Schematic and/or repair advice for Performa 6400 150W PSU (Apple part #614-0060, Delta model number DPS-150GB B)

[TheMightyMadman]

Hi all,

The power supply has unfortunately died in my Macintosh Performa 6400 - it won't start up at all.
It is a 150W unit, Apple part #614-0060, Delta model number DPS-150GB B.

The PWM controller (TOP200YAI) had failed dead-short across all pins. I'm not sure whether this was the cause of the fault, or just a symptom. I did some basic checks on all of the other actives, and they seem OK in-circuit, and the two output rectifiers (STPS3045CP) seem OK out-of-circuit.

I swapped the PWM controller for an uprated part, but the unit is still dead.

Does anyone have schematics for this or a similar unit, please?
Failing that, does anyone have any advice on how best to go about diagnosing it?

Many thanks,

Adam

 

[TheMightyMadman]

Some additional notes:

• The Macintosh G3 desktop appears to use the same (or very similar) power supply: https://www.eevblog.com/forum/repair/psu-repair-vintage-macintosh-g3-desktop/
• I've done a thorough visual inspection of the board and top side of the components, but I haven't actually checked the 1Ohm resistor at R4 with my multimeter. I've noticed in the following picture that it could in fact be burned out, so that's my next port of call. What wattage is this part supposed to be, 1W? (look near the mains connector / fuse).

 

[TheMightyMadman]

R4 is indeed open-circuit - it's supposed to be a fusible resistor, probably 0.5W. I've ordered a suitable replacement part.

FRN50J1R0/S Te Connectivity / Neohm Resistor , Fusible , 1R 5% , 0.5W | eBay

Find many great new & used options and get the best deals for FRN50J1R0/S Te Connectivity / Neohm Resistor , Fusible , 1R 5% , 0.5W at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk