Double Dragon - Repair Log - Day 3

Double Dragon - Repair Log - Day 3

Fixed the 1 & 2 player buttons I/O.. and all looks good for this one!

Though on my bartop i do get the occasional sync roll!?! :( .. I found the schematic to see where the sync pin leads to, but if goes off one page & must become Japanese on another. :/

I scoped the signals around the video connector and supply, and I get a god solid 5v power rail, RGB going from 0-1v and the sync line going from 0-2v .. Large 0 pulse (v blank) with finer 0-2v pulses in between (h blank).

I compared the signal with some other boards and it looks legit :D which suggests another theory..

Are the sync issues due to the CGA-VGA converters I'm using on my flat-panel?

Short answer.. Yes. The pcb was verified working by the owner on his CRT.

WARNING! (To anyone working on one of these boards!)

I had to re-fit the four board spacers back between the two boards before it was taken away..

Oh boy!!! :S

On double dragon there are two plastic spacers ... and two metal ones ...  
Yeeeeeeeah...

I placed them in a rather arbitrary arrangement, tightened the bolts & powered up.. 
Wait for it... F***in shite loads of smoke poured out of my Jamma loom!!!

Turns out that.. Well you know the big fat traces that run around the outside of the PCB'S? They're usually earth / ground / 0 volts, right?

Not this time! One surface of each board is 0v and the other is 5v. Two of the corner bolt holes are seperated buy a split in the PCB track (running round the edge) - two are not.

If you get the metal corners wrong then it's smoky time - so please be careful and make a note of where they came from when you take the boards apart!

I assume the metal rods actually carry the power and ground from the top to the bottom board (when in the right corners) & the 0 & 5v on each side of the board is acting as RFI suppression.

Luckily there was no real damage done.. The direct short through the metal board spacer rods protected the board.. I'm just gunna need some heavier cable for my 5v line. ;)

"A dragon with two metal teeth!"

Double Dragon - Repair Log - Day 2

Double Dragon - Repair Log - Day 2

Okay.. I did something a little silly ..not in a baaaad way tho.

I've bought another broken Double Dragon board on fleaBay to assist in the repair.. (hope I wasn't bidding against Beaps!! :D) - cost £37 all-in - ruuning at a lose, but hey, at least I can keep the scraps.

It arrived last night & I immediately swapped the top board from the new one with Beaps rusted one (remember the resistor pack issue?):



As the one I received locks up on boot, I fitted Beaps brand-new processor & US Rom set:



And... drum-roll....



We have a good picture - all that remains now is the player 1&2 start buttons don't respond, booo.. :(

Bet £1900 some one had previously rear-ended the 12v line.. (reversed the Jamma connector)

There looks to be some previously attempted repairs around this region of the board, so I know where to look first..

Double Dragon - Repair Log - Day 1

Double Dragon - Repair Log - Day 1

Today Beap's Double-Dragon board that came out to play..


Some repair work had previously been carried out on this board, and it looked like Ram & sound substitutions primarily.. The CPU had also been replaced.

But on power up there was an unnerving buzz for two seconds and blocks of corrupt data in a static pattern across the screen. :(

First I had to remove some rust from the sound side of the board..



And there was a region of the board where a 5-pin-resistor-pack had been previously removed..

Cleaned the rust & crusty flux & ordered some parts..

Will have to completely rebuild the tracks - this damage shouldn't stop the board from booting - but I won't expect the sound to function too well until it is resolved.



And from below:



Also removed a big metal pin that was shorting a transistor:



The soldering around the previous repairs didn't look too healty, lots of dry flux, a couple of shorted traces and maybe even a split track or two. :/



Cleaned it all up a bit.. reflowed the solder - removed all the shorts, and attempted a power test..

It' booted! - Not without issue though.. but its playing and makes a few sound effects on start-up!

Some progess at least.



The sprites & BG-layers looked to be functioning.. looks like the Font layer is glitched - will have to probe those Ram chips, to see if they have to be replaced.



























To be continued...