Re: Fixing up a ProFile after a PSU failure, analogue board pulling down voltages?

Am Montag, 26. September 2016 00:31:31 UTC+2 schrieb Adrian Graham:
>
>
> Trouble is the ST506 won't spin up with the electronics board connected to
> the ProFile controller in either ProFile box. If I disconnect the ribbon
> cable and just leave power the drive will spin up happily. Measuring the 5V
> line on the ProFile controller board shows that with the drive connected
> it's pulled down to +1V on one PSU and 0.8V on the other so clearly
> something on the drive electronics module has popped too, but what?
>

So +5V is down with the analog board connected and ok without it? All other voltages are present with and without the analog board?

First check C40. These radial type capacitors fail with a short, so this is the most likely cause.

Next, apply 4.5 V from a lap psu to the +5V rail with current limit set to 2-3 A. Get a good voltmeter, and measure VDD at each capacitor. You should be able to locate the area where the voltage is a couple of mV lower than the rest or where something is getting warm. Check ICs and ceramic capacitors in this area.

Schematic diagram 050-5005-H ProFile Analog.pdf is at bitsavers org but I assume you already got it.

Regards
Patrick

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