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

42-355 B+ Tolerance
#1

I just finished rewiring and recapping my 42-355. I get nothing but some hum, so I'm starting the troubleshooting process by measuring voltages. The B+ seems to be low, compared to the schematic values.

The AC is about 121 volts, and the output of the rectifier (across the 1st filter cap) is 277 VDC instead of the 290 on the schematic. The B+ across the second filter is about 165 instead of 190, and I get 160 and 165 at the plate of the two 41 output tubes. Schematic values are 185 and 190. I didn't replace the candohm resistor because the resistances are close to spec, but I could try that next.

I'm not sure this is enough difference to matter, but I thought I'd ask some wiser heads here on the forum before I went any further. I'm concerned that the plate voltage on the oscillator XXL will not be enough if the B+ is 25 volts low.

I get audible clicking when I touch my soldering iron onto the plates of all the tubes except the oscillator, but I don't get anything when I inject a 455KHz modulated signal into the signal grids of any of the tubes, so I might have wired something wrong somewhere.

Any thoughts? I have another 42-355 chassis that I could pull the power transformer from if needed to get the proper B+ voltage (assuming that transformer is good.)

John Honeycutt


Messages In This Thread
42-355 B+ Tolerance - by Raleigh - 09-01-2009, 11:56 AM
Re: 42-355 B+ Tolerance - by Raleigh - 09-08-2009, 06:40 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Hickok AC51 tube tester
Absolutely no one is going to reverse engineer that circuit. Even the iron core is missing.RodB — 10:37 AM
IF can wire size and Rubber mounts?
Thanks to both members for your help regarding wire and tuner mtg supports. regards--Johngeorgetownjohn — 09:33 AM
Hickok AC51 tube tester
Note that no power cord, power switch, or power transformer switch are shown. That (along with my experience with full s...DaleHCook — 07:09 AM
IF can wire size and Rubber mounts?
A pair of wire strippers can give you an idea of what the existing gauge of the wire leads are in the IF can, I think it...Arran — 06:07 AM
My last cabinet for this year
Hello Dan, That is really beautiful what great looking radio you have ! I have friends who live in Calgary and the wea...radiorich — 01:51 AM
Philco Predicta Siesta picture over time getting dimmer
I found that the wire insulation was burnt.  The fly back needs corona dope! Why would someone put that there?Platinumblonde36 — 01:09 AM
Philco Predicta Siesta picture over time getting dimmer
This is what it looked like beforePlatinumblonde36 — 01:01 AM
Philco Predicta Siesta picture over time getting dimmer
Platinumblonde36 — 12:58 AM
Philco Predicta Siesta picture over time getting dimmer
Platinumblonde36 — 12:57 AM
Philco Predicta Siesta picture over time getting dimmer
I'm finding some strange things in my set and for the most part it's also original, so I need to start going over everyt...Platinumblonde36 — 12:55 AM

[-]
Who's Online
There are currently 5042 online users. [Complete List]
» 2 Member(s) | 5040 Guest(s)
AvatarAvatar

>