Re: [SEGA Space Ship] Some update...

Bill wrote:
> Those 2101s fail quite often on just about every board that uses them. I
> would socket and replace that third one as preventative maintenance
> regardless of whether or not it is bad right now, especially if the two
> others failed.
>
> Bill
>
>
Agreed, particularly if they share the same date code - we should track
the date codes of bad ICs (right).

John :-#)#
> -----Original Message-----
> From: owner-vectorlist@vectorlist.org
> [mailto:owner-vectorlist@vectorlist.org] On Behalf Of Andrew Welburn
> Sent: Tuesday, February 23, 2010 3:46 AM
> To: vectorlist@vectorlist.org
> Subject: Re: VECTOR: [SEGA Space Ship] Some update...
>
> Sounds like good work!
>
> A few things though.. it sounds like your sound board is bad, if i read your
>
> message correctly, you are saying that the game works in attract mode, but
> there is a constant noise? the only thing you can hear is the fire noise
> when the button is pressed? It sounds like all sounds are 'on' and enabled
> at the moment.
>
> I would say your sound board, or the sound control latches are bad, i would
> not say you have a ram problem at all ?
>
> but.. on a side note, (i know nothing of CCPU workings) does the ccpu not
> have 'internal' registers for its own math functions that you can use as
> temporary storage for ram checking routines? I wrote a ram checking routine
> for Galaxian pcbs that worked without using any ram at all, i used the
> internal cpu registers creatively when i needed temp. storage instead. (this
>
> was all on a z80, and i don't know how 'slimline' the ccpu is) Does the CCPU
>
> have a status flag register? i'm sure its possible ;)
>
> Andrew Welburn
> www.andys-arcade.com
> ----- Original Message -----
> From: "Fabrice GIRARDOT" <f4brice@gmail.com>
> To: <vectorlist@vectorlist.org>
> Sent: Tuesday, February 23, 2010 8:04 AM
> Subject: VECTOR: [SEGA Space Ship] Some update...
>
>
>
>> Hi all.
>>
>> This is an update to my Sega Space Ship fixing task.
>> The PCB is a 99% clone of Cinematronics's Space Wars.
>>
>> Some weeks ago, I could successully fix the PCB.
>> For the first time I could see the game picture... :-)
>>
>> Only player #1 's fire button was not working.
>> I quickly checked that the button itself was wrong.
>> So I simply removed it from the panel, open it and
>> fix it.
>> When I powered again the game, bad sound could
>> be heard and no picture was displayed...
>> Scope says the PCB is reseted again by watchdog timer !
>>
>> When I press a fire button, fire sound can be heard
>> which is good but abnormal when game is not credited.
>> I highly suspect the last chip of RAM (I already changed
>> 2 bad chip of 3).
>>
>> This time it'll more difficult to have proof of a bad RAM,
>> because CCPU is able to execute a lot of instruction before
>> failing/looping.
>>
>> Last week-end, I wrote a software tool called an "assembler"
>> for the CCPU planet.
>> This tool reads a input text file called "source code",
>> generally written by hand. In this file CPU instructions
>> are written in an (almost) human readable format.
>> The tool writes corresponding CCPU hex opcodes to a binary
>> output file.
>> This binary file is to be written into an EPROM.
>> I'll spread the tool source code under the GPL license.
>>
>> Now, I'm writting my own CCPU program to test RAM chips.
>> It's not that easy because one would need little RAM storage
>> to test RAM.
>> So my program test at first 2 RAM storage before being able
>> to test the whole banks & addresses.
>>
>> Since I can't ouput anything as debug display, if a bad
>> RAM storage is found, my program makes CPU jumps to an
>> infinite loop doing :
>>
>> 1: read last RAM storage to B accumulator
>> 2: read any input (so activate signal /READ)
>> 3: reset watchdog timer
>> 4: jump to 2
>>
>> If my CPU is caught in this infinite loop, I'll use the DSO
>> to find what is the current selected RAM bank & address.
>> "I" register stored in chips I12 & J12 will give me this info.
>> By comparing A & B registers, I'll kown what was wrong.
>>
>> If all RAM storage is found good, then 2 possibilities :
>> A/ my test is incomplete ;-)
>> B/ something else is wrong
>>
>> In case of (B), I'll write an other program that makes CPU
>> execute every possible instruction and I'll check them with scope.
>>
>>
>> I already scanned and converted to PDF all the SEGA
>> documentation I have.
>> The PCB pinout file is updated.
>> The screen pinout file is in progress.
>>
>>
>> To be continued...
>>
>> --
>> Fab
>>
>>

-- 
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
                 www.flippers.com 
"Old pinballers never die, they just flip out"
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