Friday, June 03, 2011

Another broken EC-Apparatus high voltage power supply!

The 'stickers' up top say "OK to use 8/25/94" and "DEAD 2/3/97". Took it 14 years to rotate into the scrap pile. The AC cord has been cut. I understand the motivation to cut power cords; it remains annoying.

On cracking the shell, this was the first sight to greet me.

I must admit, I'm having a little difficulty identifying this part. Initially it struck me as a wirewound resistor, but the remains don't exhibit the centralized burn characteristics I'd expect to see from a resistor. Additionally, this part appears to have let loose in a rather prompt manner as opposed to a slow and steady heat build up.

Then there is the ochre build up at center band, which appears to be an original compound as opposed to corrosion products. Electrolyte perhaps? Yet the plate structure, if this is a cap, seems wrong to me, and an electrolytic cap of this dimension sitting on a ladder in the filtering section of a 2000 volt power supply makes no sense either.

Whatever it was, it clearly was not up to the task it was asked to do.

The unit over-all looks pretty service friendly, just peeking above the stack of 47u 450v is a blue backplane connector which allowed removal of the board containing most of the sophisticated circuitry.

Of course, that circuit board offers a mystery of its own.

I should give a big fat sandfilled power resistor a shot in lieu of a 3000-3500 ppm/K tempco on a supermatched pair! That would probably cause a quiver or two in the synthesizer community.

My initial response to this structure was, as is known in the internet parlance, WTF?!

But wait, it gets better:

This is apparently the stock part having failed.

As usual, once the amusement has died down a bit, I stopped associating this structure with a similarly built (though altogether different) structure, and reason that the 16 pin DIP package may not be an IC, but a thermistor housed in a DIP package as part of the current regulation circuit.

I remain unsure. Cool enclosure though, perhaps I will have a go at repurposing it to house a supply that offers a more immediately useful range of voltages, eventually.

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