transistor amp not working after shorting output

[anatech]

That is why we are using capacitors instead of wiring the heat sinks directly to ground.

 

[sg97]

if answer is yes i can do it then, btw what is good spot for ground here ?

 

[sg97]

up there is input connection maybe i can use its ground ?

 

[sg97]

also one thing when pot is at 0 percent there is not buzz only when i turn volume up

 

[xXBrunoXx]

up there is input connection maybe i can use its ground ?

From transformer there is bridge recrifier then capacitor, from the capacitor there are two wires that go to the amp , one is + ,one is - ( ground). Wire one leg of each capacitor togheter on the ground, where the - comes from the big power supply capacitor. Then the other two legs of the caps one on each transistor collector ( case , heatsink).

 

[sg97]

ok thanks btw it is not labeled on the transformer it has white and black wire to cap and from there blue and purple blue is on black purple on place of white, so if this is right there is a ground. on this rail it goes all the way up to input ground

 

[anatech]

See the negative on the main filter capacitor? Where that goes, or something close to it on teh board.

Not the signal ground!!!

 

[sg97]

i did it on main ground and no effect, i will try to change input pot it acts strange and i will report if other one i have will make a difference

 

[sg97]

my pot is bad i have to replace it but i dont think it will fix the issue 100% i am not sure

 

[sg97]

btw on other pot i added when i touch one of 3 connectors it works perfectly so i should ground that but where ?

 

[sg97]

btw i think that i have not wired input pot the right way. i have old pot its not like new 10k ones, i dont have any new at hand but i dont know if i wired it right way

 

[sg97]

i tried two pots and nothing , still i don't fix grounding issue

 

[Netlist]

I'll ask again:
Please post a picture of the input pot, wiring, TRS and connections to the amp.

It could be RF but if the hum disappears with grounded input (pot at 0) I would suspect a problem at the input connections.
This is how the pot should be wired:

The black trace is your ground connection:

Where is that 1k resistor going? To the input pot?

 

[sg97]

yes resistor is connected to input wire

 

[sg97]

as i said before it is not usual potentiometer, it only work when wired in this configuration i tried other ways but this way it only amplifies. input jack is labeled in picture 2 it is trs female plug i made it to be mono , it is ok btw

 

[sg97]

problem is that this pot is not arranged as usual so i dont know where input and output is tbh

 

[sg97]

also i power the amp without pot and buzz is still there so something is not grounded a input i think

 

[sg97]

if i remember well old case for this amp was all metal and pot was grounded to that , i dont want to do it, i want it to be grounded proper way

 

[Netlist]

Take your ohm meter and measure the pot.
Between two of the tree pins you should measure a fixed resistance, no matter how you turn the pot.
Attach one of them to ground and sleeve from TRS,
the other to tip from TRS.
The third one is your output to amp in.
Ref. post #853

 

[sg97]

i will try that if does not work i will buy new pot