Initialization hangs on Power Macintosh 8100/80

[V.Yakob]

Hi there!

The other day I got a Power Macintosh 8100/80, which has long wanted to experiment with vintage machines. But it turns out that the salesman wasn't honest with me and sold me a non-working...

The Mac turns on, there is a bong, the PDS of the video cards gives an image - the gray screen, sometimes the cursor appears there, they can be moved for a while then the machine completely freezes.
After I washed it from the age-old dust, removed the dried spider and the web, I put the motherboard on the antiseptic bag, connected the power supply and turned it on and immediately noticed that the processor was very warm.

I tried to boot without stick of RAM, Cache, FDD, CD-ROM, HDD, Keyboard - the situation is always the same.
In one of the attempts, when everything was connected, there was only one attempt to start the OS installed on one of the disks, but it was unsuccessful due to an extension failure. All other attempts in the last 3 days to make it work have been unsuccessful.

Is the motherboard damaged?
Could there be a problem with capacitors? It looks normal outwardly, but I understand that they are about 30 years old.

Has anyone had experience in restoring such machines?

 

[trag]

Have you removed the heat sink and cleaned off the old heat sink compound which has turned into useless chalk by now?

I first ran into this on a 7100. Very similar symptoms, except it would usually finish booting, at least the first time and then crash. One time I saw video artifacts that I knew (somehow? can't remember how) were sometimes heat related.

All of the X100 machines need their heat sink grease replaced. Probably they all needed it 20 years ago...

 

[V.Yakob]

@trag, Of course, the motherboard is washed from dirt and old thermal grease, the radiator is also washed. A new thermal grease that I use in all my Power Macs is smeared.
I found a motherboard with part umber 820-0557-B on sale, on the board I have 820- 0473-G. Are there different revisions of boards for the same Mac model again? I remember I learned with it with G3 MT. In the 90s, Apple apparently everything was really bad with the control.

 

[Kai Robinson]

Hi there!

The other day I got a Power Macintosh 8100/80, which has long wanted to experiment with vintage machines. But it turns out that the salesman wasn't honest with me and sold me a non-working...

The Mac turns on, there is a bong, the PDS of the video cards gives an image - the gray screen, sometimes the cursor appears there, they can be moved for a while then the machine completely freezes.
After I washed it from the age-old dust, removed the dried spider and the web, I put the motherboard on the antiseptic bag, connected the power supply and turned it on and immediately noticed that the processor was very warm.

I tried to boot without stick of RAM, Cache, FDD, CD-ROM, HDD, Keyboard - the situation is always the same.
In one of the attempts, when everything was connected, there was only one attempt to start the OS installed on one of the disks, but it was unsuccessful due to an extension failure. All other attempts in the last 3 days to make it work have been unsuccessful.

Is the motherboard damaged?
Could there be a problem with capacitors? It looks normal outwardly, but I understand that they are about 30 years old.

Has anyone had experience in restoring such machines?

Try not to put it on an antistatic bag - the bags themselves are conductive - put the board on a non-conductive surface. Have you installed a PRAM battery for it?

With x100 series Power Macintoshes - the ROM and Cache are both on a stick - you'll need at least the ROM SIMM installed to get it to chime. It can go in EITHER the ROM SIMM slot or the Cache SIMM slot since they're just bus-breakout slots that have identical connections.

 

[V.Yakob]

@Kai Robinson, A new battery is installed, the ROM is installed in ROM slot.
When I got it, here instead of a battery there was a design of 2x AA 1.5 batteries, as far as I understand, it only gave 3V, not 3.6V as it should be. One of these batteries was leaking, and it dried up.

 

[Kai Robinson]

Can you get a good quality picture of the logic board on its own, with nothing connected or plugged in to it?

 

[V.Yakob]

@Kai Robinson, Of course. I took the board out of the body.
Near some capacitors I see strange white traces, and like dust on the contacts, but it is not washed. At first I thought there was a leak, but it doesn't look like it.



Otherwise, except for some strange soldering on the board, I don't see any problems: The cache and ROM slots look normal, the stick ROM looks normal.

