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desertrout

SE/30 - new simasimac / no chime after PSU and analog recap

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OK, so I recently recapped my SE/30 mainboard and it went smoothly, and it resolved a weak sound issue. Little guy worked just fine. Great, I thought, I'll get ahead of the curve and recap my (Astec) PSU and analog board. That goes smoothly as well, and I resoldered a few grey-looking connectors on the ab while I was at it. Reassemble, power on... thin vertical simasimac and no chime.

 

Weird, but OK, time for some obvious checks:

- checked voltages, all rock solid coming off the ab, and the usual checks on the mb

- double checked the ROM SIM and make sure it's clean and seated. A few greyish pads toward one end, clean them up, do a iso clean of the slot, dry it out, test some continuities, seems ok, reassemble, no change

- check continuities on some IC's I reflowed (UE8 for instance), all good

 

There are other paths I can go down, but I have a question: what is the likelihood that the PSU or ab recap could be the cause of this? It's the only thing that changed from a working SE/30 to now. I'm going to wash the mb one more time to be sure, but it WAS working before now, so I'm unsure. I know coincidences are more common that I'd like, but it's not the first place to be looking... so... thoughts?

 

The only possibly weird thing I'm noticing is a series of about 8 very faint clicks coming from either the ab or psu a few seconds after power on... I'm not sure if that's normal or not.

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Yeah, the PSU or ab I don't think are at fault here... voltages are all good. That clicking was just the hdd. I'll pull UE8 as well just to see anything is amiss under there...

Edited by desertrout

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Out of curiosity, can you post a photo of the simasimac? That might narrow things down. I was in a situation like yours with the following simasimac. The problem turned out to be the ROM SIMM wasn't making contact, even though it was securely seated... – one of the ROM clips had broken. 

 IMG_3976.thumb.JPG.1e678879dae2527ca9d7674d3ee24a8e.JPG

Edited by rplacd

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That is indeed the version I have. ROM is seated very well, and clean, slot is clean, clips are solid. There is no corrosion anywhere near the ROM SIM or muxes, though ringing the traces is on my list. Unfortunately I don't have another SIM to swap in there to check if it's the ROM itself, but for the time being I have some other things I can try.

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I'm getting back to this project, starting to check continuity along the data and address lines (so far, all ROM -> CPU all check out) as the consensus this is the most likely issue. I've already replaced UE8 with no change. I've also cleaned and dried the board again just to rule out possible lingering capacitor goo effects, but so far no change - no chime, and 'vertical' or 'herringbone' somasimac.

 

One thing I'm noticing now is that all the video PAL's get warm - not hot, but noticeably warm. I don't remember them doing that before. I've checked the board and IC's thoroughly for solder blobs or other causes for shorts but can find nothing. I'm a little freaked out that maybe I did something to the vias of C11 or C2 and messed up something in one of the other layers, but I think I'm just being paranoid.

 

I'll keep going with data and address line checks, and also do some RAM swaps, but if anyone has some insight into what could possibly be making the PAL's warm (or even if that's an issue to be concerned about), I'd love to hear it!

 

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16 hours ago, dochilli said:

I had a simasi SE/30 because of corroded F258 chips. Changed them and the mac worked.

 

Thanks - I'm checking continuities to those at the moment, but they are pristine, probably because this board is Rev 2 (I believe) where C12 is 'outside' the ROM SIMM in column 1.

 

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22 hours ago, desertrout said:

Thanks - I'm checking continuities to those at the moment, but they are pristine, probably because this board is Rev 2 (I believe) where C12 is 'outside' the ROM SIMM in column 1.

 


I kept on troubleshooting for weeks without success. It turned out to be the F258s that was the problem. They all had continuity when I measured with the multimeter. I replaced three of them that looked like they were in bad shape, then the computer started! But there continued to be problems with RAM Bank B, and when I finally replaced the remaining three chips (which all looked to be in good shape), the RAM problem also disappeared. So replace all six chips if you don’t find any other solution. 

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13 hours ago, blindowl said:


I kept on troubleshooting for weeks without success. It turned out to be the F258s that was the problem. They all had continuity when I measured with the multimeter. I replaced three of them that looked like they were in bad shape, then the computer started! But there continued to be problems with RAM Bank B, and when I finally replaced the remaining three chips (which all looked to be in good shape), the RAM problem also disappeared. So replace all six chips if you don’t find any other solution. 

Yeah, it's starting to look like that's the direction I'll have to go - bringin' out the ol' "parts cannon"...

 

But what would be making UI6 get warm???

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