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Oh My God. My 5150...is dead :(

C

crazypigeon

Member
Joined
Sep 17, 2006
Messages
12
Location
Moraga, Ca
So, today, I got one of the original PCs, an IBM 5150, complete with a ton of software and all of the manuals...for free.

The guy said that last time he used it, it worked fine, but, he hasn't turned it on since 1990, so, he's not sure if it still actually works.

I've been tinkering with it for an hour or so, and, it dosn't seem to work. I looked at the manuals, and it seemed that the PSU wasn't working, as, I can't get it to put out voltage across pins 1 and 5. I looked on ebay, and the cheapest psu for the 5150 was $20. I figured I'd get it, but, try some more tinkering before hitting buy.

Well, I remembered that I had a psu from a 386 in my closet. I checked the voltage across pins 1 and 5, 5.25 volts, perfect. NOT.

I plugged it in to the mobo, nothing happened for a couple of seconds, then POP, the capacitator at C6 EXPLODED, hitting me, and leaving a burning ember of what once was a capacitor burning on the mobo. I quickly unplugged the psu, and realized what I had just done. I just ruined a IBM classic, I want to die.

But once I got past that, I examined tho mobo, and it seems the only thing visibly wrong with it is capacitor C6. I figured I'd ask one of you guys that have a ibm 5150 with the 16k-64k mobo, could tell me the details on the capacitor at C6, so that I could consider replacing it with a new one when I get a chance, or even sell me a 16-64k mobo so that I can have an original mobo, as the only one on ebay is a 64k-256 mobo
 
If you search these forums for the word "tantalum", you'll see a few posts where tantalum capacitors have blown, either on old motherboards or other old equipment such as floppy drives.

On the 16-64KB board, I count six capacitors designated C6. They are identical: 10uF/16V tantalum.
The combination of C6 capacitors filter (cleans up) the +12V line that runs from the PSU to the expansion slots. The motherboard will operate without them. In your case only one is dead which is less of a problem.

So why did C6 blow? Probably old age.

The blown C6 may have gone short circuit in which case it will be preventing the PSU from working properly. Even if the C6 has gone open circuit, it's best to remove it.

With the blown C6 removed, if other C6's immediately blow on power up, check the +12V. The 5150 expects an approximate range of +11.5 to +12.5 (source: 5150 Tech Ref). If other C6's are blowing, a severe overvoltage is happening on the +12V line (in which case I would have expected a decent PSU to shut itself off).

Note that the +5V line out of a 5150 PSU can range from approx. +4.75 to +5.25 (source: 5150 Tech Ref)

A related thread on this forum (concerning an XT motherboard though) is: http://www.vintage-computer.com/vcforum/showthread.php?t=5323
 
crazypigeon said:
I plugged it in to the mobo, nothing happened for a couple of seconds, then POP, the capacitator at C6 EXPLODED, hitting me, and leaving a burning ember of what once was a capacitor burning on the mobo. I quickly unplugged the psu, and realized what I had just done. I just ruined a IBM classic, I want to die.

But once I got past that, I examined tho mobo, and it seems the only thing visibly wrong with it is capacitor C6. I figured I'd ask one of you guys that have a ibm 5150 with the 16k-64k mobo, could tell me the details on the capacitor at C6, so that I could consider replacing it with a new one when I get a chance, or even sell me a 16-64k mobo so that I can have an original mobo, as the only one on ebay is a 64k-256 mobo
Click to expand...

Yea, don't be too discouraged. Capacitors commonly explode if the units haven't had juice through them for a while. Providing they don't take anything else with them when they burst, a replacement may be all that's needed.

This has happened to me three times. The first time was with my beloved Osborne when I first switched it on. I also wanted to die. However, the capacitors were easily replaced. (it then developed another fault which is now fixed, but that's another story).

In fact, when I boot up an old computer now I almost expect it to happen. I find myself stepping back a few paces and placing my hand near the wall socket switch for an emergency shutdown when I hear the "pop". :)
 
I put a hard drive in to my 5150, unfortunatly the 63? watt power supply was not pumping out enough juice to spin the drive up, so I gutted the power supply chassis and stuffed the guts of another AT power supply in the casing of the original IBM one, had to use a little "creativity" but its worked fine like that for almost a year now!

