Sansui AU-20000 troubleshooting

[BoBBa72]

The KSC1845 has half the collector current rating of 2SC1313. The KSC1815 is the better substitute.

Apologies, the -85V value I gave you was not correct. Your measurement looks ok. What are you getting on the positive terminal?

+67,7V on the positive.
I found another thread with similar issue and it was the connectors that where put in wrong to filter boards so i swapped places with the two connectors and now i get -77,3V on pin 1 and +77,3V on pin 2.
Still no 35V+-

 

[richardpp]

You need to be more specific and give the board identifiers and connector numbers so I know exactly what you're doing.

Looking over F-2508, your use of films in place of the electrolytics at C03 C04 seems out of the ordinary.

Did you test or replace the Zener diode ZD02?

(I need to sign out for the evening)

 

[BoBBa72]

You need to be more specific and give the board identifiers and connector numbers so I know exactly what you're doing.

Looking over F-2508, your use of films in place of the electrolytics at C03 C04 seems out of the ordinary.

Did you test or replace the Zener diode ZD02?

(I need to sign out for the evening)

Sorry i ment i swapped places with the connectors going from F-2512 to F-2504 (Filter Circuit Board) and F-2496 (Meter Circuit Board).
After i measured the pins under F-2508 under F-2512 and got the 77,3+- readings on pins 1 and 2.
I have 3,3uF electrolytics in stock now and will replace those.
Yes i changed ZD01 and ZD02 with BZX55B15-TR and both test ok.

Update: i disconnected the wires going to F-2504, F-2496 and F2502 from the motherboard and then i have +-35V on pin 5 and 7.
Now i found what was doing the none existing +-35V.
I had put one of the small filter boards on F-2504 in the wrong position and now i have +-35V on pin 5 and 7.
Will check the bias issue tomorrow since this amp is killing me and its late here
Thanks for your patience and guidance Richard!

 

[richardpp]

Great find, the F-2498 boards are easy to orientate the opposite way, I've done it myself, and buried deep in the amp so I appreciate the amount of work you've had to go to to find the problem. Will check in with you about F-2507 later.

Edit: What are the voltages on pins 1 and 2 now you have 35V back?

Sorry i ment i swapped places with the connectors going from F-2512 to F-2504 (Filter Circuit Board) and F-2496 (Meter Circuit Board).
After i measured the pins under F-2508 under F-2512 and got the 77,3+- readings on pins 1 and 2.

Thanks, I can see now those connectors have the orange and grey wires reversed.

 

[BoBBa72]

Great find, the F-2498 boards are easy to orientate the opposite way, I've done it myself, and buried deep in the amp so I appreciate the amount of work you've had to go to to find the problem. Will check in with you about F-2507 later.

Edit: What are the voltages on pins 1 and 2 now you have 35V back?


Thanks, I can see now those connectors have the orange and grey wires reversed.

81,5+- on 1 and 2.
Still no luck with my F-2507 boards and i have triple checked them and 0 bias.
+0.5V on TR-05 and +69V on TR-04, should be -69V on TR-05 emitter?

 

[richardpp]

81,5+- on 1 and 2.

So we have a clear reference point, can you post the latest +/- values for:

the supply voltage at TM01 on F-2511,​

the input voltage on pins 1 and 2 on F-2508,​

the low-side output voltage on pins 5 and 7,​

the high-side output voltage on pins 8 and 10.​

​

 

[richardpp]

post# 25

Still no luck with my F-2507 boards and i have triple checked them and 0 bias.
+0.5V on TR-05 and +69V on TR-04, should be -69V on TR-05 emitter?

post# 9

Well i got +66V here on emitter TR04 and -66V on emitter TR05.
Should it be +6.3V on TR04 or is it just a error in the schematics?

What's changed here? It looks like you had -66V on the emitter of TR05, now you're reading is +0.5V ? Is this on both boards?

TR05 emitter should be -63V.

 

[BoBBa72]

So we have a clear reference point, can you post the latest +/- values for:

the supply voltage at TM01 on F-2511,​

the input voltage on pins 1 and 2 on F-2508,​

the low-side output voltage on pins 5 and 7,​

the high-side output voltage on pins 8 and 10.​

​

TM01: +- 68,2V
Pin 1-2: -+ 81,5V
Pin 5-7: +- 35,5V
Pin 8: +69,8V
Pin 10: +0,5V

 

[BoBBa72]

post# 25

post# 9


What's changed here? It looks like you had -66V on the emitter of TR05, now you're reading is +0.5V ? Is this on both boards?

TR05 emitter should be -63V.

I have no clue but i have changed all transistors but i have the originals left but im sure i had the new ones in when i had -63V

 

[richardpp]

Remove both driver boards and recheck Pins 8 and 10.

 

[BoBBa72]

Remove both driver boards and recheck Pins 8 and 10.

Pin 8: +69,3V
Pin 10: -69,3V

 

[richardpp]

Error

 

[richardpp]

Reinsert the driver boards and remove the two small connector boards from F-2512, the ones connecting the driver boards to the heatsink assemblies. Be careful not to let the exposed pins come into contact with any part of the amp. Recheck the emitter on TR05.

 

[BoBBa72]

Error

Reinsert the driver boards and remove the two small connector boards from F-2512, the ones connecting the driver boards to the heatsink assemblies. Be careful not to let the exposed pins come into contact with any part of the amp. Recheck the emitter on TR05.

Still +0,5V
I have KSA1381/KSC3503 in TR-4, 5, 8 and 9 if thats totally wrong?

 

[richardpp]

Reconnect the boards back into F-2512.

Try one driver board at a time in each positions to see if it makes a difference.

 

[richardpp]

I have KSA1381/KSC3503 in TR-4, 5, 8 and 9 if thats totally wrong

That's ok as long as you're pin out is correct. Post a photo of one of the driver boards, both sides, as close up as you can.

 

[BoBBa72]

Reconnect the boards back into F-2512.

Try one driver board at a time in each positions to see if it makes a difference.

Same results on both cards on both slots.

 

[richardpp]

Ok, as above, post a photo of the driver board. Sounds like a component error duplicated on the boards.

 

[BoBBa72]

That's ok as long as you're pin out is correct. Post a photo of one of the driver boards, both sides, as close up as

Yes pin out is correct and probably me that has made the error on both cards.

 

[richardpp]

... can you post a close up of trace side of one board, thanks.