Strange issues with a TZ (solved)

(Topic ID: 234688)

Strange issues with a TZ (solved)


By BlackEuropa

58 days ago



Topic Stats

  • 13 posts
  • 5 Pinsiders participating
  • Latest reply 56 days ago by BlackEuropa
  • Topic is favorited by 1 Pinsider

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#1 58 days ago

Hello All,

My first post. I guess I've been lucky so far and able to fix my issues in the past, but this one has me confused.

To start, I did have some very light alkaline leakage. I brushed off the bloom and played a few games with no issues. I thought I’d neutralize any remaining alkaline so I pulled the board and dabbed on some vinegar solution. Reinstalled and got a ton of problems. Ground short row 1 stuck closed, Row 1, 3, 4, 6 and 7 errors, clock broken and ball popper stuck. Flash lamps behind the gumball, in the right corner and next to the slot entrance are now stuck on. Random coils firing, etc.

Seemed like the CPU board was toast so I replaced 74LS374 with no change. I punted and bought a new Rottendog CPU board… No change. Grrr.

I could find no wiring issues under the playfield. The clock HAD been working well (PinLizard board from maybe 15 years ago). I unplugged it and it cleared up many of the issues. With the clock unplugged and all flash lamp and coil plugs removed from the power driver board, I now get one error: Clock Broken.

So the issues now:

• I tried to start with the coil and lamp plugs installed on the power driver board and it instantly blew the 8 amp fuse before the transformer. (I pulled them back off)

• Left magnet and gumball entry optos not working in switch test

• Power Driver TP 8 reads 36 V, fluctuating to 7 (should be 18 v)

• Clock broken (disconnected)

• DMD is scrambled on initial start-up but works fine after (Didn’t used to do that)

Not sure what to try next. My first thought was the custom 10 opto is blown and to replace the LM339 chips. And / or to replace the 2 opto pairs that aren’t working. Looks like also the 18 v circuit needs help (BR1 and associated components).

I guess my main concern is what did I do to cause so much carnage, and am I causing more issues trying to diagnose things? Thankful for any ideas.

#2 58 days ago
Quoted from BlackEuropa:

Reinstalled and got a ton of problems. [...] Flash lamps behind the gumball, in the right corner and next to the slot entrance are now stuck on.

For these - the ribbon cable between the MPU and the 8-Driver board (small ribbon cable that plugs into the side of the MPU opposite te one that goes to the power board) is not on correctly. Remove and reseat, being very careful of where Pin 1 is.

#3 58 days ago

Thanks for the logical suggestion Coyote... If only it were that easy. I've re-seated and double checked all the ribbons many times. All are correct. None are plugged into only a single row of pins.

I would consider bad ribbons after 25+ years, but I wouldn't think that a bad wire or 2 could cause the number of issues I have.

#4 57 days ago

The Scrambled DMD and locked on flashers remind me of a very similar issue I had with my Twilight Zone. It turned out to be the large ribbon cable. I tested this by swapping it with a cable from my Judge Dredd. I full set of cables is $45.00 from Marco. https://www.marcospecialties.com/pinball-parts/RC1821

#5 57 days ago

I believe Coyote and Going4 are right. What you’ve described is either ribbon cables or a prior owner/would be tech replaced some connectors and didn’t key them and things aren’t plugged in wrong. It’s embarrassing. We’ve all done it. I’ve worked on this stuff my whole life and I still make simple errors like this at times. And after you said the problem was still there after you put in a Rottendog is what jumps out to me as connectors. Also, make sure that ASIC chip is seated properly and no pins are bent or broken. If I were working on this, I’d disconnect the clock, worry about it least and start with some ribbon cable swaps.

#6 57 days ago
Quoted from ryanbrooks:

I believe Coyote and Going4 are right. What you’ve described is either ribbon cables or a prior owner/would be tech replaced some connectors and didn’t key them and things aren’t plugged in wrong. It’s embarrassing. We’ve all done it. I’ve worked on this stuff my whole life and I still make simple errors like this at times.

