(Topic ID: 203770)

Gottlieb system 1 memory issue

By ChrisPINk25

6 years ago



Topic Stats

  • 8 posts
  • 4 Pinsiders participating
  • Latest reply 6 years ago by ForceFlow
  • Topic is favorited by 1 Pinsider

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#1 6 years ago

Hey all,
I'm a newbie to working on pins. I found the awesome pinrepair site and read it top to bottom. My only idea left is to get a new cpu, so wanted some guidance first.

Some quick background. Dad bought dragon as an xmas present back in the 90s. It worked great! No free play mod. He said it was a way for us to save for college (we knew where the key was hidden). Years later I have a game room want to have pinball. It didn't start up... Bad power supply. So, bought a new one. It is now working great, but has two issues.

1. Won't save high score and credits don't decrease. High score showed 444444 on all displays. Voltage to memory chip was good, so I bought a new chip from docent. Put that in tonight, reset memory, still doesn't store. Shows 155555 now.

2. It takes 4-5 off and on cycles to get displays to work. First its black, then ghosting, then works until turned off. I have new cables on order from docent.

Any help or advice would be greatly appreciated!

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#2 6 years ago

Machine looks fantastic but you have an old capacitor on the board - the white cylinder

Replace it with a battery or new cap and it will store your scores.

Surprised you missed that on the site you mentioned.

Look up system 1 pins on pinwiki. It’s the best resource for you.

#3 6 years ago

First, get rid of that battery. It looks like it already started leaking.

You'll have to clean up the MPU and remove the affected components. It sounds like it has already affected the operation of the board.

Or, replace it with a ni-wumpf or pascal MPU

http://www.ni-wumpf.com/System1CPU.html

http://www.flippp.fr/pi1.php

#4 6 years ago
Quoted from Black_Knight:

Machine looks fantastic but you have an old capacitor on the board - the white cylinder

That's a NiCad battery, not a capacitor.

Quoted from Black_Knight:

Look up system 1 pins on pinwiki. It’s the best resource for you.

http://pinwiki.com/wiki/index.php?title=Gottlieb_System_1

#5 6 years ago

Thanks guys. The nicad was a replacement that was still reading around 4v on pin 22 of the memory chip. I don't think you are seeing corrosion, it's old tape. I pulled out the battery and installed the recommended AAs. Reset the audit memory several times with no luck. Good news is that it turned on fully on the first try. Here's the weird thing. The voltage at Pin 22 now reads 1.471v. What could cause that? I checked the battery pack multiple times and it was reading just below 4v.

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#6 6 years ago
Quoted from ChrisPINk25:

... Here's the weird thing. The voltage at Pin 22 now reads 1.471v. What could cause that? I checked the battery pack multiple times and it was reading just below 4v.

Hi, looking at your battery pack, everything looks OK. The three cells delivers about 3 x 1.5 volts, so 4.5 volts. Then the protection diode (your pictures show it mounted in the right position) drop the voltage for about 0.6 volts, and you get at final a bit less than 4 volts. So, nothing wrong here.

On GTB SYSTEM 1, the memory power schematic is quite simple.
The diode CR26 prevents the current from going back in all the circuit. The R133 is use to charge the original NI-CAD battery.
VAB is the memory voltage, that power the 5101 RAM and the 4528 CMOS (Z2).
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There is no reason for the voltage to drop to 1.4 at pin 22 (VAB for 5101), unless:
- the diode CR26 is died, and don't stop the current
- you connect the battery pack at a wrong point

In both cases, the whole board is powered by battery, that is of course, insufficient. This can cause the voltage to dramatically drop.

Check the voltage on both pins of CR26 (this diode is located just above the NICAD battery): on cathode you should have about 4 volts, and nothing on the anode.

#7 6 years ago
Quoted from noflip95:

There is no reason for the voltage to drop to 1.4 at pin 22 (VAB for 5101), unless:
- the diode CR26 is died, and don't stop the current

Thanks noflip95! The diode is bad. I assume it is a 1n4004 - 400V/1A Diode?

#8 6 years ago
Quoted from ChrisPINk25:

Thanks noflip95! The diode is bad. I assume it is a 1n4004 - 400V/1A Diode?

Yep, that will do the trick.

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