Blast off system 1 namco , only blue,

[Retroman839]

CE on 11 is active low donated by te CE Bar, which means its fine and is enabling output. Faulty if stuck high.

To completely rule out the customs you need to probe the 8 data lines G and R. You already highlighted G in red box on the schematics above.

Thanks for this info really helps

I’m assuming I’m counting pins correctly
1 starting top left and going clock wise round.

My probe has the tone which really helps..
When Matching the signals..

 

[Retroman839]

What will I be looking for whilst probing the 8 data lines of
Rgb? Sounds like I don’t whant to be getting STUCK HIGH signals from what you have already mentioned.

I have probed some of them whilst probing cus116 originally just for a
Differing signal..

So I know i was getting signals.. from them..
But should I be getting equal signals from data lines

R-0 G-0 B-0 Will get Same probe signal ?
R-1 G-1 B-1. Will get Same probe signal?
Etc…

I’m trying to establish the cus116 is ok.
It’s just I might get signals but I want to know what signals
I’m looking for… stuck high sounds bad.

Retroman8392022-06-23 19:07:38

 

[John Bennett]

You're just looking for stuck bits. You might find all the bits for red and green are stuck at zero coming out of the custom.
Doesn't mean the custom is knacked though - it'll be reading those RAM chips, so if they're duff and returning zeroes for Red and Green, then the custom won't put anything out.

 

[Retroman839]

Agh ok
Yeh I have some chips that seem to hot
This could be the issue

 

[Retroman839]

Ok been on the logic probe..

Collector of the 3 transistors tr4 tr5 & tr6 is stuck high.

Along with on cus116 Pins 34,43,53,67. Also stuck high

Retroman8392022-06-26 16:39:41