IIsi logic board burnout

[apm]

Looks like I have literally burned out the logic board on my IIsi. I powered it up today after a few weeks in storage to test some RAM sticks, and it was behaving strangely: lots of crackling through the speaker with flickering LED, plus some chimes of death, not wanting to stay powered or randomly powering off.

At one point, pushing the power key would result in a click through the speaker, a brief flash of the LED, and nothing more. I tried this 5 or 6 times in quick succession. On the last one, I got what is best described as a loud motorboat sound through the speaker, at which point a fairly surprising amount of smoke came up from underneath the SCSI cable to the hard drive, accompanied by that "classic" smell of burning silicon. Great.

It looks like Q10 and Q11 on the logic board have been thoroughly cooked. Now it is back to "click" and not staying on, and I'd guess that may be a permanent condition until this is fixed.

Anyone seen anything like this before? For those privy to the schematics, what are the part numbers and function of Q10 and Q11? I would guess either speaker-related (from the location) or soft-start (from how it was behaving).

 

[MJ313]

It looks like the little guy under UK3 might have bit it as well?

 

[apm]

Might be. It didn't look quite as bad to me as the transistors, but who knows. At least the part number there is marked, and easily replaceable.

Judging from the traces on top, I guess Q10 and Q11 are probably power drivers for the speaker, with UK3 the preamp. In which case the loud noise and smoke would be directly related.

 

[joethezombie]

No schematic, but here's what mine looks like.

 

[uniserver]

this my friends is what happens when you make a vintage mac run with bad caps / cap goo leaked all over.    went from fixable to maybe fixable.

 

[uniserver]

its like driving a car with a rod knock... its trying to tell you that any seconds the engine will let loose..    more more you drive it the more its gonna cost you.  if it blows,  went from a crank resurface + new bearings ...  to a completely shot motor.   or driving a modern card with a leaky water pump...   most are driven from the timing belt, if equipped,  and automatically you know chances are pretty good the timing belt is old as hell.  because water pump is always changed when you do the timing belt, that is just how its done...  you can keep adding water but one day, Bang.. total failure...   Valves through the pistons and all.

 

[Macdrone]

I agree with Uni.  Don't push a mac with bad caps.  Get it recapped and be ready to go.

 

[rsolberg]

Timing belt procrastinators make my eye twitch. Umm yes, that rattle noise getting gradually louder on idle is a sign... So is 120,000 miles on the original belt. But it's an excuse to junk the vehicle when it goes. I don't get it. Timing chains (and sensible maintenance) FTW.

 

[techknight]

speaking of which, my 04 toyota camry is making a "timing" like noise and its at 170K so it  might be time to get it changed. Not sure if its a belt or a chain. Car lot car, so I have no idea of its service history. 

 

[360alaska]

I would also make sure the speaker is not shorted, the proper ohms should be listed on the back...

 

[rsolberg]

Techknight, the four cylinder is a chain, the V6 is a belt on an '04 Camry.

 

[techknight]

its a 4 cyl. doesnt have a whole lot of power either. feels less than my old 96 dodge 4cyl. 

 

[CC_333]

The '04 I4 wouldn't happen to be a 1zz-fe, would it?

If so, our '06 Pontiac Vibe (aka Toyota Matrix), probably needs a look at (it's pushing 200k), as it's been making some odd rattling sounds when cold for some time now which could be from the timing chain (seems fine when it's warm, though). Power seems ever so slightly less than I remember as well.

c

 

[unity]

I would at least wash vintage boards to prevent this. And wash them very well.

 

[apm]

Yep I guess this is a lesson to be learned the hard way (once!). I previously recapped a couple SE/30s with problems but got lazy on this one because it was working flawlessly until this happened. I admit it was a pretty surprising failure mode.

I'll see if a recap, wash and replacing those components brings it back at this point.

Incidentally, what's the view here on the IIsi power supplies? I've seen no end of problems with them on this forum, and I wouldn't discount it being faulty on this machine too. Does anyone find a preventative recap makes a difference there?

 

[techknight]

power supplies in the IIsi is a known leaker. 

 

[rsolberg]

The '04 I4 Camry has a 2AZ-FE 2.4L which uses a timing chain. Timing chains generally don't need replacement until multi-hundred-k miles, when an engine would be rebuilt anyhow. If you're experiencing valve noise on a timing chain engine, checking valve clearance is a good idea. I believe it's recommended every 100,000km/60,000mi in my Acura service manual. Lifter springs might need replacement, or adjustment may be required.

CC, that sounds like you could use a valve clearance check too.

I promise I'll stop posting car stuff in the Mac II subforum. To the Lounge!

 

[uniserver]

the first thing i would do with that toyota is dump 3/4 of a bottle of this in there.

most modern cars will not let you rev the engine too high while in neutral

so you will have to put it in ( L ) or (1)  maybe somewhere there is not other cars around,

And stomp er to the floor, let it wind out in 1st gear, let it hit the rev limiter, then slow down, let off the gas,  Then stomp it to the floor again.

so a total of 2 or 3 times.

What this does is 2 things...  

1 - it will reset your hydraulic lifters.

2 - it will allow the oil pressure to reach max and with a little help from lucas will make sure it reaches maximum. (unless your oil filter is plugged as well)

and this will intern fully pressurize your TC tensioner witch is a good thing because the ratcheting mechanism will click

and your chain will now be nice and tight... however if your tensioner is already at its maximum travel then it won't do anything.

but its always good to dump Lucas products in your oil / trans / gas,  They have a product for each.

if your timing chain is massively streched,  that could be a reason the car has no pickup as the valve timing is retarded.

So much so the computer cannot spark compensate for it, so it always runs retarded, Witch is why it's a slug.

witch can plug up your catalytic converter, and might even throw your O2 sensors off, maybe even tricking you into thinking they are bad.

 

[CC_333]

Last car-related post here for me!

Our car has decent power still, it's just a bit less than I remember, and it's a bit noisier than I remember too.

It's due for a tuneup anyway, so we better start saving up so we can take it to the shop.

c