IIsi fault ...

[franklyn]

I have a IIsi that works before fine and now it take some time until the sound of dead sounds up. The motherboard looks good except for a little oxidation on the four 74ALS245 chips. I desoldered these all and cleaned everything up and checked connections and soldered on four new chips but the error persisted. Because the error sound takes so long to sound, it may not be the RAM?

Does anyone have an idea where I should look for the error?

 

[Phipli]

The powersupply in the IIsi is the worst powersupply for failing of any Mac, and the logic board caps are some of the worst for leaking. If the logic board and powersupply haven't been recapped, those are the first things that need doing as an absolute matter of urgency. If they haven't been done on a IIsi especially, they are your first and highest priority to getting it reliable.

Don't leave it or the damage will get worse.

 

[Phipli]

Perhaps you and @rbdr (also in Germany) can work together to find someone who has experience recapping and repairing Apple Macsiifyyouddon't haveeexperience yourself(whichyyoupprobably do have given you were desoldering chips!).

Side note, the corrosion is always worse than it looks. The symptoms of bad corrosion don't look that severe, and people who haven't seen it before usually overlook mild corrosion.

It's best to share high resolution, well lit, photos when making posts like this because it really helps to see the condition of the board

 

[franklyn]

I recapped the Mainboard last Year with Tantal ones and all was fine. The PowerSupply is original and not recapped.

 

[Phipli]

I recapped the Mainboard last Year with Tantal ones and all was fine. The PowerSupply is original and not recapped.

Excellent, just to verify, how did you clean the board?

Next is to pull the case off the power supply and have a look. There is a little daughter board in the PSU that has the same type of electrolytics as the logic board. They usually need doing. I suspect recapping the daughter board and repairing any damage it caused is your priority. I'd probably recap the whole PSU while I was at it, although I usually remove and test caps in PSUs rather than just replace them all. Cheaper and saves replacing good parts pointlessly.

 

[franklyn]

I think next is recapped the PowerSupply but my Voltagemeter say the +5Volt is fine ...

But I do it.


What surprises me is that the error sound takes a long time to appear. And when you plug in the power, the computer turns on immediately, which is strange ...

 

[3lectr1cPPC]

I do not necessarily think the PSU is at fault for this particular issue, but it MUST be recapped. The IIsi PSU uses ELNA LongLife Series caps which are the single worst in terms of leakage out of any I’ve ever seen. They’re replace on sight and you’ll regret not doing so later if you leave them alone.

 

[Phipli]

I think next is recapped the PowerSupply but my Voltagemeter say the +5Volt is fine ...

But I do it.


What surprises me is that the error sound takes a long time to appear. And when you plug in the power, the computer turns on immediately, which is strange ...

It could be noise on the power rail, or perhaps varying over time? You could stick a scope on it, but regardless, the PSU needs recapping to prevent further damage.

It still might be something else though.

 

[franklyn]

I soldered the one ram on the Powersuppy connector a little messily because you can't get to it without unsoldering the connector, it doesn't look that great but it's okay

 

[Phipli]

I soldered the one ram on the Powersuppy connector a little messily because you can't get to it without unsoldering the connector, it doesn't look that great but it's okay

How come you didn't replace C5?

 

[franklyn]

forgotten ...

 

[JC8080]

I have a IIsi that works before fine and now it take some time until the sound of dead sounds up. The motherboard looks good except for a little oxidation on the four 74ALS245 chips. I desoldered these all and cleaned everything up and checked connections and soldered on four new chips but the error persisted. Because the error sound takes so long to sound, it may not be the RAM?

Does anyone have an idea where I should look for the error?

I have a death-chime IIsi I have not been able to resurrect. It was working when I got it, then after a few uses it started the death-chime, though mine does the death chime rather quickly after the startup chime. I recapped my board, replaced all ALS245 chips, and replaced the onboard RAM with known-good chips harvested from 4x 256kb SIMMs. I am curious to see what you find with your machine.

 

[franklyn]

How come you didn't replace C5?

replace it but nothing has changed ...

 

[franklyn]

The PowerSupply caps looking good ...

... except the 56uF capacitor on the side that had leaked. I install some new electrolytic capacitors but not all of them ...


Is there a schematic from the Sony IIsi PowerSupply?

 

[robin-fo]

Is there a schematic from the Sony IIsi PowerSupply?

The schematic should be inside the BOMARC IIsi schematics document

 

[alectrona2988]

just noticed the coin cell socket, should try that even though my IIsi already has a working half AA pram battery because i just replaced it

 

[franklyn]

The coil cell works well but empties quickly !

 

[alectrona2988]

yeah, i'm sure it does... lol. they're definitely cheaper than the half AA batteries, and they don't last as long. but they're more convenient when you do need to replace the battery for sure.

 

[Phipli]

The main thing is they are much less likely to leak.

 

[franklyn]

The new electrolytic capacitors were in the mail today. I equipped the power supply with new electrolytic capacitors and now the IIsi reacts correctly to the power button and can also be switched off again, which was no longer possible before.

The chime of death is coming straight away now after switching on and the start chime come first up.



I have no idea what the problem could be. Don't think it's the Dram...