38-116 code 125 volume issues
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City: Paducah, KY
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.
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City: Jackson, NJ
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).
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.
(This post was last modified: 05-28-2020, 10:18 AM by morzh.)
Posts: 86
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City: Paducah, KY
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.....
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Both 6L6 get plate voltages?
Have you checked the interstage and output transformers?
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.
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City: Roslyn Pa
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.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 05-30-2020, 07:39 PM by Radioroslyn.)
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...and considering it is with one finger on touch keyboard with a minimum of one correction per word...
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.
Posts: 86
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Joined: Sep 2012
City: Paducah, KY
yep, yep and yep, All check out fine.
That is why this is kind of frustrating.
Posts: 15,704
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Have you changed the other tubes yet?
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.
Posts: 86
Threads: 15
Joined: Sep 2012
City: Paducah, KY
I have not changed any tubes yet, They were supposedly "new" ones put in by others.
Posts: 15,704
Threads: 551
Joined: Oct 2011
City: Jackson, NJ
I don't trust "others".
If you have subs, it's a dandy time to break them out.
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.
Posts: 86
Threads: 15
Joined: Sep 2012
City: Paducah, KY
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
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Joined: Dec 2009
City: Roslyn Pa
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?
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 86
Threads: 15
Joined: Sep 2012
City: Paducah, KY
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.
Posts: 7,283
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Joined: Dec 2009
City: Roslyn Pa
Sorry meant #120 and 121 the two eletrolytics. And you are using a tube rectifier and not silicon diodes?
https://philcoradio.com/library/download...l.%202.pdf
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 06-01-2020, 08:07 AM by Radioroslyn.)
Posts: 86
Threads: 15
Joined: Sep 2012
City: Paducah, KY
.33 not 33 cap listed in schematic is a .3
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