Viglen CRT monitor intermittent jumping

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Ive got it all back together and powered up and it seems quite happy and tube lit up. Still no picture when connected to PC though. I had a another go at testing for a video signal on the pins that carry the RGB signals. I used the Isotech scope this time and I got this display that does look different to what I get from the pins on the dsub connector. I read a article online that covered measuring video signals on a anolouigue and digital scop[e and it says its very hard to get a decent display with out something call a video trigger which I dont think this scope has. Anyway does this picture look anything even remotely useabe?

[R_J]

Re: Viglen CRT monitor intermittent jumping

If you really want the video to be stable and triggered you are just looking to see where it is being lost.
If you really want a stable video signal for one video frame or one line, feed the vertcal sync pulse from the pc into channel 2 of the scope and have the scope set to trigger on channel 2
That could be good video? what is the pc outputing? a single c:> prompt a bios menu?
Adjust the variable on the trigger control should provide a single frame of video.

Type stuff on the keyboard and you should see the waveform change

Remember this is a video signal that has NO sync pulses within it so it is hard to display a steady pattern. It is NOT like a regular broadcast composite video signal, that has the sync as part of the video waveform.
On the computer the vertical and horizontal sync pulses are on seperate pins.

I will take a guess at the video displayed on the scope and also guess that the scope trace did not start at the start of the scan (likely triggerd by some part of the video)

[R_J]

Re: Viglen CRT monitor intermittent jumping

Check if there is any video on the neck board, R in, G in, and B in. also check if you have voltages on Q807 e-b-c.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Check if there is any video on the neck board, R in, G in, and B in. also check if you have voltages on Q807 e-b-c.

Q807 has between 2.4 & 3.6v on all pins
The RGB wires conected around the tube dont show any signal. The scope screen goes blank. (There is a Red, Green, Blue, & Yellow on that group of wires, is the yellow a sync or something?

That could be good video? what is the pc outputing? a single c:> prompt a bios menu?

The PC boots straight to a graphical type desktop call GEM (graphical environment manager)

[R_J]

Re: Viglen CRT monitor intermittent jumping

You say the scope screen goes blank when checking for a signal on these 3 points? What is the input voltage range on the scope set to and is it also set to AC and NOT DC.
You should have a similar signal on the neck board as you measured where the DB9 connector connects to the mainboard, only the amplitude would likely be larger.

I am starting to suspect there are no or low voltages to the area that does the signal processing on the main board.

I also don't see any yellow wire going to the neck board, The r,g,b wires between the neck board and main board are thin coax cables.
There are no sync signals that go to the crt board.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

You say the scope screen goes blank when checking for a signal on these 3 points? What is the input voltage range on the scope set to and is it also set to AC and NOT DC.
You should have a similar signal on the neck board as you measured where the DB9 connector connects to the mainboard, only the amplitude would likely be larger.

I am starting to suspect there are no or low voltages to the area that does the signal processing on the main board.

I also don't see any yellow wire going to the neck board, The r,g,b wires between the neck board and main board are thin coax cables.
There are no sync signals that go to the crt board.

Looks like a misunderstanding, I was thinking when you said neck you meant around the base of the tube where where are 4 wires RGBY solderd on. These come up from the 4 pin connector on the pcb. Sorry about that I ested the right 3 coax wires on the tube pcb and they do have the same signal as that on the 9 pin D connector.

[R_J]

Re: Viglen CRT monitor intermittent jumping

So you are getting the video signal to the crt neck board (the board that plugs onto the crt). Now see if you are getting it to the transistors on that board.
On the plug that goes to the neck board that has the 3 video signals, there is also a red wire, what is the voltage on it?

That picture you provided is the side of the deflection yoke, you don't need to check anything on it.

[petehall347]

Re: Viglen CRT monitor intermittent jumping

wondering if the power has been knocked out for the neck board . wouldn't think it was all dead otherwise .

