7100 no video

[joshc]

Got a 7100 that won't output video.

It chimes, the CPU gets warm and the BART chip (NuBus controller) gets warm, nothing else seems to.

Tried two different NuBus cards, PDS video card and onboard video (HDI-45) with no luck.

I have done the following:

- Replaced all electrolytic capacitors
- Tested without any RAM, so only using onboard 8mb
- Tested with nothing connected to internal or external SCSI
- Tested with no cards installed
- Reseated ROM, cleaned ROM socket/ROM card pins (already knew ROM was ok as I get a chime)
- Testing with a good PRAM battery
- Tested the PSU's output voltages, 5v and 12v are almost exact and stay that way
- Left it running for a bit, tried numerous reboots, tried PRAM reset, nothing made any difference

Looking at the block diagram, the common link betwen the external video, PDS and NuBus is the data path - but I'm not sure what to try/look at next?

 

[cheesestraws]

This is the point where I tell you once again that your life would be significantly easier with an oscilloscope, isn't it

 

[joshc]

isn't it

Yes, yes it is.

 

[MacKilRoy]

I have some VRAM SIMMs that are problematic on my LC, and they just show black screen (the monitor shows input but nothing is displayed). The 7100 uses system RAM for video, what if the part is the RAM that is used for video is bad (or a trace to that part)?

 

[joshc]

I have some VRAM SIMMs that are problematic on my LC, and they just show black screen (the monitor shows input but nothing is displayed). The 7100 uses system RAM for video, what if the part is the RAM that is used for video is bad (or a trace to that part)?

I thought that would result in death chimes as the whole 8mb onboard would be checked at startup?

 

[slomacuser]

I have the same problem with 6100. I had it working with Nubus card and suddenly it went blank. So I I thought the Nubus card broke. I connected than the monitor to the built-in video output and it worked, ... for a while, the built -in video went off too. Replaced the cache and ROM and RAM with the working ones, the same result. The 6100 shows no video anymore. The board is reccaped...

 

[joshc]

Interesting. The 6100 shares the same architecture and a lot (all?) of the same custom chips I think with the 7100 and 8100. @slomacuser Do you have a scope that you could use to poke around a bit and see what's happening on the data bus? Does the CPU still get warm on your 6100?

 

[MacKilRoy]

Just curious, but is the machine booting with no video, or is it hung up on chime and black screen? Question to both JoshC and SlowMacUser.

One way to check would be to let it sit long enough to boot and hit power key on keyboard to see if an alert beep is sounded when mouse is clicked.

 

[slomacuser]

I do not have scope. Mine 6100 is in a box in a garage, will have to take it out to test again ...

 

[slomacuser]

Any news on this @joshc ? I tested mine 6100 again. No bong, no video. CPU is cold, Cache is warm. ROM, RAM cold. Some other chips are hot ...

 

[joshc]

No progress. Without a scope I can't properly diagnose it. Hanging onto the board now as it might be good for components salvage. Yours could be a bad CPU as you get no chime @slomacuser

 

[slomacuser]

Could be these bubbles on cpu?

 

[CC_333]

@slomacuser I'm not an expert in these maters, but I think those bubbles are the least of your problems, for that CPU die appears to be cracked, unless that's just discoloration from partially cleaned old thermal paste?

This isn't related to @joshc 's problem per se, but it might offer a clue or two: I had a similar problem with my PowerBase years ago (boot with chime, no video, no disk activity, no death chime). It turned out to be a bad L2(?) cache module, which I discovered when I chanced upon a working PowerBase logic board with its own RAM and L2 (the cache from the new board worked in the previously dead old board).

c

 

[cluster_fsck]

So, my 7100/80 just started exhibiting the same behavior -- no video from either the onboard video or the PDS video card. Tried zapping the PRAM, but that didn't help either. I don't see anything that looks out of sorts on the logic board (at the least the top-facing side - I haven't pulled it completely out). I guess I'll go and remove all the various pluggable chipsets and reseat them, but kinda stumped. I just got my BlueSCSI in the mail and was getting ready to upgrade it this weekend

 

[Fizzbinn]

So, my 7100/80 just started exhibiting the same behavior -- no video from either the onboard video or the PDS video card. Tried zapping the PRAM, but that didn't help either. I don't see anything that looks out of sorts on the logic board (at the least the top-facing side - I haven't pulled it completely out). I guess I'll go and remove all the various pluggable chipsets and reseat them, but kinda stumped. I just got my BlueSCSI in the mail and was getting ready to upgrade it this weekend

PRAM battery okay?

 

[cluster_fsck]

PRAM battery okay?

Yeah, I ended up reseating everything I could on the motherboard and then got it back to life. Replaced the 700MB Quantum drive with a BlueSCSI this morning and rebuilding the system now. So strange not to hear the chatter of the spinning disk as it boots, though.

 

[MrFahrenheit]

I have a question regarding the 6100/7100/8100 and video on boot process.

These machines require a good PRAM battery to initialize on-board video. What happens on a known good working machine where the PRAM battery is missing or dead, and you try booting with video connected to a NUBUS video card instead of using on-board? Or is the internal video needed for first boot to set the primary video to external (upon reboot)?

I have not used multiple video cards much in Macs and someone has asked me whether their 8100 is dead or not, because there is no video output to a NUBUS video card at the moment (and they do not have a HDI45 adapter to try internal video).

 

[joshc]

What happens on a known good working machine where the PRAM battery is missing or dead, and you try booting with video connected to a NUBUS video card instead of using on-board?

I am pretty sure it's the same behaviour regardless of how you're trying to get video, but I'd love to know for certain and I am interested in knowing more about what these Macs do that requires the 3.6V battery to output video.

 

[MrFahrenheit]

I am pretty sure it's the same behaviour regardless of how you're trying to get video, but I'd love to know for certain and I am interested in knowing more about what these Macs do that requires the 3.6V battery to output video.

Yeah, I’m not sure why Apple engineered the x100 PowerMacs to require a good PRAM battery just to boot. But it’s definitely a thing as I’ve run into it on all my boards myself. I don’t have a video card I can try on one to experiment with.

There is an HPV card that apparently works, on eBay right now for $30 free shipping. I’m considering buying it so I can experiment.

@joshc Did you ever get any further answers with your 7100 board ?

 

[joshc]

@joshc Did you ever get any further answers with your 7100 board ?

I didn't and I ended up using it to pull some parts from (spare sockets etc) so it won't get fixed now. Definitely one that needed a scope to do some investigation on.