The Three Stooges, I mean Bezerks. Blowing life into them again....

[level42]

....
Bad: The third working ZPU died. I don't know why yet, but I was installing the backup battery on my and Superully's board and for some reason it doesn't want to boot anymore. The second (my) board works great after the back-up mod, just as Muerto's and I'm 100% sure it is not because of the mod......
Already replaced a transistor that was definitly defective, but still no go....

Will have to wait to tomorrow night though...

SO, I decided today I was going to fix that board. For a change, I was lucky in finding a problem ! The board was booting up but giving only 2 beeps/flashes.
I first replaced the ROMs but that didn't help. Next I tried the RAMs (although that should give another beep) and as expected this didn't help either.

With the manual and schematics (and comparing with the working PCB) I pretty soon found out that there was no connection between one pin of R28 and pin 8 of RAM 1E. Pretty soon found out which track was affected and bridged it by a wire.

And YES it ran 100% again. However, while I wrote this message it spontanously rebooted while in attract mode.....rats ! I just played a couple of games and now it seems to be stable. I will revers the RAMS and ROMS and do more extended time testing tomorrow.

If this shows one thing is that these boards are probably always going to be suspect to possible problems. The acid creeps to places you can't see it or detect what it did.

I'm pretty convinced that at some point in time switching to ZZPU's might be the best way to go, but for now, these are not available.

At least, a major leap in getting the working board working again (it was working when I received it from the US).

[petieken]

After all those repairs you've already done you'll soon be the Berzerk-repair-expert

[Muerto]

fantastic! - i think ully agrees!
 

[level42]

We're not there yet. Just let it run again a bit and again it rebooted spontaneously.

(Didn't change the ROMS and RAMs yet though). I also switched Ully's PS board (that I had in the machine over the last 4 weeks or so) to my own PS, so this may be a problem too.

To be continued...

[Superully]

thx andré, your efforts are highly appreciated!

[level42]

Wait 'til you get the bill 

Just found another broken track....no time to fix now though...to be continued tomorrow night....

[METALHEAD]

I love following these hehe

[level42]

Thanks !

I just repaired the second bad track.....it was actually  pretty interesting. I measured an "open" between the emitter of Q1 and diode CR26 in diode test. I was just randomly testing some tracks in the area around the other bad track. When I switched to the ohms setting it read about 500 Ohms, a bit later around 1000 ohms. So apparently the track was sometimes conducting "just enough" to let the board run and sometimes not. Again I just bridged that bad track, and I've been playing about 5 games and it's been running in attract for 45 minutes now and not a single re-boot....so I think we can say: Ladies and Gentlemen, We Got Him !

Will give this board the vinegar "bath" tomorrow. Although it worked when I received it, it went dead pretty quickly. There are obvious spots of acid still on the PCB, and clearly, it is doing "it's work" still.... need to stop it !

After that it's backup-battery installing and it should be done ! Phew....

[ckong]

Now I know what the term 'Die Hard' means  

[Muerto]

.... damn you´re good

[Superully]

.... damn you´re EXTREMELY good 

[Muerto]

is there an echo here??? 

[petieken]

Will give this board the vinegar "bath" tomorrow. Although it worked when I received it, it went dead pretty quickly. There are obvious spots of acid still on the PCB, and clearly, it is doing "it's work" still.... need to stop it !

So the vinegar stops the acid from eating the copper? Good to know!

My friends' T2 pcb has spots around the bad ram chip that look like acid damage, but the thing is there isn't a battery near them... There is a lithium cell on the board but it's on the other side, and there's no damage there. I'll try the vinegar trick on the ram area and see what happens.

[level42]

Use what we call "schoonmaak azijn" and not the kind you put on your salad

I've read somewhere that people actually mixed it a bit. So far I used the pure stuff, not sure if that's the best way to go. Vinegar is also an acid.(you can smell it).
SO be sure to rinse with water richely after the vinegar has done it's work.

It's actually quite fun to see the reaction when you apply it: http://www.youtube.com/watch?v=0gDi--jrAdk

Regretfully the bubbling already stopped mostly when I shot this...

PS, from what I remember from my chemists lessons, shouldn't we fight an acid with a base instead of with another acid ?

[petieken]

Hmmm, I should have paid more attention during chemistry class when I was still in school....