I also had a cap blow up at me, one on my sixpakplus card, may have to look in to getting that replaced.
 
Oh my God! You killed a 16-64K mobo? Those are so rare! Well, I hope you get it fixed. I've never(NEVER) had a cap blow up on me yet. But I usually go for vintage PCs that are in prisine condition from their original owners, unless it is cheap or free. I know my day will come, and I will crap myself(out of fear) when it happens...LOL

--Ryan
 
Yzzerdd said:
Oh my God! You killed a 16-64K mobo? Those are so rare! Well, I hope you get it fixed. I've never(NEVER) had a cap blow up on me yet. But I usually go for vintage PCs that are in prisine condition from their original owners, unless it is cheap or free. I know my day will come, and I will crap myself(out of fear) when it happens...LOL

--Ryan
Click to expand...

I'm in the same situation as you, but I haven't got/used too many vintage computes either. The oldest one I have is an XT and the second oldest is a NES (PAL).
 
Yzzerdd said:
....I've never(NEVER) had a cap blow up on me yet. But I usually go for vintage PCs that are in prisine condition from their original owners, unless it is cheap or free.
Click to expand...

It's more the length of time they have been shut down more than how well they have been cared for. Hence you can still get mint-looking units blow a cap if suddenly the juice flows after decades of inactivity.

Tez
 
modem7 said:
If you search these forums for the word "tantalum", you'll see a few posts where tantalum capacitors have blown, either on old motherboards or other old equipment such as floppy drives.

On the 16-64KB board, I count six capacitors designated C6. They are identical: 10uF/16V tantalum.
The combination of C6 capacitors filter (cleans up) the +12V line that runs from the PSU to the expansion slots. The motherboard will operate without them. In your case only one is dead which is less of a problem.

So why did C6 blow? Probably old age.

The blown C6 may have gone short circuit in which case it will be preventing the PSU from working properly. Even if the C6 has gone open circuit, it's best to remove it.

With the blown C6 removed, if other C6's immediately blow on power up, check the +12V. The 5150 expects an approximate range of +11.5 to +12.5 (source: 5150 Tech Ref). If other C6's are blowing, a severe overvoltage is happening on the +12V line (in which case I would have expected a decent PSU to shut itself off).

Note that the +5V line out of a 5150 PSU can range from approx. +4.75 to +5.25 (source: 5150 Tech Ref)

A related thread on this forum (concerning an XT motherboard though) is: http://www.vintage-computer.com/vcforum/showthread.php?t=5323
Click to expand...

Thanks so much for the information, and the reassurance. I know longer am pacing around my room in disbelief that I have broken it.

To the person that used an AT power supply in theirs, how did you power the monitor? The monitor just uses one if those extention 120volt cables, but, I'm not sure if it takes 120 in, and, I really don't want to actually break it.

Thanks again everyone.
 
crazypigeon said:
To the person that used an AT power supply in theirs, how did you power the monitor? The monitor just uses one if those extention 120volt cables, but, I'm not sure if it takes 120 in, and, I really don't want to actually break it.
Click to expand...

I actually disassembled the power supplies from thier housing and put the stronger (250 or 300watt) guts in to the original power supply's housing. This was last year some time.. im not 100% sure, but I think* i just spliced wires from the input to the monitor.. but that doesnt sound right. I could probably take a picture if you need me to, mind you its a PITA to get the PSU out and then take the cover off, after I dig it out of my closet... but if you need me to, I will... I remember the process being pretty straight forward. Had to do some "clever" engineering though...
 
crazypigeon said:
I plugged it in to the mobo, nothing happened for a couple of seconds, then POP, the capacitator at C6 EXPLODED, hitting me, and leaving a burning ember of what once was a capacitor burning on the mobo. I quickly unplugged the psu, and realized what I had just done. I just ruined a IBM classic, I want to die.
Click to expand...

I can't believe what I'm reading... this EXACTLY the same thing that happened to my 5160 motherboard some time ago. Is the C6 a three-legs capacitor or a two-legs one ? If it is a three-legs capacitor, I bought a few replacement caps here: www.mouser.com.

