Hi all,

I'm having a curious problem with my GnR pinball machine and I need some extra eyes on the matter to shed some light into this mess!

So this is what's happened:
Last year Q52, of the green-yellow wire (only used for the pops and slings), was fried.
No problem, I replaced it and all was well once again.
What I did notice than is that the previous owner had disconnected all the green-yellow wires from the switches and resoldered them.
This is when I suspected there might be another problem but after looking into it everything looked to be in order...
So I put in a paper with the date of when I replaced Q52 just as a reminder.

A year further, the exact same thing happened.
So now I'm certain there's something causing Q52 to die.
What I did was cut all zip-ties and inspect the complete wiring to make sure there was nothing causing a short of some sort.
Inspect all mechanics so that they can't make a short with the switches etc.

Alas I can't find anything wrong or any cause to fry Q52.

Hence why I would like to hear some other opinions regarding this matter.
There's no single problem with either the slingshot nor the popbumper switches and no short or cable break anywhere at the green-yellow wire.

The two times the fault occured was at the Belgian pinball championship when we have a LOT of machines playing at the same time and the GnR also got a lot of heavy play for at least 10hrs on end.

I look forward to hearing some other thoughts and discuss some solutions to make this GnR reliable again!!!

Yes they all have diodes on them and they're connected the correct way.
When I measure the diodes, they measure exactly as they should.

All voltages are checked and fine.
Good remark about the RA6! Sadly enough this also isn't the cause with my game as the three resistor arrays are all fine.

I also have the idea that the previous owner changed out the CPU with another one when he had the problem but I'm not quite sure of that of course...

I'll check ALL switches on the playfield just to make sure there's not a switch out of the green-yellow string causing Q52 to short out.

Replaced Q52, played only 5 games and it's dead again... The search continues!

So I worked a little bit further on this and cut open the wiring loom to find any shorts which might cause the Q52 to short out every time.
I couldn't find anything out of the ordinary and every wire out of this string is fine and not touching anything else.

The search continues... Any tips are appreciated though!

On a sidetrack though, the CPU from this GnR does not have a matching serial number so I suspect the previous owner must have had the same problem years ago since he did solder already on those wires. The game has worked in my collection at least for 2-3 years flawless...

It's frustrating that this machine has been out of order for almost 2 years now
Basically because I don't have much time either too

Okay back at this one again…
Worked flawless for a while with Q52 replaced for like the 4th time.
I suspect a few years without an issue.

Few weeks ago Q52 was bad again, now it worked 20 games after replacing and it fried again.
No idea what could be causing this.
Are there differences in the 2N3904 chips?
All diodes from this column have been replaced too just in case even though I don’t think these can kill Q52…