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Mac SE/30 boots but... CRT displays diagonal lines and no actual video


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Good evening,

 

I'm new to the forum as I haven't had any classics for the last ten years.  I was heavily into Color Classic and have modded several Takky's.  Wished I still had one of them...

 

I've recently purchased a collection of old Macs.  Two SE's and an SE/30 came in the pile.  The SE/30 had the typical leaky capacitors so I went tantalum style.  UE8 had some sludge on it and I cleaned it several times.  I fluxed the legs and re-flowed them to try and clean them up.  The SE/30 chimes, the hard drive spins up and you can tell it boots to OS because there is a "bleep" when the OS loads likely referring to some sort of dumb system error (like set the clock).  The main issue is I have no video.  When I place one of my SE boards in this machine all is well and normal so that isolates out the PS, AB and CRT.

 

So you see the photo attached.  This is the video display I get when I power on my SE/30.  Disregard the black swath as it's a camera issue.  I've checked all my PSU Voltages and they are all very close to +5, +12 and -5, -12 on J12.  My Hor and Ver Voltages are like 1.5 or something close (would have to measure again).  As stated my UE8 was filthy but I've since cleaned most if not all of this board with a lot of isopropyl alcohol.  The PRAM battery was dead but luckily had not exploded/corroded.

 

I've done quite a bit of searching for the past week or so and have not found anything useful regarding this particular problem.  I'd love a hand with this if any of you have seen this.  There were some 2013 threads that sounded a bit like this but the photos were 404 and many of the threads dead-ended.


Anyone seen this before?

More Diagonals.jpg

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might want to start with recapping the logic board, and if you get a hold of the schematics start buzzing out connected around the video circuitry. you mentioned that UE8 had  sludge around/on it so its a good place to start being that that would be leaked electrolyte form the leaking caps. these machines are over 30 years old now so those caps leak and endup damaging traces etc

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Outstanding info here guys.  As stated I already recapped this board so that's out of the way.  ;)  I am curious - can any of you point me to a "parts thread"?  Simple Google searches for UE8 don't turn up much.  I imagine I'll have to  grab the numbers off the IC unless there's already a comprehensive list somewhere.  Hoping Digikey or Mouser has these parts.

 

Thread edit:
After drinking my second cup of coffee I realized I should search the PN on the chip.  That yielded the link below.

https://www.digikey.com/en/products/filter/logic-shift-registers/712?s=N4IgTCBcDaIDYGcCMA2FBDEBdAvkA

 

Edited by PotShotScott
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5 minutes ago, PotShotScott said:

Outstanding info here guys.  As stated I already recapped this board so that's out of the way.  ;)  I am curious - can any of you point me to a "parts thread"?  Simple Google searches for UE8 don't turn up much.  I imagine I'll have to  grab the numbers off the IC unless there's already a comprehensive list somewhere.  Hoping Digikey or Mouser has these parts.

 

The UE8 is a 74LS166, I believe. It should be written on the IC as well. Just make sure you get the SMD version, it should be widely available at the usual electronics parts stores.

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Very good Daniel.  Appreciate your comments.  I realize that I am pressing the "noob" button here looking for the easy answers.  I will find the SMD version.  Do you advise replacing all of these chips or just the UE8 that is suspect?  Is there a resource somewhere that shows block diagram and an idea of what these chips do?

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3 minutes ago, PotShotScott said:

Very good Daniel.  Appreciate your comments.  I realize that I am pressing the "noob" button here looking for the easy answers.  I will find the SMD version.  Do you advise replacing all of these chips or just the UE8 that is suspect?  Is there a resource somewhere that shows block diagram and an idea of what these chips do?

 

I personally didn't replace them, though it really depends on if the capacitor leakage got to them or not. UE8 is right under a cap, so it tends to be the culprit for issues as it takes the brunt of cap goop. 

 

There are schematics available here, it's the first download (se30schems.zip) on the page. There are Apple schematics, which are a bit hard to read and incomplete if I recall correctly, as well as BOMARC's. BOMARC schematics are third party, and I do believe they're known to have a few errors here and there (they were made by BOMARC by hand, rather than using Apple's own schematics as a reference), so they are a decent reference, but not the end all, be all. It's why there is a current effort to create modern SE/30 schematics with those mistakes corrected: 

 

 

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I need some additional help please.  Four of my traces are so trashed underneath that I simply can't use them.  They are marked in the image in yellow and green.  I am 99% certain the green traces simply go to the small test points below them.  I have followed the yellow dots on my UE8 and I THINK they go to the areas circled in the images but I am not going to pull the other chips on the board to look.

 

Hoping one of you has a photo of a "bare" board or can do me the honors of VOM these pins to verify?  I believe I can do some trace repair jumper around the bad pads/traces, clean the flux and give this board a test.

 

 

UE8 traces.png

Edited by PotShotScott
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Well, after 2 hours of VOM probing in front of the Macintosh SE/30 schematics I believe I am out of ideas.  If I had to guess maybe UF8 is wasted or UF7 as I was able to plot out all the pins.  The pins circled in the photo are longer questionable but I did have two pads under UE8 that were wasted.  After restoring the traces with two very small gauge temporary wires I am back to square one with the same video output as in the first photo in this thread.

 

If anyone has any cheap last minute ideas (under $10~15 USD) I'll give it a go otherwise expect to see this board (and perhaps the entire SE/30 unit) on eBay.

 

Scott

Edited by PotShotScott
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