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Figuring out dead PowerMac 6100

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This one has stumped me. It has the symptoms of a broken CPU but I've got two boards and they both don't LOOK broken. I've also got two power supplies, two ROM SIMMS, multiple RAM sticks. None of these parts mixed together produces a working 6100... When power is applied the power light comes on, PS fan spins up, I see the keyboard LEDs blink but then absolutely nothing else happens. No chime, no video, no evidence that it's trying to boot off HD or floppy. Tried with a good PRAM battery and doing the on-off-on trick.

 

What am I missing here? I don't see caps leaking but even with caps going bad I suspect the machine would still show some life. Pretty sure the thing worked before I stored it so I have no idea.

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Likely caps still. All of these should be re-capped immediately. In the process of refurbishing my fleet, I won't even attempt to power them on without re-capping first (lest I cause damage). I'd start there and then see how it works out.

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They are on the tip of needing them. If you figure, given that we are at 2019 practically, that would make the oldest Power Macs roughly 25 years old or so. None of my classic Macs from the 1980s needed anything 10-ish years ago, and now they all need some work. Time sneaks up on you like that.

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Ive ran into a Power Mac 8100 and even an 8500 that needed capacitors replaced on the logic board in order for them to boot, before they had no chime and a blank screen, ive heard of 6100s needing logic board and PSU caps replaced as well.

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OK well I'm feeling a little better about my situation then. I don't mind doing the recapping so long as it may help fix my problem and I'm not just wasting time on a dead board. I'll order up the caps I need for the job and try this within the next couple of months I guess.

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Also make sure you're running with an actual ROM, not a cache card. If you have a proper ROM and a cache card installed, try removing the cache card. I've had a few cache cards go bad and prevent the Mac from booting.

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On 12/31/2018 at 7:59 AM, AwkwardPotato said:

Dang. I guess I should look into recapping my 6100. :-/

For sure.  I recently recapped a 6100 where the caps were literally falling off the board at the slightest touch.  The thing is it worked fine a year ago.

I also have an 8100 and I checked the caps on that board and they are not showing any signs of leakage or corrosion as the solder joints are still shiny.  I will still recap it within this year though, just to be safe.  

 

Those were made in 1994 so next up would be my 7200 or 640CD, although neither of those show any leakage or even a hint of corrosion.

Edited by Zippy Zapp

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All the PowerMac x100 machines are nearing the age of capacitor failure. I’d say at the moment most will probably run fine, but definitely the first wave of dead caps has arrived for them. Another few years and I think we will be at the point where a majority of them will be needing new caps.

 

And so time marches on :)

 

If that doesn’t work let us know and we can go from there.

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21 hours ago, Franklinstein said:

Also make sure you're running with an actual ROM, not a cache card. If you have a proper ROM and a cache card installed, try removing the cache card. I've had a few cache cards go bad and prevent the Mac from booting.

 

Yeah I've got two ROM cards and one cache card, already tried running it without the cache card.

 

I'll be trying the board recap first and see what happens.

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do you have a good battery?  If not the 6100 needs a power button double tap.  Turn on, turn off then turn on again.  6100 will need caps but should work, but a bad battery will require a double tap to boot.

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Second the battery advice.   The 6100 is one of the few models that doesn't power on properly with a flat battery.

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On 2/5/2019 at 8:03 AM, Macdrone said:

do you have a good battery?  If not the 6100 needs a power button double tap.  Turn on, turn off then turn on again.  6100 will need caps but should work, but a bad battery will require a double tap to boot.

Yeah I tried a new battery from a small stash I ordered last year and didn't make any change. Also tried the double tap method. I haven't gotten around to the recapping yet but I'll try that first and hopefully it solves my problem. 

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On 12/31/2018 at 7:52 AM, Johnnya101 said:

I've never run into a power Mac that needed caps, hope this isn't the start of them.

 

 

 

My 1995 7100/80 has started to have its caps leak after being in storage for years in a semi parts state.

 

Oddly my older 1994 7100/66 hasn’t leaked yet, nor have my collection of HPV and AV cards.

