Viglen CRT monitor intermittent jumping

[R_J]

Re: Viglen CRT monitor intermittent jumping

I should also mention, make sure the CRT ground strap is always connected to the chassis, and there should also be a ground connection to the crt board. you do not want the crt floating at 15-20kv.
You can leave the degausing plug disconnected if you need to

[petehall347]

Re: Viglen CRT monitor intermittent jumping

on all crtv.s i remember working on the board slides out to work on . always had a mirror set up so i could see the screen . to access solder side i might turn the unit upside down and screen towards the mirror .

[R_J]

Re: Viglen CRT monitor intermittent jumping

If I was working on it I would connect the crt, and lay the monitor on its face or its side so I could access the botom of the board.

I marked two ic's, I suspect one you measured 4.93v is likely a 5 volt regulator that syupplies the ic's in that area. The other ic I marked also looks like a regulator as it has the center pin at ground.
Without a scope how can you tell where the video signal is being lost? Did you connect another monitor to be sure you have a signal?
That scope you linked to would work fine, just make sure the trace is nice and bright.
If the trace is dim its worth nothing.
I took your picture number 20181015_123005 and flipped and rotated it. that way the components match the bottom picture 20181015_205603. then with them side by each you can figure out what components connect to the traces.


My scope is always on my bench, I use it on almost every job I do. I use it for tracing audio & video signals, checking the ripple in pwer supplies, checking lvds signals in lcd monitors.
I rarely pull caps to check them, I check the circuit with the scope and if the cap. is bad I will see lots of ripple, then I can check it or replace it. If the caps job is for coupling a signal I would hope to see the same signal on both sides, if one side was low I would suspect the cap was bad.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

oscilloscope wise would that cheap one get up by because if not I can get a scope like this one here which is only 50 miles away from me:

https://www.ebay.co.uk/itm/tektronix...ezj:rk:50:pf:0

Its whether I will get the use out of it to justfy spending 40 odd pounds or more for it by the auction end plus fuel getting it. I would love a scope but would i ever use it enough. If the cheap one would suffice its not such a big outlay.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Here is a picture that might help locate the screen control.
By turning up the screen control it should display a white raster, that will indicate you have High voltage, and horzontal and vertical deflection.

Yes have a raster when U turn it up a bit

If you have those, then the loss of video is in the video signal path somewhere. Make sure the transistors or ic's in the signal path have voltage, maybe the short took out a supply resistor for one of the low voltages

Do you have any voltage on R219 for example?

I have marked what look like voltage regulator ic's and a couple resistors, If those are regulators, do they have there voltages in and out?

R219 has 8.4v and the other resistor you marked has 18.4v

One IC has 4.93v at one leg and the other 11.88v

I was wondering do I have to have the CRT connected to the PCB to check these sort of voltages? Its was a bit tricking getting into some of those bits without touching something else by accident or getting a shock which I did a bit. I will put some rubber gloves on I think next time. haha only a little kick nothing that would kill you or shock your heart into starting again..lol....

[R_J]

Re: Viglen CRT monitor intermittent jumping

Here is a picture that might help locate the screen control.
By turning up the screen control it should display a white raster, that will indicate you have High voltage, and horzontal and vertical deflection.
If you have those, then the loss of video is in the video signal path somewhere. Make sure the transistors or ic's in the signal path have voltage, maybe the short took out a supply resistor for one of the low voltages
Do you have any voltage on R219 for example?
I have marked what look like voltage regulator ic's and a couple resistors, If those are regulators, do they have there voltages in and out?

I have never used one of those scope boards, It might be ok for audio or low frequency data, (its only 200Khz) It might work for tracing the video signal.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Talking of a scope, until I can find a good quality scope would one of these little hand scopes make do?

Review here:
https://www.elektormagazine.com/news/review-mini-scope

[roadrash]

Re: Viglen CRT monitor intermittent jumping

I would always change a few caps at a time, then check the operation,

I will remember that in future.

[Quote]Does the monitor have high voltage? if it does, turn the screen control up a bit (located on the flyback) and see if you get a raster.[quote]

How do i know if high volts are there? I hear static crackle when i power it up. Still not sure where screen control is (still learning here).

Check if you have the 115 volt screen supply on the neck board (it is marked)

Yes it is. It did get detached and unsoldered during removing a cap but i resoldered it back.

Where was the cutoff attached?
The only component I know of that is magnetic is the horizontal linarity coil located near the yoke connection.

I cant temember know and wish i took a photo.

Check that all the plugs are connected back correctly

All are connected

Sometimes people question the usefullness of a scope, this would have been the perfect time to use it to locate the jumping video problem and replace only the bad component.

Might have to find one if i am going to fix a lot of crt's.

