Gorf Monitor problem maybe K4600?

rchadd

New member
Joined
Jul 21, 2005
Messages
41
Reaction score
0
Location
United Kingdom
Help I switched my gorf on today and now getting a bad display. I hope someone can assist.

Please see attached screen shots.

The game can just been seen to running/playing ok but the colours are wrong and very faint also there seems to be scanlines displayed too.

any ideas what could be the problem? would a cap kit help? is the tube dead?

I think it is a K4600 monitor (a label seems to indicate K4605/6)

I connected the video signal from the game to another monitor and it appears perfect, so this is definitely a problem with the monitor.

When i disconnected the video signal the scan lines still seem to be visible on a dark grey screen - i am not sure if that is relevant.

thanks for any advice/assistance
 

Attachments

  • P1010740.JPG
    P1010740.JPG
    92.3 KB · Views: 61
  • P1010741.jpg
    P1010741.jpg
    116.2 KB · Views: 52
  • P1010736.jpg
    P1010736.jpg
    96.2 KB · Views: 57
  • P1010742.JPG
    P1010742.JPG
    95.7 KB · Views: 38
hi unfortunately it seems that the capkit did not help the situation. as shown in original photo i am still getting same issue with the colours being off. the background is supposed to be black but appears as purple and text that should be yellow is appearing as white. i am also still seeing those scanlines that were in the original pic too.

i tried to adjust the screen, RGB and RB drive pots on the neckboard and that seemed to make the image either a more/less red or blue shade of purple and brighter. i did notice that the G pot did nothing to affect the appearance of the image. i am not sure, is that is significant?

could the problem be related to lack of green or too much red or blue signal to the tube from the neckboard?

would the next thing to check the transisters on the neckboard? any advice on how to test and verify if they are faulty?

i do not see any obvious burnt out components, short circuits or dry solder joints.

alternatively could this be fault with the tube itself? is there a way to test other than trying another tube?

i would appreciate any advice on how to proceed with the investigation!

many thanks
 
If you bought your capkit from Zanen Electronics, it would have included a brand new "black level" adjustment pot for the video interface board. Did you install it and adjust it?
 
hi ken

i haven't replaced the pot - do you think that could be related to problem?

i bought the caps locally from supplier here in uk. i couldnt get a pot looking like the one already there (eg 4 legs) . the only pot i could get was 3 legged sub-miniature type like this:

http://www.maplin.co.uk/Module.aspx?ModuleNo=6499

i wasn't sure if was ok to replace it with it or not? eg. how to wire this mmaller 3 legged version up?

should that be the next thing to do?

what about the green pot on the neckboard not having any effect? does that indicate a problem?
 
Ok thanks ken

i will need to check to see where i can get this tested. i guess a TV repair place would do this? Would they have tester compatible with arcade monitor tubes?

do you think bad tube is now the most likely problem? Any other components I should test? I am still wondering about the neckboard.

i suppose will need to first verify the tube is good

if the tube is found to be bad could i use old tube out of a MTC90 monitor? I have old one here. I see there is different connector on the end of it, but would it be electrically compatible if i just fit a different connector to the neckboard?

otherwise is it possible to buy new tubes these days that would be compatible with this chassis?
 
Check your RGB board mounted on the side of the cab. I just fixed a gorf that was barely visible and had scan lines and a cap kit didn't help. Swapped that RGB and it works great.

http://forums.arcade-museum.com/showthread.php?t=154920&highlight=gorf

Based on your pics, I'm confident that is your issue. Gorf is an unusual game due to that extra board and people don't always stop to think about it. I know I didn't!
 
i tested the game with a different monitor and it looked great so i think that indicates the gorf RGB board is ok. this is a monitor issue i think.
 
i seem to have fixed the issue :)

when i tested the transistors on the interface board with mulitmeter in diode test mode it seemed that following transistors were bad:

tr201, tr202, tr207, tr208

I replaced all these with new 2N3904 transistors and reflowed the edge connector solder and now it seems display and all colours are now good.

glad that it wasn't the tube :)
 
Last edited:
Back
Top Bottom