SE/30 PSU Sony CR-44 troubleshooting

[zigzagjoe]

So, I'm in the process of fixing up two SE/30s that I haven't played with for 18 years.... one is the favorite, and has 128MB of RAM and an ethernet card. So I want to get it 100% internally. I did a full recap job on that one, where the second is being kept as a control as the analog board and original PSU seem OK (for the sake of testing).

So: the CR-44 from that unit was fully recapped and some trivial load testing looked good. Put it in either unit - nothing. Brief pop from speaker, no fan or power on any connectors. Nothing connected but the motherboard and speaker, no drives...

PSU Tests OK outside the units. Even load testing to 75% on each rail simultaneously outside of the unit showed no problems, voltage regulation looks great. Put inside units? Nothing. Acts like overcurrent protection is being tripped, though I'm not even sure if these have that. Unfortunately, I neglected to test it before recapping.... so maybe it was bunk beforehand?

Long story short - skipping a lot of troubleshooting - I was about to give up and post here for help. Taking some pictures of the inside, I noticed I left out the thermal pad on IC252 (big transistor, looks like it's for 12v disk rail per schematic) during reassembly. Put it back and problem solved. I have no idea how it passed load testing if that was truly a problem, but I have no desire to take that power supply back apart for the 6th time to confirm....

Hopefully this helps someone....

 

[Phipli]

So, I'm in the process of fixing up two SE/30s that I haven't played with for 18 years.... one is the favorite, and has 128MB of RAM and an ethernet card. So I want to get it 100% internally. I did a full recap job on that one, where the second is being kept as a control as the analog board and original PSU seem OK (for the sake of testing).

So: the CR-44 from that unit was fully recapped and some trivial load testing looked good. Put it in either unit - nothing. Brief pop from speaker, no fan or power on any connectors. Nothing connected but the motherboard and speaker, no drives...

PSU Tests OK outside the units. Even load testing to 75% on each rail simultaneously outside of the unit showed no problems, voltage regulation looks great. Put inside units? Nothing. Acts like overcurrent protection is being tripped, though I'm not even sure if these have that. Unfortunately, I neglected to test it before recapping.... so maybe it was bunk beforehand?

Long story short - skipping a lot of troubleshooting - I was about to give up and post here for help. Taking some pictures of the inside, I noticed I left out the thermal pad on IC252 (big transistor, looks like it's for 12v disk rail per schematic) during reassembly. Put it back and problem solved. I have no idea how it passed load testing if that was truly a problem, but I have no desire to take that power supply back apart for the 6th time to confirm....

Hopefully this helps someone....

Perhaps the casing wasn't grounded when you were testing, so the transistor's tab was shorted in the machine, but not on the bench?

 

[zigzagjoe]

Perhaps the casing wasn't grounded when you were testing, so the transistor's tab was shorted in the machine, but not on the bench?

Yeah, that is what it looks like to me. The negative provided off the power cable is separate from the system ground (derived from the power cable) until you plug the logic board in. The analog board itself keeps system ground and power negative separate. Only on the logic board does it seem like they are connected. This theory is backed up by the analog board starting and running by itself with the motherboard not connected (by accident - oops).

 

[alectrona2988]

Funny because I worked on the exact same thing! The computer boots after I put a thermal pad in between the regulator and the PSU chassis, which is great. Only issue I am having now is that the system says that the disk inserted is not initialized and it tells me to eject or initialize, whether one is present or not... thinking it might be a bad floppy drive, but idk. If someone could help, that would be appreciated!

 

[zigzagjoe]

If you're going for a full rehab, I had one of my drives stick with a head not lowering onto the disk. The root cause was old grease in the mechanism not letting the floppy fully settle into the closed position. It's a bit of a puzzle to disassemble but not too bad.

 

[alectrona2988]

I've already cleaned and re-lubed the drive. Not sure if there's a switch causing the issue? But I do not hear any noise from the drive at all... I noticed on my board that some of the solder was corroded which was likely causing issues so I'm re-soldering whatever chips had been affected to ensure they are making good contact. I think I may also need to recap the drive. It is an MP-F75W-01G...

 

[zigzagjoe]

If it's complaining about the disk, at least it's aware a disk is inserted so I wouldn't think it's a microswitch issue... I'd suggest visually confirming when inserting the disk that you see the spindle spinning, the head moving back and forth, or any obvious activity. Sounds like this is probably not happening.

I did have an issue on one board where a damaged SWIM was causing the floppy to forlornly click when booting but otherwise be inoperable

 

[alectrona2988]

Ahh... if the SWIM is the issue, where can I locate the existing SWIM chip and what can I replace it with?

 

[zigzagjoe]

It's UJ11 on a SE/30. One of the lines on the chip should read 344S0061. Unfortunately the only sources I know of it are from other SE/30s or IIsi, it's a bespoke apple chip. Probably best to do some more troubleshooting first (check voltages on the connector, etc) and maybe see if you can find another drive to test with...