Twin Cobra PCB (US, Romstar) Freeze

PCB problems and fixes
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goatboy
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Twin Cobra PCB (US, Romstar) Freeze

Post by goatboy » February 5th, 2014, 3:29 pm

Hello,

Just received an original Twin Cobra PCB (US, Romstar). Played fine for a couple of minute. Came back in the room after a break and the game was locked/frozen in attract mode. Turned it off and on again and the game freezes now at startup.

Blue screen and these messages:
- ram check ok
- rom check ok
- sound ok

The game just stops there.

When i insert a credit i can still hear a sound of inserting a coin. That's it. Really bummed as i just received this and i kinda like the game 'a lot'. Anyone got any ideas how to troubleshoot this? Read about this error before but couldn't find anything about this being resolved. The voltage was just a tiny bit below 5V when this happened.

Thanks in advance, Henk.

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emphatic
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Re: Twin Cobra PCB (US, Romstar) Freeze

Post by emphatic » February 5th, 2014, 4:01 pm

Have you tried raising the voltage to 5.1 and see it it runs?

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Re: Twin Cobra PCB (US, Romstar) Freeze

Post by goatboy » February 5th, 2014, 4:30 pm

emphatic wrote:Have you tried raising the voltage to 5.1 and see it it runs?
No luck, Still hangs at the same spot.

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Re: Twin Cobra PCB (US, Romstar) Freeze

Post by goatboy » February 6th, 2014, 10:43 am

Sent Vectorglow a message. Let's see what he has to say and hopefully help out. Will update if there's any news.

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Re: Twin Cobra PCB (US, Romstar) Freeze

Post by trmatthe » February 8th, 2014, 12:16 pm

I would remove and reseat the interboard connectors a few times. I've had a number of TCs which seemed terminal and this often fixes them without having to start scoping out the 68k. Not sure why but they seem to suffer from dodgier than average IDC cables.

You could also try setting DSW1-3 and DSW2-7 to on to see if you can enter service mode (DSW1-3) and show DIPS (DSW2-7). The service mode is pretty crap but it'll show whether the 68k is continuing to run at least.

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Re: Twin Cobra PCB (US, Romstar) Freeze

Post by goatboy » February 8th, 2014, 3:50 pm

Thanks for your reply! Tried reseating the connectors several times but no change. Entering service mode is also not possible when setting the dips correctly. Even reseated all the eprom has no positive effect. I did notice when firing up the board i can see some stripes flickering across the screen but maybe this is normal. Will send this off to a pro. :)

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Re: Twin Cobra PCB (US, Romstar) Freeze

Post by emphatic » February 8th, 2014, 6:48 pm

trmatthe wrote:I would remove and reseat the interboard connectors a few times. I've had a number of TCs which seemed terminal and this often fixes them without having to start scoping out the 68k. Not sure why but they seem to suffer from dodgier than average IDC cables.
I wonder if this would help my TC board? :think: Mine has some sort of glitching in the sprites (the top layer of the sprites seem to disappear).

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Re: Twin Cobra PCB (US, Romstar) Freeze

Post by Jamtex » February 10th, 2014, 10:17 pm

I fixed a broken TC board by just removing the connectors and swapping and inverting them. Went from black screen to fully working game. Make sure they are clipped in after.
A:>

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Re: Twin Cobra PCB (US, Romstar) Freeze

Post by emphatic » February 10th, 2014, 10:39 pm

Will IDE cables work as replacements for those connectors? :think:

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Re: Twin Cobra PCB (US, Romstar) Freeze

Post by trmatthe » February 10th, 2014, 10:58 pm

Am not near any PCBs at the moment but if the pin count is correct then they're all wired the same on the inside. Just like people :D

Losing half/much of the GFX and still having the game run would make the interboard connectors my first port of call definitely.

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Re: Twin Cobra PCB (US, Romstar) Freeze

Post by emphatic » February 10th, 2014, 11:11 pm

trmatthe wrote:Am not near any PCBs at the moment but if the pin count is correct then they're all wired the same on the inside. Just like people :D

Losing half/much of the GFX and still having the game run would make the interboard connectors my first port of call definitely.
:awe: x 2! I guess I'll have to pull my board out and check these cables.

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Re: Twin Cobra PCB (US, Romstar) Freeze

Post by goatboy » March 18th, 2014, 10:58 pm

Before i forget; Unfortunately the fault couldn't be traced. The 68k CPU was replaced but this wasn't the failure. After several more hours of checking all hope on repair was lost, Bummer! I donated the board as spares / junk. Another Twin Cobra PCB gone. :cry:

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