38-116 code 125 volume issues - Printable Version
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38-116 code 125 volume issues - simplex1040 - 05-28-2020
I am looking at a 38-116 for someone and it has been fully recapped and out of tolerance resistors replaced ( not by me but well done, nothing sloppy).
Complaint is ,the volume is low and sounds like a crappy transistor radio. This thing should boom.
I checked the bias voltage at the 6l6 tubes ( pin 5) and they have -25v on them so that is not the issue.
Plate voltages seem a bit high, I attribute that to DMM. ( about 44 volts high on 6l6 plates and screen) .
It also seems like there is lack of tone. every thing is tinny sounding. output xformer check, field coil checked.
speaker subbed to rule out speaker , still sounds like crap.
Supposedly new tubes were put in.
I don't know if an alignment was done.
point my in a direction of what to check next.
RE: 38-116 code 125 volume issues - morzh - 05-28-2020
Short of injecting an audio signal....check your audio path.
If bad, start either scoping or tracing, or subbing tubes.
Check your volume/tone.
Check the audio kill switch in the dial assembly for non-dead short.
Align radio to make sure your IF is not totally screwed up (they use it coupled with the tone control).
RE: 38-116 code 125 volume issues - simplex1040 - 05-30-2020
Injected audio at volume control, Sounds like crap. took volume control out of the test and it still sounds like crap.
it is def in the audio section. I have to trace this all down.
Volume control is good.
As a test I pulled one of the 6l6 to run it with one and got distorted sound. swapped tubes between sockets and got same issue.
tracing on.....
RE: 38-116 code 125 volume issues - morzh - 05-30-2020
Both 6L6 get plate voltages?
Have you checked the interstage and output transformers?
RE: 38-116 code 125 volume issues - Radioroslyn - 05-30-2020
Would check to see if the have plate voltage on the 6J5 driver tube. May have a bad driver transformer, hope not. If you have plate voltage on both 6L6's plates that rules out the primary of the opt. And if you have bias on the control grids of both 6L6's that rules out the secondary of the driver transformer.
Mike is a faster typist than I.
RE: 38-116 code 125 volume issues - morzh - 05-30-2020
...and considering it is with one finger on touch keyboard with a minimum of one correction per word...
RE: 38-116 code 125 volume issues - simplex1040 - 05-30-2020
yep, yep and yep, All check out fine.
That is why this is kind of frustrating.
RE: 38-116 code 125 volume issues - morzh - 05-30-2020
Have you changed the other tubes yet?
RE: 38-116 code 125 volume issues - simplex1040 - 05-31-2020
I have not changed any tubes yet, They were supposedly "new" ones put in by others.
RE: 38-116 code 125 volume issues - morzh - 05-31-2020
I don't trust "others".
If you have subs, it's a dandy time to break them out.
RE: 38-116 code 125 volume issues - simplex1040 - 05-31-2020
I have subbed the driver and then the 6l6 s and it made no diff, however plate voltage is 361v on the driver and should be 260v
plates on 6l6 344v should be 300v screens 344v should be 290
RE: 38-116 code 125 volume issues - Radioroslyn - 06-01-2020
Check #117 pin 1 to 2 for 4K of resistance. Add clip leads from pin 8 of each of the 6L6's to the chassis. What value caps are #121 and 122?
RE: 38-116 code 125 volume issues - simplex1040 - 06-01-2020
117 checked out correct. (I will check again)cap 122 is a .33 cap 121 I have will have to see as it was a restuff of the original. I will do the clip lead test when I get home.
RE: 38-116 code 125 volume issues - Radioroslyn - 06-01-2020
Sorry meant #120 and 121 the two eletrolytics. And you are using a tube rectifier and not silicon diodes?
https://philcoradio.com/library/download/service%20info/wiring%20diagrams/vol2/split/Part52-Philco%20Wiring%20Diagrams%20Vol.%202.pdf
RE: 38-116 code 125 volume issues - simplex1040 - 06-01-2020
.33 not 33 cap listed in schematic is a .3