Audiowave Aspire Pro Repair

       Now, here's something that doesn't happen too often.

       A friend sent me this amp for repair. Each one costs more than my car so This pair is easily the most expensive thing that has ever sat ontop of my workbench.

       Only one unit is defective. The other is fully functional but was only sent just in case I needed a working one to compare to given the price of these things (which, you'll see later, I didn't have to).

       The problem on the defective amp was that one channel was not working. And given that the two channels are separated by a clean layout, it was an easy job to trace out the problem.

       I'll just put in the description on each pic as I went along with the repair. Enjoy.

Serial Number 54 and 55:

The two amps on the bench:

Now there's your problem:

Popping the hood:

All hardware is stainless steel. Each screw uses a wave washer and a flat washer:

Power transistors and drivers taken out to test:

Drivers are MJE340/350, Output transistors are MJL21193/94:

Power supply MOSFETs and output rectifiers:

A peek under the aluminum heatsink:

I see some sub boards and relays:

Definitely hand built. The 1206 parts have some icicles on the solders:

Input jacks. Yes, that's an Alps Blue Velvet pot:

Burr Brown input op amp on a socket.
No desoldering on this one if you plan on rolling op amps:

Amplifier input stages on sub boards.
All part numbers for the small signal devices had been sanded off:

Pre drivers and output stage:

Each amp has a pair of rail fuses. Two empty ones blew due to the shorted output transistor:

Under the board. I originally thought those are bodge wires but on closer inspection,
the designer decided to use wires rather than compromise the ground plane:

Under the power input terminal blocks:

Under the speaker output terminal blocks:

Another look at the jumper wires:

A clear view of the thermal management. Look at that slab of aluminum:

Toroidal tranformer uses a double stacked core:

Input filter uses a bank of low ESR Panasonic FC caps:

I spy a thermistor to detect overheating of the main transformer:

Turns out I have a spare set of output transistors in the shop. Off we go:

After installing the output devices, replacing the fuses and readjusting bias, amp works like new!:

Test setup. Dummy load on the floor. Amp pushes about 250W/ch into 4ohms with a 14V supply:

Page created and copyright R.Quan © 13 Apr 2014.