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IBM 5154 Ega Monitor Help Please

D

dabone

Veteran Member
Joined
Feb 26, 2009
Messages
1,286
Location
Chattanooga, TN - USA
I just picked up a 5154 Ega Monitor, I've been wanting one for a long time, but with the current pricing.... ouch.

Got this as a from someone local who bought a storage locker auction, covered in years of dust. Wiped everything down and popped the lid to inspect that everything was plugged in.

Firing it up I got the following that you see in the video that I linked.

Symptoms were the same after I replaced all the caps I listed.
Tube looks ok and unbroken. No spot in the front.

No Power LED, and no high voltage.

I already replaced c11,c113, and c114 in the psu.
I also replaced the following caps on the mainboard
c101,c116,c119,
c204,c207,c208,c254,c260,
c302,c312, c402,c405,c406,c409


PSU outputs some voltages when not connected to the mainboard, and doesn't squeal. I don't have the pinout for the psu to see what I'm checking for on voltage out.

I know the samsfacts are available, I'm just not sure I'm throwing $22 more into something that maybe a bad flyback or some other unobtainium part.
 
Reading some more on this thing, I'm going to set it to the side for a bit and order all new caps for it. After I swap all of those, then I'll start actually trouble shooting.
 
First check all the output voltages from your power supply.
I had similar issue (at the beginning) - no power led, no raster, black screen only.

In my unit, the 12V regulator (IC2, 7812) had been shorted in the psu. 5V is derived from that
and without it there will be no power on led.
 
This might be helpful. I spent hours figuring out the psu board recently.
Note, that my unit is european, 230V psu.
 

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VintageVic, are those with the PSU connected to the main board or separate?

I have a ton of voltages with just the psu plugged in, but connecting it to the main board drops all the voltages to nearly nothing, along with the squealing sound.
 
Unfortunately the IBM5154 "Ran Hot"

For some odd reason, and I have never figured out why, they removed the ventilation slots in the cabinet which were on the 5153 monitor.

As a result, most 5154's have moderate thermal damage to the phenolic pcb's in the power supply, Vertical scan area and video output stage area and the components on them. If you look at your pcb photos you will see areas where the pcb has become dark in color, due to thermal stressors. These are the areas to check for faulty components.

If anybody has a good working 5154, I would advise adding ventilation slots to the cabinet, and a low noise fan to evacuate hot air from the cabinet.
 
dabone said:
VintageVic, are those with the PSU connected to the main board or separate?

I have a ton of voltages with just the psu plugged in, but connecting it to the main board drops all the voltages to nearly nothing, along with the squealing sound.
Click to expand...

Yes,

those are the two connectors where psu board is connected to the main board.

You should find these voltages, when psu is connected to the main board.
 
Finally getting some time to look at this, all caps on the mainboard and psu are replaced, digging deeper the HOT has the base and collector shorted together.
(T251) This is a BUX32B, and I might be able to grab a nte328 from my local store tomorrow, but before I swap it, any other parts to exchange at the same time?
All diodes and transistors seem to check out on the rest of the board. No open resistors that I can find either.

(I've mainly worked on arcade monitors, and with most of them, if the HOT is gone, so is the fuse, so I never bothered to check it in a semi powered failure mode)
 
Well the new Hot gave me back high voltage, and now the psu isn't being shorted out.. Now I'm greeted with a single vertical line, so I'll be going over the horizontal section of the sams fact when I'm better rested... I'm not poking around in high voltage land after a looooong monday at the office.
 
This display has separate high voltage and horizontal drive circuits. One vertical line means the HV section is now running but the horizontal drive to the yoke is not so the problem
is still in T251 drive but now it's not shorted so the power came up for the HV section.. BTW C257 is a non-polarized cap. If you replaced it with polarized, put the old one back in. It is part of the ground return for the hor yoke. Since T251 was shorted, check the voltages on T400 (it might be open) since that seems to be the power source for it and might have got cooked as well.

Larry G
 
Last edited:
Yeah, I found that out. I forgot to solder one the legs of the new transistor after checking for shorts.. After soldering, back to short circuit.
I had to remove T400 to test, and it did show bad, so I replaced it along with t401, and it enter a different failure mode. After scratching my head for a bit, my electronics shop gave me a tip30 instead of a tip30b, so the new t400 is blown, it needs more voltage handling (40v isn't going to cut it.). I'll see if they have the correct one tomorrow, if not, I'll have to order one.
 
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