JAMMArcade.net – Page 171

CPS1 A-BOARD (new revision) repair log

Oct 242014

Contradicting the current tendency to sell all the CPS1 stuff due its extreme unreliability (my mate Porchy knows something about…) I decided to buy a faulty CPS1 motherboard (also know as ‘A-BOARD’).Seller claimed board was good except for the audio completely missing.

When the board arrived (it was actually a ‘CPS DASH’ so the last revision with 12MHz oscillator), I immediately noticed it was missing the volume pot:

So, I took this pot (2.2KOhm to be exact) from a dead CPS1 motherboard sure that this was the cause of the missing audio.But I was wrong since still I got no audio.Touching with fingers the solderside pins of the HA13001 main amplifier gave me some noise from speakers so fault was elsewhere.

First I started to test Z80 audio CPU with my logic probe and no activity was present on data/address lines.I knew from other CPS1 repair logs that bad Z80 CPU is a very common fault on this boards so I decided to replace (using a round machine-tooled socket) it without thinking twice.

And this was enough to restore full sound back.

SOIC-n to DIP adapter

Arduino 2 Responses »

Oct 122014

I recently came across a nice looking IC that I wanted to try out.
The actual device in question is the AD8400ARZ1 from Analog Devices and is a digital potentiometer that in a narrow SOIC package.
As Im wanting to use this with some Arduino projects I wanted to be able to use it on prototype board which requires a DIP package.
I made a nice small board up in Eagle and am currently waiting on the boards coming from OSHPark. It ended up costing me something like 70p for 3 as they are tiny.

EDIT: Mike kindly pointed out in the comments that I should have checked eBay first. This is a very good point and ive got into the routine of not checking eBay for anything these days but when there are big savings in both time and money to be made then its definitely worth a go.
Thanks Mike for pointing this out. At least there was no great amounts of cash spent on it.

Varth (USA 920612) ‘handcrafted’ PAL added

PAL Updates Comments Off

Oct 102014

Some days ago ‘Palindrome’ created by hand the missing ‘VA63B’ PAL dump from Varth: Operation Thunderstorm (USA 920612) CPS1 board and Tafoid submitted it to MAME source.Today Tafoid gave me permission to add it to our database.As said, this is not the real dump from PAL device but a manual recreation of its equations.Anyway Palindrome tested it and reported it as working on his board.Thanks to Tafoid and Palindrome.

UPDATE

I can confirm the PAL is 100% working since I succesfully tested it in my Varth converted PCB.

Jumping PCB info

General, Technical Info 1 Response »

Oct 052014

Been doing a few bits with muddymusic’s Jumping PCB.
I wanted to see how the C-Chip substitute ROM was wired into the circuit so ive made a small schematic and reversed the address decoder PAL.

click the pic for full size.

Here are the equations for the address decoder too. Ive renamed to the pins to something more suitable for human consumption.
/* Inputs */

Pin 1 = A23;
Pin 2 = A22;
Pin 3 = A21;
Pin 4 = A20;
Pin 5 = A19;
Pin 6 = A18;
Pin 7 = A17;
Pin 8 = A16;
Pin 9 = A15;
Pin 10 = A14;
Pin 11 = A13;
Pin 13 = FC0;
Pin 14 = FC1;
Pin 23 = FC2;

/* Outputs */

Pin 15 = CA12; /* A12 of C-Chip replacement ROM */
Pin 16 = CA13; /* A13 of C-Chip replacement ROM */
Pin 17 = CA14; /* A14 of C-Chip replacement ROM */
Pin 18 = CA15; /* A15 of C-Chip replacement ROM */
Pin 19 = LROM; /* Chip enable for other ROM’s */
Pin 20 = A; /* Pin 1 of 74LS138. Input A */
Pin 21 = B; /* Pin 2 of 74LS138. Input B */
Pin 22 = C; /* Pin 3 of 74LS138. Input C */

/* Equations */

!CA12 = !A23 & !A22 & !A21 & !A20 & !A19 & !A13 #
!A23 & !A22 & !A21 & A20 & !A19 & !A18 & !A17 & !A16 & A15 & A14 & !A13 #
!A23 & A22 & !A21 & !A20 & !A19 & !A18 & !A17 #
!A23 & A22 & !A21 & !A20 & !A19 & !A18 & A17 & A16 #
A23 & A22 & !A21 & !A20 & !A19 & !A18 & !A17 & !A16 & !A13 #
!A23 & !A22 & !A21 & !A20 & A19 & !A18 & !A17 & !A13 #
A23 & A22 & !A21 & A20 & !A19 & !A18 & !A17 & !A16 & !A15 & !A14 & !A13;

!CA13 = !A23 & !A22 & !A21 & !A20 & !A19 & !A14 #
!A23 & A22 & !A21 & !A20 & !A19 & !A18 & A17 #
A23 & A22 & !A21 & !A20 & !A19 & !A18 & !A17 & !A16 & !A14 #
!A23 & !A22 & !A21 & !A20 & A19 & !A18 & !A17 & !A14;

!CA14 = !A23 & !A22 & !A21 & !A20 & !A19 & !A15 #
A23 & A22 & !A21 & !A20 & !A19 & !A18 & !A17 & !A16 & !A15 #
!A23 & !A22 & !A21 & !A20 & A19 & !A18 & !A17 & !A15;

!CA15 = !A23 & !A22 & !A21 & !A20 & !A16;

!LROM = !A23 & !A22 & !A21 & !A20 & !A17;

!A = !A23 & !A22 & !A21 & !A20 & !A19 & !A18 #
!A23 & !A22 & !A21 & A20 & !A19 & !A18 & !A17 & !A16 & A15 & A14 #
!A23 & !A22 & A21 & !A20 & !A19 & !A18 & !A17 & !A16 & !A15 & !A14 & !A13 #
A23 & A22 & !A21 & !A20 & !A19 & !A18 & !A17 & !A16 #
A23 & A22 & !A21 & A20 & !A19 & !A18 & !A17 & !A16 & !A15 & !A14 & !A13;

!B = !A23 & !A22 & !A21 & !A20 & !A19 #
A23 & A22 & !A21 & !A20 & !A19 & !A18 & !A17 & !A16 #
!A23 & A22 & !A21 & !A20 & !A19 & A18 & !A17 & !A16 #
A23 & A22 & !A21 & A20 & !A19 & !A18 & !A17 & !A16 & !A15 & !A14 & !A13;

!C = !A23 & !A22 & !A21 & !A20 & !A19 #
!A23 & !A22 & !A21 & A20 & !A19 & !A18 & !A17 & !A16 & A15 & A14 #
!A23 & !A22 & !A21 & !A20 & A19 & !A18 & !A17;

The A, B and C outputs from the PAL feed into a 74LS138. In order to select the C-Chip substitute A and B must be HIGH and C must be LOW. From the equations (or just looking at the MAME source code) we can work out that the C-Chip ROM lies at address 0x80000.

So, not a great deal of info but its pretty interesting all the same.

Another Jumping PAL dump

PAL Updates Comments Off

Oct 052014

I dumped another PAL from the Jumping board today. Like the other this one was unlocked so now we have a full set of PAL dumps for the Rainbow Islands bootleg.
This PAL is found on the lower PCB of the stack.

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