[ctviggen]

Hi All,

My Jeff Rowland #10 no longer turns on.  I contacted the JR company, and he said the following:

"Is your amp a Model 10? It is likely a problem in the power supply. You will have to check for a high voltage at the inputs of the DC/DC converters. There should be 380 volts dc on the inputs of the converters which supply the +_/- 28 volts dc to the amplifier. The amplifier section rarely fails so do not look there."

This model has a power supply (left) connected to an amp section (right):



I show a close up of the power supply here:



These are the voltages I measured:



Are these the locations he was talking about? 

I have a BSEE and MSEE, but it's been a while since my last amplifier repair. I repaired my Creek 4140 amplifier some years ago.  I have a voltmeter and an oscilloscope that connects to my computer.

Do I have to "drain" the caps before I take off the motherboard for the power supply?  If so, how do I do this?

What do you think are the likely culprits and what should I check? 

Thank you.

[FullRangeMan]

Are these the locations he was talking about?
For the correct location you need the schematic, the service manual could be useful too, you need ask these to Jeff.

Do I have to "drain" the caps before I take off the motherboard for the power supply?  If so, how do I do this?
For drain the caps you need discharge its tension, usually its made by put a screw driver on its poles, but its not mandatory, in this case you need more careful.

What do you think are the likely culprits and what should I check?
This is a rare amp on the bench, who can answer this is Jeff.

[Mike B.]

I think I would start at the end of the power connector and check for the + and - 28 volts DC getting to the amp section. A number of commercial amps have resistor bleeds on the power supply caps to drain off stored voltage. If you can't verify that unplug and let it set for a day.   

[poseidonsvoice]

I think I would start at the end of the power connector and check for the + and - 28 volts DC getting to the amp section. A number of commercial amps have resistor bleeds on the power supply caps to drain off stored voltage. If you can't verify that unplug and let it set for a day.

Exactly.

Check downstream on the umbilical first and verify if +/- 28V DC is there.
Best,
Anand.

[art]

I forget the details, but he used some off-the-shelf "bricks", to power the main converters. If you take that PCB off of the chassis, there should be 3 power modules, on the bottom side. Two for the +/- supplies, and one to power those two. Probably the latter, and it should be one that can be easily sourced. Maybe not the exact one, but something close enough.