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7100 with various problems, namely no video

tattar8

Well-known member
I got my hands on a barebones 7100, in not the best shape. I cleaned the logic board, but have not yet recapped it (I'll do that eventually, but caps take a few days to arrive and I want to make it work before then if possible). I'm using a modded ATX PSU since the stock one immediately turns off.

When I power up the machine, I get a chime, but only out of the headphone jack. I'm assuming there's an issue with the switch that tests for the presence of headphones, since the jack is super rusted. After that, I get no other signs of life. I connected a SCSI2SD hoping it would try to boot off it and I would see activity on its LED, but no dice. Any ideas? This machine doesn't have its PRAM battery installed, so I also tried the on-off-on trick.

I don't have one of those HDI-45 adapters (they cost an absurd amount on eBay), so I'm just trying a NuBus video card I had laying around (an eMachines one) since I read that these machines work with NuBus video. Are there any restrictions on them?
 

tattar8

Well-known member
Upon further research, I came across some info that suggests that the 4 1st generation Power Macintosh lines all need to have something in the PDS slot to boot. I currently have nothing. However, the service manual for the 7100 says that it must be a video card. Does that mean that I can't get one of the terminators from the other lines to put in there?
 

trag

Well-known member
Any of the PDS video cards (A/V card or HPV (High Performance Video) card can go in that slot. Or one of the G3 upgrades. Or a terminator board.

And yes, Apple stated that something must be in that slot for proper operation, although I've heard from a number of folks operating with it empty. YMMV

The PDS slot is the same for all four machines, so any card from any of them would be okay in the 7100.

On the 7100, at this age, it is essential to clean the old heat sink grease off of the CPU and the heat sink and apply fresh compound. Be careful not to over-apply the new compound. It only take a little dab. You don't want it running off onto the CPU pins. That can cause shorts and kill the board.
 

tattar8

Well-known member
I'm getting intermittent chimes of death (well, car crashes of death), so something is definitely up. I guess doing something about the PDS slot should be my top priority. Turns out those terminators are super hard to find, since they apparently only came with the 9150, itself a super-rare machine, and a couple of clones, so I might as well just grab one of the video cards since they're pretty cheap.

I did notice the dry thermal compound when I took off the heatsink for my cleaning of the board. I ordered some Arctic Silver to replace it, but in the meantime, that should only be an issue if the computer has been on for a while, right? It wouldn't overheat so quickly that the board can't even boot?
 

Byrd

Well-known member
Ideally go for the faster HPV PDS graphics card, the PDS AV card also has it's merits though if you want some input options. Both are pretty cheap.

Dry thermal paste on a crappy little heatsink on the 7100 is like wrapping it a blanket as soon as you turn it on. The 601 CPU on the 7100 is incredibly fragile and I've come across a few boards where the core has cracked, perhaps from overheating. I'm amazed Arctic Silver is still sold - it's horrible stuff being conductive; be careful not to smudge your fingers somewhere to avoid shorts.

JB
 

demik

Well-known member
I'm getting intermittent chimes of death (well, car crashes of death), so something is definitely up. I guess doing something about the PDS slot should be my top priority.

Intermittent chimes of death can come from the ROM or Cache sockets. Try to remove and reseat them to see if it's any better. Both slots and the PDS slots share a lot of data/address lines.

I've seen 7100s running fine without anything in the PDS slot as well. The Logic Board is really similar to 6100s which do run without anything in the PDS slot. However, as you find out, some revisions have strange bus issues which are resolved bu putting something on the PDS slot. Sometimes adding or removing a cache, helps as well.

Hope that helps
 

tattar8

Well-known member
Wouldn't a poor connection to the ROM prevent the chimes (both boot and death) from playing at all, since that's where they're read from?

I don't have anything in the cache slot at the moment, I guess I should get something then.
 

tattar8

Well-known member
I did find that the death chimes always come when I do the on-off-on trick, and never when I don't -- so not really that intermittent. I also found that moving the ROM SIMM to the cache slot doesn't change anything.

At this point, I have a cheap card for the PDS slot coming this week, as well as caps to recap the board, so I hope one of them helps.
 

trag

Well-known member
I did notice the dry thermal compound when I took off the heatsink for my cleaning of the board. I ordered some Arctic Silver to replace it, but in the meantime, that should only be an issue if the computer has been on for a while, right? It wouldn't overheat so quickly that the board can't even boot?

I had a problematic 7100 and overheating would happen before the machine could finish booting. If not completely cold (after several attempts) it could crash before looking for a hard drive.

The PPC601 overheats really fast if not cooled properly.

If you've got chalky compound on there, I wouldn't power the thing on again until you've had an opportunity to clean it off and replace it.
 

tattar8

Well-known member
I was trying to research whether that was the case or not, so thanks for the tip. I also sorted out the thermal compound and reattached the heatsink, but no dice.

Is it normal for the reset button to not always properly reset the machine? Many times I'll press it, hear the audio pop, but no chime.
 

joshc

Well-known member
Does the CPU heatsink get hot while the machine is on? Some 601s suffer from cracking or shorted pins.

Depending on the answer to the above, if this machine isn't recapped yet, I wouldn't diagnose/troubleshoot further until you've recapped it. The 7100 is from 1994/1995 - so those caps are quite old now and definitely due for replacement. The board should be well cleaned too.
 

tattar8

Well-known member
Yes, the heatsink is hot. I would think that if I hear the chime at all then the CPU is actually running and thus not cracked, right?

I've ordered the caps but they won't come until next week, so might as well just sit tight for now.
 
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