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

Setchell Carlson Model 427 fluctuating volume
#20

Intermittents- the nightmare f any mechanic, technician, engineer, etc.!

One interesting observation, you have 2 of these and when you replaced the e-cap and 2 wax caps the same issue occurs.  Did the other radio play correctly until the caps were replaced?

If you have an o-scope or a DVM that can read AC ripple, measure the junction of C10 and R4  Does the ripple increase as the plate voltage drop?  Does the same thing happen on the other side of R4 (the side that connects to R3 and the 2nd Lytic?  Either the caps are funky (like a bad batch) or something is loading it down.  

Another interesting point is that the 36V supply is not just to the RF amp plate and screen, it is to the IF amp screen.

If the other radio played well till you changed its lytic, reinstall the originals one at t time (if you have them).  Whatever fixes it, do to the first radio.

One other trick would be to remove the 12SK7 and bridge the heater connections with an 80 Ohm 5W resistor, then connect a wire antenna to the stator of the convertor section of the tuning cap, essentially making it a 5 tube radio. If the issue still exists, the RF Amp is not the issue.

But If I read all the posts correctly and you had another working radio that exhibited the same issues after you replaced the caps, then Occam's razor indicates that a batch of bad caps may be the issue.

Finally, are the caps connected to the exact same points (not schematic-wise but physically. Is the common negative of the 2 caps connected to the exact same point on the negative bus?


Good luck!!

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis

Best Regards, 

MrFixr55


Messages In This Thread
462ron - by 462ron - 04-29-2023, 07:56 AM
RE: Setchell Carlson Model 427 fluctuating volume - by MrFixr55 - 04-29-2023, 09:49 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Philco 42-345 Restoration/Repair
That silver can capacitor is an aluminum electrolytic. You should replace it with an aluminum electrolytic with the valu...RodB — 11:46 PM
Philco 42-345 Restoration/Repair
Thank you Rodb and Gary for helping with clarification on these capacitors. Other than the Tiny 630volt one I'm not sure...osanders0311 — 10:17 PM
1949 Motorola 5A9M
Hello All; I found the CMB41L down in the basement, it is definitely a 1950-51 model, the capacitors have date codes ...Arran — 07:48 PM
Philco 42-345 Restoration/Repair
Hi, all the caps I order, other than the electrolytics, are of the 630V rating. No worries on it being too high, and no ...gary rabbitt — 05:46 PM
Philco 42-345 Restoration/Repair
Hi, there's a lot to consider when designing these circuits so you shouldn't have a lot of concern when replacing caps. ...RodB — 02:03 PM
Philco 42-345 Restoration/Repair
I have ordered and received new caps for this radio and hope I've ordered the correct ones. I tried matching them to the...osanders0311 — 11:35 AM
Philco newbie with P-1891-WA console questions
Hello Jeff , Far as the Electrolytic capacitors go here is a list of parts. that will work . I like using Nichicon and...radiorich — 09:50 PM
Philco newbie with P-1891-WA console questions
Well, I've been stumped at trying to get the first of 11 electrolytic capacitors. I got a schematic and have a list of t...Jeffcon — 07:54 PM
Model 80 Antenna Issue?
Thanks Gary and Rod.  I also found an article in the Philco Repair Bench under Service Hints and Tips, about installi...Hamilton — 12:32 PM
Model 80 Antenna Issue?
Hello Hamilton, here is a little information found in our Philco Radio Library at the bottom of the Home page. Hope it ...GarySP — 11:28 AM

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

>