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Fixable IBM 5155?

CannedBread

Member
Joined
May 1, 2012
Messages
29
Location
England
I bought a broken IBM 5155 a while ago, and cosmetically it's fine, but it doesn't do anything when I turn it on. I've taken some of the boards out and one of the batteries has leaked, and a few capacitors exploded. I have a very limited understanding of these old computers, but I would really like to get it working. Do you think there would be any chance of that happening? would replacing the broken boards fix it, or could it be the power supply?
 
Start with the PSU and work out from there. PC/XT (5160) motherboards come up on here fairly frequently.
 
Please learn to solder and repair electronics. Please don't be one of those who operate on the basis of "if it doesn't work right away, it's garbage". Capacitors age and can be replaced. Power supplies use capacitors and if anything, are more prone to that type of failure.

The bottom line is that you can probably resurrect it with a little determination--unless it's been through extreme conditions, of course.
 
The quick and simple answer is yes it can likely be fixed. Just a little practice work and determination and you can replace those bulging capacitors and likely fix the problem for minimal cost. Chris's help will probably be a good experience too.
 
Sure, I'll take some pictures and put them up tomorow. From what I remember, one of the boards was fine, one had exploded capacitors and one a corroded battery. From what I could see the rest seemed fine, but I didn't delve any deeper than that... I think I need a screwdriver with a different bit to get to the rest.
 
I started to take it apart again, but I only got as far as the cards and one floppy drive (it's got two, but one is different). I'll get the motherboard out over the weekend, but I could see the 8088 in the back :)

So here are the pictures (sorry some of them are a bit blurry):

P5032180.jpg

The Computer itself, with two floppy drives

P5032183.jpg

Here's how the boards are laid out. The thin cable coming in from the left goes to the far left board (board 1), the two coloured ribbon cables are coming from the middle board (board 2), going out the back of the computer. One of the thick ribbon cables is coming from the smaller board on the right (board 3), and goes to the floppy drives. The 8088 is in the top left behind the cables (there is an empty slot for a similar size IC beside it, I don't know if there's something supposed to be there.

Board 1

P5032196a.jpg

Here's a close up:
P5032197.jpg

The exploded capacitor is the only fault on that board, and so far (I haven't taken it apart fully yet) the only exploded capacitor.

I can only attach 5 files a post, so I'll do another one in a minute. Sorry for the long posts :p
 

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That capacitor is a tantalum--they detonate on old gear with remarkable regularity. But that isn't going to keep your system from booting, so keep digging.

If I'm trying to work on a system, I'll take it apart and reassemble the boards, peripherals and power supply on a tabletop, so I can see what's going on.
 
While I haven't used a 5155 PSU, the power supplies normally have an auto-cutoff if their outputs are shorted. You can tell if this is the case because when you turn them on you see the fan nudge a little but not spin. To keep it alive, my 5160 board has had to have ~4 capacitors removed now.

Just to clarify, is the system turning on but not displaying anything, or does literally nothing happen when the power switch is flicked?

p.s. http://www.minuszerodegrees.net/5150_5160/MDC/minimum_diag_config.htm (test at bottom is extremely useful, still applicable to a 5155, would recommend you follow it through)
 
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Please learn to solder and repair electronics. Please don't be one of those who operate on the basis of "if it doesn't work right away, it's garbage". Capacitors age and can be replaced. Power supplies use capacitors and if anything, are more prone to that type of failure.

The bottom line is that you can probably resurrect it with a little determination--unless it's been through extreme conditions, of course.

I really missed the "Like it" from facebook :cool:

Get the PSU disconnected from everything, and turn on the PSU, take a look if the FAN spins, if not, then it's time to disassemble it, and try to fix. If it spins, then it's time to begin to repair that dead components.
 
I can't remember weither or not the 5155 has a fan :(
If it doesn't then you can use a sacrificial hard drive (make sure it's a hard drive you don't like, just in case).
If it does, then ignore this post :p
 
I can't remember weither or not the 5155 has a fan :(
If it doesn't then you can use a sacrificial hard drive (make sure it's a hard drive you don't like, just in case).
If it does, then ignore this post :p


Whops, I didn't think about this... One time I grabbed a 5155 Clone around here, and there was a fan on him... my bad.
 
5155 fan is mounted such that it is drawing air mainly through the back of the CRT. You can't see it without removing the shield but you can certainly hear it. Note to the OP - exercise extreme caution working with the CRT shield removed as there are serious voltages in there.
 
I really missed the "Like it" from facebook :cool:

Sorry, I don't do Facebook:

7775.jpg
 
Yeah Chuck, you're right about Facebook. But it's a very good way to stay in touch with people, maybe it's a Brazil fever, like Orkut. We've the highest users numbers on every social network.
 
...Get the PSU disconnected from everything, and turn on the PSU, take a look if the FAN spins, if not, then it's time to disassemble it, and try to fix. If it spins, then it's time to begin to repair that dead components.

Don't disconnect it completely. The power supply fan won't come on without a load on it(One hard drive may not be a big enough load). So if you disconnect it completely and turn it on, the fan won't spin up and you might mistakenly assume that the PSU is bad. (I did that myself once but fortunately the good people hear straightened me out)

I suggest removing ALL cards including the display adapter (I've seen two of the old IBM CGA display adapters go bad causing a short that prevent's the power supply from starting up.) Leave the power supply connected to the mother board and turn it on. If the fan spins up, let it run and after a minute or two you should hear the speaker beep (as long as it's connected) . At this point you can assume that the PSU is fine. If when you turn it on, the fan spins up, but you don't hear any beeps, then check the voltage at the floppy power connecter with the mother board power leads still connected. You should have + 5v and + 12v. Then, if it's determined that the PSU is ok, power it down and plug in one expansion board, like the CGA card and turn it on. If the fan doesn't spin,then that board is probably shorted. Keep pluging in more boards(WITH THE POWER OFF) one at a time untill the bad one is found.
 
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Don't disconnect it completely. The power supply fan won't come on without a load on it(One hard drive may not be a big enough load). So if you disconnect it completely and turn it on, the fan won't spin up and you might mistakenly assume that the PSU is bad. (I did that myself once but fortunately the good people hear straightened me out)

Are you 100% certain about this?
I've never used an original IBM PSU, but all others PSUs I've ever seen spins the fan when you power on, even with nothing connected. I will try to find a 5150 PSU schematic to take a look, I'm very curious to understand this circuit now.
 
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