I hate to say it, but it literally just happened to me a week ago. On my TZ, even. I plugged them all in - double-checked everything and... STILL had an issue. Peer more closely - this time, I somehow reversed one end of a cable. *facepalm*

The flashers that are stuck on in blackeuropa 's case are all controlled by the 8-driver board - the small, additional board in the backbox. It also reports the 9th switch column (the clock). If it's not plugged in properly, the transistors are powered, turning on all the flashers. It's possible that the ribbon cable is correct, but the 8-driver board's not getting power, or wrong power.

In either case, I'm follow - I'm curious to see what it does turn out to be.

#7 57 days ago

-NFL referee voice-
"Upon further review... Coyote was right on the first post. Replay first down".

Thanks Coyote and everyone for the replies.

Data cable to the 8 driver board was reversed on the left side of the mpu. I never did that before because the ribbons are all molded into a particular shape after 25 years. That ribbon appeared to be oriented the right way but it was 180 degrees out.

There had been a paper holder that suspended that ribbon. It ended up in the bottom of the cabinet and let the ribbon fall down. It changed the orientation. Lesson learned... Follow the red stripes. Pin 1 to pin 1.

I have to say these electronics are pretty tough! After the torture I subjected mine to, the damage is minor. I just played a game. The clock even works now! If nothing else, my post documents the specific symptoms of reversing that cable.

I still have a few optos out. It won't let me load the gumball, and the gumball entry is dead among others. Do you think I fried the 10 opto?

#8 57 days ago
Quoted from BlackEuropa:

-NFL referee voice-
"Upon further review... Coyote was right on the first post. Replay first down".
Thanks Coyote and everyone for the replies.
Data cable to the 8 driver board was reversed on the left side of the mpu. I never did that before because the ribbons are all molded into a particular shape after 25 years. That ribbon appeared to be oriented the right way but it was 180 degrees out.
There had been a paper holder that suspended that ribbon. It ended up in the bottom of the cabinet and let the ribbon fall down. It changed the orientation. Lesson learned... Follow the red stripes. Pin 1 to pin 1.
I have to say these electronics are pretty tough! After the torture I subjected mine to, the damage is minor. I just played a game. The clock even works now! If nothing else, my post documents the specific symptoms of reversing that cable.
I still have a few optos out. It won't let me load the gumball, and the gumball entry is dead among others. Do you think I fried the 10 opto?

Ah, good to hear!
So the only things out now are the opto switches?
No, the opto board has no wires in common with the 8-driver board, so something else is up.

GO into switch test, and see which optos are reporting blocked.

#9 57 days ago

Yeah. All else seems functional but the select optos. A bit easier to diagnose than the multiple issues I caused before!

Switch test shows non functioning switches 81, 83, 84, 85 and 87. All on plugs J3 (receiver) / J4 (emitter) on the opto board. Looks like they all pass through U2 and U3 LM339 chips on the opto board.

I'll double check my plug connections to the opto board. If all checks out, would it seem logical to replace those 2 chips?

#10 56 days ago
Quoted from BlackEuropa:

Yeah. All else seems functional but the select optos. A bit easier to diagnose than the multiple issues I caused before!
Switch test shows non functioning switches 81, 83, 84, 85 and 87. All on plugs J3 (receiver) / J4 (emitter) on the opto board. Looks like they all pass through U2 and U3 LM339 chips on the opto board.
I'll double check my plug connections to the opto board. If all checks out, would it seem logical to replace those 2 chips?

Is the opto board getting power?

#11 56 days ago

Yes. There is power to the opto board. All the optos that pass through chip U1 on that board work fine.

#12 56 days ago

Before replacing those chips, I would make sure that they are not working correctly. This thread is incredibly useful for using a logic probe: https://pinside.com/pinball/forum/topic/terrybs-guide-to-logic-probes

#13 56 days ago

Thanks for the caution, lyonsden. I planned on verifying dead chips before replacing.

I unplugged the connectors and the pins seemed to read ok on the logic probe. So I plugged them back in and all the optos are back up!

I possibly had a connector not really on the pins? Not sure... Just had cataract surgery so close range vision is a bit off. Anyway, seems to be working 100%.

Thanks again everyone for your help.

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