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LaPorta

SE FDHD Restoration

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Well, I can start you (and anybody else reading this) off with.....

When using a DMM, put the positive (red) lead on ground, and probe with the negative (black) at the chip, therefore your probe won’t try to power up the chip, or chips!

O scope.....  yeah. Someone else chime in...

 

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I got the connectors I needed, made a much longer connector, and set up a test rig. Now I can track the traces and test the voltages in-circuit:

 

setup.thumb.jpg.04c74b5aaf1e9330004765f2e726b98b.jpg

Edited by LaPorta

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7 hours ago, LaPorta said:

I managed to find it on Mouser:

Thank you for doing that!

What about the male connector? Got links?

 

A lot of people talk about fixing / repairing their machines, a lot of people help them, a lot of people question...........

 

..... And then that person comes back with “I found it at “parts supply” & fixed it, Hey thanks!”

But never give information on the part, or replacement part....

Yeah, we can all look at “parts supply” .com, but xxxx, don’t tell me “I found it at “part supply .com”! Give us a link, or more information about it..

Damn, looking up parts, even in the age of internet, can take days (and many brain cells).

Thank You!

I wish more people would give exact part #s..

I’ve thrown exact part #s at people many times, and I love it when they say “ 

Thanks, it’s working again”.

Edited by jimjimx

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Yes, what happened was that I was rifling through the digital parts manual and said "Geez, there are so many and they all look alike...I'll never find this thing." So, I went to a somewhat local parts store with my original cables, and the guy found the identical piece in about 30 seconds. I used his part number to match to what he had on his website, and found the manufacturer's part number, which I then tracked online. The sad thing for the parts store guy is that, as helpful and awesome as he is, he sells the connectors for about $3 a piece, while Mouser has them for about 79¢ each...

 

I was willing to purchase to have them on hand (and get you guys part numbers), but in the long term, if I buy a good number of components at once, saving $7.99 on shipping vs pickup will not offset his high prices.

 

I did not purchase the male version, as I did not need one. However, usually via the data sheet PDFs on Mouser for each part, there will be a section that will say "Use With..." and give the part number of the exact male counterpart.

 

As for the Mac 128k-Plus style, I got a 12-pin version of the same (instead of 11 that it is), but it can be clipped off. I am still looking for the equivalent part online.

 

Hopefully soon enough, I can actually start tracing what the heck is wrong with this logic board!

Edited by LaPorta

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Man, I really have almost had it with this thing. I’m just not sure what the issue is. I’ve been checking voltages all over the board, and they are within spec with regard to my reference board. I’m going to keep checking all the vias for continuity. Any more suggestions, I would really appreciate it.

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I've never heard of it failing, but maybe try swapping that big socketed VLSI chip next to the CPU, just to rule it out (just be very gentle to prevent cracking the socket). Also, maybe there's a rotted trace under the SCC or SCSI chip?

Edited by AwkwardPotato

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9 minutes ago, AwkwardPotato said:

I've never heard of it failing, but maybe try swapping that big socketed VLSI chip next to the CPU, just to rule it out (just be very gentle to prevent cracking the socket). Also, maybe there's a rotted trace under the SCC or SCSI chip?

I’ll try swapping it. What I would want to know is what the SCSI or SCC chip would do to stop the machine from working entirely and stop it from doing anything.

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I'm pretty sure that you would at least get a raster on the display if the SCSI and/or SCC chips were bad. After seeing all the crud that was under the Bourns filters, though, I'm wondering if there's more under one of those chips and it's shorting some signals together.

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I agree. I have no way of checking the traces under the SCC without hacking it out, and I don’t have a spare SCC. The solder is so corroded on the legs that desoldering it intact proved impossible (I tried). If I could get a replacement SCC...

 

PS - I did swap in a known good BBU...no dice.

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The serial and scsi chips won't prevent the computer from posting (it won't boot though). But crud and shorts under them will. For removing chips, a desoldering gun is best.

 

I understand your frustration though. And spending dough on something that looks like a time/money pit may not be a viable option... It's your call.

Edited by BadGoldEagle

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Eh, in for a penny, in for a pound ;). I don’t mind spending a few bucks here and there. If someone knows a source for those chips, I’d appreciate it, then I can hack out the ones there and get under them.

 

Obviously if it looks like it will never work, I’ll salvage all the removable stuff and move on.

Edited by LaPorta

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It appears you can get both the SCC and SCSI controller off eBay for roughly $10 each (not my listings). BTW, when buying obsolete parts like these, it's wise not to buy from sellers in China as they have a reputation for relabelling parts as others.

Edited by AwkwardPotato

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I was hoping mouser and the like would have them. I saw similar items...but can’t be sure they are exactly the same. Has anyone ever purchased them?

 

i appreciate you guys taking the time and helping with this.

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I ordered three SCCs (in case I need replacements later, or someone else does and I have them on hand). Hacking out the old one will show me what is under there.

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and...SUCCESS!

 

I received my SCCs today. I cut out the old one, and, indeed, one through-hole via was not electrically conductive! I had to actually drill through it with a drill bit and a pin vise. Once that was gone, re-soldering it was a simple matter. New SCC installed and soldered. Bam! Started up, no issue. Connected mouse and external floppy so far - works fine. Included RAM chips are 1 MB each, I know that now. Well, thank you to EVERYONE who helped figure this one out. I hope that it will inspire others to repair boards that appear too far gone. I also started coating the traces that were exposed with green liquid electrical tape: it looks just like the original coating in color and makes for an awesome repair that looks original!

 

Stay tuned for the restoration of the rest of the unit.

 

SCC hacked out. Look at the crud!

IMG_4500.thumb.JPG.6490c5bdef69d5ea4fd1e124db8cd25b.JPG

 

Here is the through-hole via. The one right in the middle that looks crusty.

 

IMG_4501.thumb.JPG.28aee05cd77b2143eef5c75f8e80057d.JPG

 

Cleaned and ready to re-mount:

 

out.thumb.jpg.935ddd8af909c650f6389f9df0be90cd.jpg

 

New SCC replaced:

 

done.thumb.jpg.240a79bbf64d0c0637f5bd3a12899036.jpg

 

Up and running!:

 

IMG_4503.thumb.JPG.32b0dc1f33d36a96ebf050579ffa58a3.JPG

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Excellent work!

 

Can you elaborate on how you found the non-conductive VIA underneath the SCC chip? On one of my broken SE/30 boards, many vias have the same sunken look and corroded color. Did you probe each VIA with a multimeter to find the broken connection? How were you able to drill through the board without damaging it?

 

Good luck on your SE/30 Resurrection!

 

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The only way I found the degraded via was by hacking out the SCC on a hunch: I didn’t know for sure it was there. Once there, I tested continuity from under the board to the end of the trace on the top side, and there was none. As far as drilling, it was all by hand. The drill bits are the kind you find at a model store: they are even smaller in diameter than the via hole. So, I drilled out the crud/solder but the via hole itself is spared. The board itself was not drilled. I had to do it because the solder was so far gone inside the iron would not touch it.

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Congrats! I can imagine how happy you must have been when you saw it post!

7C73001D-6385-4899-9978-F39D3D01A025.gif.e0f24e696edb205eb90a00761785c0e4.gif

Edited by BadGoldEagle
Brent Rambo approves this repair

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