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View Full Version : Are there any TV or monitor engineers here on AmiBay?



Merlin
10th October 2009, 21:59
At work, we have a Norbain SD Vista PVD1700DG colour CCTV monitor that used until recently on our site CCTV system. This has recently developed a faulty picture (doesn't look to be too major though) and as such has been earmarked for the electrical scrap pallet. The monitor itself is in immaculate condition and it's a multi-standard unit too, with S-VHS and Composite inputs along with audio inputs too - this would be ideal for a retro computer monitor as it displays up to 750 TV lines at 0.28 pitch. It sort of looks like a larger version of a Microvitec Cub monitor.

It seems to be a shame to scrap this monitor, so, are there any TV or monitor engineers around the Manchester area in our membership that maybe could repair this unit?

rkauer
11th October 2009, 06:21
I can do wonders for that monitor, but I'm out of reach, sorry. :sigh:

Merlin
11th October 2009, 16:00
Thanks for the offer anyway, Rogerio. I can't believe that they want to just throw it away, this is a monitor that cost 450 new :shock: !!

I guess that I'm going to rescue it and see if a local TV repair shop can fix it.

rkauer
12th October 2009, 17:38
What kind of fault it developed, friend?

Merlin
12th October 2009, 18:57
The best way I can describe it is, it has 'half a picture'; the top half of the image seems to be OK, however the bottom half of the image is compressed into what looks like 2 or 3 lines - the rest of the screen in blank.

Ordinarily, I would have said that someone has messed with the vertical framing, but since that affects the top and bottom equally, that can't be the fault.

It could be a faulty component forward biasing the LOPTX so that the picture shifts upwards, but until I take a look inside, I'm not sure. Not owning an oscilloscope is limiting as to how much poking around I can do anyway. De-gaussing the tube may help.

One thing; The CCTV is located in a room that has just seen a big increase in PC activity in the same room, as a server was upgraded. It's doubtful, but could the increase in spurious RF activity have caused this?

TheCorfiot
12th October 2009, 19:36
@Merlin

Replace the Frame IC.. If you have, or can find schems, I will point you to it...

TC :mrgreen:

Merlin
12th October 2009, 20:55
It was made by Vista - the manual is here:-

http://www.norbain.com/support//manuals ... 8BC1A1D12/ (http://www.norbain.com/support//manuals/act:openfile/ref:M3F018BC1A1D12/)

I can't find a schematic for it yet.

Merlin
22nd June 2013, 19:30
Arise, old thread!!

I've been having a bit of a tidy up and I came across this monitor again tonight. I powered it up and I've managed to take a photo of the screen problem with the brightness turned right up. The same lines appear on a colour image if an input is sent into one of the BNC sockets - I used an Xbox 360 that I'm working on to test the screen and I could make out the image among the lines.

A search around of the t'Interweb suggests that this might be a capacitor fault in the horizontal oscillator circuit. Can anyone give me any clues as to if this might be the cause? If this isn't the cause, what might it be?

It's been a very long time since I rummaged around inside CRT TVs and monitors and I'm inclined to take it to a TV repair shop, unless it's a simple fix.

Edit: I've had a rummage around inside and there's nothing glaringly obvious. The chassis appears to be a CCTV-HP-CMB-17, Part No: 1840-0055-015 Rev.F. If anyone knows where I might get hold of a circuit diagram for this chassis I'd be really grateful.

direktorn
23rd June 2013, 22:44
I guess that I'm going to rescue it and see if a local TV repair shop can fix it.

Would be my bet to, are a lot of these analog guys out there doing repairs. It would help if you could dig out a schema for it, as fault checking without it takes a lot of time and could be dangerous as there are a lot of HF things inside.

ShambleS1980
24th June 2013, 14:14
Bash it till it works :thumbsup:

Personally id be having a look for bad solder connections around that funy looking thingy with the magnet thingy in it..
usually controlls contrast and brightness..

no idea what they are called but usually when a old crt tv goes kaput its around the area that thingy lives..

(thats right i am no expert)

roy_bates
24th June 2013, 14:29
im wondering what frequency this accepts.

have you got anything that outputs around 15khz?

rkauer
25th June 2013, 00:11
Go for the smaller electrolytic caps in the vertical and horizontal circuits. Replacing those are cheap and can cure the problem.

What Shambles mentioned is the flyback and it surely have nothing to do with the mentioned problem, other than the odd bad solder joint issue.

Refreshing the solder joints in the flyback is always a good idea, as it provides voltage to other areas of the main board and a bad solder can do a lot of iffy issues.

ShambleS1980
30th July 2013, 03:45
Go for the smaller electrolytic caps in the vertical and horizontal circuits. Replacing those are cheap and can cure the problem.

