Revolution X not starting

Ez9

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Dear All,

this is my first post here, I've recently found a Revolution X (3 players version) that won't boot.
I've re sold some chips that was not showing in optimal conditions, replaced all the electrolytic SMD Caps, cleaned the board , fixed 2 damaged tracks close to C22 and C17 but game it's still not booting.

+5V Led is solid On
Status Led it's randomly blinking
All the 3 Clocks are present (40 - 8 and 25MHz)

Now, since I have the cab far from mine lab , let me ask you, can I just test the board without having the cab with me?
Can I just test the main board without connecting audio board and gun board?
what should i connect? just +5V, -5V, +12V and video out cable to a monitor for testing?

From where I should start from?
Reset signal High and stable ... then? Video Chip? GAL? Rom? Ram?

Thanks to everybody would like to help me
 
Check the voltages both on the jamma connector and on the board if there are test points to do so (or on the legs of any non surface mount chips.) Low +5v has left me scratching my head many times and that's all it turned out to be.
 
Back on this board for testing... I need some help to understand what I should check first.

Reset signal it's ok, al tensions and clocks are correct and stable.
on bus i see signals, but screen stay off...

What are the steps on boot?
CPU start reading ROMS which one? Does the RGB signal should start even if not able to read the ROMS ?
what is the Chip generating the video output ? U5 ? U10?
 
Ok could be but the board really look in good conditions. There was only 3 caps that was leaking and damaged the board but are in a part of the board that should be not critical for the boot.
C22 and C17 damaged 2 tracks that I've repaired and also C16 that have oxidized all the pin of the nearest U17.

See pictures before cleaning the board

I've just cleaned U17 and reflowed but not replaced yet. (this one could be critical for the ROM read at boot)

All the rest of the board have no sign of corrosion, all the caps has been replaced

Maybe I can try to reflow the CPU, and the ABT 374 & 245
 

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Ok could be but the board really look in good conditions. There was only 3 caps that was leaking and damaged the board but are in a part of the board that should be not critical for the boot.
C22 and C17 damaged 2 tracks that I've repaired and also C16 that have oxidized all the pin of the nearest U17.

See pictures before cleaning the board

I've just cleaned U17 and reflowed but not replaced yet. (this one could be critical for the ROM read at boot)

All the rest of the board have no sign of corrosion, all the caps has been replaced

Maybe I can try to reflow the CPU, and the ABT 374 & 245
See @irepairsega 's message.

This needs someone with an expert touch. You have found some of the problems, but I can assure you, if those caps have leaked, others have.

You haven't found them yet because the leakage hasn't gotten as bad. All those caps came from the same lot basically so if some are leaking, they ALL are leaking.

You are Easter-egging. I wish you the best, but it's a Sysiphean task at best. I'd get professional help. You could incur more damage than repair. Best to leave this to the best.
 
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I've just found some more time to look at it...
I've replaced U17 but didn't find any changes, still not booting.
then I've removed the rom U51,52,53,54 if i'm not wrong this should be the 4 rom needed for the initial boot and compared to the mame rom files.
all good except for U53 have a different check sum looking deep on it I've found one single byte that differ at address 00000200: I read 00 while should be 4C.
does the system interrupt the boot if the checksum is not correct?
Should I get a video message with Rom checksum error or it's correct that no video it's showing at all?

I need to find a replacement rom or a UV rom eraser in order to try boot with the correct checksum

@ArcadeTechGW you are right infact I've replaced all the Caps even the one that have not damaged the board yet.
@irepairsega definitely I would like to come and meet you but you are a bit too far from Italy.
 
I've erased the ROM U53 and wrote again but no luck , same issue! I start checking a lot of connections and pin, and all my doubt was on CPU not been able to load the 4 rom correctly so after checking all the wiring I start doubting on Tristate buffers 245 and I've replaced U45 the one that was more close to the electrolytic cap and was looking bad. and... Bingo! the board finally started

I'm using a CRT for test not the one in the cabinet , the image goes outside of the screen and error on U67 U77 but then it continue and goes to the gun calibration pages. Definitelly I need to test it on the cabinet, but i'm happy because at least I manage to boot again!

Clipboard_11-06-2025_01.jpg
 
That board is notorious for leaking caps which kill tiny traces and vias.

Look under magnification around all electrolytic caps. If you found one that doesn't look good I'm guessing you have more damage from that or others.

I repaired mine. Multiple traces and vias, mostly fixed under microscope.
 
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Use a logic probe and look for missing signals on those red flagged RAMs.
 
I've put back the board inside the cabinet and powered on. the game start and stop at the diagnostic when U67 and U77 fails and the test abort but after calibrating the guns (all 3 are working) the game start and it play without any issue (apart sound issues).
Why the game works also if this rams are failing?
Whit the probe I can see traffic on both RAM maybe the issue it's with one transciever on data bus or some flip flop in the addressing side.
For the audio, at the power on I hear the classing bong, sometimes only one , and sometimes also 2-3 times. Why it sound different number of times? is it like a error code?

Also I have a distortion on the CRT but this one I will figure out later

Here a photo of the cabinet that still need to be cleaned (It's full of dust)


RevX.jpg
 
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