Zapco Studio 500 repair

[Zeptoplix]

1. 2.6
2. 2.6
3. 034mv
4. 172.6mv
5. 2.07
6. 3.83
7. 2.07
8. 4.936
9. 1.73
10. 025.1mv
11. 2.87
12. 013.4mv
13. 17.32
14. 2.96
15. 17.28
16. 5.2

those numbers look better.

Sorry about that.

 

[Perry Babin]

Those are OK.

What is the DC voltage on all legs of q50 and 51? Only post for one if they're the same.

 

[Zeptoplix]

q50

1. 059.6
2. 013.3
3. 013.3

q51

1. -015.8
2. 013.7
3. 013.7

I double checked Q51 pin 1 and it is negative. All measurements in MV

 

[Perry Babin]

Is D13 lit?

 

[Zeptoplix]

D13 is not illuminated.

 

[Perry Babin]

Did you check earlier to see if there was a delay for it to become lit?

 

[Zeptoplix]

It does not come on at all. The amp was powered on while I reviewed the diagram to find it

 

[Perry Babin]

Initially, didn't you state that the 2 SMD LEDs were lit?

 

[Zeptoplix]

There are two other SMD, D10 and D11 which illuminated on power.

 

[Perry Babin]

If you short between pins 7 and 8 of U8, does the amp produce audio?

If you have speakers and a signal source connected, have the volume low.

 

[Zeptoplix]

Yes, I do actually.

 

[Perry Babin]

It's not in protect mode, is it?

Did both channels produce clean audio?

 

[Zeptoplix]

No it is not in protect mode. I'll have to redo the test as I only had one speaker connected

The audio was clean though

 

[Zeptoplix]

I tested again with both channels driven. Clean and no protect light. This was jumping pins 7/8 on u8

 

[Perry Babin]

Post the DC voltage on all pins of U3 and U7.

 

[Zeptoplix]

Negative prob on battery negative still?

 

[Perry Babin]

Yes, but it's likely easier to make the connection to the ground on the ground terminal of the amp.

 

[Zeptoplix]

Thank you, will do tomorrow

 

[Zeptoplix]

U7

1. 11.5
2. 11.5
3. 013mv
4. 014mv
5. 11.24
6. 11.6
7. 015mv
8. 11.26
9. 016.2mv
10. 11.65
11. 11.39
12. 015.8
13. 016mv
14. 11.68

U3

1. 11.63
2. 9.75
3. 016mv
4. 016.7mv
5. 016.4mv
6. 016.6mv
7. 016.6mv
8. 11.3
9. 11.63
10. 016.6mv
11. 11.65
12. 016.6
13. 016.6
14. 11.68

 

[Perry Babin]

U6, pin 3 and 14.