(Topic ID: 219465)

Stern Hot Hand

By AntennaMan

2 years ago

Topic Stats

  • 8 posts
  • 3 Pinsiders participating
  • Latest reply 2 years ago by AntennaMan
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#1 2 years ago

1979 Stern Hot Hand, it's a M-100 MPU. About the only thing functional is the GI. The guy I got it from said it was working well, then everything went out at once. He thought it had to do with the tiny red push button with a short section of attached white wire, breaking off something. I believe the button is the diagnostics button?

At first the LED flashed 5 times at power on. I switched U10 & U11, then it went to 6 blinks. There doesn't appear to be any battery damage. There's an external battery holder mounted to the inside of the cab, but there were no batteries in it.

I've left the machine on & a couple of times the displays will later for no apparent reason light. First time I rebooted, the GI came back on, but not the displays. The next morning the displays were on, and stayed that way for a couple of days until I turned the machine off.

All fuses test good, voltages on rectifier board TP1-4 are as they should be, but TP5 is 0. It should be +43. Seat unseat connectors, nothing. Push on the corner of the board and it acts like a bad connection. Remove the rectifier board from the metal backing plate and everything lights up, GI, feature lights, even the giant rotating flipper bat at the top of the playfield. I touch a drop target, it registers 500. Drop a quarter in the slot, push the start button and the ball pops out. Everything is looking the way it should. Plunger back and we're playing. Hit the right flipper button, it starts to flip, but stops and sadly returns to the down position. Now it's back to just GI, the way we began. All fuses still check good. The coil isn't binding, it moves freely. Reboot and now I'm getting just 1 flash from the LED. Any ideas?

#2 2 years ago

Sounds like headers and connectors. One of the first things I do when I get a game is replace all the headers and connectors. You'll be forever chasing your tail until you get good connections.

#3 2 years ago

Sounds a bad PIA that you moved from U10 to U11 to get one more POST blink.

unplug everything but MPU j4 and see if you get past the PIA blinks. Otherwise time to try new PIA since it is in a socket.

In theory shorting to the diagnostic input button to something like the solenoid or GI voltage cold potentially blow up the PIA like your symptoms are. There is only a 110 ohm resistor between the PIA chip and the diag button unlike all the other ports with a 1.2k resistor.

#4 2 years ago

Quick flash then 2 regular flashes, with just J4 connected, but then I added the rest of the connectors one at a time, but the flashes stayed the same, 1 quick, 2 regular.

#5 2 years ago
Quoted from AntennaMan:

Quick flash then 2 regular flashes, with just J4 connected, but then I added the rest of the connectors one at a time, but the flashes stayed the same, 1 quick, 2 regular.

Time to try a new known good PIA.

#6 2 years ago
Quoted from barakandl:

Time to try a new known good PIA.

Are you still selling them?

#8 2 years ago

I pulled an Alltek board I had in a game in storage, but only get 7 of the 8 blinks. Missing 43 vdc. Checked fuse again, okay. Traced wire back to the transformer, continuity through fuse to transformer. Checked for voltage from this point on the transformer, 0. Is the transformer bad?

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