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Sansui BA2000 issue

M

mifune

Member
Hi, I'm trying to repair my amplifier.
The amp was not working when I bought it: powers on, lights on, goes off protection mode but no sound. Also the meters don't do that little movement at startup (I have a working one as a reference).

I recapped the driver circuit board and replaced a few bad transistors.
I recapped the power supply board for circuit stage (F2630). Nothing still.
I replaced the F-2631 (level volume $ meter board) with a spare one (that I know is working) but no luck.

Any suggestion?
Thanks
 
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Have you checked the all the fuses and the power supply voltages?

The rule of thumb is to find the fault first before any re-capping work - otherwise you risk introducing further faults thus adding to your confusion.
 
So, +/- 55v and +/- 57v coming out of the PSU.

Can you measure any bias current, and if you can does it adjust?

Same for DC offset...
 
Measure the power supply voltages. Tape the end of your meter probe so only the very tip is exposed in case you slip.
 
I read values similar to the ones on the manual:

43v (blue and purple)
35v yellow
53v red

57.7 out of the power supply (red and blue)


Left 3.9 mv
Right 3.9 mv

I didn't try to adjust it yet
 
I went ahead and checked voltages on F-2630.
I have +70v before the diode D607 but nothing at C621 (pin 26)
I read -71v at D608 but nothing at C622 (pin 27)
Nothing at 16 (right before the relay, the wire from the switch)

Should I check TR07 and TR08 at this point?
 
mifune said:
I went ahead and checked voltages on F-2630.
I have +70v before the diode D607 but nothing at C621 (pin 26)
I read -71v at D608 but nothing at C622 (pin 27)
Nothing at 16 (right before the relay, the wire from the switch)

Should I check TR07 and TR08 at this point?
Click to expand...

Please measure the voltages on TR607 ECB.
 
I've fixed more than a few of these with this exact symptom. The amp is loaded with fuse resistors that need replaced. Amp driver board as well as the power supply.
 
elnaldo said:
If you can, post a link to the schematic here.
Click to expand...

There is one here - http://akdatabase.com/AKview/displayimage.php?album=28&pos=93

ManyMoonsAudio said:
I've fixed more than a few of these with this exact symptom. The amp is loaded with fuse resistors that need replaced. Amp driver board as well as the power supply.
Click to expand...

I see 4 fuse resistors in the dead +/- 57v regulator - especially R621 & R622 (but also R605 & R606).

mifune - follow the 'Doc' or 'ManyMoons' - they have put many of these back in action... :yes:
 
Last edited:
Bingo. R605 and R606 are bad. I'll replace them and report. I will then replace them all with fresh ones (all the ones that I will find).
 
I replaced the resistors but still have a wrong voltage at pin 26 (.44v) and 27 (-1.3v)

As for TR607 I have
E 0.36v (keeps going up slowly)
C 70.5v
B 0.89v
 
My readings:

TR611:
E: 1.5v
C: 71v
B: 0.15v

TR612:
E: 1.5v
C: 71.6v
B: 71v

TR613:
E: 0v
C: 71v
B: 0.3v

TR616:
E: 0.2v
C: 71v
B: 0.9v

ZD602
anode: - 1.26v
 
mifune said:
My readings:

TR611:
E: 1.5v
C: 71v
B: 0.15v

TR612:
E: 1.5v
C: 71.6v
B: 71v

TR613:
E: 0v
C: 71v
B: 0.3v

TR616:
E: 0.2v
C: 71v
B: 0.9v

ZD602
anode: - 1.26v
Click to expand...

Check R617, looks like it's open.
You have all positive voltages on TR612. Is that correct? They should be negative. I know you had -70V on the collector originally. Don't leave off any - signs, it screws me up.
If those voltages are negative, check R618, should be 220 Ohm. If that's ok, TR612 is probably bad. Do not rely on a Diode test, it has to be tested on an HFE tester. If your meter doesn't have that, replace it.
 
Both R617 and R618 are open.
As for the TR612 (2SA850) I have some 512-KSA1013YBU which should be a good replacement. I think I'm gonna replace it anyway.
Sorry for the positive and negative voltages, I'll check them again and report.
Thanks
 
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