60 in 1 iCade PCB - red colour missing

Yesterday i got a 60 in 1 multiboard from my friend Henrik

it had a error... the red colour is missing!
Perfect for a littel field action.  I still need all the practise i can get :o)
So lets hook it up to the super gun and see what we got

Well that sure dont look right... i have hooked it up to the super gun, but am here using the VGA port (for use on an old PC monitor, but my test TV also have a PC in)

Lets try to put in in test mode by moving dip switch nr 4 on

Yup, still bad clours. So its time to finde our magnifying glass and pretend that we are mr sherlock holmes :)

If we look at the Jamma Pinout, we can se that nr 12 on the parts side is the RED clour.

By following the trace on the PCB an confirming with my multimeter on connectivity (with beeb sound) i first trace it to resistor R78 on the left side of the VGA port

To be sure i am on the right track i used a "poker" ( a test lead hooked directly to +5V.. a trick i found in my master and mentor Elgens repairs blog) and hit resistor R78 with +5V. When i did that the screen quickly flashed red... OK.. we are on to something here. Those SMD components are sure small, and the PCB looks nothing like the old one from the 80´s and 90´s we are used to work on.. Phewww, be carefull with the "Poker"!!!

I also found the resistor R79 is green, and R80 is blue... so lets continiue up stream

The trace ran fro R78 under the cap C77 and ended on resistor R52

On the other side of the resistor it went to a HC273 TTL Octal D Flip-Flop and thats were it ended. So by eliminating all other options, it got to be a faulty TTL..

Luckily Henrik gave me a spare 60 in 1 that had sound issues, so now i had a good reason to use my new SMD rework station :)

Man those SMD components are small

I replaced the the right TTL that i have traced the signal back to, tested it in the super gun, still using th PC input...

And hey presto.... nice clours all around :o)

 But when i went back to the scart cable (using Jamme RGB ) the clours were still a little off !????
Well , there were 2 x HC273 TTL´s , and lets guess.. If there are 2 TTL´s next to each other, and 2 RGB outputs, maby they each controll an output, and if one TTL is bad, maby the other one is also faulty.. Lets change the left TTL also, just for the hell of it.... And wouldent you know, all the clours is now back on the Jamma out put also

 Thanks to Henrik for the boards :o)