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Monitor IBM 5151 truble

A

aitopes

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Joined
Dec 9, 2008
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27
Hello!
I am Ariel, from Argentina.

In last week i can buy an older IBM 5160 with an IBM 5151 monochrome monitor.

The PC (i am very happy!) work fine, but the monitor .....is dead :(

I try use the PC XT with an old Samsung monitor, and work. But the IBM 5151 only show this:

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I have a god electronic idea (i am technician), and open the monitor. The PCB is CLEAN, without visible bugs. :dontgeti:

I need repair this monitor. ¿Ideas?

(please.....very sorry for my english!)

PD: The XT work:

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Well, it looks like the monitor is almost completely alive - the solid green screen means that the HV and everything is working. Assuming all external factors are correct (video card, PC, etc), then I'd start following the signal path into the monitor. Will it give you the solid green screen wether the video cable is plugged into the PC or not? This is a digital monitor, so the video input goes through a logic gate pretty much first thing, then off to the video amplifier. I'd check that chip...

-Ian
 
Are you sure the PC has a monochrome video card ? Are you sure the switch settings on the motherboard
are set correctly for a monochrome video card ? You would think it's already set correctly if the PC and
monitor were together, but you never know....best to check.

On Switch block 1.....switches 5 and 6 should be in the off position.
 
It seems like the brightness is turned all up while the contrast is turned all down. The lines vissible is actually a sign that the monitor is receiving proper sync and processes it correctly, and these will go away if you turn down the brightness.

If this is not the problem, however, then it's problably a broken connection on the video signal in the monitor cable.
 
I agree with Per's guess, that would be the first thing I would try if you haven't. It's the knob on the front of the monitor, just turn that to the left and see if the green goes away and if the text is visible then.

How did you get the screen shot of the system working? Best of luck!
 
Hello again!

In first place, thank for you replies!

1) The videocard is a monochrome video card: The amber Samsun monitor works fine in this XT (see the photo in the firts post)
2) The signal path is ok....I found continuity between the pins of the cable conector and the PCB of the monitor...
3) When i change the bright control, the image goes from 100% dark to 100% bright. (Works fine for my....)
4) The contrast control ...not change the image. :(

¿Understand something? ;)
 
The first thing that I would do is to buzz out (check for continuity) the monitor cable. A bad connection anywhere along the cable will produce the symptom that you describe. In particular, check the plug at the end of the cable for broken or bent pins.
 
Chuck(G) said:
The first thing that I would do is to buzz out (check for continuity) the monitor cable. A bad connection anywhere along the cable will produce the symptom that you describe. In particular, check the plug at the end of the cable for broken or bent pins.
Click to expand...

Ok. I test this, and work fine. I use the Tester to check for continuity in all six pins of the conector cable, and the six are conected to PCB. The "data cable" is not broken. This was my first idea too :)

Thanks!
 
Did the contrast control not do anything at all or did it just not fix the problem? It looks like maybe Tezza and Lorne might have a copy of the service manual for the 5151 or 5153 monitors (found them referencing that they had it in other posts) but I wasn't able to easily find one on the web for you.
 
Last edited:
The 5151 is one of the simplest monitors made for the PC, and it consists of four separate parts. It's the powersupply, the sync processing unit, the video processing unit, and the CRT driver (signal amplifiers, the flyback, etc..).

In your case, the powersupply, sync processing unit and most of the CRT drivers are known to work based on the picture you provided, which must mean that the video processing unit or it's amplifier must be the failing part.

Here is the technical reference manual with schematics of the device:
http://members.dodo.com.au/~slappanel555/oa/OA - IBM Monochrome Display (5151).pdf
 
Do you own an oscilloscope? That could be very useful in getting to the cause of the problem.

Otherwise, you may want to replace TR18 (2SC2026) and IC201 (SN7406).
 
per said:
The 5151 is one of the simplest monitors made for the PC, and it consists of four separate parts. It's the powersupply, the sync processing unit, the video processing unit, and the CRT driver (signal amplifiers, the flyback, etc..).
Click to expand...

Yes! Big Blue, thanks for this! ;)

per said:
In your case, the powersupply, sync processing unit and most of the CRT drivers are known to work based on the picture you provided, which must mean that the video processing unit or it's amplifier must be the failing part.
Click to expand...

Good! You eliminate 3/4 of the posible problem sources.

per said:
Here is the technical reference manual with schematics of the device:
http://members.dodo.com.au/~slappanel555/oa/OA - IBM Monochrome Display (5151).pdf
Click to expand...

Downloading....thanks!
 
yes, i have an oscilloscope. Is an medium range INSTEK GDS-830, 100MHz. I use it with digital projects.

I have one SN7406 in house. Tomorrow change it. The 2SC2026 could be problematic to found.....but i search for this ;)

Thanks!
 
Fortunately, the 5151 is very simple. With the schematic from the technical reference, you should be able to use your oscilloscope to trace the video signal from the input to point V1 on the video board.
 
Ok. I am go to bed now. Tommorrow i search the schematic... ;)

A lot of thanks for the support ;)
 
Hello!
I am back.

I am testing the circuit, i have the schematic ;)

- TR18 is ok
- IC201 (74LS06) have 5v in pin 14 and GND in pin 7.
- TR20 collector have 55V....is ok for me.
- TR20 base have 6.8V....is ok for me.
- L202 is ok...
- R211 have aprox 820 ohms...ok.
- R212 240 ohms, ok.
- TR20 is ok.
- TR19 is ok

continue analizing... :)
 
Sucess!!!!!!!!!

The IBM 5151 is working fine!!!

The problem was....a broken cable between the main PCB and the ray cathode tube PCB.


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Tanks (a lot) for your help! The schematics was very usefull ;)
 
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