I know I'm making too many posts in one night.

I couldn't go to bed until I at least figured out the reset problem....

ummm?? Ya...You know those src's? And when the alternative is used the 10th pin needs to be cut off? Ya....I forgot!!

So.... I took the easy way out and just cut all of the ground traces to pins 10.

But now reset is working! I think....

IRQ 4.9v,VMA is 4.4v, and A14 4.9v. I've checked and rechecked the traces and sockets over and over I keep looking for a bad trace or short. Kind of stumped....... but looking at U36 now. My only reasoning is that It's common to A14 and IRQ.

VMA? I have no clue at all yet, not even an off the wall guess. yet!

Added...Nope, not U36 it's working! But I now know how to read that and what it does!

For you guys that know this stuff......Or system 11a

Can someone tell me if I have to have sound roms (U21,U22) or the CPU at U24, to get this too try to boot?
It didn't look like it. But I still don't know enough. It looked like it was it's own circuit for the most part, but I wasn't positive.

I have a mess and want to try to rule out what I can. After looking at this thing over and over...I'm convinced it's a bad Ic somewhere or maybe even a few. Or I keep overlooking a multiple shorts.

Thank you! I'm trying to find things to eliminate until I find(stumble into ) the problem.

What would cause CPU's not to pulse but have the correct V on most pins. I stuck them in my "parts board" gave it power and the lines are pulsing.

Added...
Nevermind.....I have one CPU that Pulses and one that doesn't. Might explain my problems....I thought it was good and it must be bad too! I'm chasing some problems that seem to change depending on which CPU I had in. Ugggghhhhhhhh!!!!! Hopefully, I have a good one now!!! I thought they were all good...But it's not looking that way.

That solved the A14 problem....This is the 3 CPU I've had in....

I might be mixed up since I've read so much stuff the last couple of days and my memory stinks...

I thought I read something somewhere that if a Motorola (6802) was used in a system 11a board something else had to be changed. Can someone tell me if I misunderstood or where that's at? I can't seem to find it again.

Added.... Finally found it again ....If anyone else would happen to run into this looking....

Taken from http://techniek.flipperwinkel.nl/wms11/index1.html

"If a Motorola microprocessor is used, W16, W17 must be connected. If any other brand of microprocessor was used W16, W17 must not be jumpered."

I'm guessing W16 if it's used in U15, And W17 if it's used in U24..

I looked and looked, and couldn't seem to find it. Then after I posted I ran into it again...That's happened a few times now.

Thank you! For confirming that. after looking at the board...I thought, I don't need to change both jumpers. If I'm using it in U15...But wasn't positive,Just a guess.

I think I have most of the board stable(meaning found all the iffy connections) ... Reset works at every power up now.

Right now Everything on the cpu checks out except the voltages for Pin 4 IRQ pulsing at 4.2v and pin5 VMA at 4.9v not pulsingt. It doesn't check out with the Link in the earlier post. That link says they are supposed to be around 2 to 3V.

Still at it! If I could just get a flash..Something... out of it I'd be happy for now!!

Thank you!

I'm Having a blast working on this but at times I'm ready to 12ga it!

SR2 is good. I swapped it with a new one. I checked it before I put it in the board. I was also able to pull one of the lines back down some (can't remember which one now) With a 4.7k resistor. Not sure if it was the right way, my way of checking for a short in that case.
IRQ quit pulsing...Maybe it had a weak connection and finally unconnected. haha

For anyone else reading...
And something I would have never thought about.
My PF is pretty much empty. I have a flourescent desk lamp sitting on it pointed in the back box.....If the wires for the logic probe get near the base of the lamp the logic probe will pulse when I get it near the board. If my elbow is touching the base, probe in hand, towards board it will pulse. No clue if the plastic base static is what causing it... Just really weird!! Now I have an extra ground wire running to the machine! I'm just taking a wild guess... I know I had at least one CPU set on that lamp base, may be why it's bad when I thought it was good originally. I also had all my transistors laying on it when building the board and who knows what else. I probably fried everything with static!

Just plugged U31 in the board backwards...... I can't believe I just did that. I smelled something getting hot! Looked up and noticed the notch was on the wrong side!

I need a video of this stuff! The bloopers reel!

I'm not even going to try it. I hope it didn't fry anything else.

I have to look this up..And I know someone told me this before. But I'll ask here in case someone knows before I find it. Can I use a 74HCT00 in the place of the 74LS00? I know someone told me you can interchange sometimes, but I can't remember which way.

Added... found it from what I understand the The HCT can be used in place of the LS, can't go the other way.
In case someone else wanders around looking for the answer..
https://electronicsclub.info/74series.htm

IRQ will start pulsing if I touch the top of the transistors in the reset section. That's with me grounded. So there is something flaky there. I don't have to put pressure on them, just touch the top. I found it by trying to flex the board a little, and started pushing around a little looking for a bad connection. So, I'm guessing it's in that section? Time to redo it with new transistors, just in case. Then I can rule it(that section) out for sure!

Maybe I got them too hot, I was on them pretty long when soldering, they were also on this static lamp base too.

VMA and IRQ started pulsing after I redid the reset section...Again.

Ok everything is now down to A9 not pulsing.

But I have a locked on diagnostic LED now. Not sure if that's moving forward but It's at least something different!!!

My V went up too for some reason. 5.4V now. Not sure why it went up. It was at 5v. until today.12 is a little high now too!

