Classic II – won't start after cleaning

[blindowl]

So I have this re-capped Classic II that used to work, but only sometimes (CRT wouldn't turn on). I decided to do another cleaning of the logic board to get rid of some corrosion. I soaked it in vinegar over the night, rinsed it with water and let it dry. Now the machine doesn't start at all... No life from the fan, HDD or CRT – but there is a fast clicking sound from the speaker, tick-tick-tick-tick-tick.. I've measured the 12 V rail on the floppy port and it's unstable just around 5 V (before the cleaning: 11,98 and 5 V). I'm suspecting there is a short somewhere and I haven't let the machine run more than a few seconds.

Any advice where to start troubleshooting? What can cause the issue described above, what might be shorted with what? And where to start measuring? I've found the Bomarc schematics but I find them a bit hard to follow.

 

[joshc]

You should rinse with isopropyl alcohol not water.

Can you post some pics of your logic board and analog board?

 

[Paralel]

You should rinse with isopropyl alcohol not water.

Can you post some pics of your logic board and analog board?

Preferably 99%, if possible. If not, the next highest available %.

 

[ironborn65]

some pictures would help
what I would do:
since the CRT did not always turn on, first test the analog board voltage in isolation from the MB and the CRT, check all the readings, they must be stable before turning your attention to the logic board. Was the analog board recapped as well?

If it passes the test I would soak and clear the logic board with 99% IPA, limestone is conductive, some residue might create a short.
Inspect the board with a magnifying glass, microscope or with the zoomed camera phone, look for residues around all IC pins.
Gently brush them all with a toothbrush. IPA does not clean the limestone but it will not worsen the situation while cleaning it again.
This is not enough sometimes because shorts can be under the ICs. You can use the vinegar again with IPA this time.

You said it was recapped: check all the new capacitors, are they SMD? If the job was not done properly some might have detached during the cleaning process, very gently check all the sides and see if they stick to the pad.

You said the CRL did not always turn on, but did you hear the happy chime? or was it completely silent?

we hope for the best!

 

[blindowl]

Background:

When I got the machine I removed the battery and cleaned of the worst gunk around the capacitors, and turned it on. It showed a garbled screen like this (this is a later picture):



I removed all caps, cleaned the logic board with a toothbrush and vinegar and IPA, and then re-capped the board. After that the CRT didn't turn on anymore. I put the machine away for a couple of months and continued some days ago.

Now the CRT turned on again, but back to the black bars. I measured the voltage rails and they where on the low side (11,28/4,71). After some tweaking they were now better (11,98/5,02). Still same black bars at boot.

I changed the RAM modules and now the machine started. Happy Mac and chime (very low volume though). But only from cold boot. If I turned it off and on again the CRT would stay black and no seeking activity from the HDD (but spinning).

That's when I decided to clean the board more properly. And now I guess I have a short somewhere. Without the logic board connected the machine starts just fine.

I have since yesterday rinsed the board with IPA (99,7%). But I think I will go for another round with vinegar and a toothbrush, then rinse with distilled water and then soak with IPA. There's still a lot of residue on the board, and for some reason this IPA always leaves a lot of white stuff (dirt left on the board maybe).

Current state:

 

[beachycove]

Is there a pad lifted at C5?

 

[rollmastr]

Did you just recap the logic board? On these machines usually the analog board also needs work.

 

[ironborn65]

apparently it needs to be cleaned again and again.
It's my practise to dry the board using a hair dryer, in this way there are less residues left.
Then I leave it try in a warm place for at least 12 hours before powering it up.

C13 pads seems to have not enough pond. I'd very gently and carefully exercise a small push with a toothpick to check if the are properly soldered in place: again "very gently" while looking with a magnifying glass in case they move. Most of my random failed boots were due to cold/bad soldering or lifted pads.

The open question here is ... has the analog board been recapped?

PF

 

[3lectr1cPPC]

Definitely look into the analog board - they always need caps and sometimes other parts as well. The chip directly below the CPU in your last photo is the EGRET chip - it's responsible for starting up the Mac. I still see some corrosion around it, I'd give it a good clean around the legs and even remove it and clean under if possible. They're very picky about being clean.

 

[Paralel]

I have since yesterday rinsed the board with IPA (99,7%). But I think I will go for another round with vinegar and a toothbrush, then rinse with distilled water and then soak with IPA.

It's a good idea. I've had boards take two cleanings before they started to improve.

some pictures would help
what I would do:
since the CRT did not always turn on, first test the analog board voltage in isolation from the MB and the CRT, check all the readings, they must be stable before turning your attention to the logic board. Was the analog board recapped as well?

