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Very annoying opto problems

Tim R

Tim R

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Joined
Apr 18, 2015
Messages
289
Location
Almondbury, West yorkshire
has anybody ever had, and bear with me on this because it sounds stupid but I am about to kill myself... A problems with Optos whereas it would appear they are wired in series?

I have a dr who in bits at the minute which has a 10 way opto board fitted with 3 lm339 quad comparators fitted.

The opto for the time expander and the one for the ball popper won't register unless both are uninterrupted. As soon as one beam is blocked, both Optos extinguish in switch test. Both Optos run through u3 on the opto board, which is an lm339, which I have changed, 3 times now. I have checked voltages, which are on the high side of 12v, so I will investigate that soon, I have checked wiring looms back to the boards and it's all fine, I have even shorted the strobe and data lines with a diode across the correct colours at the output side and it's spot on, so the problem definitely lies with the opto board itself or the opto / wiring thereafter, not having a spare board to check with that's as far as I got. All the other Optos are perfect, just those 2. Has anybody every experienced this before?

Thanks in advance guys, Tim
 
Did you replace either of the two opto's? I think one has either been installed the wrong way round or that maybe the blocking diode part has failed...
 
I haven't changed them yet as my oscilloscope would lead me to believe they were OK. But I guess I'm going to give it a shot tomorrow, you never know. The diodes I checked them twice they test out bang on. It's a head scratcher but I'll try the Optos themselves tomorrow. Thanks for the help
 
I have had a very close look at it and can't see anything but what I have noticed is that the fault is also on the target optos it's hard to explain but basically the opto uses 2 columns (2 and 6 I think) and row one and 2 of both of them columns are exhibiting the same fault.
I'm going to get my head back into it this weekend but what I have done is taken the parts list for that board from the manual to rs components and just bought the lot and I intend to basically rebuild the board if needs be. Also I'm going to order replacement u19 and 20 just in case. But I can't see it being that as I say I have shorted to correct rows and columns with a diode and those inputs work spot on.

I'll keep you posted as I'm sure this thread will help others in the future.

I just wish I had a board to try so I can narrow it down to a local area. Right now I feel like it's guesswork.

Just one other thing... I noticed that my 12v is coming in to the opto board at nearly 15v, I know this needs looking at but could this cause any of the symptoms I'm getting or just shorted the life of the components?
 
Pity this didn't happen a couple of months ago as I had a Dr Who then and as I am just down the road from you you could have borrowed mine.

Do any other machines share this opto board (although I am down to just two Bally/Williams DMD games now) ?
 
Ha sods law that. I'm not sure. From the games I have seen I haven't seen many. I think there is anot her board that does more inputs which is a lot more common. I'll get to the bottom of it. Just got to stick at it.
 
If you want to try a different batch of LM339s, I have plenty. :thumbs:
 
@T-Dawg

I don't have a spare loose U20 as such but I do have a fully working WPC MPU board you can borrow for some fault finding if you wish.
 
The uln2803an located at position u20 on the cpu. Dosent matter though as Chris B sorted me out. However...

So the plot thickens.. I have been to Chris's today and obtained a new 2308 ic and also a new cpu board just in case. After fitting the 2308 I still had exactly the same fault. So I installed the new cpu with a different 2308, Asic and processor. All that remained the same was the rom. No difference. Now get this, I unplugged the deck from the switch inputs and using diodes and jump leads, I shorted the troublesome switches and replicated the exact fault!!! How in the hell!! It's a brand new cpu!!! All that was left was the game rom, so I dug out my wh20 rom from storage, threw it in and hey presto, all the gremlins have vanished (I hope) while it is half past 1 in the morning and I'm still stuck under the deck of this thing, I feel like I am getting somewhere!!! Will now have to order a replacement rom and hope for the best but here's hoping!!!

14650862253101053568968.jpg
 
Morning pal, I'm not an eprom expert but a quick Google search of the code says it's a 4meg which sounds about right to me. The code is 27c040-12 if that helps?
 
Just read back up the thread an just noticed the offer to lend me a board. That's really appreciated means a lot. However I got ants in my pants yesterday and got one of Chris ha ha.

Gotta love the pinball community :clap:
 
T-Dawg said:
Morning pal, I'm not an eprom expert but a quick Google search of the code says it's a 4meg which sounds about right to me. The code is 27c040-12 if that helps?
Click to expand...
I think I have some. I'll have a look and burn you one if I do.
 
Holy Jesus if you do that would be great! Save a 3 day wait again with a headache!

I know my thread seems to make no sense as you read through it but let me just clarify, this machine has numerous faults not just one and I haven't been clear which one I'm working on ha ha
 
@Andrew Stockdale thankyou for burning me the Rom today it worked a bloody charm, one of my switch matric problems has now vanished! From a game rom error. And the good news dosent stop there. I think I may have also located the cause of my ghost opto errors... it would seem that the wires to the connector on the opto board for the rows and columns, are starting to fray in the header, which is causing hi resistance to all further switches, making them act in a series like manner! I really just fell into this while looking at the board itself and the switch matrix started going crazy.

Not going to rush the repair however I'm pretty confident that it's going to solve a lot of my issues so I'm going to order some heatshrink and a header crimping too to do a proper job.

Hopefully there should be big improvement once complete. Many thanks again to Andrew for his big help today too.
 
IDC connectors are the devil's work. Glad you are making progress mate. :thumbs:
 
Are those two diodes (above the green wires) meant to be ar$e over tît ?
 
Ha well spotted guys but those are the column lines and as such are supposed to be upside down. I did think that myself when I first saw them though but like moonraker says the silkscreen under them shows them the correct way :)
 
Ok so here's an annoying update after hours and hours of maticuloulsy checking and double checking all the wiring and diodes etc etc, seems it was the power driver board causing most of the gremlins as as soon as I unplugged it the switches worked fine, so this morning I replaced the 5 ic's that drive the solenoid outputs as I had some in stock, but this did not cure my problem, there are some more ic's that drive the lamp matrix but I don't have these. However I did have my power driver board from the Addams family to hand, so I installed that and the game is now working spot on,

Has anybody experienced a similar fault and could point me in the right direction on this pdb? I can relax a little now knowing I have localised the fault and can sent the dr who on its way, but I would like to get this board repaired before it gets forgotten.

Also, a new cpu, cpu board and power driver board did not cure a silly fault I was getting where 3 flashers were pulsing with every coil activated, this was when I had LEDs in the sockets, when I reverted to incandescent lamps the fault was not there, am I correct in assuming this could be down to a game code fault and/or cheap led flashers? If anybody knows any different please give me a heads up. Cheers
 
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