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6100: black screen, no boot, no BEEP, faulty mother board?


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Hi pals,

 

I just got a - externally looking - fine 6100.

I tested the power supply: OK.

I replaced the 3.3v battery: OK

I looked for macroscopic leaking from the capacitors: OK

the HD works fine, I connected it to another Mac: OK

I turned it on: black screen, no BEEP

5V, 12V stable: OK

reset PRAM

quick on-off-on

It turned it on: black screen, no BEEP, no HD activities

 

I did then a closed inspection at the mother board, and I saw some sign of corrosion (see attached photos) close to some SM capacitors.

It did not look so bad to me but I decided to do some cleaning with isopropyl alcool and a cotton swab.

WTF!! A small capacitor went off :(a very very tiny one, I believe it is a capacitor (it is visibile in a one of the pics). The fact that it went off some easily it means to me that the capacitors have leaked significantly.

 

I'll recap the mother board, but the tiny capacitor is very small, probably beyond my skills and tools.

Can anyone please provide some comments? 

Enjoy the photos

 

Please be kind to me :(

thanks

best

PF

detached capacitor

 

IMG_20201115_145204.thumb.jpg.426e0507ed06f80cbc34159e37da36cf.jpgIMG_20201115_145714.thumb.jpg.db16a2a80d667026a9e293ccc24db6e8.jpgIMG_20201115_145204.thumb.jpg.426e0507ed06f80cbc34159e37da36cf.jpgIMG_20201115_145213.thumb.jpg.bfbecf0212f8407c9cee6b3f946d644b.jpg

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I replaced all the capacitors, the picture shows only three of them and the tiny capacitor I was somehow able to solder back (it was rescued from another device, same colour of the original that went lost :().

I tested the continuity from each capacitor pin and the trace it's laid, everything looks fine, I checked the polarity numerous times.

I assembled it back.

Same checklist as above: it chimes as the fist but then I hear the nasty car crash sound, of course still a black screen.

I tried with another pair of SIMM I had, known to be working, but with no luck.IMG_20201116_223516.thumb.jpg.922f8efa9446a7e272c4bf34a7195e9c.jpg

Ah, the hardware reset works.

 

Any hope?

thanks 

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31 minutes ago, ironborn65 said:

If the Mac plays the crash crash sound after the startup bong can I assume at least the CPU is not compromise?

 

Yeah, that is... it being well enough to notice it is unwell, if that makes sense.  About how long is the interim between the chime and the crash?

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Do you have a way to hook a monitor up to it? If so, do this and see if you get an error code. I should note that the 6100 needs the battery to output video at a cold boot, without a battery you will need to reset the machine by either hitting the reset button or quickly power cycling it after the first boot chime, to get a video signal. So don't be alarmed if you get no display on a "normal" cold boot.

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thanks Daniel, cheesestraws for the reply.

 

I tested the power supply: OK.

5V, 12V stable: OK

I replaced the 3.3v battery: OK

I recapped the mother board, please notice the replacement  of the tiny capacitor (is it?) near C94 C95 C97. It came out and lost when cleaning, I replace with one of the same color from a scrapped device.

Monitor connected

I turned it on: black screen, classical chime and after about 1 sec i got the chime of death (car crash)

 

I did several tests:

reset PRAM

quick power cycle

remove the RAM SIMM, just the on board RAM

switch ROM to the other slot

no SCSI cable, no floppy cable

 

Every timer I turn it on:

black screen, classical chime and after about 1 sec the chime of death (car crash)

 

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10 hours ago, ironborn65 said:

I turned it on: black screen, classical chime and after about 1 sec i got the chime of death (car crash)

 

What happens if you power it on, wait for the chime of death, then do a reset (note, not a power cycle)?

 

 

10 hours ago, ironborn65 said:

what is it?

 

The Egret is a chip that deals with quite a lot of miscellaneous functions associated with the CPU.  It's a bit notorious for getting cap gunk stuck under it and failing for that reason.

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On 11/20/2020 at 10:31 AM, cheesestraws said:

The Egret is a chip that deals with quite a lot of miscellaneous functions associated with the CPU.  It's a bit notorious for getting cap gunk stuck under it and failing for that reason.

can u please help me to locate the chip? I can not find schematics or a MB layout 

thanks

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3 hours ago, ironborn65 said:

can u please help me to locate the chip? I can not find schematics or a MB layout 

thanks

It's U11. It's in the right upper corner (with the I/O ports pointing upwards), under C3. If C3 leaked, it's very likely the EGRET has gotten gunked up.

 

EDIT: It's seen in your picture here, 341S0788:

 IMG_20201115_145204.jpg

Edited by Daniël Oosterhuis
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Thanks Daniel, that area is not very clean, the cap leaked, as you can tell from the greenish around it.

At this point I have IMO some options:

- desolder it, clean it and put it back. I do not have special tools, I'm just good enough to solder SMD tantalum capacitor, it's probably behind my skills and I do not want to make practice on an Apple MB.

- put it the dishwater for a couple of rounds

 

Reading around, a mixture of water and acid citric (lemon) would help removing the conductive acid of the capacitor.

Isopropyl alcohol does not help, it's good for removing flux

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2 hours ago, ironborn65 said:

finally I got it working! Lovely!

I did a thorough cleaning, using vinegar, I also re-soldered a couple tantalum SMD, my bad one was loose and it booted up!

But ... now the audio is not working, it make some white noise for a minutes or so, then it stopped.

It might be another DMS.

Thanks you all!

 

That could be the Crystal Audio IC on the board. On a PowerMac 8100 board that I got from Japan, the caps too had leaked fairly heavily, and it seems to have killed the audio chip, even despite the fact I didn't power it up until after recapping and cleaning. Mine's just making horrible digital noise, so I think that's the DAC in the chip audibly failing. Yours might be bad too, if there are no signs of corossion or damaged traces or components around the chip or other parts of the audio circuitry. The part number on the chip is CS4217, they seem to still be for sale relatively affordable online, though as usual, beware of fake/dead remarked chips from China.

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still there are strange (to me) issues

After re-controlling and re-soldering again some SMDs to try to make the sound work (before committing to replace the sound chip) ... the motherboard did not boot at all, sadness:

- silent

- with additional RAM, with only onboard RAM

- the PSU provides stable and precise voltage

- the CPU goes up to 48 degrees centigrade 

- I replaced the silicone heatsink compound 

- PRAM battery ok

- rapid on/off/on

- reset keyboard

- recapped of course

 

I was almost due to store it in the RIP section of the self, when is started to show life, flashing bands on the screen first, restart again, then the smiley face, it freezes, restart again ed again .... apparently it works only when warm.

The more it warms up the more likelihood that it boots and it remains on till the OS allowing me to work with it, but it might still freeze.

Ah, the rest button does not work, all the section is rusty and not in good conditions.

I was looking around those STEWARD ICs, any clou what they are for? I could only find a Chinese only web site

thanks

 

PS: the camera decided to apply HDR, the pads are not so bad

 

IMG_20201129_233820.thumb.jpg.e8d8052410c1fcb1baa85faf7bea4087.jpg

 

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