If it passes the test I would soak and clear the logic board with 99% IPA, limestone is conductive, some residue might create a short.
Inspect the board with a magnifying glass, microscope or with the zoomed camera phone, look for residues around all IC pins.
Gently brush them all with a toothbrush. IPA does not clean the limestone but it will not worsen the situation while cleaning it again.
This is not enough sometimes because shorts can be under the ICs. You can use the vinegar again with IPA this time.

You said it was recapped: check all the new capacitors, are they SMD? If the job was not done properly some might have detached during the cleaning process, very gently check all the sides and see if they stick to the pad.

You said the CRL did not always turn on, but did you hear the happy chime? or was it completely silent?

we hope for the best!

Limestone? What do you mean? Why do you suspect that calcium carbonate is involved? I mean, calcium ions would be an issue if he didn't use deionized water and his water is "hard", but where does the the carbonic donor come from? There shouldn't be any carbonic acid anywhere strong enough to cause a precipitation of calcium carbonate. If you are thinking of the interaction of calcium in the water with the acetic acid in the vinegar, it could cause a precipitation of calcium acetate, but that would be acetate of lime, not limestone.

 

[blindowl]

Is there a pad lifted at C5?

I don't think so. Board is currently drying, will check tomorrow!

 

[blindowl]

C13 pads seems to have not enough pond. I'd very gently and carefully exercise a small push with a toothpick to check if the are properly soldered in place: again "very gently" while looking with a magnifying glass in case they move. Most of my random failed boots were due to cold/bad soldering or lifted pads.

The plan was to clean the board, then go over and double check my soldering. I'm sure things can be done better. The board is currently drying, will have a look when I have some time over!

The open question here is ... has the analog board been recapped?

Like with the rest of my compact Macs, plan is to do it.. "later". The original issues with this Mac might very well be to a bad analog board. But the current, bigger, problem happened after my cleaning.

 

[blindowl]

Definitely look into the analog board - they always need caps and sometimes other parts as well. The chip directly below the CPU in your last photo is the EGRET chip - it's responsible for starting up the Mac. I still see some corrosion around it, I'd give it a good clean around the legs and even remove it and clean under if possible. They're very picky about being clean.

I didn't know the EGRET chip is responsible for starting the Mac. It's one of the chips with most residue on it's pins. I will definitely look into that!

 

[ironborn65]

be careful if you opt for removing the EGRET for a thorough cleaning, it's very sensitive to heat

 

[AwkwardPotato]

An effective method I’ve found helps with EGRET issues is to put a healthy amount of flux on the pins and touch them up with a soldering iron. If the solder doesn’t take to the pins due to corrosion, you can flood all the pins with solder and remove any bridges later with solder wick (look up “SMD drag soldering” and you’ll find several demonstrations). The flux will clean up any cap goo or corrosion left around the EGRET, especially comes in handy if you don’t have a hot air station to remove the chip.

 

[blindowl]

I have this Chipquik SMD removal kit, with it it's fairly easy to remove SMD components.

I started the machine today and the second cleaning did nothing – still same issue.

What would the typical symptoms of a failing Egret chip be? Where in the machine's startup would it fail?

As mentioned, this Mac is completely dead (no fan, no HDD activity) except a ticking sound from the speaker and there is around 4-5 V on the 12 V rail and 0,5 V on the 5 V rail. Could that be a failing Egret or something else?

 

[joshc]

This is an analog board problem most likely, not a logic board issue. You should get power (fan, HD, CRT power) even with Egret problems.

There may also still be logic board issues, but getting the power rails behaving first is the next step.

Got any pics of your analog board, I assume it’s been recapped too?

 

[blindowl]

This is an analog board problem most likely, not a logic board issue. You should get power (fan, HD, CRT power) even with Egret problems.

There may also still be logic board issues, but getting the power rails behaving first is the next step.

Got any pics of your analog board, I assume it’s been recapped too?

The machine started fine before my cleaning of the logic board. With the LB disconnected the machine starts. And now I just swapped in a LB from a Mac Classic and it starts fine again. Of course this might be an AB issue but to me this still points to something with the LB.

Edit: just put the Classic II LB in the Classic – same issue.

 

[joshc]

OK, not sure what's going on there then. That is odd! However, I would highly recommend recapping the analog board because these always have very leaky caps.

What I would try is, on the logic board, removing any ICs near capacitors and cleaning well underneath them. The DFAC/Sound Chip is also a key part of the startup process and could also be causing problems.

 

[pball52998]

I would highly recommend recapping the analog board because these always have very leaky caps.

I looked at my board and thought "how leaky could it really be"? It didn't look that bad, but I couldn't see that well between the giant group of caps at the bottom.

Then took off all the caps at the bottom of the board to replace and I couldn't actually see anything on the board besides gunk. Lots of scrubbing later.. and a board like new. Working perfect

Will never trust a board before removing all caps again (on boards that need it)