Viglen CRT monitor intermittent jumping

[petehall347]

Re: Viglen CRT monitor intermittent jumping

1 to one transformer . no problem then ..

[stj]

Re: Viglen CRT monitor intermittent jumping

Some (if not most) UPSs use live-connected batteries... so an UPS probably won't work. But a car 12V to 120/240V inverter should be okay.

i meant unplugged

btw, getting back to the monitor.
the correct way of checking stuff is:
connect a video signal with the HT transformer isolated and meter the B+ voltage with a 40w lamp bulb connected across it.

it should be between 80 and 140vdc.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Still waiting here for those probes. I ordered a set then after week showing not despatched. Then the seller said there was a fault so couldnt send them. He wasnt in the UK as he claimed he was and still hasn't refunded me. Anyway ive orderd another pair from someone else.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Hooray at last my probes arrived so now we can get back to sorting out this monitor. Hope these probes will be ok. Thanks for your patience. So what do you want me to check 1st. Remember this scope is new to me?

[roadrash]

Re: Viglen CRT monitor intermittent jumping

I dont believe this. The scope appearrs faulty. I followed a online guide and i can get it to show a trace on the screen not even using the calibratiion point. I rang the guy and he said it may be faulty then and refunded me. Great back where i started needing a scope. Will one of these digital scopes off ebay get me by for now?

[roadrash]

Re: Viglen CRT monitor intermittent jumping

.What a stroke of luck I just found a nice "working" scope and its just 30 miles from me so I bought it so were back in business. Its a Iwatsu SS-5802 3 chanel Dual Trace Oscilloscope with 2 probes, .5uS timebase and comes with probes. I thought it was a 40mhz scope but it turns out it might only be 10mhz so I hope it will still do. If it is, I will collect it in the next few days. What do you think is it a good one? The guy says its been great although it has a slightly noisy fan but he says its been like that for years. Any Good???

[vinceroger69]

Re: Viglen CRT monitor intermittent jumping

That looks a nice scope pity if it is only 10mhz lets hope it can do the tests you need im sure a more experienced member will advise if its ok, have you used a scope before? or are you a newbie like me with them ive been watching a few youtube videos too try and get my head around all the settings etc.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

HI everyone Thanks you all for your patience through all these oscilloscope woes. Anyway Ive got a goodun now and it came with probes and a full manual as well. The guy was a radio amature and he demonstrated it all working for me using a frequency generator or something so I know its 100%. I hope this will let me get this Zenith monitor repaired now.
Do you think this scope will be any good RJ & stj?

[R_J]

Re: Viglen CRT monitor intermittent jumping

It will work fine, I would start by checking the signals on the cable that come from the pc plug, that way you can see what the video, vertical and horizontal sync signals look like, any probing on the cold side can be done safely with ground on chassis.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

It will work fine, I would start by checking the signals on the cable that come from the pc plug, that way you can see what the video, vertical and horizontal sync signals look like, any probing on the cold side can be done safely with ground on chassis.

I am new to scopes RJ, what settings should I set it to? These pics show how they are set now. Sorry for this I have to learn, never worked with video signals and a scope.

[stj]

Re: Viglen CRT monitor intermittent jumping

probes on x10 - always,

scope to dc input, 100mV per division.
v-mode chanel1,
trigger auto on chanel1

[stj]

Re: Viglen CRT monitor intermittent jumping

i forgot, first you need to tweek the probe.
same setting as above,
connect it to the test-point - you may need 10mv per division - just ajust it for a visible squarewave.

on the probe or plug is an ajuster screw - it will have come with a PLASTIC screwdriver.
you need to ajust it so the wave is a nice square with straight corners.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

on the probe or plug is an ajuster screw - it will have come with a PLASTIC screwdriver.
you need to ajust it so the wave is a nice square with straight corners.

Thanks for those tips. I ddint know about the plastic screw driver so that was especially useful. Ive got both my scopes showing a square wave and calibrated probes on both of them. This proves I supose the Isotech scope is fixed as well I guess. Although the vertical lines are quite feint on both scopes but the horizontal very visible. Have to urn up the intensity a bit to see the vertical lines.
Just got to do what RJ asked me to now and check the video output of the PC. Do I just power on the PC without monitor connected and check the outputs on the 15 pin D connector RGB etc?

[R_J]

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

[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?

[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

[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

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

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).

[petehall347]

Re: Viglen CRT monitor intermittent jumping

reversed caps appear as short circuit .