Rabbit Punch PCB Problem

mastercello · Post by **mastercello** » Fri Sep 05, 2008 8:01 pm

Got a Rabbit Punch PCB of ebay, seller sold as working board.
Unfortunatly i got it in the following state:

- All moving sprites are the same, changing the type of the object constantly.
- Background is perfect, also the bullets are shown normal.

Here are a few pictures of it:

What i've done already:
- Checked voltages, all fine with +5 and +12V
- Cleaned up the boards (2 Layer pcb)
- Reseated all socket EROMS and cleaned the sockets
- Reseated the connections between the boards
- Checked for bent pins
- Checked for visual cuted pins

When i run my fingers around two of the RAM IC's (HD74LS273) the pattern is stop moving from one to another object and stays in the same object.

Do i have a bad RAM?
How can i check this?
Do i have another problem?

Thanks for any advices

mastercello · Post by **mastercello** » Sun Sep 07, 2008 7:04 pm

Anyone?

rtw · Post by **rtw** » Mon Sep 08, 2008 7:17 am

Is the RAM socketed ? If so try swapping them around to see if the behaviour changes.

It looks like you have a logic problem i.e. your address decoding might be broken. This problem is normally releated to PAL/GAL but you might also need to check the TTL logic connected to the PAL/GALs.

rtw

mastercello · Post by **mastercello** » Mon Sep 08, 2008 7:56 am

rtw wrote:Is the RAM socketed ? If so try swapping them around to see if the behaviour changes.

It looks like you have a logic problem i.e. your address decoding might be broken. This problem is normally releated to PAL/GAL but you might also need to check the TTL logic connected to the PAL/GALs.

rtw

Unfortunatly the RAM are soldered, so not easy to change them around.
Here is the pdf maunal of the game, wich include 6 pages of schematics of the game.
http://www.masto.ch/egret/pdf/rabbitpunch.pdf

Would be nice if you could point me in some direction rtw.

Thanks in advance

rtw · Post by **rtw** » Mon Sep 08, 2008 7:04 pm

mastercello wrote:Would be nice if you could point me in some direction rtw.

I'm sorry but this is not a trivial issue

The schematics are a bit vague and it's hard to make out the logic. What happens if you enter setup mode ?

rtw

mastercello · Post by **mastercello** » Mon Sep 08, 2008 7:16 pm

rtw wrote: I'm sorry but this is not a trivial issue The schematics are a bit vague and it's hard to make out the logic. What happens if you enter setup mode ?
rtw

I know...

There is no setup mode at all.

rtw · Post by **rtw** » Mon Sep 08, 2008 7:31 pm

mastercello wrote:There is no setup mode at all.

Check page 18 in the PDF

rtw

mastercello · Post by **mastercello** » Mon Sep 08, 2008 8:01 pm

rtw wrote: Check page 18 in the PDF
rtw

Sorry, i was not reading it right.

All fine in test mode, there is just one page were you can see the dip switch settings. Another were you can test all the inputs and the last one wer you can switch through the sound register.

Everything is fine in this three test modes.

mastercello · Post by **mastercello** » Mon Sep 15, 2008 7:36 am

Anybody

Jockel · Post by **Jockel** » Mon Sep 15, 2008 7:58 am

There is at least a partial solution.
Beat the ebay-seller to death with a blunt object.
(And claim your money back)

sven666 · Post by **sven666** » Mon Sep 15, 2008 8:00 am

Jockel wrote:There is at least a partial solution.
Beat the ebay-seller to death with a blunt object.
(And claim your money back)

..and then buy a new board off me

mastercello · Post by **mastercello** » Mon Sep 15, 2008 8:29 am

sven666 wrote:
Jockel wrote:There is at least a partial solution.
Beat the ebay-seller to death with a blunt object.
(And claim your money back)
..and then buy a new board off me

Thanks boys, he put a claim for the parcel already.
So i might get back the money, but the game still will not work.

@sven666 - do you have a Rabbit Punch for sale?

Post by **system11** » Mon Sep 15, 2008 8:36 am

If you're up for a learning experience, try this:

Locate the RAM chips on the schematics, they're probably sprite ram given what happens. The fact that they're changing constantly and stop when you interfere with the chip, probably means one of the address or I/O lines are floating. For an interesting test, put your finger in the place that stops the cycling and power the game up just to see if there are any differences.

Really you need a logic probe for this, you need to test each leg of the affected RAM chip, to see which one(s) aren't pulsing as you'd expect. As a rule of thumb, anything which is connected (which will probably be every leg on the RAM) which isn't showing high/low or a pulse, can be considered a floating input or output. If the leg is an address line, then usually it's the chip connected to it at fault. If it's I/O, then it could be the RAM or the chip connected. Either way, replace the relevant chip(s).

If you don't have a logic probe, try to work out as best you can which legs on the chip have the effect of stopping the sprite cycling, it should be fairly easy to identify which chips are possibly bad.

This may not fix the game of course, I'm self taught but it's where I'd start personally.

Edit: by the way, the LS273 is not a RAM chip

Sorry I didn't read more closely to begin with. You'll probably find it's connected to some RAM or ROM chips though, similar theories to above apply.

sven666 · Post by **sven666** » Mon Sep 15, 2008 8:40 am

mastercello wrote:
@sven666 - do you have a Rabbit Punch for sale?

yup, lmk if you want it

mastercello · Post by **mastercello** » Mon Sep 15, 2008 1:39 pm

Thanks for your help bloodflowers, but i dont have a Logic Probe.
But i will try your hints and tips.

LS273 is some kind of Flipflop Chip.

@ sven666 - will contact you if the seller refunds me.

Post by **system11** » Mon Sep 15, 2008 2:25 pm

mastercello wrote:LS273 is some kind of Flipflop Chip.

Yup - they're often a source of simple PCB faults, I had -three- bad ones in a chain on a Psycho Soldier board a while ago.