(Topic ID: 299944)

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

By finman2000

48 days ago


Topic Heartbeat

Topic Stats

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

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#3 47 days ago

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.

#7 47 days ago

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.

#10 46 days ago

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

2 weeks later
#14 32 days ago

The pin directly across 1 is 14 - supply voltage for the IC. DIL package pinout is like this:

14.........8
>
1...........7

You should have voltage on Z1 pins 1 and 2. Those connect to Z2 pins 7 and 9, so check their voltage also. If Z2 pin 9 stays low, then replace C32 (0.1 uF) and if that does not help, replace Z2 (4528).

The capacitors C31 and C32 do fail sometimes, so probably a good idea to replace both while you are at it.

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