Do RunRun graphic problem

[Pflaugi]

Hello,
there are graphics problems with my Do RunRun.







I checked out the board. Noticeable are a SN74LS74AN and a SN74LS161AN.



With the SN74LS74AN there were 5 volts at PIN 14 normally, but at PIN 2 I have 0 volts and at PIN 3 only 0.05 volts ... I don't think so much ... The values are constant.







The SN74LS161AN has constant 0 volts on PIN 3 and 4 ...
I'm a beginner in board repairs. Could it be that these two ICs are defective?

 

[Pflaugi]

I was wrong. when I see that, PIN 3 and 4 on the SN74LS161AN are on GND. Sure that they then have 0 volts.



on the SN74LS74AN PIN 2 is also on GND ... but the 0.05 volts at PIN3 make me wonder ...



Does somebody has any idea?

 

[Pflaugi]

Do RunRun is working again!

the bit from E6 pin14 floated at 2.5V. So I changed the 4164 IC from E6.
D6 was wrongly unsoldered by me. But that was okay. I put it on a socket and built it back.







Many thanks to the Arcade friends who helped with the repair.

 

[stj]

did it not have a ramtest built in?