RED ALERT help

wrongdon

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I have a irem red alert.My question is this,on one of the top boards M-27BC i have a chip in location 1a and an empty socket at location 1b.The schematics show both of these locations as empty.
The game boots to just a pattern of garbage basically,but in test mode it passes all tests and shows correct graphics.So im hoping the lack of this chip is the answer.
Any red alert owners out there that can take a peek for me.
thanks

 
I have a irem red alert.My question is this,on one of the top boards M-27BC i have a chip in location 1a and an empty socket at location 1b.The schematics show both of these locations as empty.
The game boots to just a pattern of garbage basically,but in test mode it passes all tests and shows correct graphics.So im hoping the lack of this chip is the answer.
Any red alert owners out there that can take a peek for me.
thanks

I believe your board is correct. Looking more closely at the schematic, there's a 512x8 PROM at 1A. Connected to the same address are two uPB426D (512x4) PROMs at 1B and 1C, each of which handles four data lines. Instead of having two 512x4 PROMs, they used one 512x8 PROM.

(Back in the day, board space was cheaper than chips, so they designed in an option to go with 512x8 or 2x512x4, and went with whichever was cheapest when it came time to actually build the boards.)

Are you powering this up in an original cabinet/harness, or building a conversion or JAMMA adaptor? I vaguely recall something weird about getting these boards to cooperate in a conversion situation, once upon a time, but have forgotten the solution.
 
I believe your board is correct. Looking more closely at the schematic, there's a 512x8 PROM at 1A. Connected to the same address are two uPB426D (512x4) PROMs at 1B and 1C, each of which handles four data lines. Instead of having two 512x4 PROMs, they used one 512x8 PROM.

(Back in the day, board space was cheaper than chips, so they designed in an option to go with 512x8 or 2x512x4, and went with whichever was cheapest when it came time to actually build the boards.)

Are you powering this up in an original cabinet/harness, or building a conversion or JAMMA adaptor? I vaguely recall something weird about getting these boards to cooperate in a conversion situation, once upon a time, but have forgotten the solution.

Thank you,that makes pretty good sense,the chip in position 1a on my board is BP18S42N i can't seem to find any info on this chip with google yet.It has a sticker on it that says W3 .I'd like to verify it is a 512x8.
I am powering it up in an original cab with all original hardware,it seems to run off a pretty basic switcher with the exception of some return lines.I would really like to get this going as it is a very clean machine with the exception of the control panel.The way it runs self test so flawlessly and yet no sign of game activity outside of test mode has me very stumped.
 
Thank you,that makes pretty good sense,the chip in position 1a on my board is BP18S42N i can't seem to find any info on this chip with google yet.It has a sticker on it that says W3 .I'd like to verify it is a 512x8.
I am powering it up in an original cab with all original hardware,it seems to run off a pretty basic switcher with the exception of some return lines.I would really like to get this going as it is a very clean machine with the exception of the control panel.The way it runs self test so flawlessly and yet no sign of game activity outside of test mode has me very stumped.

According to this ancient USENET thread, both an 18S42 and a TBP28S42 (Texas Instruments) are both 512x8 bipolar PROMs.

I also found my board set - on mine, 1A is populated with a socketed TBP18S42, and neither of the other two spaces has a socket. Both of the empty spaces are silkscreened with uPB426D.
 
According to this ancient USENET thread, both an 18S42 and a TBP28S42 (Texas Instruments) are both 512x8 bipolar PROMs.

I also found my board set - on mine, 1A is populated with a socketed TBP18S42, and neither of the other two spaces has a socket. Both of the empty spaces are silkscreened with uPB426D.

Thank you very much for your help.With that mystery solved,i can start looking for the next problem.I'm sure ill be posting for more help before it is up and running.I have a feeling it is something simple hanging it up,but finding it will be a chore for sure.
take care
 
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