Repair Toft ATB08 Power Supply

[morls]

Hi,

I've been doing some mods on my Toft ATB08 console. As I am on a learning curve, mistakes are inevitable, and I've blown the -ve power rail in the power supply. Although I'm going to take it to a qualified tech (I don't want to mess with 240V AC!) I thought I'd see if anyone else has had this happen? If so, how big a job is it? Is it something an intermediate DIYer like myself could take on?

Cheers

Stephen

 

[beatnik]

Are you sure the problem is in the power supply itself ? Might be a shorted or dead component in the audio path

Have you tried measuring the power supply voltages without connecting it to any of the audio circuitry ?

 

[morls]

Yes, I'm sure. I have done a lot of work on the master module, and have double- and triple-checked everything. The fault in the power supply originated on the master module - I made a classic beginners mistake involving a decoupling capacitor and the negative power rail.

I've tested the output of the supply, at the socket which goes into the console. There are 5 pins -  chassis ground, Electronics ground, +48V, and +17V and -17V for the power rails. The negative rail reads 0V. There are also 3 indicator lights on the supply case - +17V, -17V and 48V. The -17V light is not on. There is also some visible damage to the circuit board in several places.

On a side note, a lot of the work I did involved upgrading opamps, and installing small caps from their power pins to ground. In order to check I was connecting to ground, I checked continuity between the point I was soldering to and the sleeve of the output TRS connectors. After seeing that the power supply has both a chassis ground and an electronics ground, I'm not sure I've done the right thing. Can anyone help?