Hertz HP 1KD

[caraudioguy2100]

Amp will power up and idle perfectly .

Problem is there is 115 volts of dc measured directly across the speaker terminals .

I tested the outputs in the board none are shorted .

Haven’t pulled them yet to check for leakage .

Any ideas what might cause this amp to have full rail voltage across the speaker terminals?

 

[Perry Babin]

DC voltage on all terminals of U2 and U3 on the driver board?

 

[caraudioguy2100]

U2
Pin 1:-0.57
Pin 2:-1.19
Pin 3:-1.06
Pin 4:-0.58
Pin 5-0.21
Pin 6:1-0.28
Pin 7:-0.71
Pin 8:0.25

U3
Pin 1:-0.58
Pin 2:-0.48
Pin 3:0.34
Pin 4:-0.58
Pin 5:0.24
Pin 6:-0.01
Pin 7:0.24
Pin 8:0.25

 

[Perry Babin]

Missing ±5v

 

[caraudioguy2100]

With the black probe on leg 3 I get 5 volts on leg 2 and 3 volts on leg 4 of U7

5 volts on leg 1 of U8

So I’m assuming the problem is between the regulator and the audio driver board

 

[Perry Babin]

See attached.

 

[caraudioguy2100]

Found the problem I had 2 bad inductors on the main board

 

[Perry Babin]

Were they the ones feeding the regulators that I highlighted?

 

[caraudioguy2100]

They were feeding the input to the 12 volt regulators

 

[Perry Babin]

The 12v regulators feed the 5v regulators.

L9 and L11, correct?

Others may find this useful.

 

[caraudioguy2100]

Yes

 

[Lenin89]

I've repaired 3 of those so far.

Something i've had 2 of 3 times.

The +-5v regulators failed in those 2 cases, i know they should not be generating too much heat but this is what've seen so far. I've replaced them with TO-220 style ones, vias are large enough.