Viglen CRT monitor intermittent jumping

[roadrash]

Re: Viglen CRT monitor intermittent jumping

I just had to lift the cover & take a peek inside. Its prety clean except for a kind of white soft almost chalky coating over the HT lead. It might be from damp where it was kept in his garage. I didnt want to remove it in case it was a special anti-static coating that meant to be there. I am sure its not conductive. Take a look.. As soon as those probes arrive I can get back onto fuixing my monitor which I tried again yesterday and it definitely has no picture. Its a EGA monitor and I think its the only computer and monitor that I have here that uses EGA so cant test it on anything else. I cant see the PC being at fault so sure its the monitor.
Hopefully this Scope wil now give us an answer.

[stj]

Re: Viglen CRT monitor intermittent jumping

dont go over the rated voltage on the probes - just saying.
and keep the probes set to x10 if they have a switch.

[vinceroger69]

Re: Viglen CRT monitor intermittent jumping

That looks a like a nice scope, ive got a trio 20mhz i really need too learn how to use one first though, i only got it to check lvds signals etc.

[R_J]

Re: Viglen CRT monitor intermittent jumping

That scope looks like it will work just fine, I would'nt worry too much about the deposits on the high voltage leads, clean it off of you like, It looks like this scope was used in a humid/salty environment. That would not deposit on the leads unless it was in use.

[stj]

Re: Viglen CRT monitor intermittent jumping

http://www.ionpool.net/arcade/tech/s...les/scope.html

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Thanks for that info Stj. I didnt get any probes with it and may have just ordered the wrong ones. I bought these ones as they looked like the best fit for this scope buty from what ive read I may be wrong. I have no info on what the input resistance or capacitance of this scope is. Ive seen on manuals for other ISO-TECH models of this scope that the input impedances are 1mΩ - 20Pf if that makes sense.
.
Anyway hope these ones i ordered will do for now

https://www.ebay.co.uk/itm/2x-100MHz...frcectupt=true

[stj]

Re: Viglen CRT monitor intermittent jumping

those are o.k.
you paid maybe a £ more than you needed, but they should be good.
i have a pair of 6100's somewhere.

[vinceroger69]

Re: Viglen CRT monitor intermittent jumping

i wasnt sure what probes too get for mine as my scope is only 20mhz i got these like you I had no info on what the input resistance or capacitance of this scope was mine was about £6.00 delivered
https://www.ebay.co.uk/itm/P6020-Hig...item41df7233d4

[stj]

Re: Viglen CRT monitor intermittent jumping

probe frequency de-rates as the voltage rises - so higher is better.

[Per Hansson]

Re: Viglen CRT monitor intermittent jumping

Please watch this eevblog video before going anywhere near a CRT monitor or Switch mode power supply with the scope.
It is very very important to know about the dangers of an oscilloscope before using it.

https://youtu.be/xaELqAo4kkQ

[R_J]

Re: Viglen CRT monitor intermittent jumping

Thats why you need an isolation transformer when working on the hot side of a smps, on the cold side of this monitor you will be fine.

Even some of the early crt tv's had a completely hot chassis, so you had to be carefull and not have any ground touch the chassis when the set was open. touch a grounded cable and bang out went the bridge and fuse at a minimum. the cable input was actually isolated.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Please watch this eevblog video before going anywhere near a CRT monitor or Switch mode power supply with the scope.
It is very very important to know about the dangers of an oscilloscope before using it.

https://youtu.be/xaELqAo4kkQ

That was very interesting and I must admit i never thought about the earth and mains referebced earth being differnt. But what if you just remove the mains earth connection to any equipment while you are probing. Wouldn't that isolate it from mains referenced earth making it isolated?

[momaka]

Re: Viglen CRT monitor intermittent jumping

But what if you just remove the mains earth connection to any equipment while you are probing. Wouldn't that isolate it from mains referenced earth making it isolated?

It would, most of the time (if the equipment uses isolated transformers inside for its power supplies).
But them using this piece of equipment can become dangerous, because it's no longer earthed, whereas you still are. Even if you put on thick shoes and think you are otherwise isolated, you could still get a minor shock when you touch something live, because of body capacitance. I've experienced that on 220/230V mains and it still hurts a bit. On 110/120V, you probably won't feel it.

In any case, this IS still dangerous, regardless of line voltage. One wrong move (touching something earthed/grounded while also touching live equipment/lines) and you will get shocked quite badly.

[stj]

Re: Viglen CRT monitor intermittent jumping

this is on my list
https://www.aliexpress.com/store/pro...350679999.html

[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...)

[vinceroger69]

Re: Viglen CRT monitor intermittent jumping

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

[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

[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.

[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

[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.