(Topic ID: 299944)

GTB SYS 1: Sinbad won't add more than 1 credit

By finman2000

48 days ago


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  • 14 posts
  • 4 Pinsiders participating
  • Latest reply 32 days ago by Tuukka
  • Topic is favorited by 2 Pinsiders

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#1 48 days ago

Sinbad won't allow me to add more than one credit, and it doesn't retain high scores. I already replaced the 5101 ram chip, replaced C2 on the PS board and replaced C24 on the CPU board. No improvement. Anyone have any other ideas?

FYI - I have had the game for 20 years and it has been pretty solid.

#4 47 days ago
Quoted from Rikoshay:

what battery back up do you have installed

I have three AA batteries. I'm getting 4.5 volts to the 5101 RAM when the machine is off, so I should be good there.

#5 47 days ago
Quoted from Tuukka:

Looks like there is a problem with CMOS RAM. Does it hold replay settings and other bookkeeping data?
I would check the reset circuitry next.

When you say CMOS RAM I assume you are talking about the 5101 ram chip at Z22? I will check to see if it holds replay settings, but I don't think it is. I also changed out the diodes to match what was in the later run of these boards, as suggested in Clay's guide.
R159 Change 2.7meg to 3.9meg ohms
R160 Remove.
R161 Change 27k to 43k ohms
R162 Change 6.8k to 2k ohms
R163 Change 27k to 6.8k ohms

#6 47 days ago
Quoted from Tuukka:

Looks like there is a problem with CMOS RAM. Does it hold replay settings and other bookkeeping data?
I would check the reset circuitry next.

I checked tonight. It does not hold replay settings or bookkeeping data.

#9 46 days ago
Quoted from Tuukka:

Might be that the 5101 CMOS RAM is not properly enabled.
It is controlled by the reset circuit monostable Z2 (4528) and gate Z1 (4081). With power on, check that pins 1-3 of the 4081 are near the battery voltage.

Just turned the game on tonight and it suddenly started saving high scores and registering more than one credit. I discovered that my 5 volt pot is starting to fail. It seems to have caused a couple game resets. When I made a very small adjustment, it went down to 4.4 volts. When I pushed down a little on the blue dial, it went moved back up to 5.08. Could that have caused the my credit/high score issue?

#11 45 days ago
Quoted from Tuukka:

Yes that is very likely, since the reset circuit locks out the 5101 when voltage drops.

Thank you for all of the help. I will report back once I change out the pot.

#12 39 days ago
Quoted from finman2000:

Thank you for all of the help. I will report back once I change out the pot.

I changed the pot out last night and everything is back to working 100%.

#13 34 days ago
Quoted from finman2000:

I changed the pot out last night and everything is back to working 100%.

I’m having an issue with it saving high scores and showing more than 1 credit. I check the voltage on Z1 pin 1 and I am getting the same voltage as I am getting on the 5101 ram. I am also getting the same voltage on the pin directly across from pin 1. Is that pin 2 or is that pin 8? I am not getting voltage at any other pin on z1. What do you conclude from that?

Also, I have had the correct number of credits appear during the middle of a game. One time it happened after the ball was kicked into the shooter lane. I don’t remember if that was to start ball 2 or ball 3, but it definitely wasn’t on ball 1. Later on while I still had the machine on it went back to only keeping 1 credit. Not sure if that helps at all?

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