I found this on the DMD diver in an AFM I got recently... is this someones way to turn a normal fuse into a slo-blow fuse??

I used this driver (which was working fine on the AFM) in a Congo (to see if it would fix a flickering DMD on Congo that is proving very hard to fix), and it appears to have killed the DMD totally... I'm scared to put it back in the AFM now in case it kills the DMD in that game too...

I'm guessing I should pull this cap-bridged fuse with something more standard before I fire it up in any game again... Anyone know what fuse should really go in F602?

Any clues as to why it would blow the DMD? It's totally dead... It's a Babcock, so all the components are exposed (as apposed to Cherry), so possibly fixable?

Any advice/guidence greatly appreciated before I slowly destroy everything I've got!!

Cap_on_fuse.jpg

You should see the other hacks on the AFM, it's quite entertaining

My concern with the driver is why the hack is there... I can easily swap the fuse with what should be there, but I'm guessing there's an underlying problem that made the hack necessary in the first place, and this problem could be what blew my DMD, and potentially others...

What I could really do with is some basic knowledge on how to trouble-shoot the DMD driver for WPC 95... Any links to good sites for this now the Marvin repair sire is no longer...?

Thanks for that link tpf, that looks the ticket!

You're probably right, and that's probably why I have a dead DMD now instead of one that was just flickering a bit... although the yellow thing is a capacitor, so not a direct short, just a way to smooth out sudden large currents I guess, like a slo-blow fuse would, although the peak current and time factors of the original fuse are probably not accurately reproduced by the hack

Thanks johnwartjr, your help is humbling!!

On the original driver, where the DMD was flickering, I played the game for ages without an issue (apart from the flickering), I tried to cure this by changing the DMD and by adding a ribbon cable that had a ferric core on it... This original driver looks very clean. My last step to try and stop this flickering was to install the driver from another game which was working well on that game. On inspection, this has a lot of charring on the top right corner and on the rear, with some hacking/jumping going on. Here are the voltages I measured on each driver:

(Edit: I see Pinside has removed the spaces so the table's a bit messed up, but I'm sure you can work out what figures relate to what board)

Original that flickered DMD New that blew DMD
Pin1: -77 -117
Pin2: -55 -93
Pin6: +5.07 +5.07
Pin7: +11.86 +11.84
Pin8: +62 +66

Looks like the one furthest from spec is the one that didn't blow the DMD... I guess the +66v on Pin8 of the new board is what blew the DMD...??

So, what's your diagnosis?

Thanks again for all your help!!

Edit: On looking back at the voltage ranges, the 'bad' one (i.e. that resulted in the DMD dying) is pretty much in spec except on Pin2 where it's a bit low... but no-where near as bad as the board that was working but with a flickering display... Now I'm thinking that the original board is bad, and this somehow damaged the DMD, so that when I put the in-spec driver in, it couldn't cope with the sudden increases in voltage... so maybe the DMD was faulty anyway... Does this sound possible??

That's what I thought!

I turned the game off while changing any connectors (the the DMD and the driver). Yes, maybe it was on it's way out, and the higer voltage of the in spec driver pushed it over the edge...?

I'm OK with all of this, except the pair of dykes... where I come from this means lesbians... so am a bit lost on the nomenclature on this one

Thanks for the link to the greatplanes electronics, they certainly do cater well for the pinball community, and order will be placed!! And thanks for all your help... I can do the repair, I just have a lack of understanding of electronics... a big negative in this hobby, so I really appreciate all the advice I get... I'd love to sit down with someone who knows about all this for a day or two and get taught the basics so I don't have to ask such dumb questions all the time...

By the way, on the now dead DMD (which wasn't outgassed, so a shame to lose), I seem to remember reading that these are not so hard to repair... maybe greatplanes sell a kit for them too which includes all the common components that will fix 90% of duff ones?? The board looks like new, there was no smoke or bad smell or audible 'pop' when it went... I just saw around 30 dots light up in a roughly vertical line in the middle when I powered up, and that was the end of it...

I'm not aware of any 'slang' term for these in UK English... we just call 'em 'side cutters'...

I've doug out an almost dead DMD from my stash this morning (lines out, de-gassed and a bad ghost) which I'm going to try with the most in spec driver (the one that apparently blew the display that was in there) and see if it blows this one too (clearly not an issue if it does apart from me losing a good board to do tests like this!!).

I've managed to fix lines out in the past on pin leg types (i.e. not ribbon connector type) by granding the glass away at the failed leg with a Dremmel 'till I can see the shine of the metal as it goes through the glass, and getting some solder to stick to that... it's very tricky though, and I'm not sure it's good for my health, all that glass dust flying around can't be good!!??

Maybe I was dreaming, but I could have sworn that I read somewhere that 90% of blown DMD boards are easily fixed...??

Damn, they're out of stock on these... I've asked to be notified when they're back in... Alternatively I could work through the list of parts and order 'em seperately I guess...