Got a Jokerz project. Had battery acid damage but not too bad. Got it to go into attract mode once our twice using the cpu test button, but wouldn't play a game. Removed battery holder and replace with a remote holder. Cleaned acid with vinegar solution. I now have blinking diagnostic led (no error detected) and blanking circuit is correct. But the 5v led is not lit. I.checked voltages off the supply and they look good. 4.95 with no load, but down to 4.9 when connected to cpu and nothing else. Display has a few digits showing and seems to be responding to buttons on the coin door but I can't read what it says. No sound. If I.push the sound button on cpu, I get constant tones. I am getting 4.9v on the cpu at the test point and at a resistor near the 5v led, (4.86.or so). All other voltages on the power supply look good.

Had anyone ever seen the diagnostic led blink like normal but then no 5v light? Can't seem to find anyone who has had that issue. Hard to tell if it's a logic issue or a power issue at this point. Figured I would stay by hooking it up to an external supply (really needed to build one so this is my excuse) to see if the 5v light would work then. If not, I'm guessing it must be a logic issue?

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Can I reuse components? How hard is all this to do? I am fairly good with a soldering station but have never sanded down a board before. Past experience is that it's a pain to get solder to stick when there's corrosion.

Looks like the LED is blown. Now just to figure out why I have no audio and only a few segments on the display...

I tested continuity there, but will double check. I'll also pull the ribbons off my Grand Lizard, which are new, and see if that helps anything. The ribbons seemed reasonably OK, but it certainly explains why sometimes the display was working before, and other times not.

The headers on the board look OK, could be a timing issue, too. The sound tests on the CPU produce repeat tones, so I know the amp & sound board are OK. Might as well start with the simple stuff, and go from there. Unfortunately, I accidentally blew up my newly completed bench power supply while trying to adjust the voltage, so back to square one there. UGH.

It's a real pain to have garbled displays, since I can't use the diagnostics.

While I recognize this could be a problem down the road, doesn't the blanking light LED indicate all is working OK (at least for now)? Otherwise, the game wouldn't be booting up into diagnostic mode, etc., right?

OK. I will buzz it out again tonight. Really pissed about zapping my power supply - building another will probably take priority so I can examine the logic on the board.

Just concerned about sending the board off not knowing if the board (at least at this point) is actually causing my issues or if it's something else.

Vias?

And so if I and it, do I have to install new components immediately it's can I.put the nail polish on and then install later?

So here is where this project stands. I am thinking there is no need to sand under the pias, just perhaps at the leg holes and that ill need to sand above u42 to clean that up. Seem ok? Worried about damaging traces when Sandi may be unnecessary. I.did find a sorted pin on u51, but I don't believe that would have caused the issues I was experiencing. I.think u43 may have been the culprit, even though it buzzed out ok. Have not found any broken traces.

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Yup. It is what I.used to pull everything so far.

I have the Aoyue 701A++ All Digital Dual Function Soldering and Desoldering Station. I think it's a knock-off of the Hakko. It seems to do a decent job? Sometimes I have to go through and clean up the through-holes of remaining solder and pull the legs. I hadn't done that in this picture, though I think it looks worse than it is.

So:
I can just use the scotch brite to shine up the pads, but avoid sanding the green protective covering? What do I do near U43, same thing?

Does the damage make sense given the symptoms I had - namely that all the LED lights on the board worked, but no display or audio and no gameplay?

Also, with the "B" passive capacitors, they have no polarity, right?

My biggest concern, to be honest, is not the removal and installation of the components. It's more making sure I have the correct stuff aligned correctly.

I replaced all the components near and including u43 including all the ics in the area. On the bench, all the leds are doing what they are supposed to now (replaced the 5v led). Will put back in the machine tomorrow and see what happens. 20150409_221108.jpg

And yes, I know it's not pretty but better than it was before. If this doesn't get things going, and I still have garbled display and no sound, I'm gonna start looking at the power supply I think.

Update: machine boots and will play a game! But no background music, only voice...ugh...sapped ribbon cables to no avail. Rewrote and installed new Roms. Seeing a lot of dead pins on the audio board, no dad pins at the j21 connector off the CPU, so presuming I have some kind of issue on the audio board. May be missing addressing or something like that....

Ok.but if they were open, wouldn't I have dead pins at the ribbon cable connector?

Processor was definitely bad. Replaced with a known good one and now much more activity. I.had 0 addressing before but now am going strong. Still a few dead pins on the processor, so I'm suspecting another chip is bad too. Ugh!

You mean for the eprom? Could be. But I. Think the dead pins should trace to somewhere and tell me or so id hope!

