VOGONS


First post, by jesolo

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I recently acquired a complete 286 PC.
Specs are:

  • Intel 286 12 MHz
  • 1.5 MB RAM
  • Hedaka HED-986 motherboard (http://arvutimuuseum.ee/th99/m/E-H/30430.htm) - the previous owner had the old barrel battery removed and replaced it with an external battery (so, no acid damage).
  • 1.2 MB floppy & 1.44 MB floppy disk drivers (the latter is definitely a late addition)
  • 20 MB Conner hard drive (CP3024)
  • MDA graphics card
  • 16-bit IDE controller
  • 180W PSU (this one still has a switch on the side of the case).
  • 12" B&W Monochrome monitor

Here's a picture of the PC:

286-12.jpg
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286 12 MHz PC
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When I fired up the PC the first time, I could hear some "crackling" sounds coming from the PSU.
I also had problems getting the hard drive to unpark itself (after a while it would unpark and then work without any problems).
At first, I thought the hard drive was going, but when I installed it in another PC, it booted up without any problems (no delays).

This now leads me to believe that the PSU might be going.
Before I poke around inside the PSU, what could possibly be the problem? A bad capacitor perhaps or something a bit more technical?

Reply 1 of 12, by kenrouholo

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Problem likely involves a dead capacitor, which could then spread to transistors and drivers and protection diodes and such. Dead caps that leak can also cause shorts on the board. Or if the fan died then quite a few components would have been vulnerable to overheating. Could also be full of dust, or bugs. Could also be a bad solder joint or a broken component from vibration and time.

Last edited by kenrouholo on 2017-03-18, 22:16. Edited 1 time in total.

Yes, I always ramble this much.

Reply 3 of 12, by Tetrium

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h-a-l-9000 wrote:

> "crackling"

Visual inspection first.

^This

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Reply 5 of 12, by jesolo

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Some pictures of the PSU after I had opened it up.

First picture is the PSU on its side - the switch is on the top.

WP_20170321_001.jpg
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PSU - Pic01
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The two capacitors on the right hand side seems a bit bloated. Maybe I should start there and perhaps just replace all three of these. It appears they "bonded" these as well with some glue (which has now gone brown over the years) - you can notice it at the bottom of the capacitor furthest to the right.

WP_20170321_002.jpg
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PSU - Pic02
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Since I'm not an electronics expert, I have no idea what these two black circular objects are (also some type of capacitor?). However, the one on the left appears to be quite bloated, compared to the one on the right.

WP_20170321_003.jpg
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PSU - Pic03
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No obvious faults on this pic

WP_20170321_004.jpg
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PSU - Pic04
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Reply 6 of 12, by jade_angel

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jesolo wrote:
Some pictures of the PSU after I had opened it up. […]
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Some pictures of the PSU after I had opened it up.

First picture is the PSU on its side - the switch is on the top.

WP_20170321_001.jpg

The two capacitors on the right hand side seems a bit bloated. Maybe I should start there and perhaps just replace all three of these. It appears they "bonded" these as well with some glue (which has now gone brown over the years) - you can notice it at the bottom of the capacitor furthest to the right.

WP_20170321_002.jpg

Since I'm not an electronics expert, I have no idea what these two black circular objects are (also some type of capacitor?). However, the one on the left appears to be quite bloated, compared to the one on the right.

WP_20170321_003.jpg

No obvious faults on this pic

WP_20170321_004.jpg

Yes, the two black objects are electrolytic capacitors, and they look farkled to me. Probably want to go ahead and replace all of them.

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Reply 7 of 12, by Richo

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picture nr. 2 the black capacitors, replace them all, 2 of them are in the progress of bursting.

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Reply 8 of 12, by Deksor

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My 8088 and my pcchips 486 were both unstable with their psus. I checked them and the caps weren't bulging. However, on things that old, if you have problems, do not think "hm they seem fine" because even if they look fine, they can be completely dead or in the process of dying. I recapped my two psus and now they're working perfectly now. Capacitors are cheap and easy to replace so you don't risk a lot at replacing them.

Also that's maybe just me, but when I recap something, I usualy prefer to replace every caps of the object so I'm sure everything should be fine for the years to come 😀

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Reply 9 of 12, by kenrouholo

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is the LT-13 transformer as messed up as it looks to me?

Not sure on those caps from that angle. I see goo but it could be electrolyte or it could be glue. In any case, with their age, I wouldn't trust them especially on an old PSU,

Yes, I always ramble this much.

Reply 10 of 12, by gdjacobs

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The PSU will be old enough that it's probably worth replacing all the caps. Generally the bulk caps see the least amount of stress compared to filter caps, so more of them are likely in bad condition.

All hail the Great Capacitor Brand Finder

Reply 11 of 12, by TELVM

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All or most of the smaller caps are Rubycons, that's why this PSU is still alive @ 2017.

The three larger PCE-TURs close to the yellow 'donut' coil are probably busted, from a distance they look like two 10V 2200uF on +5V and one taller 16V 2200uF on +12V. Also replacing the two bulk caps ('Nitsuko'?) wouldn't harm.

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Reply 12 of 12, by gdjacobs

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Well, you know the only thing better than real Japanese caps is new Japanese caps.

All hail the Great Capacitor Brand Finder