 

These early PPCs are a pain to recap. So many SMT electrolytics were used by Apple to cut costs instead of the Tantalums commonly used on the Q800/650 and Q950. Usually the higher end machines got tantalums but right around the Q840 launch that changed.

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I don't mind the recapping. I don't do a pro job because I only care about functionality over how clean the job is, so it isn't overly difficult for me to get it done. I'm just super lazy with getting projects going so I have yet to recap the 6100.

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Have you looked under the heat sink?   Every 7100 I've had my hands on needed its heat sink paste cleaned off and replaced.   I don't know why the 8100s and 6100s didn't but that was 15 years ago.   I imagine all the NuBus PowerMacs need their heat sink paste replaced by now.  Still, you would get a good start up bong if the problem was just bad paste.  Bong and then immediately overheat...

 

So, look under the heat sink and check whether the CPU is cracked.  It's usually possible to tell by eyeball.

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1 hour ago, trag said:

Have you looked under the heat sink?   Every 7100 I've had my hands on needed its heat sink paste cleaned off and replaced.   I don't know why the 8100s and 6100s didn't but that was 15 years ago.   I imagine all the NuBus PowerMacs need their heat sink paste replaced by now.  Still, you would get a good start up bong if the problem was just bad paste.  Bong and then immediately overheat...

 

So, look under the heat sink and check whether the CPU is cracked.  It's usually possible to tell by eyeball.

I had looked under the heatsink before and the CPU did not look like it was cracked, and after my recap I also cleaned the CPU to add more heatsink compound. I've been super careful with the heatsink but I suppose something may still have broken at some point. I have a spare board with the exact same symptoms and the CPU looked OK on that one too. Now I'm not sure if I have two faulty boards or two faulty power supplies or who knows.

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This is the kind of thing that having a local club was good for back in the old days.    Then you could just find a fellow member with a 6100 or compatible power supply and test it.   

 

If I had to guess between two bad power supplies and two bad logic boards, especially after a recap, I'd guess power supplies.  

 

Also, are you certain you have the correct ROM module?  I can't remember the part number off the top of my head unfortunately.  I have it written in a lab book at home.   I ask because the form factor is the same as for the entire X500/X600 PCI PowerMac series (although most of those had soldered ROM) and also the same as the Beige G3 ROM.  A little Googling suggests that Apple 341-0741 is the correct part.  I think the 0757 will also work though.

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Idea: Contact Cleaner.  CRC QD from an auto parts store works wonders.

I have had that stuff fix inexplicable problems. Spray down the RAM SIMM slots, ROM slot, and cache slot. Heck, just bathe the whole board in the stuff, it evaporates.

 

 

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12 hours ago, trag said:

This is the kind of thing that having a local club was good for back in the old days.    Then you could just find a fellow member with a 6100 or compatible power supply and test it.   

 

If I had to guess between two bad power supplies and two bad logic boards, especially after a recap, I'd guess power supplies.  

 

Also, are you certain you have the correct ROM module?  I can't remember the part number off the top of my head unfortunately.  I have it written in a lab book at home.   I ask because the form factor is the same as for the entire X500/X600 PCI PowerMac series (although most of those had soldered ROM) and also the same as the Beige G3 ROM.  A little Googling suggests that Apple 341-0741 is the correct part.  I think the 0757 will also work though.

Yeah I've got two power supplies and I opened one of them without seeing any OBVIOUS problems... The ROM and L2 chips in there now are what was in there when the system used to work. I did get another ROM on ebay and remove the L2 chip but nothing changed. Symptoms unfortunately point to broken CPU, but it really didn't look broken.

 

5 hours ago, IIfx said:

Idea: Contact Cleaner.  CRC QD from an auto parts store works wonders.

I have had that stuff fix inexplicable problems. Spray down the RAM SIMM slots, ROM slot, and cache slot. Heck, just bathe the whole board in the stuff, it evaporates.

 

 

Actually yes I will be trying something like this, or potentially more absurd like a run in the dishwasher. I dishwashed my LC board for fun when it was completely dead and works just fine now.

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