscillator plate current is too high.

I ran out of time last night, but when I get back to it I will look at voltage on the high side of resistor #42 (2200 ohm) and replace the oscillator and see what I can see.

Any other suggestions would be welcome.

John Honeycutt


Messages In This Thread
42-350 Burned Resistor - by Raleigh - 08-09-2008, 05:20 PM
[No subject] - by Steve Davis - 08-09-2008, 05:45 PM
[No subject] - by planigan - 08-09-2008, 11:11 PM
[No subject] - by planigan - 08-09-2008, 11:33 PM
[No subject] - by Raleigh - 08-10-2008, 03:53 PM
[No subject] - by Steve Davis - 08-10-2008, 05:07 PM
[No subject] - by Ron Ramirez - 08-10-2008, 05:52 PM
[No subject] - by planigan - 08-10-2008, 09:00 PM
Progress! - by Raleigh - 08-27-2008, 01:09 PM
Re: Progress! - by exray - 08-28-2008, 06:51 AM
Got AM! - by Raleigh - 08-28-2008, 10:03 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Bakelite crack repair - what is best epoxy?
Thanks everyone. I appreciate you sharing your experience and looks like I'll work with the 24 hr two part clear epoxy....de371 — 10:25 PM
Jackson 665 j2 schematic request
Without a schematic its going to be hard tracing the wire wound spool resistors.daveone23 — 05:21 PM
Jackson 665 j2 schematic request
Looking for a schematic for the 665 j2 multimeter.daveone23 — 04:42 PM
Looking for place to donate unique Philco Philco J-1930 Prototype
>>I'll write to the Henry Ford. I heard, his secretary answers his mail, not he himself.morzh — 12:15 PM
Philco 48-200 alignment questions
Just checked the power cord and I did in fact wire it so the hot side (small prong) goes to the switch.transitony — 11:52 AM
Looking for place to donate unique Philco Philco J-1930 Prototype
Thanks for the suggestions.  I'll write to the Henry Ford.   That would certainly make sense since by the time this prod...jeibner — 11:49 AM
Looking for place to donate unique Philco Philco J-1930 Prototype
For what it's worth, the Henry Ford Museum and Greenfield Village in Dearborn, Michigan may be an option. The obvious ...GarySP — 11:39 AM
Help with Readrite 410 tube tester
Mike and I just had a short discussion yesterday about this very subject. So often it's the connections. Ya gotta have t...RodB — 10:08 AM
Looking for place to donate unique Philco Philco J-1930 Prototype
We have a regional museum here in the Twin Cities called The Pavek Museum. They have an extensive collection of communic...RodB — 09:30 AM
Philco 89B code 123 newbie
I did some nosing around and found that the original caps were 4 3/4" long x 1 5/16" in dia. Guess what 1"...Radioroslyn — 09:28 AM

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

>