Quadra/LC/Performa 630 Power Supply Re-cap

[Darth Vador]

Hi everybody, everyone knows this area is overheating between R44 resistance, C8 capacitor, IC7 (KA7805), resistance behind IC7 (same value than R44), Z6 and R15 (1500 ohms).
C8,IC7 are over, concerning resistance R44, the value tested is around 130 ohms. I would like to know the value of R44 ( normally 150 ohms but not sure…. Colors are not clear)
thanks for your reply.

 

[antiko]

Hi everybody, everyone knows this area is overheating between R44 resistance, C8 capacitor, IC7 (KA7805), resistance behind IC7 (same value than R44), Z6 and R15 (1500 ohms).
C8,IC7 are over, concerning resistance R44, the value tested is around 130 ohms. I would like to know the value of R44 ( normally 150 ohms but not sure…. Colors are not clear)
thanks for your reply.

Hi Darth. Too late I found this thread, however I hope it helps to someone maybe. R44 has value exactly as R25 on the opposite (low voltage side), of 142Ohms (brown, yellow, red, black). However it normally has a drift of a few Ohms more or less since it constantly overheats.
I'd suggest to change these two to 2W equivalent of 150 Ohms and flip them over to the back side of the PCB so they (dangerous without proper electric isolation) become in contact with metal shielding in order to disperse more heat till someone would redesign this PSU in future

 

[antiko]

Hi Darth. Too late I found this thread, however I hope it helps to someone maybe. R44 has value exactly as R25 on the opposite (low voltage side), of 142Ohms (brown, yellow, red, black). However it normally has a drift of a few Ohms more or less since it constantly overheats.
I'd suggest to change these two to 2W equivalent of 150 Ohms and flip them over to the back side of the PCB so they (dangerous without proper electric isolation) become in contact with metal shielding in order to disperse more heat till someone would redesign this PSU in future

This would look like so.
The temperature in standby mode is about 40°C for low voltage side and about 49°C for opposite side. With the lid closed I had about 49°C and 52°C max. respectively on standby, while the room temperature is 26°C.

 

[mndeaves]

This thread is awesome. Could anyone tell me the value of R75 on the PSU? That one has been destroyed on my board. It's the one right against the big 400v capacitor.

Actually noticed a few that I need:

R75
R46
R36

 

[mndeaves]

This thread is awesome. Could anyone tell me the value of R75 on the PSU? That one has been destroyed on my board. It's the one right against the big 400v capacitor.

Actually noticed a few that I need:

R75
R46
R36

So I was making some comparisons between the power supply from my Performa 630 and a Performa 6200 and noticed something weird.. a few capacitors seem to have just legs with the body removed.... so I made measurements from one board for resistors missing on the other.

630 With AA19300 PSU
R46 Missing resistor body, but has legs soldered in place, measured as 2.1k Ohms on the 6200 PSU
R36 Missing resistor body, but has legs soldered in place, measured as 1.9k Ohms on the 6200 PSU
Was burnt out R75 is Green Blue Gold Gold colour bands on the 6200 PSU

6200 With AA19300 PSU
R37 Missing resistor body, but has legs soldered in place, measured as 1.9k Ohms on the 630 PSU

The missing ones with legs appear to have been cut off.. I wonder if done at the factory or if a previous owner has broken them off.. or they... disintegrated?? I cant see any differentiating model/revision numbers on either board - both say 042-61007903c on the silkscreen.

I know for sure I need a new R75 for the 630 board at least which is 0.56Ω value on the working board from the 6200

EDIT: I am assuming its ok as studying other pictures in the thread like this I can see that board has similar resistors missing in the same place (even more than me). So I assume its a factory configuration/calibration thing....

 

[antiko]

Leaving here these hi-res photos. May be someone will find them useful.

 

[pizzigri]

While for preservation intent, trying to repair and make the 630/6200 supply work is a noble cause, this was a crazy flawed design to begin with and a good half of all the broken 630/6200/6300 out there are because the PSU is fried. IMHO, Instead of “redesigning”, the solution - also for the health of the logic board and inter peripherals - is to replace the innnards of the PSU with an SFX, making the simple soft power circuit, and forever forget this thing inside its original housing.

 

[mndeaves]

Yeah, agreed. I’m having a look into https://github.com/CyberXZT/atx-q630. The owner of that repo has offered to check if the KiCad 7 upgrade to the project is ok. If that checks out I’ll order a few of these and get an updated components list to solder a few together.