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First post, snagged an S900 in great cosmetic shape, but with problems

kruuth

Active member
Hello everybody. This is my first post here.
Today at an estate sale, on a shelf in a garage was an original S900 box. I figured it to be empty but it looks like there's a unit, dusty but otherwise in great shape on the outside. They wanted a whopping $15 for it. Anyway, I got it home, plugged it in and nothing. Battery is most definitely flat, so I'm trying to test the PSU. Are these flaky? I find an article on how to convert an ATX power supply but I'm a little scared to do that because I don't trust my skills much in this respect, also it looks like mine only has three connectors, a really long one and then a short one, and an even shorter one. Is there something I can to to test the PSU? I tried jumping the two outside pins on the three-wire plug but nothing happened. I opened the PSU and I only see one fuse, but it tests ok. What is the next thing I should check? I'd really like to get this working again.
 

Juror22

Well-known member
Incredible find, at a fantastic price! (forgive the hyperbole, but that is a really amazing deal)

I don't know how to help with troubleshooting your find, but I'm sure there are some here that will know what steps to take next. Do you have any pictures?
 

trag

Well-known member
@kruuth Start with the simple stuff. I think there's a toggle on the power supply on the back. I may be misremembering, but if it's there, make sure it's in the 'on' position.

Some times one must hold the power button of the front panel for a few seconds to achieve power on.

If that is getting no results, then there's probably a problem with the power supply. The power supply should turn on and the fan start spinning, even if there's no CPU installed or the motherboard is otherwise dead.

Although, the power supply needs to be properly connected to the motherboard. A hard drive might need to be connected as well. Some times a power supply won't detect enough load without a connected hard drive. But I think in that case, the PS fan would start to spin and then stop. Also, if there's a short on the logic board that could prevent the PS from starting up. Power supplies have a few safety features to detect no load or a short.

There are four connectors to the motherboard. Three six pin connectors and a 3 pin connector. Some times two of the 6-pin connectors are combined into a single 12 pin connector.

If the three pin connector isn't connected the machine won't power on.

And I guess if the wires from the power button to the logic button aren't connected to the headers on the motherboard properly then that would be an issue as well -- although in this single case, one should be able to power on with the power button on a connected keyboard.

I don't have a single working S900 power supply at this point. I haven't for years. They've all been replaced with adapted ATX supplies. They started failing back in 2002 (or earlier) when I wrote that article about building an adapter....

We've also seen the S900 logic boards start to fail because of leaky capacitors. This is an issue for pretty much all old electronics. They're not difficult to replace, but if you're not confident about wiring a power supply adapter, replacing motherboard capacitors probably isn't on your want-to-try list either.

You're in the right place though. Lots of people here have been dealing with similar issues on old machines.
 

kruuth

Active member
@kruuth Start with the simple stuff. I think there's a toggle on the power supply on the back. I may be misremembering, but if it's there, make sure it's in the 'on' position.

Some times one must hold the power button of the front panel for a few seconds to achieve power on.

If that is getting no results, then there's probably a problem with the power supply. The power supply should turn on and the fan start spinning, even if there's no CPU installed or the motherboard is otherwise dead.

Although, the power supply needs to be properly connected to the motherboard. A hard drive might need to be connected as well. Some times a power supply won't detect enough load without a connected hard drive. But I think in that case, the PS fan would start to spin and then stop. Also, if there's a short on the logic board that could prevent the PS from starting up. Power supplies have a few safety features to detect no load or a short.

There are four connectors to the motherboard. Three six pin connectors and a 3 pin connector. Some times two of the 6-pin connectors are combined into a single 12 pin connector.

If the three pin connector isn't connected the machine won't power on.

And I guess if the wires from the power button to the logic button aren't connected to the headers on the motherboard properly then that would be an issue as well -- although in this single case, one should be able to power on with the power button on a connected keyboard.

I don't have a single working S900 power supply at this point. I haven't for years. They've all been replaced with adapted ATX supplies. They started failing back in 2002 (or earlier) when I wrote that article about building an adapter....

We've also seen the S900 logic boards start to fail because of leaky capacitors. This is an issue for pretty much all old electronics. They're not difficult to replace, but if you're not confident about wiring a power supply adapter, replacing motherboard capacitors probably isn't on your want-to-try list either.

