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RE: oh no, I shorted an output....

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In Reply to: RE: oh no, I shorted an output.... posted by walkstoslow on December 15, 2023 at 11:11:10

I am finding it a bit hard to understand what happened. I assume that you shorted the input to the preamp but this should not cause any problems. In fact you can get "shorters" to help silence noise from unused inputs. Also, I don't understand "half the signal on both channels". Do you mean the volume is decreased by 1/2? Have you tried plugging the CDP into different inputs? In general, if you have a problem in both channels, the issue lies in an area common to both channels, which is usually the power supply. Also, take a look at the schematic and see if the headphone jack precedes an amplifier stage in which case the problem may lay downstream from the jack. As far as tracing the signal, start upstream (at the input).
Good luck.

"Our head is round in order to allow our thoughts to change direction." Francis Picabia

Follow Ups:

RE: oh no, I shorted an output.... - walkstoslow 11:50:05 12/17/23 (4)
Sansui au317 integrated amp, and Sony 707 CDP.
Correct I shorted one of the stereo inputs to the integrated amp from the cd player "out put".
By half the signal, I meant that the "presence" is gone,example, Miles Davis "A Tribute to Jack Johnson", the opening tune,"Right Off" opens with a guitar riff, 3-4 minutes later Miles joins in, trumpet should be "upfront", it is barely audible, also on Chic Corea's, "Return to Forever", opening tune,"Return to Forever", Flora Purim's vocal after 3-4 minutes starts, should also be "Upfront", again barely audible.
This condition is the same on "Aux, Tuner and Tape inputs".
As I said the headphone output is fine, I built a patch cable from headphone jack to speaker terminals.
All inputs are working fine with speaker switch set to headphones, A&B speakers off.
My volume setting was normally at 9:00, now it is at 12:00.
Looking at the schematic the headphone Jack inputs come straight off the speaker switch, after the output stage.
I am no means an expert with schematics.
I have a "Heath Kit" Breadboard with a variable signal generator, a 2 channel oscilloscope and a digital VOM.
Also I have the "Heath Kit" Electronics Course to use as a reference.
I hope to signal trace with this equipment.
I have been making cables for the signal input and output for my scope.
I ordered a temporary receiver to listen to while attempting to figure out this problem.
I hope this description makes more sense to you.
Thanks for your response and suggestions...
From a fellow tweaker.
- RE: oh no, I shorted an output.... - JRMA 14:46:34 12/17/23 (3)
  check the speaker cables for proper polarity. Sounds like one cable has +/- reversed.
  - RE: oh no, I shorted an output.... - walkstoslow 15:01:20 12/17/23 (2)
    I will check that out, thanks for input
    - Also,... - Lew 10:26:16 12/22/23 (1)
      are you saying the trumpet is reduced in SPLs in the condition where the short circuit to ground has been eliminated? If so, make sure it actually is eliminated before drawing any other conclusion. (It's a stereo signal,so it is possible that with one channel out, Davis's trumpet is less present because it was recorded on the channel that is not working.) Although your error should have been harmless to the equipment, maybe an output transistor has failed. Switch cables, L to R and R to L, to be sure that the shorted channel is still up and running, for example.
      - RE: Also,... - walkstoslow 14:27:09 12/22/23 (0)
        
        In Reply to: RE: Also,... posted by Lew on December 22, 2023 at 10:26:16
        
        Thanks for the input, what happened is this,
        I was cleaning connectors, instead of putting the cleaning liquid on a q tip, I actually sprayed inside the pin into the amp,I suppose I wetted something inside and short circuited something.
        I am hoping to "open the hood"and take a look, after xmas.
        Hopefully I blew a fuse.
        Thanks for your input...wish me luck....
        The out put at the headphone jack is still sounding just fine....70-75 db.
        I have been studying the schematic for two weeks now and boning up on my signal tracing skills via a breadboard.....life is what happens when you are making other plans.
        
        Edits: 12/22/23

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