PM8500 no signs of life

[haemogoblin]

While i'm struggling with my Plus, i thought i'd drag my 8500 out the attic, it was my first ever Macintosh computer. So i have fond memories of using it. Hooked everything up and it powers up, lights up, but no boing, no picture, no nothing.

I've tried resetting the PRAM, which is via the button at the rear of the board, if i remembered correctly.

Was wondering if anyone has any thoughts

James

Spec

8500

Sonnet G3 333mhz

ATI rage128 PCI

Ram - can't remember

 

[Macdrone]

First as many say here, power cycle it a couple of times. If no life there most obvious next thought is motherboard caps followed by power supply. Very few macs have 100 percent tant caps (quadra 700 and 950 to date for me so far) and thus used or not they leak (look close as motherboard dust will usually look greasy).

Good luck

 

[haemogoblin]

I've been looking through past posts and one thing that came up was memory might need reseating.

Going to look at it further tomorrow, thanks for the suggestion. Obviously a bit concerned with it not making a single sound.

 

[Macdrone]

Try booting from keyboard power button rather than machine button, sometimes you can get some activity that way. But my other statements still stand.

 

[haemogoblin]

I have tried powering from keyboard, which did work. Is that any indication the logic board is working?

 

[classic]

If its got power going to it, your in with a good chance to get it functional again.

Do you still have the original daughter card?

Try booting with that.

If not, maybe the Sonnet processor may need reseating..

 

[haemogoblin]

I no longer have the original daughter card, i think it might...can't believe i'm going to admit this..it might have met the bin back in 2004-2005, when it's value was very little and i didn't see much point in keeping it...*headbutts desk repeatedly* DOH!!

I've had the logic board out, but i have not removed the ram. Only the pci cards and cpu card.

 

[Macdrone]

If it powered on from keyboard, the motherboard is probably fine but again recapping is probably due. Leaky caps will short the board and stop it from booting.If the board has no dust and the caps are original then thats probably enough reason to replace them.

 

[CC_333]

Hi,

This definitely sounds like it could be a capacitor problem.

This is a disturbing, if not inevitable time where eventually even late model G4s (and perhaps G5s) will need to be recapped.

I always thought this stuff lasted forever!!

But apparently that isn't so.

Enough of that: does this model have a SIMM-based ROM? You might try reseating that. Or if it has individual chips in sockets, carefully reseat those. Of course if it's soldered down, there isn't much that can be done.

c

 

[haemogoblin]

I had a thought and i want the Powermac owners input on this..

If my ATI video card was dead and motherboard has not video ram on board, as i removed it when i installed the video card. What would a powermac do? would it beep? or would it just power up and do nothing?

I can't find my video ram anywhere, so i'm guessing it went with the CPU card.

 

[ClassicHasClass]

If the video card failed, you could try removing the video card and seeing if you get a breaking glass sound. If this occurs, then good news: add VRAM, it was a bad card. If it doesn't, this doesn't necessarily mean you're hosed, though.

That said, I haven't heard of that sort of failure much.

Your other thing to do is reset the CUDA. I don't remember where this is on the 8500, but it looks like a little push button marked "CUDA RESET". If that doesn't work, unplug the unit, pull the PRAM battery, press the main power button, and let it sit for at least 10 minutes.

 

[haemogoblin]

I have pressed the CUDA it is locate at the rear of the case, near the CPU card slot. I need to check my PRAM battery, there's a damn good chance it is dead.

I tried booting the Mac with the cpu card removed and did not get anything from it. Would faulty ram cause this? I'm going to clean them all and reseat them.

Does anyone know where i can find some VRam? i have none which to test. I do have another PCI video card i can test, a vodoo3 in my B/W mac. Which was originally in this machine back when it was my main computer in 2004.

Thanks everyone for the help.

James

 

[haemogoblin]

well I have got it to boing, but no display out of either on board or PCI. If I remove the PCI card, it will boing but I get not shattering sound or display.

 

[Macdrone]

recap recap recap.

 

[haemogoblin]

Does anyone do a recapping service for these boards? I'm in the middle of reviving a Plus and simply dont have the energy to recap one of these boards.

Is there a way to test caps?

I've one last ace up my sleeve, going to take the vodoo card from my B/W G3 and try it in the 8500 and see what i get.

 

[ClassicHasClass]

Faulty RAM would not cause this. You would get the breaking glass sound if it detected it in POST, or random behaviour in the OS if it didn't, but it would at least get some distance into booting.

The machine will not start at all without a CPU card, because the CPU has to execute instructions from the machine's ROM.

Frankly, I think you have a bad video card based on your previous testing. It makes sense you would get no display from the internal video with no VRAM installed. The Voodoo would be my next move.

While recapping wouldn't be a bad prophylactic here, I don't think the caps are the problem in this particular instance.

 

[haemogoblin]

I shall retrieve the gfx card tomorrow and post my findings

if that wasn't bad enough, my power button broke, the plastic snapped :-( hopefully fix it with some super glue, otherwise turning the machine on and off with the lid on might pose a problem.

 

[trag]

The x500 class machines will power-on even if there is no CPU card installed, but they will not "bong". To get the "bong" or any other sound, you need a CPU card to run the Power On Self Test.

The reason they will power on even without a CPU card is that the little 7805 microcontroller in the CUDA chip handles the ADB bus and the Power-on logic. If it is getting 5V trickle, it's happy to turn the power supply on when someone presses the power switch either on the logic board or on the keyboard.

I think CHC's advice is spot on. Try another video card.

I think I have some VRAM around here. I'm trying to remember whether it only works in Catalyst-based machines (7200 and clones) or doesn't work in Catalyst-based machines. I know it has a flaw that causes one or the other, but I don't remember which. For that matter, I'm not all that sure where it is....

 

[haemogoblin]

Okay guys, spent a good portion of today working on this and i have found out of few things

1. If i remove all the ram and install the cpu card, the PM with give me the broken glass sound. Which stopped after i reinstalled two 32mb sticks in banks A3 & A4

2. The machine boings only when the CPU card is installed, in addition CPU card is getting warm.

3, If i disconnect the scsi hard drive and insert a floppy disk in the floppy drive, the PM with try booting from it and then spit it out, so the logic board is working me thinks

I have no VRAM and i am not getting a display from the onboard video port, however i am using a mac video to VGA adaptor with the dip switches. I'm pretty sure it works as i was last using it on my 6200.

4. I brought down my B/W Powermac from the attic and removed the video card which is a Radeon pci, not sure which. I tried the ATI Rage128 in the B/W and initially it didn't work, gave it a clean and it works fine. I then tried the radeon in the PM8500 and got nothing, the machine does not display a picture. I have tried it in every PCI slot.

Question - does the PM8500 have onboard video memory? As i have no VRAM will the machine even display a picture from it's onboard video port?

Oh in addition i examined the board and not one of the cap is showing sign of leakage.

James