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Quadra/LC/Performa 630 Power Supply Re-cap
Posted by: Darth Vador on 2025-01-18 02:51:40 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.
Posted by: antiko on 2025-07-10 12:55:17 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 🙂
Posted by: antiko on 2025-07-10 17:59:58 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.
Posted by: mndeaves on 2025-10-19 01:18:00 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
Posted by: mndeaves on 2025-10-19 04:38:14 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....
Posted by: antiko on 2025-10-31 17:21:48 Leaving here these hi-res photos. May be someone will find them useful.
Posted by: pizzigri on 2025-10-31 23:54:03 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.
Posted by: mndeaves on 2025-11-01 01:52:17 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.
Posted by: indibil on 2026-02-08 23:39:10 Hello. I have an LC630 that was working fine, with the motherboard recapped, and yesterday it froze. I unplugged it and plugged it back in, and now it doesn't respond to the power button either on the tower or the keyboard. Could it be because the PSU is bad? Can the failure be that abrupt?
Posted by: mndeaves on 2026-02-09 00:29:10 Hello. I have an LC630 that was working fine, with the motherboard recapped, and yesterday it froze. I unplugged it and plugged it back in, and now it doesn't respond to the power button either on the tower or the keyboard. Could it be because the PSU is bad? Can the failure be that abrupt? Could be, one of mine went like that, the other was much more dramatic with a bang. I ended up modifying 2 ATX 1u style PSUs to get my machines working again, there just isn’t enough room for the PCB adapter and the supplies I had available. Are you in the uk? I actually have 2 original PSUs that are in mint condition (no leaky capacitors at all). If you’re good with soldering I also have a couple of of the 1u stye ATX power supplies that can be converted to fit inside the original PSU case - so don’t throw your original out as if you go that route you’d want to keep the 6 pin adapter for soft power and the main power loom/header.
Posted by: indibil on 2026-02-09 09:09:27 Could be, one of mine went like that, the other was much more dramatic with a bang. I ended up modifying 2 ATX 1u style PSUs to get my machines working again, there just isn’t enough room for the PCB adapter and the supplies I had available. Are you in the uk? I actually have 2 original PSUs that are in mint condition (no leaky capacitors at all). If you’re good with soldering I also have a couple of of the 1u stye ATX power supplies that can be converted to fit inside the original PSU case - so don’t throw your original out as if you go that route you’d want to keep the 6 pin adapter for soft power and the main power loom/header. Well, I haven't had any luck. This afternoon I recapped the PSU and it's still the same. The capacitors looked great, no acid leaking onto the PCB, it was in very good condition. I also checked the fuse, the optocouplers, and the diode bridge, and everything is fine, but it's not showing any signs of life. The LC630 had been overclocked to 40MHz a week ago, and everything was working perfectly. At that time, I had added a CompactFlash card to the IDE port and copied quite a bit of data from an external BlueSCSI drive. Then I turned it off to switch the SD card to the BlueSCSI drive, turned it on, and when I started copying data, it froze. I unplugged it and plugged it back in, and it hasn't shown any signs of life since, neither with the power button on the case nor the one on the keyboard. I removed the BlueSCSI drive and the CF card, but nothing. Completely dead... I tried another 68LC040 and it didn't work either. I removed the battery and still nothing. With the overclock, I added heatsinks to both the CPU and the video processor. It seems I'm having a run of bad luck with Macintoshes...
Posted by: indibil on 2026-02-15 08:40:17 I ran more tests, and the PSU is dead. It's not even getting +5VSB voltage. I replaced the optocouplers, I replaced the 7805, and nothing changed. I remembered I had an old micro-ATX PSU in a drawer, and this weekend I adapted it inside the LC630's PSU, and it's back to life. I would have preferred to keep the original PSU, but I wasn't lucky. At least I can still use the LC630.
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