 

[Kai Robinson]

That's corrosion - you'll need to recap that board - the 'dust' is corrosive gunk from the capacitors for sure. Just because there's no visible signs doesn't mean the board hasn't been subject to it. All the solder joints on those caps are dull.

 

[V.Yakob]

@Kai Robinson, Thanx, I'll check it out -- I'll replace the capacitors and resolder other chips whose contacts look the same as in "dust".
When I'm done with this, I'll let you know the result.

 

[Kai Robinson]

Would be a good idea to clean board after removing the old ones, and before installing the new ones.

 

[V.Yakob]

Today I ordered 16V 47μF SMD capacitors, but delivery from China will probably be very long.
I also ordered a motherboard on eBay in case the trick with capacitors does not help to revive the motherboard.

820- 0473-G -- motherboard that was originally.
820-0557-B -- motherboard from eBay.

It will be interesting to look at the ROM version and generally compare the components on the motherboard.
I'll probably have some news in a month and a half.

This PM8100 will definitely work again!

 

[trag]

Is the 'new' board also an 8100/80? There were also 8100/100 and 8100/110s, IIRC.

And somewhere in there they changed the NuBus controller, I think. There was some detail about the original NuBus controller having na issue with I can't remember what and the new one being desirable for no reason I can remember. It was a deal at the time...

 

[V.Yakob]

@trag, The board says "Power Macintosh 8100/80"
/100 and /110 and AV options are other.
The /80 has an HDI-45 connector, and I also paid attention to this so that I would not have problems with installation and because of the possible differences in the case.

 

[trag]

Okay, I got nothing. I don't know about any board revisions beyond the speed changes.

The HDI-45 connector should be present on all X100 boards. If you find an 8100 board that lacks an HDI-45 connector, then it is almost certainly a Radius 81/110 board. Radius used the exact same board design and layout as Apple but ditched the HDI-45 in favor of a more normal monitor connector, which I guess lacks the AV features of the HDI-45.

 

[V.Yakob]

@Kai Robinson, You're right!
Today several capacitors fell out and tested them on the resistor tester, the results surprised me.
According to the marking, it is 16V 47μF, And in fact, μF has changed in 30 years.

I've always believed that the value can decrease, and here it increases.

 

[V.Yakob]

Checked the remaining capacitors.

Only 13 pieces:
7 --show knowingly incorrect values;
2 -- completely not working, because the tester could not determine them;
2 -- the values are close to marking, but I consider them defective;
2 -- looks completely working.

 

[trag]

Checked the remaining capacitors.

Only 13 pieces:
7 --show knowingly incorrect values;
2 -- completely not working, because the tester could not determine them;
2 -- the values are close to marking, but I consider them defective;
2 -- looks completely working.

Remember, the specs on the caps are likely +/- 20%

 

[V.Yakob]

Hey!!
The parcel from China arrived faster than planned. I got it yesterday and soldered the capacitors.
I've never soldered such capacitors before, it took a lot of patience to figure out how to do it. The textolite in two places has darkened a little due to many unsuccessful attempts.
However, it worked, now the computer boots and works fine. I have 2 SCSI drives that have Mac OS 8 and Mac OS 9.0.4. Mac OS starts up and looks good at first glance. And I finally found out that the memory bars are installed here - 4x16 Mb. Not enough.

Now I'll think about how to improve this computer.

Thanx guys, @Kai Robinson, @trag, for helping me in this matter.

 

[V.Yakob]

And so, time went by and I finally received a parcel with a different motherboard, as I understand a newer revision than it was.
This board was stored under normal conditions because I don't see any obvious signs of corrosion.

I installed this board, and everything seems to be working properly.
Moreover, the nubus ports apparently did not work on the old board, I have one SuperMac Thunder/24 video card that did not work there and was not even detected. Maybe there are some other malfunctions in that board or I overheated something with a soldering iron.

It works here.

Just in case, I'll leave photos of these motherboards here for history. Apparently, newer revisions of chips are used on the new board, because in general they do not seem to differ.