Sansui BA2000 issue

[mifune]

So I replaced R617 and R618.
The unit did power up and went into protection. Then nothing. No power, nothing out of the power supply

R652 and R653 are gone. Why?

 

[dr*audio]

So I replaced R617 and R618.
The unit did power up and went into protection. Then nothing. No power, nothing out of the power supply

R652 and R653 are gone. Why?

You have a major short somewhere. Something drew a whole lot of current. Start checking between every power supply and ground with you meter on ohms, looking for some really low reading. Also check between positive and negative supplies. All those open resistors you found make me think this amp took a powerline hit, or was connected to 220V maybe. A bunch of parts got fried and you have to find them all.

 

[mifune]

This is what I read:
Purple: 1.7 ohms
Grey: 1.1 ohms
Blue: 1.7 ohms
Yellow: 5.8 ohms
Red: 8.2 ohms
Green: seems to be open. Shows 1 on the meter and does not go to ground at all if I check for continuity

 

[dr*audio]

This is what I read:
Purple: 1.7 ohms
Grey: 1.1 ohms
Blue: 1.7 ohms
Yellow: 5.8 ohms
Red: 8.2 ohms
Green: seems to be open. Shows 1 on the meter and does not go to ground at all if I check for continuity

Check the DC power supply outputs, not the transformer windings. +/-70V, etc. Measure each to ground and then from + to - the same supply (+70V to -70V.)

 

[mifune]

You mean the +55/-55 on the F-2629? (red and blue couples)

 

[dr*audio]

You mean the +55/-55 on the F-2629? (red and blue couples)

Specifically:
F2630:
Pin 26, 27 to ground and to each other.
F2629:
Pins 6 and 7 to ground and to each other.
Pins 1 and 2 to ground and to each other.

 

[mifune]

My readings:
26 to ground: open
27 to ground: open
26 to 27: starts from 120k and it goes down

6 to ground: 3.14k
7 to ground: 3.21k
26 to 27: 6.40k

1 to ground: 1.30k
2 to ground: 1.45k
1 to 2: 3.5 (non K ohms, just 3.5 ohms)

Thanks for your help and patience

 

[mifune]

I'm back on this project. Does the latest readings make any sense?
Thanks

 

[dr*audio]

My readings:
26 to ground: open
27 to ground: open
26 to 27: starts from 120k and it goes down

6 to ground: 3.14k
7 to ground: 3.21k
26 to 27: 6.40k

1 to ground: 1.30k
2 to ground: 1.45k
1 to 2: 3.5 (non K ohms, just 3.5 ohms)

Thanks for your help and patience

Sorry, I missed this post. You have blown output transistors on one channel. Follow the wires from F2629 pin 1 and 2 and they will go to the bad channel. Pull all the output transistors on that channel and test them. If you don't know how to test transisitors, search AK for Testing Transistors. In addition, you must test every transistor on the driver board for that channel, starting with TR24 and TR26 and working back towards the input until you stop finding bad transistors. Be sure to test TR14, the bias transistor, and the white ceramic emitter resistors on the output transistors. When you have replaced all the bad parts, build a Dim Bulb Tester (search AK for how to build and use it) and power the amp up with the dim bulb tester. If the bulb gets bright and stays bright, shut the amp down immediately.