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IBM 5154 EGA monitor fried... is it a goner ?

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
340
Location
Finland
Today I stumbled upon a lot of old ibm retro stuff.
It was saved in a cold storage, only good thing was that there was
roof on top of it, but it was exposed to dampness and temperatures of every season.

Yet, I could not pass on the chance to make offer on the items. Deal was agreed at 150 euro.
No shipping, because I was already there with my car.

Deal included at least
Japaniese IBM 5551 with monitor, keyboard and external 3.5" floppy drive (I assume floppy is for this unit).
IBM 5154 EGA monitor
Some 200+ floppies (maybe more)
expansion cards, including ibm 5050 motherboard, ram expansions, i/o cards, display adapters.

ibm_5551.jpg

stuff.jpg

ega.jpg
adapter.jpg


Well, I wanted to know if that EGA monitor is working. My IBM 5150 with green monitor
could use some updated colors! The lot has OTIVGA vga/ega adapter and I quickly found proper dip
switch settings for EGA. Installed the card to the 5150.

But the monitor. I knew it was a risk to hook it to power cord, but one has to try, right ?
Immediately there were some loud cracking sounds and white smoke pouring out of the monitor.

Obviously, I pulled the power cord and run the monitor out of my house. Smell probably lingers for a while... doh.

So to the topic. My IBM 5160 power made the same smoke come out of it and it happened to be repairable.
That was the AC filter cap that smoked in the 5160.

Could I be so lucky, that the monitor has similar issue - filter cap needs to be replaced ?
Or, is the monitor goner for sure now?

Any advice how to _safely_ open the EGA monitor? I do not want to damage anything inside
while opening the case, just in case if the monitor could be saved.
 
Probably rifa caps in the riveted power supply. There isa video on YouTube from technology tangents, I think, where he fixes one.
 
Thanks for the hint!

Found Tech tangents video about blown cap in CGA 5153 monitor. Mine is the EGA 5154, but
I guess the case is exactly the same.

Yes, rifa caps blew in my 5160 power, that's what I was wondering if it is the same issue here.
Fingers crossed that I can fix this one too.
 
Oh I must have been remembering wrong. Maybe it’s another channel that did a 5154 PSU.

I’m not sure. I’ve only got a 5153 I’ve never had it open, fortunately.

I do recall people saying that you have to drill 3 or so rivets for the 5154 though.
 
But the monitor. I knew it was a risk to hook it to power cord, but one has to try, right ?
Immediately there were some loud cracking sounds and white smoke pouring out of the monitor.
Coincidentally, my IBM 5154 emitted much white/grey smoke a few days ago. Ruptured line suppression capacitor in the power supply cage. This one was made by WIMA, not RIFA. It damaged the plastic on a nearby capacitor. Photos at [here].
 
Seeing as you paid euros and at least part of your pickup was japanese-exclusive hardware what are the chances that the 5154 was also a 100-120v version and you just plugged it into a 230v outlet?
That would certainly cause problems as it would blow up the primary side transformer instantly.
 
Excellent point, NeXT! Good thing, I did not try to hook that IBM 5551 or its monitor to the 230V power cord.
I had not thought about that at all, thanks for pointing it out!

The EGA monitor however - and luckily - was 200-240VAC unit.

I found two caps, C5 and C6 that have blown inside the power.
These are not rifa brand, but they look exactly the same as in the unit Modem7 had.

I guess the value for these are 1uF / 250VAC, I will try to locate suitable spares.
 

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I guess the value for these are 1uF / 250VAC, I will try to locate suitable spares.
The "0,1" is 0.1 µF

Mains/line suppression type, of class X - see [here].

Try an internet search using "0.1uf mains suppression".
( a search using "x rated capacitors" may display unintended results )
 
The "0,1" is 0.1 µF

Mains/line suppression type, of class X - see [here].
Try an internet search using "0.1uf mains suppression".


I stand corrected, again. 0.1uf of course.

I managed to find correct substitute caps that I ordered, but although being domestic
provider, it is a short week since friday is holiday I don't expect to see my order until
next week.

