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

Candohm replacement
#1

Am working on a 42-322 (my first restoration, unfortunately I didn't realize this had the rubber wire issue until after I bought it and started reading this phorum, but what the heck...).  The candohm filament resistor (#46 in schmatic) is faulty although it seems to have failed in an unusual way.  The 40 ohm section reads 250 ohms while the 80 ohm section reads 84.  Thought these usually failed open or shorted to chassis.  Anyway, my plan is to drill out the candohm and replace with a terminal strip and some 5 watt wire wound power resistors.  Does that sound right to you folks or is there another approach that works better?
Thanks for the help!
Bob  
[Image: https://www.dropbox.com/s/ckazdphd7vfl59....jpg?raw=1]
[Image: https://www.dropbox.com/s/3pvuhfhf88u0e9....jpg?raw=1]
#2

Yor're right on target. Dress the sand resistors against the corner of the chassis for most heat dissipation and you will be all set! Can't go wrong with 20 watters, but do ade a fuse too.
#3

did you take the incandescent bulb out when measuring the forty ohm section? that can explain 250 ohms instead of a full open.
#4

Thanks codefox & morzh! Yes the bulb was out of the socket, but good point, I should check to be sure there isn't something else amiss causing that reading. I had recapped, rewired, etc. and started to power up with a dim bulb tester. The dial bulb blew and the dim bulb flickered and went dark so I shut down and am back to checking things. Learning as I go.
bob
#5

If the candohm is otherwise working I would leave it alone, the worse that is going to happen is it will open up and the radio will quit working as it is in series with the filament string.
Regards
Arran
#6

So the 40 ohm side is probably open or even worse intermittant. It'll keep blowing out those bulbs.[/align]
#7

Thanks Arran & Phlogiston. I'll go ahead and replace it, I just don't trust it.
bob
#8

Recapped a 42-322.  Part #43 was a multi-section 20, 20, 10 uF (red, yellow, green w/ black common wire) electrolytic cap. I wired the negative leads together as the black common and the positive leads to the red, yellow and green wires respectively.  Did I get the polarity right?

[Image: https://www.dropbox.com/s/siqnuvnlc3trnc....jpg?raw=1]
[Image: https://www.dropbox.com/s/ckazdphd7vfl59....jpg?raw=1]
[Image: https://www.dropbox.com/s/1dxql2due9iimy....jpg?raw=1]

Reason I ask is that I only measure -1vDC between the common lead and the point where I should see 100vDC.  Rectifier tube filaments glowing (don't have a tube tester), field coil measures ~500ohms, dim bulb power up went OK.  New 35Z3 on order but your thoughts on other next steps I should consider would be helpful.
Thanks!
Bob
#9

Your cap wiring is fine. You should check your B+ at a few other spots:

1) Cathode of the 35Z3
2) input side of the field coil
3) output side of the field coil.

Is your dial lamp working? If not, check that and the resistor (40 ohm) in parallel with it that goes to the plate of the 35Z3. Check for ~120VAC on the plate of the 35Z3.

Make sure you have connected your common B- to the proper point. This will have a floating chassis, so no DC between the chassis and B+ line.
#10

Thanks BrendaAnnD.

a) 35Z3 cathode is -1vDC
b) 35Z3 plate is 108vAC (line is 110vAC through isolation xfmr)
c) both in and out of field coil are -1vDC
d) B- common is same wire as original wire (but heat shrink covered to replace old rubber) and has continuity to other B- points
e) dial lamp is working (now that candohm was replaced with some power resistors http://philcoradio.com/phorum/showthread.php?tid=5697 )

Regards,
bob
#11

That sounds for sure like an open cathode on the 35Z3, or a tube that's REALLY flat.

Do you have a silicon diode you can temporarily sub across between plate and cathode of the 35Z3 (just for test purposes, don't leave it in.)? The band end of the diode would go to cathode. If you get voltages at that point, it would verify a dead tube.
#12

Good thought, thanks! Don't have one but easy to get.
cheers, Bob
#13

Been awhile but the rectifier tube arrived before I got the diode and that solved the B+ voltage problem. Still had no response at all except if I touched the output tube grid. Without a tube tester I swapped tubes to find the problem and finally get good broadcast volume on our local am stations. Lost my radio virginity to a 42-322 Icon_biggrin There does seem to be more hum between stations than there should, any thoughts on that? Need to see if SW comes in tonight.
Time to work on the cabinet too.




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Philco 610B oscillator wiring
Some info from Beitmans says late production. David   David — 06:06 PM
Restoring Philco 96
Oh wow! Just found this thread.  Brings me back to early days on this phorum.  I did a 96 back in 2017.  Thread here: ...rfeenstra — 06:05 PM
Philco 610B oscillator wiring
Thanks for the replies. It's not the really the hum that I am after. Just trying to understand why only the shortwave ba...Tubester — 04:01 PM
Restoring Philco 96
70 and 90 are Superhets, but at least the 2x45 model of 90 uses the Plate detector (and so does 70). Also the Atwaters,...morzh — 03:28 PM
Restoring Philco 96
Morzh, Prayers for your mom. I am sure that there was enough pain living through the Holocaust as a child. I pray dail...MrFixr55 — 02:19 PM
Philco 610B oscillator wiring
Hi Dan, Divide and conquer. First off trry to differentiate between 60Hz and 120 Hz hum. 120 Hz hum has a higher pit...MrFixr55 — 01:49 PM
Restoring Philco 96
Yes, other than takin a toll on your back, they are undeed way more repair friendly than many other Philcos. To me, som...morzh — 01:04 PM
Philco 610B oscillator wiring
If the wires look like they were this way from the factory (very neat and very dull soldering joints), I'd leave them be...morzh — 12:58 PM
My Philco 37-116 Restore
I managed to open up the Expander Unit and replace the grid cap wires. Tested the connections found they looked good and...dconant — 12:19 PM
610B Oscillator Questions
I've included a picture of the 'actual' schematic I created. I double checked several times and it appears to be accur...Tubester — 09:26 AM

[-]
Who's Online
There are currently 2446 online users. [Complete List]
» 2 Member(s) | 2444 Guest(s)
AvatarAvatar

>