You're in the right place though. Lots of people here have been dealing with similar issues on old machines.
It looks like I only have three Mobo connectors. One longer one, single pin row. The next is shorter, then there's the three pin you mentioned. I checked the board, but I don't see any leaky caps on there. The PSU doesn't look as though there's a power switch on it, only a toggle between 115 and 220. I can post a picture of the connectors. I mentioned this to my neighbor and he offered to help me solder something but he read hoping for a 1-to-1 wiring list but the I've that we found, the colors don't match.
 

iJol

Member
It looks like I only have three Mobo connectors. One longer one, single pin row. The next is shorter, then there's the three pin you mentioned. I checked the board, but I don't see any leaky caps on there. The PSU doesn't look as though there's a power switch on it, only a toggle between 115 and 220. I can post a picture of the connectors. I mentioned this to my neighbor and he offered to help me solder something but he read hoping for a 1-to-1 wiring list but the I've that we found, the colors don't match.

Hey,
I got two S900s a few months ago and also had issues with the PSU of one unit.

Swapped them around, but one PSU was dead.

So I've did this ATX conversion and the colors of the three-pin connector didn't match too, but with a little bit fiddling around (and find out, that maybe not the PSU but the 3-pin connector from the original PSU was the error) it now works with a stock ATX power supply.

Note: in the description, there are two J20 connectors but in my machine, there is one big connector. The colors are the same.

I have SCSI issues with the ATX-conversed S900, don't know if its the missing -5v rail of the ATX PSU or something with the HDD/CD-Termination-crap.
 
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trag

Well-known member
So I've did this ATX conversion and the colors of the three-pin connector didn't match too, but with a little bit fiddling around (and find out, that maybe not the PSU but the 3-pin connector from the original PSU was the error) it now works with a stock ATX power supply.

Geeze, does nobody read? While the wires in that article are labeled with colors it is the order in which they are listed that matters. It matches the order the wires appear on the connectors. The article clearly states:

*Note that you should identify the wires by their positions on the connectors. You cannot count on the wire colors in your power supply matching the wire colors in my power supply.*
 

CircuitBored

Well-known member
I have an S900 myself and did a fairly big writeup of my trials and tribulations with it earlier this year. Here's a link.

The long and short of it is: clean and deoxidize everything. The connectors on the S900 aren't the highest quality and it seems common that they oxidise and start to form bad connections. I had to use WD-40 contact cleaner on everything before the machine started booting properly. The biggest oddity was the socketed ROM on the graphics card, which had oxidised so badly that the legs were black! A simple cleaning with isopropyl alcohol brough the card back to life. Starting out with cleaning the RAM, PCI and CPU sockets in your S900 will put you in a good place. You should remove the ethernet/serial module and clean both the socket and pins too.

With regard to the power supply: they don't like starting up without any load. I've never been able to get my S900's supply to start up without connecting it to the logic board. If you end up replacing your power supply with an ATX power supply I ask that you consider sending your old one to me, as I would like to investigate why these supplies fail. I still have a working S900 supply (touch wood) so can easily cross-examine the working and non-working units to ascertain precisely which component has failed.

I have a few thoughts based on your photos:
  • Your RAM is installed wrong. In the S900 you need to install the RAM in an A-B-A-B-A configuation, meaning the first four RAM sticks in the first, third, fifth and seventh RAM slots. If you install a G3 or G4 upgrade card then memory is addressed differently and you need to install the RAM in an AAAA-BBBB configuration, using the first four slots first and then the next four when the others are filled. Don't try to use an odd number of sticks - it just causes trouble.
  • On the topic of RAM you should double check that your RAM is the correct specification (168-pin, 5 volt, 64-bit wide, Fast Paged, with 70ns access time or faster, per Supermac Insider) and is in fact working. You'll need a known-good PCI PowerMac or Performa to check this.
  • There is a small, white circular thing over one of your RAM slots, marked "TLE F/T 11". I do not recognise this part and you should check what it actually is.
  • You still have the original CD drive installed, which is not a high quality item. These drives are generic versions of the drives Apple used in PCI PowerMacs and Performas (which were also bad) and can cause real trouble. For testing purposes I suggest you do not hook up this drive yet. If you have the means you should install the OS on the hard drive using a different machine. It's painful trying to boot OS 9 install media from the generic optical drives and I advise that you do not bother. If your power supply is flaky then the CD drive won't help things, as it draws a relatively large amount of power.
  • Your graphics card is installed in the second PCI slot. The S900 has an extremely picky PCI bus and you should move the card to the first slot. Theoretically it makes no difference but I have seen the opposite in practice.
  • Disconnect your SCSI devices (power and data) until you have been able to get the machine to boot to the flashing [?] floppy disk screen. This is a necessary troubleshooting step to eliminate SCSI as a source of trouble. These clones have problematic SCSI buses now that they're getting old. I don't use SCSI on my S900 at all. Instead, I am using a reflashed SIL3112 PCI SATA card for my boot disk.
Don't let this wall of possible problems dishearten you. I had an equally non-functional S900 when I first got the system but now it is one of the crown jewels of my collection. They're beautiful and brilliant machines with a fascinating history. They have plenty of quirks but this is vintage computing so that is par for the course.

