Crunch PZ1500.1

[Jason Smith 616]

Amp is stuck in protection mode..

If i remove the rectifiers the amp will power up normal..

If i leave the rectifiers in the amp and remove all of the outputs the amp will also power up fine..

Ive checked the outputs all measure fine checked the drivers also they test good as well...

Anyone have any suggestions on where to look or begin checking ?

 

[Perry Babin]

Are the outputs in or out of the circuit right now?

Have you checked all of the emitter resistors to confirm that they're within tolerance?

 

[Jason Smith 616]

All of the outputs are in the amp ..

I checked all emitter resistors and all test fine

 

[Perry Babin]

Do you see a pulse of DC across the speaker terminals (all rectifiers and outputs in the circuit) as the amp attempts to power up?

If I'm not mistaken, there is a 4-pin opto-coupler near the rail caps. I'm assuming that it switches on the regulators for the amplifier. If you bridge pins 1 and 2, the the amp power up normally with no DC across the speaker terminals?

If you power the amp up normally through a current limiter, does the amp attempt to power up?

 

[Jason Smith 616]

When i try to power the amp up i get -35.62 volts of DC measured directly across the ouputs..

Jumping the optocoupler doesnt change anything..

Powering it up thru a limiter amp still protects right away..

 

[Perry Babin]

Remove the pin1-2 jumper if you haven't already done so.

Without a diagram, it may be best to remove the drivers/pre-driver/voltage amplifier pairs to see where the DC is being generated. Starting with the voltage amplifier pairs will probably be the most efficient because they're in the middle of the chain.

 

[Jason Smith 616]

Ok if i remove all 4 of the drivers that are mounted to the heatsinks the amp will power up normal..

All of them test fine..

I checked the pr drivers and also ested every single transistor in the output section everything tests good..

I need to remove all 4 of these drivers in order for the amp to power up..

Any ideas as to why these have to be removed in order for the amp to power up?

They are marked C2073 and A940

 

[Jason Smith 616]

The drivers for the outputs in this amp are 2SA940 and 2SC2073 ..

Wondering would the MJE15030 and MJE15031 work in place of the orginals ?


2SA940 pdf, 2SA940 description, 2SA940 datasheets, 2SA940 view ::: ALLDATASHEET :::

2SC2073 pdf, 2SC2073 description, 2SC2073 datasheets, 2SC2073 view ::: ALLDATASHEET :::

MJE15030 pdf, MJE15030 description, MJE15030 datasheets, MJE15030 view ::: ALLDATASHEET :::

MJE15031 pdf, MJE15031 description, MJE15031 datasheets, MJE15031 view ::: ALLDATASHEET :::

 

[Perry Babin]

The 15030/31 should work.