Build Your Own Arcade Controls Forum

Main => Monitor/Video Forum => Topic started by: subwyking on October 18, 2011, 12:04:18 am

Title: No contrast adjustment wg 25k7193
Post by: subwyking on October 18, 2011, 12:04:18 am

Hey folks. I have a wg 25k7193 connected to an arcade VGA 3000.  I have the picture dialed in how I want it with the exception of the contrast. My colors seem a bit washed. I've already done a cap kit, and that really cleared up some of the anomalies I was having. The pot for the contrast adjustment is having absolutely zero effect on the screen.  Any suggestions on how to proceed from here?
Thanks
Russ

Title: Re: No contrast adjustment wg 25k7193
Post by: Ken Layton on October 18, 2011, 12:12:19 am

Arcade monitors expect a video signal of 2.5 to 5 volts. Computer monitors typically expect 1 volt or less.

Are you getting a strong enough signal to the monitor?

Title: Re: No contrast adjustment wg 25k7193
Post by: subwyking on October 18, 2011, 07:28:33 am

I wondered if that may have been the problem. Andy's web page made it seem that Wells Gardner monitors didn't need the stronger signal. Do you think a video amp will clear up the issue?
Thanks
Russ

Title: Re: No contrast adjustment wg 25k7193
Post by: boardjunkie on October 18, 2011, 08:13:57 am

http://www.ultimarc.com/vidamp.html (http://www.ultimarc.com/vidamp.html)

You need onna those.

Divemaster is located in the US and sells most of the U-marc product line.

http://arcadeemulator.net/ (http://arcadeemulator.net/)

Title: Re: No contrast adjustment wg 25k7193
Post by: subwyking on October 18, 2011, 10:06:46 am

Ok, I put in an order for a video amp, hopefully that clears up my issues!  Thanks for all your input guys!!
Thanks,
Russ

Title: Re: No contrast adjustment wg 25k7193
Post by: castlesteve on October 19, 2011, 02:23:41 pm

sorry, but a video amp is not going to fix your lack of contrast adjustment.  While still a good idea, you need to find the part assoc with contrast.

1st)  id check the pot itself on the control board. look for a hairline crack where the legs meet the pot. 
2nd) I know how to fix contrast issues on U2k/u5k boards off hand, but not if a cap kit didnt do it... you'll start have to checking resistors etc in the circuit.

Title: Re: No contrast adjustment wg 25k7193
Post by: subwyking on October 19, 2011, 08:50:31 pm

You hit the nail on the head. One of the legs had a cracked Pcb. Thanks!  Now only to find a suitable replacement.

Title: Re: No contrast adjustment wg 25k7193
Post by: subwyking on October 19, 2011, 09:46:32 pm

I can't upload a picture of the pot....

Title: Re: No contrast adjustment wg 25k7193
Post by: subwyking on October 19, 2011, 09:48:52 pm

Hmmmm....  Well it's a 10k ohm pot that sticks up from the PCB. Can anyone point me to a suitable replacement part from radio shack?

Title: Re: No contrast adjustment wg 25k7193
Post by: ed12 on October 19, 2011, 10:29:32 pm

small white 1 or black ?
either, there should be room in the :land's: for another size pot

ed

Title: Re: No contrast adjustment wg 25k7193
Post by: subwyking on October 19, 2011, 10:33:15 pm

Small white one.

Title: Re: No contrast adjustment wg 25k7193
Post by: boardjunkie on October 20, 2011, 08:28:14 am

Oh....I was reading that as a lack of usable range on the contrast control. Anyway....you still need the video amp.

Title: Re: No contrast adjustment wg 25k7193
Post by: subwyking on October 21, 2011, 08:22:45 am

Replaced the pot with a Radio Shack part, and it works like a charm!  Thanks for your help guys!!  I'll let you know what sort of improvement I get with the video amp.
Thanks,
Russ