(Topic ID: 335194)

Gottlieb 80B Display Out

By Cheddar

5 months ago

Topic Stats

  • 3 posts
  • 2 Pinsiders participating
  • Latest reply 5 months ago by Spybryon
  • No one calls this topic a favorite


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#1 5 months ago

I am helping a friend troubleshoot his Hollywood Heat display. The game boots and starts the attract mode but the display only shows commas and not all of them. This happened one morning when he turned the game one and had been working fine before.

I tried the game in my Genesis and get the same behavior. My display works perfectly so I know the issue is the display.

Per advice he got on facebook a while back I checked the voltages. I get 5VDC on the + side of C4, ~-48VDC on the - side of C1 and ~ -15VDC on the non-banded side of VR2. I did not check the 6.2VAC at pins 1 & 2 since they go straight to the display filament and my display and wiring works perfectly.

I theorized maybe the reset line wasn't going high so I tested it. It starts low then goes high a couple seconds later. It looks like the top glass shows some commas (always the same) whent he machine switches on, then the bottom display shows all commas when the reset goes high.

I do see some rework on the diodes in CR1-CR4 and R1

Any advice on what i can check next?

#2 5 months ago

Update, was doing some tests and this time the commas were totally random. I don't think I can infer anything about which ones light.

#3 5 months ago

Check Z1 and Z2 with a logic probe. There should be similar activity on the input pins and output pins of these 2 buffer chips.

If that all looks good then check continuity on SOP, SIP, CLK, DATA-LOAD, SCLK-DIS with the game turned off between the corresponding pins on U1, U2, U3.

U1: pins 2,3,31,40,1
U2: pins 5,2,38,40,1
U3: pins 24,23

If continuity is fine, turn on the game then using a logic probe, compare activity on the non-working display to the working display on those same signals SOP, SIP, CLK, DATA-LOAD, SCLK-DIS. Perhaps one of these chips U1, U2, or U3 has gone bad and is dragging down or pulling up one or more of these signals.

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