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
RodB :beerchug:Vlad95 — 10:22 AM
Philco 42-345 Restoration/Repair
Vlad, you nailed it. Swiss and German roots.RodB — 09:54 AM
5U4 vs 5Z4 tubes
Well this is a Hallicrafters SX/9 circa 1936. No real issues so far although I dodged a real bullet with a cap that was...bridkarl — 07:59 AM
5U4 vs 5Z4 tubes
The pinout is the same but the 5U4 has a 3 amp filament, verses 2 amps or less on the 5Z4. I think that the pinout of a ...Arran — 12:04 AM
Philco 42-345 Restoration/Repair
By the way. osanders0311 Take a look here: Dial cord stringing Guides May be here you can fount correct string settin...Vlad95 — 11:15 PM
5U4 vs 5Z4 tubes
5U4 and 5Z4 almost identical. I think nothing happened if you left 5U4 instedad 5Z4 long time. Just heater current 5U4 ...Vlad95 — 11:02 PM
Philco 42-345 Restoration/Repair
Hello Vlad95 , Very Funny ! Sincerely Richardradiorich — 11:01 PM
Philco 42-345 Restoration/Repair
RodB You are European yourself   :evil: I'm Canadian for the last 30 years  :snowman: But not Yankee  :lol: Vlad95 — 10:49 PM
Philco 42-345 Restoration/Repair
The band switch selects different oscillator coils for the band selected. I would look for a bad connection in the switc...RodB — 10:31 PM
Philco 42-345 Restoration/Repair
Hang in there...PaulPaul Philco322 — 09:30 PM

[-]
Who's Online
There are currently 921 online users. [Complete List]
» 3 Member(s) | 918 Guest(s)
AvatarAvatarAvatar

>