Mac SE/30 logic board problem

[NJRoadfan]

I didn't have a problem with him recapping my Amiga 4000 board + A3640 CPU card. A4000 motherboards can be riddled with problems and I didn't expect recapping to fix the problem, but luckily it did. The only issues I had with the board was audio output problems. In my case, I provided detailed instructions (there are silk screen errors on the A3640 board) and my own capacitors. Testing the repairs wasn't an option since Charles doesn't have an Amiga test bench, so I took all liability if the repair didn't work.

Anyway....recaps aren't the magic fix to all old electronics woes. This guy had a heck of a time diagnosing a faulty Amiga 4000 motherboard. Its a LONG 2 part video, but it does give some insight on troubleshooting various problems.

https://www.youtube.com/watch?v=Bc5HRF7zjiA

 

[bibilit]

all of the SMD electrolytics have been replaced with non-polarized ceramic caps

No problem here for me, i have used the same type for a while and never had any issue.

Also, apart from those capacitors not being flat, don't see any quality problem either.

I don't know Uniserver, have always done my recaps myself...

 

[just.in.time]

Just to reiterate my second post in this thread, the post isn't to complain of uniserver's work. I've had many boards come back working great from him.

He told me in advance that he was unable to get the board working after a cleaning and recap job. I only paid for the recapping, not trouble shooting time.

The point of this post was to find people who have had similar symptoms after a recap job, and how they fixed those symptoms.

Please try to keep all additional comments technologically constructive towards remedying the problems with the board

A few users have given me some great starting points, including looking into UE8 and the negative solder point of C2. I will begin to inspect those as time allows. For the moment this project will have to take a back seat to work and my PowerBook 500 series battery rebuild (see thread in 68k PowerBook section).

 

[bibilit]

your screen looks like the SE/30 i repaired a couple of months ago:

https://68kmla.org/forums/index.php?/topic/28519-another-se30-another-boot-issue/

don't say is the same problem though. 

 

[Brett B.]

Charles is a good guy.  I have done all my own recapping so I can't comment on his pricing or work quality, but others have been very satisfied.  I guess if I was handed a damaged board I would use whatever components I had on hand for testing purposes, even if they are technically not the right type, rather than ordering the exact replacements.  That way if the board ends up being a lost cause, the expense would be minimal.  Without his direct input we can't really say but that's what it looks like to me.

 

[Challenger 1983]

Why was uniserver banned

 

[belgaonkar]

Challenger- read this for a good laugh

https://68kmla.org/forums/index.php?/topic/27774-how-to-handle-a-deal-gone-bad-locked/

 

[techknight]

Let me update to my previous post. I thought your audio was distorted, but I checked the youtube video after I got off work, and its not. 

slow chimes + simasimac = cannot see RAM. 

So, you either have a bad trace to the RAM slots, or more than likely, one of the 74F253 muxes are bad. Easiest would be to swap them all out. Before I semi-retired, I was starting to see this one a bit more common recently. 

 

[Carboy7]

Challenger- read this for a good laugh

https://68kmla.org/forums/index.php?/topic/27774-how-to-handle-a-deal-gone-bad-locked/

HAH! :lol:

What did I just read...

 

[just.in.time]

Hi techknight, thanks for the update. Can you highlight the 74F253 muxes in one of the photos I uploaded? I'm not really sure what I'm looking for.

What causes them to fail?

 

[Johnnya101]

Challenger- read this for a good laugh

https://68kmla.org/forums/index.php?/topic/27774-how-to-handle-a-deal-gone-bad-locked/

*munches popcorn*

 

[techknight]

Hi techknight, thanks for the update. Can you highlight the 74F253 muxes in one of the photos I uploaded? I'm not really sure what I'm looking for.

What causes them to fail?

I wish we can get this thread back on track. 

Anyways. the Muxes are the 6 ICs immediately to the left of the RAM slots, and just above the ROM slot. 

 

[techknight]

Hooboy, where to begin. I took a look at the photos carefully: all of the SMD electrolytics have been replaced with non-polarized ceramic caps. I also see that your SCSI and ADB fuses have been replaced with what look like MOVs (WTF?) instead of the proper fuse type. You need to demand that he put the proper components on the board, or pay someone more reputable to do it.

the "MOVs" arnt MOVs at all, they are momentary self-resetting circuit breakers. almost like Poly fuses. Anyways, they are bone stock. I have seen them on multiple occasions. 

As far as using radials instead of axials, I will agree that if you want it to look factory correct, then put the right components in. Such as if I was doing it for another person. But if it was my own, I wouldn't care. 

 

[just.in.time]

Thank you for taking the time to clear some things up and give me some more places to check I appreciate it.

 

[james_w]

Personally I mostly replace SMD electrolytic caps with ceramics.

My reasons are twofold; firstly I want caps that'll last longer, and secondly (and I'm not saying anyone else should follow my lead) that tantalum is a conflict resource, and I don't want to financially support warlords and slavery in mining.

I've not had any problem with ceramics so far And I just use electrolytic caps where higher value caps are required.

 

[techfury90]

If you read the link, that region only accounted for 1% of the world's tantalum output. That being said, Kemet makes an entire line of conflict-free tantalum caps.

 

[techknight]

Ceramics are ok, but they do have 1 caveat. They tend to randomly short. Kinda like tantalum. Not nearly as prevalent but I have ran into gear where MLCC caps have taken a dive in ohms land and became 0. 

 

[james_w]

If you read the link, that region only accounted for 1% of the world's tantalum output. That being said, Kemet makes an entire line of conflict-free tantalum caps.

I missed that, and thank you so much for the tip - that's awesome!

 

[asapreta]

Sorry for revive this old thread but I have two SE/30 with this problem.

One I got working just by replacing the RAMs.

The other one was working but sometimes the video messed up. Then It went completely black. Sometime later there were diagonal lines, like it was a video problem but I noticed some noise from C1 and its area. The positive pin of C1 was hot so I replaced it. And again I got the same pattern from the first post.

As mentioned here UE8 (LS166D) was very corroded and I will replace it (it lost three legs while I was cleaning the board). Also I will recap the whole board. I hope this solves the issue, but as it was working, where else could I take a look to solve the problem if LS166 isn't the culprit?

Best regards