Electronics > Repair

FIXED: Power Designs 2005A repair

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motocoder:
I have purchased a Power Designs 2005A off of eBay. While it is cosmetically in good shape, it is not working.

Upon switching the unit on, the 0-10V or 10-20V lamp (depending on the position of the switch) illuminates, but the Oven light does not come on and the meter stays at zero. The voltage across the DC+ and DC- terminals is about -0.3 volts.

Does anyone have a schematic or other technical documentation for this unit? I saw a link on one of the threads here, but the link was broken. Any advice on where to start troubleshooting?

Thanks

robrenz:
PM me your email and I will send you a pdf of the 2005A manual

motocoder:

--- Quote from: robrenz on September 26, 2014, 01:06:14 am ---PM me your email and I will send you a pdf of the 2005A manual

--- End quote ---

PM sent. Thanks!

motocoder:
ok, internal fuse was blown. i don't have an exact replacement, but i had a smaller amperage fuse. I put that in and now I am getting something on the output. It seemed reasonably stable before i started messing with the dials, although it was about 20% below the set voltage value.

Oven light still not coming on, but that might just be the neon lamp.

I will definitely need to clean the contacts on the switches - anyone have a recommendation on how to go about that?

motocoder:
Ok, have a few more data points now.

The oven lamp is actually fine. The SCR that switches the voltage reference heater on/off is never switching on. This is because its gate is never going high. I briefly shorted its anode to gate, and i saw the lamp light up (this might have been dumb as i may have damaged Q11)

So next I need to determine why the SCR is not being switched on. My suspicion is the thermostat is bad, or possibly Q11 (or maybe both if I damaged Q11 in my testing).

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