Rodek 275i (ZED Audio) amp

[Dr Zeus]

This amp looks like its going to be fun to work with!

[Dr Zeus]

This amp turns on in protect mode. It looks like a real repair company took a stab at replacing all sorts of things; the TL594CN, LM358P, and several small transistors. Taking what I learned from the Hifonics Thor, I'll start tracing back through the parts and hopefully find something other than the proprietary circuits as failed.

[Dr Zeus]

TL594:

Pin1: 0.266
2: 4.90
3: 4.88
4: 0.031
5: 1.495
6: 3.539
7: 0
8: 11.92
9: 0
10: 0
11: 11.91
12: 11
13: 4.98
14: 4.98
15: 4.98
16: 8.51

[Dr Zeus]

LM358:

Pin1: 9.32
2: 5.5
3: 10.95
4: 0
5: 5.49
6: 9.61
7: 0.009
8: 11

[Perry Babin]

There's no problems with either of those components (from the voltages given) but pin 1 is driving pin 16 high. This is likely due to over-current (shorted output) or DC offset.

[Dr Zeus]

Outputs check out fine. How would I see if there is DC offset if the amp will not power up?

[Perry Babin]

Remove Q1. This will disable part of the protection circuit so you will need to have all transistors clamped and have a 10 amp fuse or a current limiter in the B+ line.

[Dr Zeus]

Removed Q1 and the amp powered up and stays on with a 5A fuse. The speaker terminals have 30vDC across them.

[Perry Babin]

Both channels (measured directly across the speaker terminals)?

[Dr Zeus]

Yes. Measuring 30vDC directly across speaker terminals.

From amp ground to non-bridging terminals I measure 1vDC, and from amp ground to bridging speaker terminals I measure -29vDC