[R_J]

Re: Viglen CRT monitor intermittent jumping

I had him check the +115 and he said it was there, I also asked about Q807 "Q807 has between 2.4 & 3.6v on all pins" which seems low?
So now I am asking about a lead (red wire)that goes from the main to the neck board as I think it could be a supply for the board.

Its hard to trace based on the pictures that are obscured by wires, and no schematic.

[petehall347]

Re: Viglen CRT monitor intermittent jumping

all i was thinking in the past i have seen a lost colour because of bad transistor . on that board . its been a long time since i played around with crt though .

[roadrash]

Re: Viglen CRT monitor intermittent jumping

So you are getting the video signal to the crt neck board (the board that plugs onto the crt). Now see if you are getting it to the transistors on that board.
On the plug that goes to the neck board that has the 3 video signals, there is also a red wire, what is the voltage on it?

That picture you provided is the side of the deflection yoke, you don't need to check anything on it.

Oh sorry that is called the deflection yolk. There is video signal on the power transistors but I can ony measure 1.0v DC on the red wire (next to orange wire) on the neck board. The tube heater light is a orange glow shouldnt it be a bit brighter than that?

[R_J]

Re: Viglen CRT monitor intermittent jumping

but I can ony measure 1.0v DC on the red wire (next to orange wire) on the neck board

That was one of the first voltages I asked about (back in post #26), you said there WAS 115 volts on that red wire

Quote:
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.

Using "the picture", point to the wire you unsoldered during cap removal.


But that is still not the voltage I asked you to measure. but that 115v needs to be there because it is the supply voltage for the R,G.B driver transistors (the big to220's on the neck board)

[roadrash]

Re: Viglen CRT monitor intermittent jumping

That was one of the first voltages I asked about (back in post #26), you said there WAS 115 volts on that red wire

Using "the picture", point to the wire you unsoldered during cap removal.


But that is still not the voltage I asked you to measure. but that 115v needs to be there because it is the supply voltage for the R,G.B driver transistors (the big to220's on the neck board)

I forgot to change the scale on the meter to 200v, I am measuring 125v now on this wire.

[R_J]

Re: Viglen CRT monitor intermittent jumping

Ok thats good, now whats the voltage on the other RED wire I asked about? It supples a lower voltage to the video circuit on the main baord and also up to the crt neck board
On one of your pictures that regulator ic looks like it could be a 7812, so the red wire should have 12 volts on it

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Ok thats good, now whats the voltage on the other RED wire I asked about? It supples a lower voltage to the video circuit on the main baord and also up to the crt neck board
On one of your pictures that regulator ic looks like it could be a 7812, so the red wire should have 12 volts on it

The other red wire on the neck board has 11.8v.

[R_J]

Re: Viglen CRT monitor intermittent jumping

Ok thats good, one more voltage to check would be the G1 voltage (green wire on crt neck board next to R82?) If my memory is correct it should be a negative voltage

[roadrash]

Re: Viglen CRT monitor intermittent jumping

Ok thats good, one more voltage to check would be the G1 voltage (green wire on crt neck board next to R82?)

G1 is a brown wire. It measures 63.3v

[R_J]

Re: Viglen CRT monitor intermittent jumping

ok brown, I don't think that voltage is correct, If I remember it should be a negative voltage, check where the wire leads back near the high voltage transformer, and check the few components that are there, I can't really see where it goes.

[roadrash]

Re: Viglen CRT monitor intermittent jumping

I am not being very observant because it is -63.3v. So sorry but maybe i can be excused as i got your reply when i was in bed and got up and went to test it quickly so it didnt have to wait until the next day. That brown wire connects into the main pcb right next to a little coil/tranformer and there are only a couple of resistors next to it.

[R_J]

Re: Viglen CRT monitor intermittent jumping

I thought that was the problem. oh well onward and upward.
Near the brightness control is a transistor marked Q212 check its voltages and see if they change when the brightness control is varied. that transistor conects to a wire at (C1) near q204 and I think goes to (C2)the area of the G1 voltage.
The brightness control should vary that -63 volts if I am correct