A glitch chasing story

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Asayuki
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A glitch chasing story

Postby Asayuki » February 20th, 2016, 1:01 pm

Hi all,
another level of my quest to defeat Brawshella has been completed. :awe:
This time it's a bootleg Twin Cobra board with some facepalm issue on an add-on card replacing some custom chips.
The repair itself definitely belongs in the hard class, 8-) but I cut as short as possible the otherwise interesting story of this troubleshooting effort. If you are curious about getting further details then let me know. I am however pretty sure the community can make good use of the reverse engineered data available in this article.

As usual, comments, suggestions and constructive criticism are welcome. Happy reading!

http://wiki.arcadeotaku.com/w/Twin_Cobra_Repair_Logs
My 15kHz cabinet Peplos will never power up, with any item, and I am quite proud of that.
spmbx
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Re: A glitch chasing story

Postby spmbx » February 20th, 2016, 7:24 pm

...
Last edited by spmbx on October 19th, 2016, 10:11 pm, edited 1 time in total.
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DaveyD
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Re: A glitch chasing story

Postby DaveyD » February 20th, 2016, 7:26 pm

I love reading repair logs like these. Always amazes me how people figure out how to reverse engineer these things. Nice work! :thumbup: :thumbupright:
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Asayuki
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Re: A glitch chasing story

Postby Asayuki » February 21st, 2016, 7:27 am

Thanks :D

spmbx wrote:Seems like with a little effort you could have recreated the entire board from scratch, or am i going too far now :)


With the information I have gathered, it would be no problem at all to create a T.T-2 replacement; but that would require way more time and money than the ones a bootleg would be worth investing into. For an original with a broken T.T-2 I would have probably done it. ;)
My 15kHz cabinet Peplos will never power up, with any item, and I am quite proud of that.
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Stompp
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Re: A glitch chasing story

Postby Stompp » February 22nd, 2016, 1:32 pm

Thank you for this. I have the same kind of bootleg T.C. with another kind of issue though (https://youtu.be/N7HT2qfqMLU). Haven't bothered about it thus far, but now you got me thinking :awe:
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Asayuki
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Re: A glitch chasing story

Postby Asayuki » February 22nd, 2016, 3:31 pm

Stompp wrote:I have the same kind of bootleg T.C. with another kind of issue though (https://youtu.be/N7HT2qfqMLU).


Hmmm.... that looks strikingly familiar. ;)
If you have a scope you might want to check HSYNC and VSYNC at the T.T-2 for amplitude and smoothness. By syncing to VSYNC and poking around the RAM address outputs you should clearly see the mess happening. The title logo completely belongs to the T.T-2 that sits close to the Z80, except the helicopter.
But your issue looks much more severe than mine. Maybe one of the ICs on the add-on card is gone?
Of course it can still be oxidised contacts in those pesky two-rows connectors or an issue with the monitor...
Let me know if you need further help.
My 15kHz cabinet Peplos will never power up, with any item, and I am quite proud of that.
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Stompp
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Re: A glitch chasing story

Postby Stompp » February 23rd, 2016, 8:41 am

Asayuki wrote:
Stompp wrote:I have the same kind of bootleg T.C. with another kind of issue though (https://youtu.be/N7HT2qfqMLU).


Hmmm.... that looks strikingly familiar. ;)
If you have a scope you might want to check HSYNC and VSYNC at the T.T-2 for amplitude and smoothness. By syncing to VSYNC and poking around the RAM address outputs you should clearly see the mess happening. The title logo completely belongs to the T.T-2 that sits close to the Z80, except the helicopter.
But your issue looks much more severe than mine. Maybe one of the ICs on the add-on card is gone?
Of course it can still be oxidised contacts in those pesky two-rows connectors or an issue with the monitor...
Let me know if you need further help.

Thx, appreciated :thumbup: I've got some other stuff that needs to be taken care of first though (as usual :( )

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