Hi all,
I'm working on a Sansui 2000a with a bad right channel. Preamp out is good. speaker out, not so much so.
Right side volume is way down and sine wave looks, well, to much trouble to describe. Adjusting pots doesn't help, even though bias current was originally way down
The famously troublesome Q806 has ac coming out of the collector. Seems the problem has been solved. Except what is there is not a 2sc458 in that spot. It is a C631. Left side also.
Please tell me I'm making too much of this. Like at one time the C631 was a common replacement and I can just drop in a pair of KSC1845 and stop worrying about it.
I'm working on a Sansui 2000a with a bad right channel. Preamp out is good. speaker out, not so much so.
Right side volume is way down and sine wave looks, well, to much trouble to describe. Adjusting pots doesn't help, even though bias current was originally way down
The famously troublesome Q806 has ac coming out of the collector. Seems the problem has been solved. Except what is there is not a 2sc458 in that spot. It is a C631. Left side also.
Please tell me I'm making too much of this. Like at one time the C631 was a common replacement and I can just drop in a pair of KSC1845 and stop worrying about it.
Whenever someone ran into a C458 that’s gone popcorn (or lightning and thunder if it was an RIAA stage) they put in whatever high gain low noise type they had on hand and trusted. Today that’s the C1845. If the replacement is working (properly) leave it.
I get rid of all C458’s even if they haven’t gotten psychotic yet. C1845’s are cheaper than capacitors. They still have those in “B” hFE rank, right?
I get rid of all C458’s even if they haven’t gotten psychotic yet. C1845’s are cheaper than capacitors. They still have those in “B” hFE rank, right?
HI. I'm back.
Installed a pair of KSC1845FTA, no change.
Replaced all electrolytics on this f-1180 board, both sides,and good news / bad news.
Sine wave is now clean but that side is limited to about 4 watts output. No clipping, just tuns out of juice. Definitely in driver board. Outputs at pins 8G and 8I are significantly lower than 8F and 8H. And that side is a little out of phase.
My service manual only has a block diagram so I'm hoping that somebody has a better schematic or knows something I don't.
Thanks
Installed a pair of KSC1845FTA, no change.
Replaced all electrolytics on this f-1180 board, both sides,and good news / bad news.
Sine wave is now clean but that side is limited to about 4 watts output. No clipping, just tuns out of juice. Definitely in driver board. Outputs at pins 8G and 8I are significantly lower than 8F and 8H. And that side is a little out of phase.
My service manual only has a block diagram so I'm hoping that somebody has a better schematic or knows something I don't.
Thanks
I don't know what that board is, but it does not match the f1180 that is in my machine.
Thanks for trying though
Thanks for trying though
That s extracted from the Sansui 2000 non A manual, boards may be different but the power amp schematic should
be the same, i have a Sansui 800 from the same years and it also use this schematic as well as a bunch of 2SC458,
it s still perfectly functional but it show its age distorsion and noise wise, for the noise the culprit is the tone control
attenuating the signal by 20dB before being amplified by a transistor and with the volume pot being
implemented at the input of the tone control, that s the same in the 2000 and 2000A.
be the same, i have a Sansui 800 from the same years and it also use this schematic as well as a bunch of 2SC458,
it s still perfectly functional but it show its age distorsion and noise wise, for the noise the culprit is the tone control
attenuating the signal by 20dB before being amplified by a transistor and with the volume pot being
implemented at the input of the tone control, that s the same in the 2000 and 2000A.