blackmasselectronics

[blackmasselectronics]

Orange Bass Terror 1000

This amp really gave me a hard time. This amp belongs to the bass player for my band. The original issue was that the signal would cut out in the middle of practice or shows and the head would just fizzle out and shut down.

My initial thoughts were that the class D power amp was failing due to overheating. On the bench, heat seemed fine, fan kicked on with no issues and parts weren’t getting too hot, but voltages were not normal in the power supply. These amps have a smps mounted on the top of the amp.

I spent some time replacing dodgy electrolytic caps in the switching part of the power supply. Didn’t help. I flipped the amp over, voltages seemed okay for the most part but at the first power amp mosfet, there was a short between all three legs. I replaced that mosfet and the amp started to blowing fuses every time I powered it up on the variac and the fan and indicator light weren’t turning on anymore. Tracing that back through the power supply, one of the switching mosfets had failed causing the bridge rectifier, and power switching IC to fail as well. I replaced the mosfets, the IC, and the bridge rectifier.

Now we had decent voltages to most of the amp except for the -53V rail which was way off.

I started testing diodes and found that D5 in the power amp was shorted.

Of course that diode is totally inaccessible without removing the huge inductor. Once the inductor was out, the diode wasn’t reading short anymore. I was able to trace this back and the only thing that made sense was another failing power amp mosfet.

I went through and replaced the rest of the power amp mosfets and we were rocking.

Special thanks to my Rigol DS1052E on this one. Couldn’t have done it without you.

-Kaden

[blackmasselectronics]

Massive power failure on this Terror Bass 1000 and boy do these things suck to work on

[blackmasselectronics]

Dual 1312 Distortion available for the very first time. The first batch already sold out but a second batch is on the way.