Centipede restoration - My first - There will be plenty of pics

Arcade Collecting > Restorations & repair

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Arroyo:
This is some EXCELLENT documentation. I like how you describe your thought process, it helps to see the approach and of course the solution. Keep it up!

wp34:

--- Quote from: Arroyo on February 18, 2020, 05:21:46 pm ---This is some EXCELLENT documentation. I like how you get describe your thought process, it helps to see the approach and of course the solution. Keep it up!

--- End quote ---

+1

Some great info in here. Your documentation is top notch.

bperkins01:

--- Quote from: wp34 on February 18, 2020, 10:07:27 pm ---
--- Quote from: Arroyo on February 18, 2020, 05:21:46 pm ---This is some EXCELLENT documentation. I like how you get describe your thought process, it helps to see the approach and of course the solution. Keep it up!

--- End quote ---

+1

Some great info in here. Your documentation is top notch.

--- End quote ---

Thanks guys - more to come as I get the video figured out...

bperkins01:
I bumped into this today: bitslicer -30v power

Great article on how the 555 timer creates the -30V circuit for the high score circuit. When I replaced it - I didn't know how it worked - but I was pretty sure it was the cause of my problem. Now I know.

bperkins01:
I've been out of town for a few days, but started back at it.
Except - I took a bit of a side route.

I've been unhappy with the the screen width (extra room below the shooter). I was convinced there was something wrong with the video circuit on the PCB. Inquiry and asking over on KLOV was interesting to say the least.

What I learned was - Go check MAME if you have questions about screen sizes!
MAME say's Centipede is: 256x240
Other vertical games such as dig dug and ms pacman are 288x224

So there is my shorter screen, 4 rows.. Even then I was a little skeptical that I didn't have some odd thing happening making the screen artificially small.

Part of digging into this is because I'm teaching myself board repair like so may others. I'm an above average problem solver - but when you don't know what you don't know - it takes a while to gain experience. I picked up a pair of dead Centipede boards from a KLOV'r purely to learn how to fix them. Having a working Centipede as a reference is helpful of course.

Long story short - I managed to get one of the two boards working enough that the game fired up and displayed. The screen width was identical (to the millimeter) as my game.. (Its on my LCD at the moment).

Here is what I did with the dead boards:

I connected them to my cabinet and checked voltages - both boards had all of them (surprised)
Board 1 - locked up dead - LED - but nothing...
Board 2 - managed to get it into self test screen.. and it all worked.. but no game play

I decided to pop, clean and reseat all of the EPROMS.
Lost the Self test screen... however I got activity on the screen - but it was a mess.. Screwed up graphics, it was the attract screen. A red block centipede was moving through green lines.
Pulled the board to check my work and ROM 211 was hot! (forget where I saw that ... feel the chips for heat.. they're probably bad)
So I swapped it from the dead Board 1
Test screen came back (I'm pretty sure, I forget the order now..)..
But no game play..
So I swapped each EPROM one at a time from the dead board.. ROM 207 was also bad it turns out.
Once I replaced that - game popped up!

Normal display screen - but during play - fleas only drop mushrooms either far right or far left..
I believe that is a RAM error, but I'm pretty happy about the progress for not really trying.

I still have to get my K4600 running a bit better and (grrrrr) converged properly.. I don't cave to stuff like that.. I'll win. But its been kicking my butt for a while now.

A friend had access to an old analog oscilloscope - I connected that up and managed to see signals on my board.. I'd never touched one until this week. I'll use a logic probe on the dead boards to find the issues for now.

Overall - happy to get to work on some other boards.
All I really have left is to get my CRT converged and the machine will be fully operational.
There are a few little items after that..
I'll update until its 100%!

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