Viglen CRT monitor intermittent jumping

[roadrash]

The picture on this monitor has stated to jump. it does improve a little sometimes when left turned on for a long time. It jerked/jumped/flickered to start with then stopped and the picture was stable for over 3 hours before i turned it off. I turned it on again today and its jumping/flickering etc again and occasionally it will stay steady for ages then give a little flicker. I tried tweaking the pots than can be accessed a little each way to find if any would help and found one pot (one on the right in photo) and when turned to full range both directions, will cause the screen to scroll and then roll round to the right or left. with careful adjustment i can almost stop it jumping/flickering but only lasts until turned off and then on again next day then i have to tweak this pot again to try and stop it. I dont think this pot has anything to do with the fault though. I have up loaded lots of photos of the monitor here:

https://drive.google.com/drive/folde...WW?usp=sharing

Please can anyone help me solve this as its a matching monitor for a very old but lovey vintage Viglen VIG1 286 system ive had many years.

[sean0118]

Re: Viglen CRT monitor intermittent jumping

...will cause the screen to scroll and then roll round to the right or left. with careful adjustment i can almost stop it jumping/flickering but only lasts until turned off and then on again next day then i have to tweak this pot again to try and stop it.

That's known as loss of horizontal sync, I think that pot sets a frequency which is used to lock the horizontal frequency of the monitor to the video source. When you turn it too far the difference in the monitor and source horizontal frequencies is too large and the sync is lost.

With regards to the problem, when it jumps, is it also to the right/left? or up/down?

Also, what do you have it connected to? I think this can also be caused by a bad computer graphics card too.

[Andrew F. Ali]

Re: Viglen CRT monitor intermittent jumping

Check/replace the e-caps in the Vertical section (I would just replace them to be certain). Resolder the pins of the Vertical output IC.

[momaka]

Re: Viglen CRT monitor intermittent jumping

If the monitor is over 20 years old (which most CRTs are these days, or getting close to), it is certainly checking out some of the electrolytic caps, as Ali suggested above (but it wouldn't hurt to replace any that appear to have been in hot spots or near large heatsinks).

Also, is this a Sony CRT by any chance?

[roadrash]

Re: Viglen CRT monitor intermittent jumping

I had another look at this monitor today and when checking the solder side of the pcb I found a very bad connection where the solder hadn't fused to one leg of a 3 legged
component. Not sure what it is but its marked as R102 on the pcb but it dont look like any resistor ive seen. You can see it in the picures, its just behind the AC power socket.
When I first tried the monitor after soldering the contact on one of its legs, the monitor had a nice steady & stable display and then after a few minutes or so it started to jump and I put my finger on the top of the component and it was pretty hot and hotter than I would say is normal. Can anyone tell me what this little black plastic box with 3 legs is and Should it get really hot and should all 3 of the legs have been soldered properly? Is there any way of testing it?

[R_J]

Re: Viglen CRT monitor intermittent jumping

Thats the degausing thermistor. there are two thermistors inside, one across ac line I believe and one in series with the degausing coil, The one in series with the coil is 8Ω ptc, It has nothing to do with anything other than crt deqausing.

Do like the others have said and replace the caps in the vertical circuit.
Also replace any caps in the sync seperator circuit, The vert. and Horz. sync. signals are carried on the green video input line. In the case of the vertical, the pulse needs to be seperated from the video and fed to the vertical osc. (part ofthe vert ic likely) for synchronization. If the video signal is poor this can also effect the vertical sync signal. IE: a poor cap in the G video signal path can clip the vertical pulse causing poor sync.

[stj]

Re: Viglen CRT monitor intermittent jumping

there is probably a lot of cracked solder joints - check everything large or bolted to a heatsink.

[kc8adu]

Re: Viglen CRT monitor intermittent jumping

+1
also noticed it has panasonic caps and crt.
lower probability of dead caps.
looks like the mfr tried to make a decent unit.
add to the above list of stuff to resolder anything that runs hot.
like higher wattage resistors.

there is probably a lot of cracked solder joints - check everything large or bolted to a heatsink.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Thats the degausing thermistor. there are two thermistors inside, one across ac line I believe and one in series with the degausing coil, The one in series with the coil is 8Ω ptc, It has nothing to do with anything other than crt deqausing.

Thank RJ I did measure it and it measures like two resistors a 631.3 and a 20.8Ω one. Do those values sound OK?

there is probably a lot of cracked solder joints - check everything large or bolted to a heatsink.

The soldering on the PCB is excellent and I could only find a few that I had to resolder.

iquote]Also replace any caps in the sync seperator circuit, The vert. and Horz. sync. signals are carried on the green video input line. In the case of the vertical, the pulse needs to be seperated from the video and fed to the vertical osc. (part ofthe vert ic likely) for synchronization. If the video signal is poor this can also effect the vertical sync signal. IE: a poor cap in the G video signal path can clip the vertical pulse causing poor sync.[/QUOTE]

Can you point me where this section is on the attached pictures with the PCB now removed from the chassis. Someone might now recognise this monitor. Its certainly very well made.

[R_J]

Re: Viglen CRT monitor intermittent jumping

The values for the thermistor are ok, they do change over time/use. Like I said, it is only for degausing the crt at startup, thats it.
You can see where the rear video plug connects to the board and near it is the plug that feeds the rgb signal to the crt board, there are a couple ic's around there, ic20? and ic201, also give the number of ic601
Also a nice picture of the trace side of the board for that area.
It looks like this monitor uses a combined horz/vert drive ic (ic601) and the vertical output are two seperate transistors

[roadrash]

Re: Viglen CRT monitor intermittent jumping

there are a couple ic's around there, ic20? and ic201, also give the number of ic601

IC601 = TDA2595
IC204 = MC 7812C
IC203 = MC 7805CT
IC202 = N825147N
IC201 = 74LS04

Here is another picture of the PCB hope its better this time.
IC604 is on the right hand side of ths picture about half way up.

[R_J]

Re: Viglen CRT monitor intermittent jumping

The vertical output is hidding, it is under the square metal heatsink next to vr604 Likely a tda1170
It looks like they are not using the vertical section of ic601 as there is no trace to pin #9

What is the ic next to ic201, the one near the OK sticker? the plug wires are covering the last digit in the ic20?

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Its IC202 so a N825147N. It has a diode across the top linking two pins.

[R_J]

Re: Viglen CRT monitor intermittent jumping

That is an S not a 5 N82S147N, thats why I could'nt find any info on it.

[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.

[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.

[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

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

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

[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?