Monitor problem Bally Game Maker - Horizonal size not adjustable

[gstanwood]

The Horizontal size of picture on the screen  is too large for the monitor and the horizontal size control does not work all othe horizontal functions work. All caps were  replaced. Unit worked fine for about 2 weeks then this occurred.
I do not have a schematic for unit monitor is a Tatung VS-14428. Any suggestions as to what to change ie or does anyone have the Schematic which would help.

[gstanwood]

hey guys anyone worked on the Tatung VS14428 which had a horizontal size problem.
It can not adjust and it is in its largest state over filling the screen.
Please let me know your thoughts
Regards
Greg

[rokgpsman]

this thread possibly has schematic and info for you:
http://newlifegames.com/nlg/index.php?topic=5513.msg29186#msg29186

[gstanwood]

Thanks a great read  but all caps have been replaced all ICs and transistors around the horizontal size area have been replaced as well . I am now replacing mylar caps and resistors.
The Schematic is close but notexactly the same any help identifying components associated with horizontal size would help. Thanks for the response

[shortrackskater]

Did you check and clean the horizontal size potentiometer, just to rule it out ?

[cowboygames]

Do you actually have a horizontal issue? Lines across the top of the screen would be vertical foldover. Or a picture that's to tall or to short or whatever. A picture that's to wide or to narrow would be a horizontal issue.

[rokgpsman]

Thanks a great read  but all caps have been replaced all ICs and transistors around the horizontal size area have been replaced as well . I am now replacing mylar caps and resistors.
The Schematic is close but notexactly the same any help identifying components associated with horizontal size would help. Thanks for the response

Can you post a picture of your screen so we can see what the problem looks like?

There's probably a resistor on the board that is in series with the horiz width adjust pot that works with it to set the width. Maybe the pot or this other resistor has gone bad. If one of them is bad that could explain why you can't get it to adjust. Can you take a close look at the board where the horiz width pot connects to other parts on the board, check for burned/broken or damaged parts?

Although the prior schematic that was shown is not exactly the correct one for your monitor I'll use it to show you what I'm talking about. Look at IC601 pin 11, it is labeled "DUTY". I think the voltage on that pin sets the horiz width of the screen image. You can see that on this schematic there isn't a pot, just R615, R617 and R618 that form a voltage divider between 12vdc and ground. On your monitor one of those resistors is the horiz width pot. Check in that area, whatever the equivalent chip is on your board. You should be able to vary the voltage on pin 11 to adjust the horiz width size. This is just a WAG, for whatever it is worth.

[rokgpsman]

The Horizontal size of picture on the screen  is too large for the monitor and the horizontal size control does not work all othe horizontal functions work. All caps were  replaced. Unit worked fine for about 2 weeks then this occurred.
I do not have a schematic for unit monitor is a Tatung VS-14428. Any suggestions as to what to change ie or does anyone have the Schematic which would help.

another idea,,,

If you mean that it worked fine (including the horiz width) AFTER you did the recapping, and then it started doing this after the recapping then you may have installed one of the new caps backwards. When this is done they will work ok for a while then fail. Double-check that those caps you installed are correctly inserted, there should be + or - marks on the board showing polarity.

[gstanwood]

Yes Pot was checked probably as you say a resitor or cap gone bad please see the picture -the horizontal is not adjusting
Thank you for your assistance
Greg

[rokgpsman]

Thanks for posting the picture. Have you taken the monitor housing cover off and made sure the yoke deflection assembly hasn't slipped backward on the crt neck like I mentioned earlier? That's probably not it since I would think the horiz width control would still have some effect even if that had happened, but possibly you can't see the leftside and rightside edges moving if the image width is way out there off screen. Another thing, if that horiz width pot is located off the main circuit board, like under the front bezel or someplace then there will be wires connecting it back to the circuit board, make sure none of them are broken at either end. Or if the horiz width adjust is a plastic shaft connected to the pot, the shaft may have broken and it turns but doesn't actually turn the pot itself. Do you feel the stop ends of the pot as you turn it from one extreme to the other?

Without an accurate schematic it is just guesswork. You can follow how the horiz width pot is connected to the circuit board, look at the board traces to see what other parts are connected to it. Maybe the circuit board has the Tatung part number written on it and schematic for it can be found. 

[rokgpsman]

I was reading an arcade repair blog and someone had a similar problem with their Tatung monitor, the width was too wide and wouldn't adjust. They said the horiz width adjust is VR2 over in the right hand corner of the schematic and it wasn't changing the screen width. When they replaced C9 and C19 it fixed the problem. C9 and C19 are 4.7 uF 50v caps in the IC1 (LM358) circuit. They also said to make sure R31 hadn't overheated or changed in value.

Were these some of the caps you replaced when you did the recapping?

see yellow highlighted areas on attached schematic:

[gstanwood]

thanks for the information sofar I metered out cables all ok measure pot and is variable 0-50k which is the value I [size=78%] did change these caos [/size]
[/size]Also change other mylar caps just to varify I changed these caps again still same problem [size=78%]
[/size][size=78%]I will chaqnge the 39 K resistor later this morning and see not to many components left to change  if all does not work I will change thew  LA7838  chip . The other op AMPs were changed out already . LM358[/size]
[/size][size=78%]Eliminating alot Thanks for the help[/size]
[/size][size=78%]Cheers[/size]
[/size][size=78%] [/size]

[gstanwood]

hey after great a due we have lift off Houston - I changed all resistors and mylar caps associated around the horizontal size area for I have no schematic
All electrolytics were replaced too
Thanks for the support

[rokgpsman]

looks good from here, what was the fix that corrected the problem?


Nice looking machine by the way!

[gstanwood]

changed out all resistors around Horizontal size area and Mylar Caps for all electrolytics were changed before.
put in some higher voltage  rated components  and it works now  as per picture
Thanks for all the help

[rokgpsman]

Do you suspect one of the resistors had changed in value or opened up? Were some of the resistors you changed on this last go-around in the same circuit as the horiz width pot? Can you put a meter on the resistors you took out, just a few of them right?

[gstanwood]

The 39k resistor in horizontal size curcuit opened up under load it reads fine statically out or in  curcuit without power applied very hard to trouble shoot but found it and it working great now.good news is the board is totally rebuilt because of the trouble shooting and I currently learned a lot about this monitor. All good times
Greg

[rokgpsman]

Thanks for that info, we like to get the final solution to any problem involved with, can help others down the road. Good job on your repair and enjoy that terrific looking machine!