It was some time ago, though... so I do not know if they still have them. I haven't had time to remove the blown cap from my motherboard and put the new one in yet, so I do not know if the repair would be successful or not.

My cap blew up following exactly the same procedure you described. The PC was not starting up, and I thought the PSU was the problem since there was a weird noise coming from it. So I used an AT power supply in its place. When I switched it on, the cap blew up after a couple of seconds. I had disconnected everything else fortunately, only the video card was installed, no drives or anything else. The weird thing is that after the cap exploded, I reconnected the original XT PSU and my motherboard did boot up! The only problem is that it doesn't seem to recognize the hard drive anymore. The hard drive certainly is not damaged because it was totally disconnected when the cap blew. The controller was not installed either. The computer now works (and the blown cap is STILL there!) but I have to start it up using a floppy disk... anyone has any idea if it's possible to get the hard drive working again ?
 
flavio75 said:
The computer now works (and the blown cap is STILL there!) but I have to start it up using a floppy disk... anyone has any idea if it's possible to get the hard drive working again ?
Click to expand...

Well, if the hard drive stopped working after the cap was blown, I'd look at replacing the cap first off. It must have served some purpose and perhaps it had a role in the hard disk circuitry.

Tez
 
This happened to my IBM 5271 last week as well. Power supply dead, motherboard dead (when I tried powering the motherboard from an AT power supply I got a brief display of actual flames from the dead capacitor). I've checked the hard drive and the 3270 emulation cards in other XTs and they seem to have survived. It was quite amusing to see a Sinclair PC200 displaying its boot messages on a 3270PCDA rather than its built-in CGA.

Now I'm wondering what to do with the bits - in particular whether it's worth trying to find a replacement IBM XT motherboard and PSU, and reconstruct the thing. I don't really have the skills to take a soldering iron to the thing myself. Fitting a baby-AT motherboard isn't really practical, because the 3270PCDA needs three adjacent 8-bit slots for the full effect.
 
Probably cost you less to have the two items repaired rather than replace them. The PSU probably just needs the fuse replaced and the cap is a 3 minute replacement job.

On the one where the HD doesn't work, tantalum caps, when they go, usually fuse the tantalum oxide innards into a conductive path between the two legs (ie: high resistance short) and, depending on what the particular cap is being used for, this may not be too good.

Try clipping the cap out and see if the HD works.
 
"cor blimey what a fuss!"

Tantalum capacitors pop, end of story.
snip it out, and if the problem goes away great, if it doesn't, there's probably another one somewhere that needs snipping.

get your meter out, look for a power supply line that's low, and then trace it to the point of lowest resistance (to ground), then snip again!

Sooner or later you're going to find the problem.

As an illustration, the MZ80K I've got on the bench has had 3 faults already, 1 capacitor duff, 1 TTL IC duff, and I'm just trying to get the memory sorted.

You've just got to hold your nose & jump in!
 
So far, so good; without the blown capacitor, the motherboard boots, which it didn't before. Now all I need to do is find a replacement, and I see the question of whether and how to replace C56 has come up before.

As for the power supply, I'll have to see where I can get hold of something that can undo security Torx bolts.
 
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OK. For future reference, a normal (16v, 10uF) two-leg capacitor seems to work fine as a replacement for C56; the positive leg goes in the middle hole, and the other one I put in the hole nearest the edge of the planar (though I think either should do).

Not sure what to do about the power supply, though. The fuse is fine. The first time I switch on, the fan turns about 1/8 of a revolution before cutting out; on subsequent attempts nothing happens except an ominous click from somewhere near the switch.

(this is without any load, but that shouldn't matter... should it? I'm reluctant to hook it up to the motherboard in case it was the PSU killed C56 rather than the other way round).
 
Did you measure the fuse with an ohm-meter? Sometimes, the little buggers break at the ends, under the metal caps where you can't see it.

If it is good, you really don't want to try and repair a switching power supply and you're probably better off slapping the case around a working supply of the same dimensions as, I believe, someone else mentioned.
 
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