No corrosion on audio board. Cleaned the rest on the mpu already and the machine plays. I also have signals to the audio board so I believe the prob less there

Agreed. That was my understanding, too, and why I suspect the problem to be on the Sound board, since I have voices and sound effects, but no music. I think the CPU is sending info. to the audio board (i have no dead pins on the 20-pin connector) but numerous dead pins on various chips on the audio board.

Here's what I've found so far, though I have yet to investigate further. I'm suspecting a bad chip somewhere is causing this, so I'm planning to look for common connections between them:

u4 processor dead pins: 8, 17, 19, 20, 22, 14, 15, 16
u16 dead pins: 4
u7: 1-4, 23, 24, 25
u5: 2, 3, 4, 23, 24, 10

On a related note, I did find that the speaker lug in the cabinet had come detached, and wonder whether it shorted to ground at some point and caused this issue. It was just floating in there when I found it.

Wouldn't the pins be low vs. Totally dead?

So how would someone troubleshoot this board if they didn't have a comparison? I was thinking that I could examine which pins are dead to determine which should, or shouldn't, be dead and then trace it back to one of the chips which should be outputting. I can't imaging all those pins as I found should be at 0v. Note that I conducted this test while a ball was in play so that the music "should" have been playing.

One final question: It looks like some of the dead pins are addressing lines...shouldn't those always have some type of reading?

So I "think" I figured it out, but am not sure. I believe the problem is at U19. It is missing all signals at 9-15. It is the Digital-To-Analog Converter and is supposedly tested when you press the switch on the side of the CPU Board. Except...

I found that U21 had virtually no signal on any of its pins (11 was low, and that was it). Then I looked at U19 and found that pins 9-15 were totally dead. It "appears" these are the pins that feed U21.

The DAC chip is a YM3012....pinout here: http://www.datasheetarchive.com/dlmain/Datasheets-8/DSA-151905.pdf

It looks like 9-15 are the outputs on this chip and that it serves as a bottleneck to all sounds coming from that board, except for sounds generated by the CPU (which seem to bypass that DAC) and leads directly to U21. I am getting something on pins 1-8 and 16 from that chip, but those look like primarily inputs.

I don't understand, then, how I am getting two tones (as I'm supposed to) when I press the CPU test button. One tone is louder than the other, but I presumed that was normal. I wonder if they are supposed to be the same or if there is a DAC on the CPU board that's tested instead of the DAC on the Sound Board. That would make sense if the CPU input is after the DAC on the sound board, which it appears to be based on the schematic.

Did you see the YM3012 somewhere online at $4? I find some on eBay for that price...or lower but they are in Hong Kong, China, etc...

Unfortunately, no dice with any of my machines. LOL. Looks like they all use different DACs. Think I'll buy a higher-price one, then get a bunch from China for the future.

I just picked up a semi-working Gogar that I hope to bring back...and guess what - no sound! Lol. That'll be the third machine in the last few months where I've faced sound issues. It would almost be comical if it wasn't such a pain in the arse. I'm hoping the Gorgar is easier to deal with as it's probably a connector issue or something. No acid damage or whatnot on that machine, fortunately, as someone removed the battery before it could puke.

Will do. Thanks for you help. Now just gotta wait for that DAC. I bought five, so get in touch if you ever need one.

So here's a quick summary as this machine still plays no music, though I do have voice effects:

CPU was it booting, repaired the acid damage and replaced key ICs. Machine now boots and plays well. Display is strong. I can play a game without issues.

I went through all basic steps as outlined in the guides including the sound test on the board and running the music test. I get a music test failed message and the machine plays no background music.

I replaced the processor on the sound boarding rewrote the rom. I can hear scratching from the speakers on certain pins when I touch them with the logic probe, so the volume control,etc is ruled out.

U19 is the digital to analog converter on the sound board. The inputs - first 7or 8 pins - all get either high, low or pulsing with machine in gameplay. I get almost nothing on the output side. The u19 DAC feeds a quad amplifier at u21. It seems both these chips are critical to sound as they are gateways the the rest of the circuit. The u21 shows life at the 12v inputs, but logic probe shows dead pins otherwise. I replaced the DAC with no change.

I am pretty darn frustrated now. It seems either something is pulling down the u19 or it's getting a bad signal that's preventing it from becoming active. Any thoughts? Could it be related to an issue on the CPU? Is there something that's supposed to signal the DAC to work?

The manual is here if anyone wants to take a look: http://mirror2.ipdb.org/files/1308/Williams_1988_Jokerz_Schematics.pdf.

Audio board is page 79.

Quietly bumping this one for the weekend crowd.

Just check to see if the cap is open?

Agreed. That board needs a gut job.