In the mean time, I pulled the offending caps out of the pcb. I do not see any other
cap leaking or bulging. Pcb itself is rather dark, almost black at some areas. I assume
those areas are exposed to heat.
 

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I got the new caps today and installed them in place. Assembled the power and tried to plug it alone
to the power cord and no new explosions. I then assembled the power back to the monitor (without the power cord of course)
connected the power to the pcb and plugged the two cables to the power inside the monitor, where they belong.
Assembled supporting metal plates and closed the case.

Then, I was ready to try to power on the monitor. Power cord on. And turning the power on button... nothing.
No green led, absolutely silent, nothing on the screen. I would expect to hear some minor hissing or twang on the monitor
and the green led on, but nothing. I did _not_ plug the monitor to the pc though, but I doubt it makes any difference. It seems,
to me, there is no power from the power.

Well... $hit.

Ha ha, I even put new rivets to the power to make it very original.

Does anyone happen to have the power pinout? I could use multimeter to check its pins if anything comes
out of the power. Perhaps I can at least check if the power-on switch is working in the meantime.
 
Step by step. Measure the DC voltage across either of the two large capacitors when powered on. Careful--this can be close to 2x the peak line voltage. i.e. if you're powering it with 120vac, the voltage can be 330 VDC or more. If you don't get anything, then work backwards (no power!) through the diodes and fuse to the line.

If you get a good reading, we can go from there.
 
On the pic of the Oak VGA card, it shows a rom labeled '2 of 2 ODD'. A: It seems to imply a missing '1 of 2 EVEN', and B: on an 8-bit card I would only expect to see one rom. It could be they didn't have any '1 of 1' stickers and slapped whatever on it, but it seems (if you'll excuse the pun) odd.
 
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Thanks for all of your comments!

I've opened the power again. Fuse is ok, earlier checked visually only, now with multimeter.
Also confirmed, that the power switch is ok on the monitor.

We have 230V system here in Finland. I'm getting 235VAC near the fuse.
I'm getting a good zero VDC at the two big blue caps. I have circled the area that I believe may be contacts for the big caps, not sure which legs exactly are in one cap so I measured accross every leg there one by one but no voltage at all!

My multimeter is capable of 600VDC only, but I guess it would read something else than just "0" if the reading is out of scope.

I have to conclude that this is a hint of something wrong with the power!
 

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Okay, so there's something not getting through. Put your multimeter on its continuity setting and, starting with each leg of the line supply, try to trace the path of current. I see two common-mode chokes (for RFI suppression), a fuse, and then you should see 4 diodes. Check them all.

In particular, pay attention to PDF page 5 of the schematic. Starting with the AC supply, you can see the current path. Do note that if the power switch isn't turned on, you won't get very far--but while you're at it, make sure that that switch works! I've been caught tearing my hair out because of a switch that I knew was good, wasn't. :)
 
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Big thanks for schematics and suggestions, Chuck!

A silly mistake by me, the power switch was not connected when I measured the blue caps. So I remeasured them, making sure
power sw is ON. The other connector was also connected that has 2 wires, but the psu unit is not plugged into the pcb of the monitor.

I noted that when I turned the power sw into on position, I did this time hear muffled "Dumm" sound as what you'd expect when old crt monitor is turned on.

I measured 145VDC at two legs, slowly decaying under 140 volts. It kept decaying, but I did not wait to see how low it drops (Yellow on the pic attacment).
Still, I get 0 VDC between the legs marked in red. I'm not 100% sure, but I think these are actually the legs to the big blue capacitors. It is difficult to see
because there is little room under the caps if these are really the correct legs. I might just pull one out to make sure.

Cannot continue until I'm back from work, but at least I can print out the scematics.
 

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Turns out, I still measured the big caps C7 and C8 at the wrong place.
I studied the schematics and marked places for many components to my own picture.
It helps me to find correct places to make measurements. What a tedious work...

But I'm more ready to make correct measurements now.
 

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I suspect that whatever happened is probably not a major issue. We've got the schematic and you have a DMM, so we can proceed from a good place.

BTW, the initial "hum" is from the CRT degaussing coil (DG1 on the schematic). It has very little to do with the power supply.
 
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