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In Progress Trying to save a Shadow from the scrapheap

So the new cmos chips arrived today so I set about removing the old chip and installing a socket

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And installing the new ram ....

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Reinstalled it into the machine and....

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He's alive! With some sound advice too....

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Nearly everything appears to be working on the playfield I even managed to play a short game, not a bad result considering the conditions this machine must of been kept in....

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The only major issue now is that I have no audio, when you first turn the game on where you would expect to hear the 'press enter for test results bongs it just a load of white noise type screeching at full volume. Nearly crapped myself when it did it.
I have reseated the proms, connectors and ribbon cable but it made no difference. Anybody got any ideas?

Also still nervously twitching for @PeteB to say wether he has the decal set :p

That's all for today :)
 
Just a quick update with the sound board, I have replaced d1 d2 d3 and d4, u25 c18 and c19 so far as these parts have turned up. Not made a difference. Still waiting on c20 and c21 and u26 (-5v regulator) but I have pit the scope on both the +5v and -5v rails and I'm getting nice smooth lines at +5v and -4.8v (the minus rails a bit lower than it should be) but I'm getting sceptical as to wether the last few components will sort it out. Anybody know what I should be checking if they don't sort it?

Cheers guys
 
happy new year everyone. I'm back on with this bloody machine and have replaced everything that has been suggested so far but with no luck. my question is this, anybody had any trouble with the DAC at u20? i was thinking of ordering one but they're not cheap to replace for fun.

also, should i get a self test bong from the audio board itself even if there is no ribbon cable connected?

would love to get this fault cracked so i can get the playfield stripped and sent to chris :(
 
happy new year everyone. I'm back on with this bloody machine and have replaced everything that has been suggested so far but with no luck. my question is this, anybody had any trouble with the DAC at u20? i was thinking of ordering one but they're not cheap to replace for fun.

also, should i get a self test bong from the audio board itself even if there is no ribbon cable connected?

would love to get this fault cracked so i can get the playfield stripped and sent to chris :(
The 2803A chip? If I told you they started socketing those buggers on later WPC revisions, would you catch my drift? ;)
They easily die when various things get shorted, best one being GI to switch matrix.

That being said - if you're guessing and don't know, don't throw your money away on guessing - get a logic probe along with your multimeter, and do a test of the CPU board in isolation - https://pinballrehab.com/1-articles...-rework-test/231-testing-wpc-cpu-on-the-bench
 
The 2803A chip? If I told you they started socketing those buggers on later WPC revisions, would you catch my drift? ;)
They easily die when various things get shorted, best one being GI to switch matrix.

That being said - if you're guessing and don't know, don't throw your money away on guessing - get a logic probe along with your multimeter, and do a test of the CPU board in isolation - https://pinballrehab.com/1-articles...-rework-test/231-testing-wpc-cpu-on-the-bench

All my switches are working fine no shorts to ground. Would that ic actually cause a phantom sound issue? Have I confused you by saying u20 as I mean the dac on the dcs board not the one on the cpu.

I have wondered wether it could be the cpu with a data fault but the flippers and dmd are working fine so I assumed the data and address lines are working ok. I also tried plugging the connector from the dmd controller onto the dcs board to eliminate that too.
Really wish I had another dcs board so I could prove my ram chips etc.

Thanks for the help this far
 
All my switches are working fine no shorts to ground. Would that ic actually cause a phantom sound issue? Have I confused you by saying u20 as I mean the dac on the dcs board not the one on the cpu.
Oops, sorry, I got that mixed up.

From your description of the noise, if it happens to go away after the Williams 'bong' noise, then you may be looking at U5 - a failing volume control chip. If not then it gets more complicated.

WPC-DCS and WPC-95 will bong while disconnected, if they pass their self-test and they have working ROMs installed.
 
I don't even get the bong noise :( there's just a small pause then when the first command is sent (entering test or opening the door to give the interlock message) I get full volume nasty screeching and need to turn the machine off because I fear frying the speakers. I have replaced the rectifier diodes, fuses, 10000mfd caps and both regulators. If checked continuity on these and they're fine. Next thing I can see is the dac.

