Viglen CRT monitor intermittent jumping

[roadrash]

Re: Viglen CRT monitor intermittent jumping

OK thats great news. I just need a ilttle help here now RJ as to where I should start testing which I gather must be done with the monitorturned on. I can keep it opened up and connect it up to that old PC it goes with. Can you just point me to where I should start connecting that probe. I will try and see if I can get a better display of a video signal
on the scope now ive had more time to familiarise myself with its controls. I would guess we start at the video input (D sub) connector, but not sure which area to go to after that.

[R_J]

Re: Viglen CRT monitor intermittent jumping

Both scopes seem to work so use either one, I woul'nt be too concerned about the one that showed signs of dampness, If it was going to cause a problem it would have when it was damp, not anymore.
The trace intensity cant be adjusted for part of the waveform (vert) its the trace speed going from the lower part to the upper part of the square wave that makes it look less bright.
It is a used scope, so the brightness is not like a new scope.
So go ahead and use the Isotech, you always have the other one as a spare.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

If you use the calibration test pulse it is likely 1 volt P/P, at 1Khz. if the timebase is set too fast it will display like you said, If you do not see a single or train of pulses it could be that the trigger source is set to the wrong input or the trigger polarity or level is wrong, try adjusting the trigger level should give a pulse.
If the square pulse itself is rounded or slopped and you are using a X10 probe, try adjusting the probe variable capacitor with a small screwdriver.
https://www.circuitspecialists.com/b...on-adjustment/

I tried what you said and the trigger settings are right. The biggest problem is most obvious on the Iwatsu SS-5802. The Iwatsu is the one ive been using and as it seemed the best because it hadnt had any problems. The Isotech scope had shown damp poblems inside after I bought it and I stripped, cleaned everything including all the switches on is ironically working the best and shows a display like it should be.
If you look at the pictures you can see the difference and see what I mean about the I Iwatsu scope having almost invisible vertical lines which makes the Calibration display look more like a series of hozizontal dashes. I would use the Isotech scope but I have no idea after it being so damp, whether it can be trusted. Is it possible to increase the brighness of these vertical lines on the Iwatsu and what do you think about the Isotech scope being any good.

[R_J]

Re: Viglen CRT monitor intermittent jumping

If you use the calibration test pulse it is likely 1 volt P/P, at 1Khz. if the timebase is set too fast it will display like you said, If you do not see a single or train of pulses it could be that the trigger source is set to the wrong input or the trigger polarity or level is wrong, try adjusting the trigger level should give a pulse.
If the square pulse itself is rounded or slopped and you are using a X10 probe, try adjusting the probe variable capacitor with a small screwdriver.
https://www.circuitspecialists.com/b...on-adjustment/

[roadrash]

Re: Viglen CRT monitor intermittent jumping

The first thing to test is if you have the rgb signals at the plug on the main board,(the one that comes from the rear jack) They should be there. Then I would check on the plug that goes from the main board to the neck board, the rgb signals should be there also but likely larger in amplitude, if they are not there then the problem is on the main board.

I am still trying to get to grips with these 2 scopes I now have. I downloaded various howto's & tutorials but cant seem to get the display on the screen as clear as shown in the pictures. What makes it hard in particular is the brightnes/intensity of the vertical line. for example in a calibration test I get the square or should I say oblong pattern and the corners are 90 degree. But it took a long time to see it like this because for a lonmg time it looks like 2 rows of horizonal lines above/below each other. This was because the horizontal lines are clear ands bright but the vertical lines are very feint & dim so its hard to see the box shapes. The intensity mainly seems to effect the vertical traces. This is the same on both of my scopes so I guess its normal but how do I adjust the brightness of these vertical traces so I can see a box shape not a series of hozizontal dashes. As soon as I can make out what I am seeing on the screen a bit easier the easier it will be to identify what I am seeing. Any suggestions?

[R_J]

Re: Viglen CRT monitor intermittent jumping

The first thing to test is if you have the rgb signals at the plug on the main board,(the one that comes from the rear jack) They should be there. Then I would check on the plug that goes from the main board to the neck board, the rgb signals should be there also but likely larger in amplitude, if they are not there then the problem is on the main board.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Your right RJ but it takes time to break through the oxidisation for example a old amplifier volume control crackles for ages. A quick squirt of Servisol and a few turns back and forth and the crackles are gone and the movement feels nice and smooth like its new again.
RJ can you help guide me what i should be testing with this scope now ive got it to find this monitors problem.
I wish I had your knowledge in this field but being a motorcyle mechanic doesnt have much in common apart from basic testing with a mulimeter. Hahhaha lol..

[R_J]

Re: Viglen CRT monitor intermittent jumping

The cap voltage won't make a difference being a bit higher. The switches get oxidized with lack of use, usually as the switches are used they self clean and you don't see much of a problem.

[petehall347]

Re: Viglen CRT monitor intermittent jumping

yep the old switches play up in mine from time to time . i have an old Hitachi 40 mhz that rarely gets used plus another old scope i have on standby . think its telequipment . seems better suited to tv work .

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Thanks for that info RJ, nice that i might at last have made some progress with the scope. Think I will give those switches and variable dials a clean with some servisol to clean and lube them. Might make them respond more consistanly. Now I have checked all ive done was alright what should my next move be in tracing what is causing the loss of video display.
It wouldn't be that 470uf 10v cap we replaced with a 470uf 16v one would it because I have the 10v caps now i can put in.

