IIsi Power Supply unknown part

[AlexMac]

Hi all, I just received a IIsi with a massively leaky power supply. Got it more or less cleaned up and all caps desoldered. Unfortunately a part got destroyed which I cannot identify, Can someone help me where to get a replacement? Thank you so much!

 

[robin-fo]

It‘s an inductor (coil). Are you sure it‘s damaged?

 

[AlexMac]

The housing is damaged. The coil itself is visible. Will it work nonetheless?

 

[robin-fo]

Possibly. Best check for continuity and make sure you didn‘t create an internal short circuit

 

[AlexMac]

This is written on it: Sony DR5K 424-365-11

 

[AlexMac]

Continuity is there. It has a line on one side and a dot on the board. These should align, i think?

 

[This Does Not Compute]

I don't have an exact part number for you, but I measured L202 to be 0.4uH. Inductors of that value appear to still be common today, though what current rating that one is capable of I'm not sure.

 

[AlexMac]

Thank you so much! I just reinstalled the part and system powers up. Even a chime is coming. But sad Mac crash sound right after it and no video - any ideas? PSU seems to be ok though

 

[AlexMac]

Well, quick Moment of Video

 

[AlexMac]

Voltages are 4.96v and 12.2v

 

[AlexMac]

More obeservations: When I pull all RAM SIMMs I am getting a chime and NO sad Mac sound. Still getting no video though. When I hold down the combination of Ctrl, CMD and Power Key I am getting yellow, green or grey video until I let the keys go...

 

[jdmcs]

Have you re-capped the logic board? If so, you might want to inspect for shorts around the replaced capacitors, especially if you used tantalum capacitors with a shorter pad spacing than the original electrolytic capacitors.

You might also check out this video from Adrian's Digital Basement where he uses the built-in test mode that the Apple TechStep makes use of, but in a way that does not require the TechStep (or clone). This could help you narrow down where the fault is located. The TechStep supports the IIsi so it should also have the test mode Adrian is using:

(Unfortunately I have yet to have to resort to using this test mode but #MARCHintosh is upon us and I have my very own IIsi slated for a complete re-cap. I may very well find myself in the same boat...)

 

[AlexMac]

Yes, I recapped the board. Measured everything out and found good continuity. Some caps I used (near the audio area) are tantalums others are the red cylindrical ones by Würth. Thanks for the hint to check the new caps for bridging something. I will definitely do that.

The diagnostic mode until now has never been working for me on any machine I tried. Maybe something I am doing generally wrong. I used ZTerm on a G3 Mac and a printer cable to connect the two modem ports (setting ZTerm up as written on the Google Doc). But never get the Asterisk back.

And I thought the PSU was the bigger challenge At least I tested on my porch to be safe and was so glad to hear the chime.