I don't have any other dcs rom/ram chips so I can't eliminate them yet. I just know it's going to be something really simple that I will slap myself when I think of it.
 
I don't even get the bong noise :( there's just a small pause then when the first command is sent (entering test or opening the door to give the interlock message) I get full volume nasty screeching and need to turn the machine off because I fear frying the speakers. I have replaced the rectifier diodes, fuses, 10000mfd caps and both regulators. If checked continuity on these and they're fine. Next thing I can see is the dac.

I don't have any other dcs rom/ram chips so I can't eliminate them yet. I just know it's going to be something really simple that I will slap myself when I think of it.
As you said earlier @T-Dawg with no ribbons connected to audio board do you still get the screeching and no bong, ie its isolated to the audio board for def ?
 
The 2803A chip? If I told you they started socketing those buggers on later WPC revisions, would you catch my drift? ;)
They easily die when various things get shorted, best one being GI to switch matrix.

That being said - if you're guessing and don't know, don't throw your money away on guessing - get a logic probe along with your multimeter, and do a test of the CPU board in isolation - https://pinballrehab.com/1-articles...-rework-test/231-testing-wpc-cpu-on-the-bench
Hi interested in what logic probe you would suggest please as i see there are various sorts available,many thanks in advance
 
I'll double check when I get back to the shop but I'm pretty sure it's going to be a no.
I thinking if no screeching when no ribbon cables connected then it could be coming from CPU board - can you try the audio board in another machine or vice versa cpu board ?
 
I thinking if no screeching when no ribbon cables connected then it could be coming from CPU board - can you try the audio board in another machine or vice versa cpu board ?

Ok so had a little luck Now, sometimes when I turn it on with the ribbon disconnected I get what seems like an attempt at a bong. But it's garbaged and out of tone. Then complete silence. But it dosent do it all the time although I may not be leaving the machine off long enough for the caps to discharge. The rest of the time it's just pops and crackles.
With the ribbon connected if I start a game and put my finger on the top of u20 the sound goes nuts. Loud and screaming although still not noise you would expect. I have reflowed all around the area which had no effect. It could just be interference from the static on my finger.

I don't have any other dcs parts lying around. Only taf and ww. Which are pre dcs :(
 
Ok so had a little luck Now, sometimes when I turn it on with the ribbon disconnected I get what seems like an attempt at a bong. But it's garbaged and out of tone. Then complete silence. But it dosent do it all the time although I may not be leaving the machine off long enough for the caps to discharge. The rest of the time it's just pops and crackles.
With the ribbon connected if I start a game and put my finger on the top of u20 the sound goes nuts. Loud and screaming although still not noise you would expect. I have reflowed all around the area which had no effect. It could just be interference from the static on my finger.

I don't have any other dcs parts lying around. Only taf and ww. Which are pre dcs :(
what was the mini discovery then ?
 
If you've replaced all of the capacitors on the board already, and you've checked all of the major transistors, pull the trigger and replace U20, in my opinion.

With that said, though - considering the condition of the backbox that it has been sitting in, and the symptoms of the board both connected and unconnected to the game - the proper thing to do, would be to test and verify all of the traces and all of the passives first before starting to suspect and replace the ICs. It's almost certainly an IC but verifying traces only has a cost of a bit (okay, a lot) of annoyance and time, repair cost being some wire and solder, and passives are similarly annoying and cheap. ICs are not. As healthy as the boards may look, consider what they must have been sitting in for the wood around it to be as rotten as it is. You likely won't have to be as exhaustive with the playfield parts, but give yourself the peace of mind and approach the backbox as if you have to prove every single component working before you can ignore it.

Good luck with finding the issue! I've said it earlier in this thread and I'll say it again - I'd absolutely have a crack at this machine and put the effort in, if I were in your shoes...
 
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