sync hookup on ancient Pit Boss monitor

[Doughbroz]

I am attempting to connect a game that uses negative sync to an old 9" Pit Boss monitor.  I can find nothing on the chassis to indicate a model number or brand, but it is obviously Oriental in origin.  The video inputs are aligned on a single six-pin connector and are obviously R G B Gd VD HD.  No combination of sync hookup will produce a stable picture, and the Pit Boss worked perfectly, so the VD and HD are apparently positive sync inputs.  I have seen tips on using a 74xx chip to invert the signal, so is this what I need to do, and how exactly should it be done?  Thanks

[Ken Layton]

The 9" color monitor used in the old Merit Industries "Pit Boss" bartop games is probably a Kaga/TSK rebranded Nanao monitor. The Pit Boss board definitely generates positive sync and I believe this monitor only accepts positive sync.

Download a Romstar "Black Tiger" or "Sky Sharp" video game manual. These manuals (and similar vintage Romstar games) had a page in the manual on building a sync inverter from a 7404 chip. The page was a reprint from Star Tech Journal magazine.

[Doughbroz]

Ken, thank you for the reply.

[dabone]

Here is a link for a self powered inverter.

(no need to find the +5 for the 7404)


http://www.mikesarcade.com/wiretap/info/SyncInv.pdf

Later,
dabone

[Doughbroz]

Thanks for the info dabone.  I'm not quite schematic-literate enough to try it, but I had already tried the 7400 fix, which did the job OK.  In so doing, I first rough wired it into the game output, using the +5 and ground on the power supply,  and it worked.  Then I decided to mount it on the chassis and make it permanently negative sync.  When I used the +5 and ground on the monitor PCB though, it wouldn't work.  After I went back to the power supply hookup, it finally struck me that I had not grounded the chassis frame, so I assume that's the reason.  Being in a hurry, I didn't backtrack to check.  My friend picked up the game today, 'cause his wife couldn't wait to get her hands on it.  Thanks again to you both.   

[dabone]

It's the same circuit as what you used, but instead of running +5 to the chip, use diodes to bridge off of the sync signals to power the ic.



Laer,
dabone