Viglen CRT monitor intermittent jumping

[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

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?

[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.

[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

[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.

[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

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?

[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

.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???

[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

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

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.

[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.

[petehall347]

Re: Viglen CRT monitor intermittent jumping

1 to one transformer . no problem then ..

[momaka]

Re: Viglen CRT monitor intermittent jumping

should work - maybe a good use for a ups

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.

[stj]

Re: Viglen CRT monitor intermittent jumping

how about using a 12 v car battery and a 12v to 240v inverter would that work?

should work - maybe a good use for a ups

[R_J]

Re: Viglen CRT monitor intermittent jumping

You won't have a problem connecting the scope to the chassis ground on this monitor, The problem would come into play IF you needed to scope anything in the power supply HOT side.
To measure scope anything in the hot side you would need to connect the scope ground to the (-) side of the bridge or main cap. This is where the problem comes into play and where an isolation transformer would be required.
There is no need to lift the scope ground.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

My probes didnt arive today so been rebuilding a engine instead. I think when i get to use this scope i will remove the mains earth connection and wear rubber gloves just to be safe for the time being fingers crossed my probes come tomorrow

[vinceroger69]

Re: Viglen CRT monitor intermittent jumping

how about using a 12 v car battery and a 12v to 240v inverter would that work?

[Per Hansson]

Re: Viglen CRT monitor intermittent jumping

Both an isolation transformer and the worse way of removing the earthing plug have the same problem:
Give the current a way to earth and there will be sparks.
Consider for example that the BNC contacts are exposed metal, so you might have 400VDC on them in a SMPS PFC section.
If you make a mistake that will be a very bad mistake.
Exactly the same will happen with stj's probes above: sure they may be 100 times attenuation so you can measure 2kV "safely"
Well, what happens when you hook up the earth lead to the wrong place? Boom!
The only safe way to do this is with an isolated probe, fuck isolation transformers and other such "tricks"

Full disclosure: I don't own an isolation probe, nor an isolation transformer, and I'm still alive
(That said I use my scopemeter for such work, so that's kinda "cheating", well, I like being alive...)