Viglen CRT monitor intermittent jumping
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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 hahhaLast edited by roadrash; 10-20-2018, 05:30 AM.Comment
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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.Last edited by R_J; 10-20-2018, 09:02 PM.Comment
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Re: Viglen CRT monitor intermittent jumping
I would always change a few caps at a time, then check the operation,
[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)
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.Comment
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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-scopeComment
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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.Last edited by R_J; 10-21-2018, 11:34 AM.Comment
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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?
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....Comment
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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.Comment
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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.Last edited by R_J; 10-21-2018, 04:20 PM.Comment
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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 .Comment
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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 toLast edited by R_J; 10-21-2018, 04:51 PM.Comment
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Re: Viglen CRT monitor intermittent jumping
just remembered my neon screwdriver was my friend with crt .Comment
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Re: Viglen CRT monitor intermittent jumping
Re the scope.. I have a choice of 3 that I can get.
I prefer ths one (a tekronix) but depends on what it sells for;
https://www.ebay.co.uk/itm/tektronix...z/273511259703
Next one is this one a GOULD ADVANCE:
https://www.ebay.co.uk/itm/GOULD-Adv...y/153227035640
and finaly this ISO-TECH but is a 20mhz bandwidth ok?:
https://www.ebay.co.uk/itm/ISO-TECH-...g/153226078874
are all of these useful to help repair CRT monitors etc?Last edited by roadrash; 10-22-2018, 11:12 AM.Comment
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