Good luck with your S900 adventure. Be sure to keep up updated!
 

trag

Well-known member
Lots of good stuff in the above posting, but this part:
Your RAM is installed wrong. In the S900 you need to install the RAM in an A-B-A-B-A configuation, meaning the first four RAM sticks in the first, third, fifth and seventh RAM slots. If you install a G3 or G4 upgrade card then memory is addressed differently and you need to install the RAM in an AAAA-BBBB configuration, using the first four slots first and then the next four when the others are filled. Don't try to use an odd number of sticks - it just causes trouble.
is just wrong.

I have no doubt the poster had some experience that convinced of that, but in general for S900s and other PowerSurge Macs, it's not true.

If you have identical RAM, you want them installed in corresponding slots A1, B1; A2, B2 to enable interleaving and gain a performance boost. The only reason to deinterleave memory is if there's something wrong with your CPU card or memory -- slow memory or wrong buffer chips on board; CPU card that doesn't set the CLKID pins properly but tries to run the bus too fast.
 

CircuitBored

Well-known member
this part:
is just wrong

Well, that's embarrassing. I have a very distinct memory of being sent a link to a Crescendo PCI manual that specifically said you should move the RAM when installing the upgrade. That said, I can no longer find said document. It was posted in my original S900 thread, which was lost in the 68KMLA crash earlier this year. It was a tiny footnote in a manual. I guess I'll go and move the RAM in my S900... Thank you very much for clearing that up. You're very likely correct but it is so strange that I remember reading otherwise.

Thanks again, trag!
 

trag

Well-known member
@CircuitBored We all have those moments. Over in the Outbound Laptop thread I was sure the SCSI adapter contained an 85C30. Nope. But I sure was certain of it.

There has been advice from CPU upgrade makers to deinterleave RAM under some circumstances. But you really should not need to unless something else is wrong.
 

kruuth

Active member
It lives.
Thanks to trag's advice I have a working mac. Now the problem I am running into is that the video is kind of whonky. Trying to get to the bottom of that now.

20211117_084312.jpg
 

kruuth

Active member
Ok, here's my problem. The unit starts up, but sometimes won't output video. The screen just throws a warning that it's not the right resolution. That being said, if I let it sit there, it eventually works but only some of the time. Sometimes on startup, it'll start and load the extensions but then it will start the desktop and immediately the resolution goes bad. Any ideas on what I should do with this?
 

kruuth

Active member
I've tried removing all the extensions and zapping the P-RAM and I am able to get it to boot when I do that, but there's no extensions. I moved all the extensions to another folder, and it now does the exact same thing, it will boot, and I get the happy mac, but then it immediately stops displaying video with a resolution error.
 

trag

Well-known member
Can you provide a photo of what it looks like when there's a resolution error? Or does the screen just go blank? What video card are you using?

I guess the LCD/monitor is displaying a message similar to "Unsupported Resolution" or something like that?

It's possible your S900 is set to 832 X 624. A number of monitors won't support that one. One of the times it boots okay, open the Monitors control panel and try setting the resolution to 640 X 480. That should work. Once that's consistent, try stepping through the other resolutions and see what works.
 

kruuth

Active member
The LCD is where it is giving the issue. However, I had it set to 1280x1024 and that was what it was set to when it actually worked. I have removed all the extensions and the control panels and this still happens. When I boot with SHIFT held down, it comes up. After removing all the extensions and control panels, it now does the same thing with the bar at the bottom of the screen at about 1/20 complete. I also tried plugging into my old HP CRT and it did the same thing there. As for the video card, it looks like a PCI card with a standard VGA port next to the old MAC video port.
 
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