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IBM 5154 monitor woes

robbo007

robbo007

Experienced Member
Joined
Jan 7, 2012
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287
Location
Iberian Peninsula
Hi guys,
I've recapped the power supply on the monitor as it did not power up. Caps were pretty shot. I've now got a screen like this when not connected to the PC. Any ideas what it could be? Visual inspection of everything else looks good. I gather I should be seeing a white screen when not connected to the PC.
 

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It's definitely a problem with the vertical deflection. Start by checking caps, and voltages around the vertical output IC (IC300).

While you're working on it, be sure to turn down the brightness so that you can only just see the line. If you leave it at normal brightness with no vertical deflection, it will leave a permanent mark in the screen.
 
ok thanks. Yes I had forgot to connect the vertical return cable to the main board. It worked, then I powered if off and now it has power but I'm hearing a "tic tic" from around the back of the tube. Its like the fly back is not starting the gun on the tube. Its seems like an intermittent problem as the monitor worked for a good 8 hours . Nothing seems blown. PSU is outputting all correct voltages.
 
On the back of the tube there should be a little PCB. Is this the case with your monitor?

If so, this little board should contain units that are spark gaps. These may look like little ceramic capacitors with a sawcut in them. Is it possible these are covered in 'fluff' or other contamination causing a spark to occur?

The other possibility is that the electron gun assembly is breaking down within the neck of the CRT. If this is the case, look at the neck of the tube in complete darkness - but beware about touching anything!

Dave
 
Interesting. Yeah... I wiggled connectors and check a few of the solder joints on the main-board. I've gave them a little solder to some that looked like they could have a crack in them. Plugged everything back in and it fires up now. Don't know if the intermittent problem has gone away or not but now I've now got another problem.

The brightness is really high on the black background. I can move my brightness and contrast but there is no way to get black as black. Are there controls for fine tuning this inside the monitor?
 

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Try turning down the screen (G2) control on the neck board, or the sub brightness control on the main board.
 

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Thanks for that. I've turned down the sub brightness and tried sub contrast on the back but its still a little white. Had to use a dentists mirror as it was the only piece of plastic I had that could fit in the holes. LOL

I'm comparing black background against my 5153. One thing I've noticed is that Vsize 2 does nothing and H.width 2 does nothing. Hwith works and Vsize 1 work. I'm referring to this guide, can't see your mentioned (G2) either? is that the brightness knob on the front?

I cant locate either RT303, RT251 or RT203 which are mentioned in the Horizontal and Vertical Adjustment?
 

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I think the excess "brighness" could be a blue colour. When leaving monitor on for a while i'm now seeing a blue tinge flashing on and off randomly on the screen when I'm oat a MSDOS prompt and when the monitor is disconnected from PC. Is this something cause by a bad component on the monitors video board? I've checked my EGA card with my other monitor and it does not do it.

Is there a good test program (MSDOS) to test EGA resolutions and everything else?
 

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Last edited:
robbo007 said:
When leaving monitor on for a while i'm now seeing a blue tinge flashing on and off randomly on the screen when I'm oat a MSDOS prompt and when the monitor is disconnected from PC. Is this something cause by a bad component on the monitors video board? I've checked my EGA card with my other monitor and it does not do it.
Click to expand...
If you look at the diagram at [here], there are two adjustable resistors for blue. So a possibility is that one of those adjustable resistors is 'dirty', in which case, a fix might be to simply adjust the resistor then restore it to the position/setting that you found it in. Otherwise use of switch cleaner liquid may be required. In both cases, the resistor setting needs to be adjusted and so you need to be confident that you can restore the settings to the proper setting.
 
robbo007 said:
I cant locate either RT303, RT251 or RT203 which are mentioned in the Horizontal and Vertical Adjustment?
Click to expand...
I see that you have the SAMS Computerfacts for the IBM 5154. On my PDF of that, there is a page (PDF page 12) that shows a photo of the main board, overlaid with a location grid. The same page shows the grid position of various components.

1680212228248.png
 
Thanks Modem7. I'll take a closer look and see if I can resolve the issue. I have noticed these things run hot. MY 5153 runs perfectly does not get too hot. Any suggestions to cool the sucker down?
Has anyone added fans?
 
robbo007 said:
Thanks for that. I've turned down the sub brightness and tried sub contrast on the back but its still a little white. Had to use a dentists mirror as it was the only piece of plastic I had that could fit in the holes. LOL

I'm comparing black background against my 5153. One thing I've noticed is that Vsize 2 does nothing and H.width 2 does nothing. Hwith works and Vsize 1 work. I'm referring to this guide, can't see your mentioned (G2) either? is that the brightness knob on the front?

I cant locate either RT303, RT251 or RT203 which are mentioned in the Horizontal and Vertical Adjustment?
Click to expand...

The screen control is the only adjustment on the neck board. It's on the component side, and has to be adjusted from above. I would return the sub brightness and front panel brightness to mid range, and then adjust the screen control so that the background is pure black.

The other controls are on the main board, in various locations. Unless you're not satisfied with the image size or centering, you don't need to touch them.

Your image does look a little blue. You might want to go through the color temperature adjustment. All of those controls are located on the video board inside the metal box. It might be easier to adjust if you remove the covers from it.

Yes, these do run hot, but that's just how they are. They managed to survive just fine when they were new, so I wouldn't add a fan. If it's a heavily used monitor, it probably could use some new capacitors, particularly in the power supply, and on the video board.
 
One problem with the 5154, compared to the 5153, there was cabinet less ventilation. Anything to improve that would help, including additional cabinet holes and or a fan. The video output stages driving the guns run very hot as does the vertical deflection IC. This all shortens the lives if the electrolytic capacitors and it can also cause darkening of the phenolic pcb's where the hot parts are. It pays to replace the electrolytics with 125 deg C rated Nichicon types or at least the 105 deg C types if you cannot get the others. The pairs of adjustment pots are switched in depending on which mode the VDU is operating it, the VDU auto-detects CGA or EGA syncs and has a logic control line which then selects different preset pots for each mode, disabling the other mode adjustment pots.
 
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