[R_J]

Re: Viglen CRT monitor intermittent jumping

That second pictue looks like it could be video, The scan on the scope (left to right) would show the video from top to bottom of the screen, (and seems to show 2 and 1/2 vertical fields) The amplitude of the signal would represent the intensity of the video.
I don't know which pins you got that from?
There should be 3 pins (3,4,5) that will look the same, R,G,B. The amplitude of the video should be about 1 volt P/P and the scan should be set to 5ms.
The vertical sync pulse, (pin9) should be around 3-5 volts P/P with time set to 5ms
The horizontal sync pulse (pin8) should be about 3-5- volts P/P with time set to .1ms
These are aproximate depending on the pc scan rate.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Well I did everything I said I was going to do. I tried other computers with a EGA output on the subject monitor and there was no display either so that would suggest the computer we are using on the monitor is working ok. I took the PCB out of the monitor again and made a thorough check just to be certain that I didnt get a cap in the wrong way round and I ddin't, they were all OK. I then looked at a picture of the PC before I replaced the caps and i then compared it to the PCB after replacing the caps and it looks like all the caps I repalced were in the right place and I counted 21 original (original blue) caps I removed from the PCB and I count 21 (Black NEW) caps I repalced on the PCB. So all would appear to be right & no mistakes. I then connected up another PC to the scopes (A Dell system 200) which has a EGA output to see what output I got on the scope from that. I spent ages tweaking all the knobs in AC mode and I found sometimes when turning the volts/division knob I almost got a display of peaks & troughs so kept persevering and managed to get a few more patterns althogh it was a bit hit or miss. I am wondering if this other scope I just got has dicky/dirty contacts in the switches & knobs causing a random result when turning the knobs back & forth. Anyway do any of these outputs look like we should be getting? I have no idea what a EGA signal should look like on the scope so its guess work to me.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

It would depend on the circuit, If it was for a supply voltage it would likely act as a short and blow something or just go up in smoke itself, if it was a small value for decoupling or signal coupling it should'nt cause any real problems.

Its OK I havent shorted any I just wonderd whatwould happen if a cap was put it wrong way round.

[R_J]

Re: Viglen CRT monitor intermittent jumping

It would depend on the circuit, If it was for a supply voltage it would likely act as a short and blow something or just go up in smoke itself, if it was a small value for decoupling or signal coupling it should'nt cause any real problems.

[petehall347]

Re: Viglen CRT monitor intermittent jumping

reversed caps appear as short circuit .

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Have you checked either the computer on another monitor? or checked the monitor on another computer? just to make sure the lack of video is with the monitor.

I did plug a CGA card in the pc and got a picture on a CGA monitor but i dont have another EGA monitor to try. Its very late at night here now but when i get up tomorrow I will try another EGA card in the pc and compare its output on the scope with what I am getting now. I also do have another pc with a EGA video output i can try on the subject monitor just to make sure the monitor is the problem. If it is confirmed the monitor is bad i will go back through it again and check every capacitor i replaced was in the right way round and a good cap as well on a meter. Just out of interest, can it cause damage putting a cap in the wong way round (polarity reversed).

[R_J]

Re: Viglen CRT monitor intermittent jumping

Have you checked either the computer on another monitor? or checked the monitor on another computer? just to make sure the lack of video is with the monitor.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

[QUOTE[That depends on whats on the computer screen, If there is only a C:> prompt that would look ok for pins 3,4 & 5, If you are getting that on all the pins, that is just noise.
Pins 8 & 9 will have sync pulses, [/QUOT
I found out it has the GEM desktop on (bit like windows) so it is giving a graphics output I believe. I havent unfortunately got another EGA monitor I can put on it. I have CGA, VGA and NEC mutisysnc LCD's and some other monitors like apple mac monitors and a big huge mitsubishi one with lots of connectors and BNC's on the back but I dont think any of these can be used on a EGA output and thats why I really want to get this one I recapped fixed as well. I could put a ISA, VGA card in the old PC to display it but that wont help me fix the EGA monitor.

Where did you connect the scope ground

I am connecting the earth to the PC Chassis where the EGA connector is.

switch the scope to AC for the input (switch is below the voltage/div select) If it is on DC any DC voltage will shift the waveform up or down and you may not see it.

I switched to AC and here are some pictures I what i got on the screen. the first is taken from pins 8 & 9 and it does look like a series of pulses. The next is what i get from the pins with a video signal and I am not sure if this is what I should be seeing but i tweaked all the knobs to see if I could get anythig better buts that seems the best. I will be happier when I know what these knobs are actually doing. Will have to follow a online tutorial when we get this monitor finished and I have time.
I also tried this again on the other 40mhz scope I fixed and get the same display so it must be right. Remember EGA is a anolouge output I believe.

[R_J]

Re: Viglen CRT monitor intermittent jumping

That depends on whats on the computer screen, If there is only a C:> prompt that would look ok for pins 3,4 & 5, If you are getting that on all the pins, that is just noise.
Pins 8 & 9 will have sync pulses,
switch the scope to AC for the input (switch is below the voltage/div select) If it is on DC any DC voltage will shift the waveform up or down and you may not see it.
Where did you connect the scope ground?

This is what the pulses could look like

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Yes you can check the output of the cable, the levels will be low, 5 volts p/p. You will see the video signal on (3,4 & 5) pins and the vert.(9) and horz.(8) pulses

I made a mistake its a 9 pin D nit 15 because its EGA. Here is the best scren display I could get from the pins putting out a video sigal Thats pins 2,3,4,5,6,7 & 8. Here are some pictures of the video signal display & pictures showing the settings I used to get them and for reference a pinout of a EGA socket.
Is this display that i should be getting from a EGS video output?