Kenwood KAC-PS401m stuck in protection

[vincegironda]

Hi I have a KAC PS401m on the bench stuck in protection mode flashing also low battery led on.

The crossover board had the usual corrosion from sticky fibre tape, I've removed the tape, cleaned up the corroded traces and pads, re run the solder and tested the traces for continuity also replaced the capacitors on the board and its made no difference, the relays don't click on and the aforementioned remained flashing/on.

Any ideas on what to check next would be appreciated.

 

[Perry Babin]

What's the DCV on the B+ and remote terminals with the black probe on the amplifier's ground terminal?

 

[vincegironda]

Thanks Perry
13.7v dc on B+ and remote

 

[Perry Babin]

DCV on both terminals of D31?

 

[vincegironda]

D31 is 0.000 on both terminals

 

[Perry Babin]

Both terminals of D21 and D22?

 

[vincegironda]

I can't find d21 or d22

 

[Perry Babin]

I don't have a PC board photo so I don't know where they are.

 

[vincegironda]

Found them
D22 and D21 13.2v dc neg leg, 13.35 + leg

 

[vincegironda]

They're behind the speaker terminal

 

[Perry Babin]

The cathode of those two are connected to the cathode of D31. Find the open trace.

 

[vincegironda]

I found the open trace (oxidised via) fixed it, no change still in protect

 

[vincegironda]

Low battery led is off now

 

[Perry Babin]

Do you have positive and negative rail voltage?

Do you have positive and negative regulated voltage on the power supply pins of the op-amps?

 

[vincegironda]

0.1v on pin 8 of op amps

 

[Perry Babin]

Which LED is lit? Circuit board designation?

 

[vincegironda]

What's the best point to check the rail voltage?

 

[vincegironda]

Which LED is lit? Circuit board designation?

D6

 

[vincegironda]

Which LED is lit? Circuit board designation?

D6 is flashing

 

[vincegironda]

Sometimes my power supply trips when I apply power to the amp, switch of and back on and its ok