Taito Lunar Rescue Board Question?

SpookySpaceKook

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Hi, I just bought a Taito Lunar Rescue upright but the Taito 3 board set is non-working. On the middle board which is the cpu I have an empty 18 pin socket. It is at IC position #1 in the lower left hand corner of the board. Directly above the empty socket at position #2 there is another 18 pin socket with a small IC size Prom labeled RE-08. Can someone who has a Lunar Rescue machine confirm if a working boardset needs this Prom at position #1 or is it supposed to be missing? The Prom may have fallen off this boardset. I could not find a schematic of this boardset, but I have confirmed that the Taito Space Invaders boardset which is almost the same as Lunar Rescue does indeed have a 18 pin Prom at location #1 and #2. Please help anybody?! Thanks, Jon Hughes.
 
They are colour PROMs, without them you'd still see a black and white image. You don't necessarily need both of them, uprights only use one, cocktails use two (one for 'normal' display, one for player 2's inverted display).
 
Hey,thanks for the response. I guess I can quit looking for the lost chip inside the cabinet and start to troubleshoot the board set now. It just has 2 vertical rows of color blocks on the screen. Will not coin up at all. Voltages are good. Most likely a problem on either the rom or cpu board. I don't see too many spare Lunar Rescue boardsets around.
 
Can you post a pic of the screen display? Could be all kinds of things causing the boardset to not boot.

Are the voltages okay?

How about the reset circuit?

Is the CPU running? Any activity on the data or address lines? (check with a logic probe or 'scope if you have one).
 
I'm just starting to get more into the board repair part of the hobby. I was always more of a monitor repair type guy. I have been pretty lucky fixing about 50% of my board issues so far, replacing some bad rams and IC's on my Gorf boards. Its nice also having a Wizard of Wor so I can swap boards between the 2 of them to troubleshoot. I still have to set my bench up more for board work with a test monitor and power supply with test clips. I will post some pics of the Lunar Rescue screen soon.
 
Heres a screen shot of the problem with my Lunar Rescue. Will not coin up, screen looks like this, occasionally a scan line will scan from right to left and slowly erase the color blocks untill the screen is black. When you power cycle the game the colored blocks return. Voltages to the boardset are good, I felt all the chips and none are hot. I have not reseated all the socketed chips yet. The CPU is a 8080. Should I start to check the CPU with my logic probe first?
 

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Pull out the ROMs - what happens then? (Remember where they came from and note the orientation when putting them back in).
 
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