With the board unplugged and one probe at the base of the ground stud, and one at the base of the 5v. I get 29.71 ohms and dropping slowly. A couple minutes later it's in the 28.15 ohms and still slowly dropping. Checked again and it's at 26.7 ohms and seems like every time I check it's going lower. Out of curiosity what is that checking for?

5v jumps around depending on turning it on. It's either at 4.9v, 5v, or 5.4v. No idea if that means anything but something I noticed.

IRQ and VMA pulses when it wants too...I think I have VMA pulsing at every turn on now. But IRQ is still hit and miss at start up.So, far it seems like it works after the machine has been sitting off and when I come back later, turn it on to check things out, and it works, then after a while just goes out(stops pulsing). I'm stilll checking stuff on that.

A9 still isn't pulsing.

A9 works now....IRQ still not pulsing..

I have a parts board, plugged it in and put the CPU in it. A9 still didn't work. Took another CPU out of another game put it in this board and now A9 works....I must have had a bunch of bad CPU's. First thoughts were bad connections on the socket, but I've checked it multiple times. I checked that line, looked up IC's checked and checked...Wish I would have figured that one out earlier! I learned a ton though by looking things up.

Looks like I need to find a pile of spare GOOD CPU's.

Well? I started out trying to make this board nicer! Now? I'm just after "make it work". When I'm done butchering this thing I'll take a pic for the "worst hack" thread.

I've soldered and unsoldered too many times with my cheap iron. I did ok at first but after a few times these boards just won't hold up. I have learned how to repair traces, solder legs on chips, etc.... pretty fast now!! I understand A lot more than I did when I started this thread, and a lot of stuff came back from previous help on a Bally from Quench. and thedefog too! And everyone else that has given me direction.

You guys have taught me a lot!

Still working (butchering and shotgunning it) on it!! I'll get it eventually!! And when I give up? I have a parts board I can patch up for the game. But I don't really want to go that route. I want THIS one to work! This is art now!! A sculpture!!

I have a dumb question...I'm trying to learn this board and what's going on..

On a 74LS00(U31) if the inputs are pulsing(1 and 2) should output pin 3 also pulse? Or does that depend on the timing of the input pulse? If that makes any sense at all. 4,5 and 6. Are the same way, inputs pulsing output high, no pulse.

Just in general if the outputs aren't going anywhere.

Can someone explain this in simple dummy terms? Does it depend on input timing? The two input pulses aren't ever hitting a high at the same time?

Added...Never mind...I now see it at U36 pin 3 and 6, the pulses are alternating(?) to pins 1 and 3 of U31. I always ask these questions then stumble into the answer after posting.

Thank you for the link. I'll play around with that.

I've been jumping around this board just looking at what does what and if it's working like it should.

I still have a VMA, pulsing sometimes and sometimes stays high at 4.9v. I wasn't sure how it's supposed to act when there isn't a U27. Going to the Leon Borre site. I still have voltages that aren't matching at the CPU. Pin 18 is a little higher, and 24 and 25 are high and aren't around the 1v.

Every time I turn this on I get something a little different. Not much, but differences of .2 to .4v everywhere. It's not consistent. Reset line can be anywhere from 4.8 to 5. Even if I ground it for a second. It just depends on something in the board at turn on. Maybe none of that matters, I just can't find why. So, I'm wandering around looking for a bad IC.

I'm using the game power supply.

Most all of the IC's that I changed were 74LSxx, I did swap one for an 74HCTxx and two others to 74HCTLSxx. I was under the impression that some could go one way but not the other, I may have understood wrong since I'm just guessing at most things . I'll look at those again. I'm pretty sure the HCTLS are ok for LS. I'm not positive about the HCT in place of the LS though. I went to this link.. https://electronicsclub.info/74series.htm

I might be all mixed up on that stuff too!

Here's what I changed..and maybe it's part of my problem with the board...
U31 is changed to a 74HCT00N
U14 is changed to an 74HCTLS02N
U32 is changed to 74HCTLS08N

I can change them back, to see if there is any change, I'm almost sure the HCTLS are ok replacements. The other I'm not positive on.

Here is the link to the HCTLS

http://www.bitsavers.org/components/samsung/1990_Samsung_AHCT_HCTLS_Data_Book.pdf

I know you said the 74xx above, but I haven't changed any of those yet . Most of the IC's I've been playing with on the board so far have been LS.

I have something messed up for sure! I can't even get it into any diagnostic flashes yet.

I changed the caps on the power supply, It's been reading the same. It's my 5v and a few others on the board that seem to change a little depending on power up by, it may not be a big deal just something I noticed. Sometimes it's at 5v even, and others 4.8v.

I have my "parts" board going into diagnostic mode and flashing...The thing is missing 2 pia's U41, U54 and U42 is half unsoldered. A couple other Ic's at U17 and U45. Has a hole cut in the board with traces out at SRC8, half corroded Bad too, I can't even believe reset works, burnt,missing transistors and the sr's src's etc... And I can get it to try to boot and flash consistently. All address and data lines work. So, I know now that this 6802 is probably good along with another one that I thought was bad. They both work in this board. I even took corroded Ic sockets from the sound section and just half ass tacked them in for U27 and U26 (I didn't have anything else laying around and barely soldered them in)!!!! haha It was missing the 555 and I found one that I've been kicking around on the floor,straightened the pins, and stuck it in there. I don't care about this board right now and I could probably get it running quicker!

So, On the board I'm trying to fix I have to be overlooking the simplest thing. I'm missing something that is probably so ridiculous, I'll be too ashamed to tell anyone what it was when I find it!!! From the looks of it they should run the diagnostics pretty easily.

Still at it!!!