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IBM PS/2 Model 30-286 No video...or anything after replacing clock chip

gobabushka

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Mar 29, 2011
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Palm Bay, FL
Ok, I've got a friend who's got an IBM PS/2 Model 30-286 which the clock chip went bad. They replaced it, and might have put it in backwards. Now, the computer shows no errors...or anything for that matter on any vga monitor we've tried. Any suggestions? Or, is there any way to get the data off of the hd, and shelve the computer for a later time?
 

Stone

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The only way you're gonna get anything off that drive is to put it in another compatable computer that works. It sucks but PS/2s are rather problematic when it comes to making nice with other systems.
 

gobabushka

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Yea...thats what I was afraid of. My next question, what woudl cause it to not boot AFTER clock chip replacement? It wont even seek the floppy or start booting from the hd on power up
 

NeXT

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I know of many chips that do not like being inserted and powered in reverse. Causes all sorts of problems.
Are you able to put the old chip back in and confirm it still works then?
 

fatwizard

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I have a PS/2 model 30 286 that did exactly the same thing. After replacing the Dallas clock chip (which was never inserted backwards in my case), the system powers up, but no post, and I can't illicit a response of any kind from the system. The power supply checks out, and I have a substituted a supply from my PS/2 model 55SX that brought no joy either.
 

Stone

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Is it possible that this Dallas clock chip is not the same one that almost every other computer uses? Maybe this PS/2 uses a special (proprietary) device here and that's causing the problem. It wouldn't suprise you if a PS/2 used a non-standard component, would it? :)

Every time I read anything about a PS/2 (and that's nearly daily) I am really glad that I decided a long time ago not to venture into that abyss. :) IBM should be castrated for that entire endeavor. I know it's hindsight but they really dropped the ball with their PS/2 line.
 

tezza

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Hmm..

I had a similar issue with one of my PS/2 30-286 units. It started to occasionally power up, but no post. Then it was more than occasionally...it was always.

I never got to the bottom of it and had to source a replacement planar eventually.

Tez
 

fatwizard

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Sep 28, 2012
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Is it possible that this Dallas clock chip is not the same one that almost every other computer uses? Maybe this PS/2 uses a special (proprietary) device here and that's causing the problem. It wouldn't suprise you if a PS/2 used a non-standard component, would it? :)

Every time I read anything about a PS/2 (and that's nearly daily) I am really glad that I decided a long time ago not to venture into that abyss. :) IBM should be castrated for that entire endeavor. I know it's hindsight but they really dropped the ball with their PS/2 line.

I couldn't agree more, they are a pain. They were then, and they are now. I'm not sure how I ended up with 3 PS/2's. The clock chip had the same Dallas part number as the replacement, so I assumed it was the same, but perhaps not. If anybody knows I hope they are reading this thread.
 

SpidersWeb

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It's not very helpful, but I wanted to chime in and mention that I too have a PS/2 Model 30-286 that also does absolutely nothing when powered up.
I've replaced the PSU in mine (Generic 200W ATX unit soldered to a new connector) and the hard drive spins - but no beeps, no VGA signal, no RAM test, keyboard gets power + HDD spins but nothing else.

Starting to sound pretty common, would be great to get to the bottom of at least one system from this thread, and see if it's the same on the others.
 

lanmanager

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Jan 25, 2019
Messages
5
I realize this post is old. Did you ever get this figured out? I just received one with the 1287 in backwards and It's dead as well. I am diagnosing now. I can detect some bus activity immediately after power up, but then nothing. My first course of action is to replace the 1287. The logic of this strategy is the at chip sits on the address/data bus and the BIOS POST routine may have the processor halted without access to the NVRAM information/table data. Further investigation reveals that with the BIOS chip removed, the CPU seems to be looped trying to load address 0 on the bus as would be expected. From the pinout of the 1287, there seems to normally be no harm in inserting it backwards. Unfortunately, in this motherboard one of the "not connected" pins on the 1287 socket is actually directly connected to +12v. When inserted backwards that would hit the address strobe input pin (likely TTL) with unrestrained current at that voltage, most likely frying the 1287. I'll post later of the results, but it's possible the BIOS EPROM is dead as well. If replacing the 1287 fails I will fire up the programmer and attempt to test the 27C210 EPROM.
 
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