What Shambles mentioned is the flyback and it surely have nothing to do with the mentioned problem, other than the odd bad solder joint issue.

Refreshing the solder joints in the flyback is always a good idea, as it provides voltage to other areas of the main board and a bad solder can do a lot of iffy issues.


woot now i know what its called lol..
i have replaced and re solderd so many of these stupid things over the years and never knew what they were called. "i always like to mess about with things till they work again, even if i have no idea what i amd doing.. its how i learn"

i did a google search, and some how you knew exactly what part i was talking about even with my bad description.!
http://www.kronjaeger.com/hv/hv/src/fly/flybacks.jpg

and just a FYI
you can get a hell of an electric shock from one of these things

Bryce
30th July 2013, 08:58
Definitely a capacitor problem on the vertical amp or oscillator. It will be one of the larger electrolytic capacitors and its associated resistor might show signs that it has been getting too hot (scorch marks on the PCB). The horizontal scan looks fine.

Bryce.

hooverphonique
30th July 2013, 14:32
I've fixed numerous crt tv's as well just by resoldering bad joints I could identify by eye.. what the exact problem with this one is, I've no idea though :-)

kipper2k
30th July 2013, 16:48
I think with most TV's the problem is normally a capacitor or a motherboard that has flexed with the constant heat and created cold solder joints. For those people that have a TV that will not turn on, do not throw it away. 99% of the time it is a blown electrolytic capacitor on the power board (The board where the wall voltage comes in). There are so many TV's chucked because of this

Bryce
30th July 2013, 22:02
True, but in todays throw-away culture, TVs are dumped even when they work perfectly :(

Bryce.

AmiNeo
31st July 2013, 01:22
We have a TV, an LG Plasma, which keeps turning itself off when coming out of stand by (by going back into standby). This only happens when its been off overnight. After about 5 or 6 attempts (sometimes one or two more) it will come on and stay on and work fine.

I don't suppose this could be easily fixed? :unsure:

Sorry to hijack the thread but it didn't seem worth opening a seperate one.

kipper2k
31st July 2013, 02:41
We have a TV, an LG Plasma, which keeps turning itself off when coming out of stand by (by going back into standby). This only happens when its been off overnight. After about 5 or 6 attempts (sometimes one or two more) it will come on and stay on and work fine.

I don't suppose this could be easily fixed? :unsure:

Sorry to hijack the thread but it didn't seem worth opening a seperate one.

This should be an easy fix. The electrolytic capacitors on the power board are probably blown. The hardest part is getting the back cover off and getting at the power inverter board, (It will be the same board where the 110v (240 in your case) power enters into the TV, Remove that board and check the caps and you will 99.9% find bad capacitors, change all of the electrolytic ones, there would probably be about 8 or so of them. Don't cheap out on the replacement, buy Panasonic caps. Make sure you take lots of pictures of the disassembly process so you can see what everything looks liek before you do each removal/disassembly step.

I notice you live not too far from New Brighton, i used to love that place as a kid :)

AmiNeo
31st July 2013, 02:44
We have a TV, an LG Plasma, which keeps turning itself off when coming out of stand by (by going back into standby). This only happens when its been off overnight. After about 5 or 6 attempts (sometimes one or two more) it will come on and stay on and work fine.

I don't suppose this could be easily fixed? :unsure:

Sorry to hijack the thread but it didn't seem worth opening a seperate one.

This should be an easy fix. The electrolytic capacitors on the power board are probably blown. The hardest part is getting the back cover off and getting at the power inverter board. I(It will be the same board where the 110v power enters into the TV, Remove that board and check the caps and you will 99.9% find bad capacitors, change all of the electrolytic ones, there would probably be about 8 or so of them. Don't cheap out on the replacement, buy Panasonic caps. Make sure you take lots of pictures of the disassembly process so you can see what everything looks liek before you do each removal/disassembly step.

Thanks, I'll keep that in mind. I had a hunch it would be something like that.

Unfortunately its my grandparents TV, so convincing them to let me open it would be difficult. I may be able to persuade them if it gets worse though, and now I know what to look for. :thumbsup:

kipper2k
31st July 2013, 02:47
They'll let you open it when they can no longer turn it on, that day will come, and won't be long now

AmiNeo
31st July 2013, 02:50
They'll let you open it when they can no longer turn it on, that day will come, and won't be long now

My thoughts exactly! :lol:

rkauer
31st July 2013, 05:29
But then the problem might go to other parts of the TV as the voltage ripple can harm the digital chips.

Tell him to do the maintenance as soon as possible. Be that you or a technician of your grandpa's choice.