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

38-7. No sound
#1

Hey guys 
Bought this radio in 2018 and put away bought it off eBay but I don’t recall seller saying it was restored  I pulled chassis out and caps have been changed and looks to be correct  problem is no Sound at all   Not even static  even when I touch 6j5 I pulled out 5y4 tube and  transformer didn’t even get warm  all tubes light and good dial light works and cone lock disconnected
What else could I check

Thanks sam

Some day, and that day may never come, I will call upon you to do a service for me. But until that day, accept this justice as a gift
mafiamen2
#2

Hello Sam ,
First All here is the Schematic to help you with this set
https://philcoradio.com/library/download...l.%202.pdf
I had a Similar issue with a set that I have on my bench and found out the Audio output transformer had a open winding !
Hopefully you have a Multimeter because that what I would do look over the set and start from the speaker .

Sincerely Richard
#3

Hi Sam,

+1 on Richard's comments.

If you have a DVM or VOM, arrange the radio with chassis upside down. Start with the output transformer and field coil. Ohm them to ensure that they are not open. The transformer secondary likely will not open but the voice coil or the flexible voice coil pigtails may open. Unsolder the leads to the voice coil terminals and ohm the voice coil and secondary.

Next, locate the wirewound resistor, #43 on the schematic and ohm across the entire resistor. It should be about 245 Ohm. If this resistor is open, it will cause the no sound, no current issue as it is between the B+ return and chassis ground (and the 6F6 output tube cathode). This resistor generates the "C-" grid bias for the audio tubes by "voltage dividing" the return from the B+ supply.

When you touched the 6J5 grid cap, was the wire attached or detached? If this set has "cone-centric" tuning, there is an audio mute switch, #29 on the schematic.

If all is good, set meter to 700V and CAREFULLY! Measure voltage across the filter caps. There should be about 350V across the input cap (#45, at 5Y4 heater), and about 250V across the cap on the other side of the field coil (#11A). Higher voltages on both sides indicates no current draw. Of course, the biggest draw is from the output tube. Since this is a class A biased output, there should be a lot of current draw even at no volume. No voltage across the input filter cap indicates an extremely bad 5Y4 (open heater) or open secondary (This would be rare as the secondary would have to be open on both sides of the center tap.

Next, check voltage between Pin 3 (plate) of the 6F6 output tube and the B supply center tap of the power transformer (ungrounded side of resistor #43). It should be about 240V. Next, check between Pin 4 (screen grid) of the 6F6 and the power transformer. It should be 250V. If no voltage at pin 3 but voltage at pin 4, then the wiring to the output transformer is open. Please note that if this is the case, the 6F6 is likely also bad, as an open plate circuit will cause such a high current in the screen grid circuit that the screen grid will glow brighter than the heater and burn out, possibly shorting the tube.

Hope this all helps.

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards, 

MrFixr55
#4

hey guys 
rechecked found cap 34 connected to tap on candacome resister
reconnected to tap for 6j5 tube and it came alive very loud too
 if i now can get kirk to help with cabinet   
thanks guys


sam

Some day, and that day may never come, I will call upon you to do a service for me. But until that day, accept this justice as a gift
mafiamen2
#5

Yeah, that would do it. Cap has to go between plate of 1st AF tube and grid of output tube.

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards, 

MrFixr55
#6

Sam

Good luck with Kirk Icon_lol

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
12' Philco
Not anymore Mike. Andre The Giant Born: May 19, 1946, Coulommiers, France Died: Jan 28, 1993 (46 years), Paris, Fran...RodB — 11:53 PM
IF can wire size and Rubber mounts?
Renovated Radios do carry what you need. As for the voltage, a wire should be at least 300V-rated.morzh — 11:13 PM
12' Philco
Andre the Giant got 2" on Kareem :lol:morzh — 11:11 PM
IF can wire size and Rubber mounts?
Thanks for the info but I doubt that a hardware store would be carrying the proper tuner assembly support mountings for ...georgetownjohn — 10:38 PM
12' Philco
Perhaps Kareem Abdul Jabbar?GarySP — 10:33 PM
My last cabinet for this year
Outstanding work, Dan! Take care and BE HEALTHY! GaryGarySP — 10:31 PM
My last cabinet for this year
They are a nice looking radio, Stromberg. I have a small tabletop octagon-dial one. It sounds surprisingly nice. And t...morzh — 09:40 PM
Philco 41-608 changer coupler
Different years but the same idea.morzh — 09:38 PM
My last cabinet for this year
That’s a beauty! :thumbup:klondike98 — 09:24 PM
Philco 41-608 changer coupler
Hi Morzh, I've searched using Mondial as the user name with various keywords such as 'coupler', 'motor', 'idler', 'p...alangard — 08:31 PM

[-]
Who's Online
There are currently 3915 online users. [Complete List]
» 1 Member(s) | 3914 Guest(s)
Avatar

>