700-t hissssssssss

[Carbsandcaps]

I just got finished rebuilding a 700-t and everything went fine. Replaced all capacitors and transistors. On the bench with some cheap test speakers it sounded fine. I got it home and set it up with some pioneer cs-701a’s just to see what it could do. After a few minutes I noticed a hiss from the right channel. Stoped the music and the hiss was still there. It sounds EXACTLY like poor radio reception hiss but it only does it on aux, tape and phono inputs. The fm sounds great and the hiss is not there.

I’ve never heard anything like it and before I go digging back into it I was curious if anyone had any ideas where to start. Thank you.

 

[larryderouin]

It sounds EXACTLY like poor radio reception hiss but it only does it on aux, tape and phono inputs.

If the sources are unused, install shorting plugs in the unused source jacks. My 700-T is Hissy, and it has factory plugs which negate most of it.

 

[Carbsandcaps]

If the sources are unused, install shorting plugs in the unused source jacks. My 700-T is Hissy, and it has factory plugs which negate most of it.

There are factory shorting plugs in the second phono jacks. I’ll move them around and see if it changes. It’s strange that it’s only one channel but anything’s possible. Thanks!

 

[Carbsandcaps]

i tried switch the shorting plugs around and the only one that helped was the recorder high but I think that’s just because it was shorting the preamp output. I disconnected the amp/preamp jumper and it went away then I went to the preamp board and swapped the transistors from one side to the other and the noise went away. It’s either a bad connection at the transistor plugs or a bad transistor either way they’re all getting replaced tomorrow. I had a problem with these during the rebuild with no output on one channel. Dumb luck wins again. Thanks for the suggestion!