[R_J]

Re: Viglen CRT monitor intermittent jumping

I would always change a few caps at a time, then check the operation,

Does the monitor have high voltage? if it does, turn the screen control up a bit (located on the flyback) and see if you get a raster.
Check if you have the 115 volt screen supply on the neck board (it is marked)

Where was the cutoff attached?
The only component I know of that is magnetic is the horizontal linarity coil located near the yoke connection.

Check that all the plugs are connected back correctly

Sometimes people question the usefullness of a scope, this would have been the perfect time to use it to locate the jumping video problem and replace only the bad component.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Some good news and some bad news here... Ive just had it powered up and it seemed to be ok, tube heater all lit etc no smells no smoke hahahha. Then I hooked it up to the computer to check the picture and if its jerkin/jumping still. But there was no picture. I immediately removed the PCB again to check everything even though I had spent a long time after finishing it just checking every joint again and double checking all caps were in the right polarity. When I checked all seemed ok again but then I noticed one of the off cuts from a cap was magnetically stuck to the PCB. I cant believe this and I was so careful to put all these in the bin. I checked my bench was clean as well after finishing. Anyway I am so sad that after being so careful its spoilt. I hope it can be rectified even if I have to replace every IC.
Damn I feel gutted, just shows you can never be too careful. Now where do I start checking? It might not have been that off-cut and maybe could be a bad NEW cap. Should I check them before fitting them?



ps. Yes RJ i did mean 10v hahha

[R_J]

Re: Viglen CRT monitor intermittent jumping

I hope you ment 10 volt not 110v and yes 16 volt will work just fine for a 10 volt.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Just replaced all these caps. Are these ones i took out a good make? But i was short of one 470 110v so had to use a 16v one. I'm sure I read that its ok to use a higher voltage. Just to put together and test it now.

[stj]

Re: Viglen CRT monitor intermittent jumping

MAME has expanded to emulate vintage pc's and home computers - even sat recievers (to a degree)
it merged with MESS.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

I would try replacing C318 and the other small elec. next to it

Ive ordered a full set of the lower voltage (Non PSU) caps incluing the 100uf 25v C318 and all the others. Might as well replace these while I can get to them.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

yes,
and you should send that firmware to MAMEDEV.
https://www.mamedev.org/

I thought mame Dev was something to do with Arcade Machines and emulators from what I remember from my emulation days. Anyway Dumps of the Dell System 200 bios and that Keyboard firmware can be found here: http://www.minuszerodegrees.net/rom/rom.htm
It was the guys over on the Vintage computer forum who worked with me to help resurect this machine when that IBM type Intel D8742 keyboard controller with the uniique Dell firmware inside failed.
That was a lucky recovery that never would have happened had we not found the firmware.
Should I send that firmware to mamedev too then?

[stj]

Re: Viglen CRT monitor intermittent jumping

yes,
and you should send that firmware to MAMEDEV.
https://www.mamedev.org/

[roadrash]

Re: Viglen CRT monitor intermittent jumping

dont damage the 82s147 series chip, it's a rom and we dont have the code to program a new one.

Thanks I dont think we need to remove that but if we do I will be ultra careful. Is this one of these chips where the maker of the product its being used in programs it with thir own firmware? I had a recent experience of this with a Dell System 200 vintage PC I was repairing/restoring after the keyboard controller failed. That controller was basically a processor and had a small amount of memory for custom firmware inside. It was the same as used on the IBM's of the time but Dell used differnt firmware and without Dell's version of the firmware the PC wouldn't work. I could get a new chip but not the firmware. I was lucky to come into contact with a ex DELL employee from that era who had one OEM chip so we read the firmware out of it before putting into the PC so the vintage computer group now have a copy for the future if its needed again. The PC now works great again. Without that it would have been useless and unrepairable.

[stj]

Re: Viglen CRT monitor intermittent jumping

dont damage the 82s147 series chip, it's a rom and we dont have the code to program a new one.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Thanks RJ I will replace all the caps as you suggest and hopefully it will cure it. It is a extremely old system that had sat unpowered for many years so its bound to have suffered a bit. I noticed that when its doing its jerking there is a tendency for the picture frame size to change its size slightly, both horizontal & vertical and occaisional gets a hozizontal line flickers across half way down the screen..
I might see if I can get you a short video of it when its happenng if that will help.

[R_J]

Re: Viglen CRT monitor intermittent jumping

I was wrong about the sync on green It has seperate vertical and horzontal sync inputs. So the vertical sync signal comes from the rear connector and is fed to the vertical ic sync input. likely pin 8 of the vertical ic
I would try replacing C318 and the other small elec. next to it

Its a pita without a schematic.