Author Topic: [Wonderboy repair log] what does a flip flop IC do?  (Read 16649 times)

anunaki

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Re: what does a flip flop IC do?
« Reply #15 on: July 16, 2015, 10:45:19 AM »
I'm a complete noob, but measuring voltages I can do and I will

My guess was that the eproms containing the sprites aren't accessed and this IC is in between (or so it seems to me). I completely desoldered the daughterboard (some wires are there from the factory) and the result didn;t change at all

I actually can play the game blind (so without the moving objects like the boy, the fruits and the villains)  and get sounds FX + die at collision

« Last Edit: July 16, 2015, 10:47:49 AM by anunaki »

Etienne MacGyver

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Re: what does a flip flop IC do?
« Reply #16 on: July 16, 2015, 01:37:07 PM »
measure a 7400 series chip somewhere on the board between pin 7 and 14.

preferably one that is far from the edge connector.

Q*ris

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Re: what does a flip flop IC do?
« Reply #17 on: July 16, 2015, 01:50:56 PM »
Cool advice! Thanks Etienne!
When measuring a chip, I was always using my monitor chassis instead of pin 7.  :oops:

anunaki

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Re: what does a flip flop IC do?
« Reply #18 on: July 16, 2015, 02:38:58 PM »
yes great tip indeed, I do this also. Picked this up from a Randy Fromm video (whitch was also a tip from Etienne btw)

level42

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Re: what does a flip flop IC do?
« Reply #19 on: July 16, 2015, 05:25:20 PM »
Since its a Z80 board I -could- hook it up to my Fluke 9100a.....however....we need info:

- memory map of Wonder Boy, that is, where are The ROMs located ?
- signature.....highly unlikely to find those for the 9100A but we could try the regular CRC32. Andy from the UK wrote a program to get this number with the 9100A.

now, if you find the memory map.....:)

ajhippel

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Re: what does a flip flop IC do?
« Reply #20 on: July 16, 2015, 05:31:42 PM »
mame is always good for memory-maps...

the system1-memory map

https://github.com/mamedev/mame/blob/master/src/mame/drivers/system1.c

starting at line 732
there is too much butter on those trays

Laszo

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Re: what does a flip flop IC do?
« Reply #21 on: July 18, 2015, 09:47:36 AM »
Do you have a logic probe?

I would check the sprite ram first. With a rom failure the game probably would not start at all. The game is playing so the problem is most likely close to the output side not at the rom side.

anunaki

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Re: what does a flip flop IC do?
« Reply #22 on: July 18, 2015, 11:11:18 AM »
Yes I do Have one.

I'm almost done reordering my workbench so then I can properly test the basics 1st.

level42

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Re: what does a flip flop IC do?
« Reply #23 on: July 19, 2015, 10:00:03 AM »
Do you have a logic probe?

I would check the sprite ram first. With a rom failure the game probably would not start at all. The game is playing so the problem is most likely close to the output side not at the rom side.

Im not familiar with Wonderboy hardware but usually there are separate program ROMs and Graphics ROMs Leo, so if the Graphics ROMs are bust but the program ROM still Ok the game plays but you don't see the corresponding graphics. At least that's how it works on Galaxian.

Jochen, thanks and I know but I wanted to keep a small challenge for Patrick ;)

anunaki

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Re: [Wonderboy repair log] what does a flip flop IC do?
« Reply #24 on: July 19, 2015, 09:07:45 PM »
1) I replaced the 74ls74 with a brand new one and the image is nice and clean again (this was distored 1st), but still no sprites

2) I measured the voltage on the 74LS74 on the daughterboard and it's a nice 5.02V

no I'm going to check the eproms

anunaki

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Re: [Wonderboy repair log] what does a flip flop IC do?
« Reply #25 on: July 19, 2015, 09:12:08 PM »
Hmmm, all 4 eproms are filled completely with FF

this doesn't look right, this menas they are empy I guess??

I'm going to look if I can reprogram them

anunaki

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Re: [Wonderboy repair log] what does a flip flop IC do?
« Reply #26 on: July 19, 2015, 09:23:24 PM »
I also know for sure now that these are the sprite eproms, thanks to the MAME rom images

I'm clearing the eproms now, hopefully they still work. If not, I need to find some 27128 eproms

edit: well, the eproms are dead I think so I need to get some new ones
« Last Edit: July 19, 2015, 09:43:12 PM by anunaki »

mikemcbike

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Re: [Wonderboy repair log] what does a flip flop IC do?
« Reply #27 on: July 20, 2015, 01:07:52 PM »
that sounds O.K., 0xFF in sprite data is often displayed as transparent color... could be a reason that there were no sprites at all.

anunaki

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Re: [Wonderboy repair log] what does a flip flop IC do?
« Reply #28 on: July 20, 2015, 01:19:13 PM »
still strange how this happened, maybe because of the failing 74ls74

level42

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Re: [Wonderboy repair log] what does a flip flop IC do?
« Reply #29 on: July 20, 2015, 11:18:47 PM »
Funny, just discussed about failing EPROMS and trying to wipe and reprogram them with Speleo....he said it's pointless in all cases he encountered bad EPROMS had died physically, it's not a case of loosing the programming through UV light.

I had tried with one from Chris's Tron board and same result. The dead 74 might indeed be the cause.

I have quite a few 27128's On stock IIRC.

Good work by the way !