Saturday, 27 July 2013

Snes Everdrive DSP1 Installation

Giving the Snes some love today. :)

I managed to get hold of one of those Everdrive cart's :D ..but sadly the one without the DSP1 chip :'(
(which is needed to play MarioKart or Pilotwings)

So to source the needed components I picked up a crappy lesser known US cart called Ballz 3D - a console-mod forum tutorial pointed me at this title - as it has all three of the required components
(And is quite frankly, a load of Ballz!).

So step-one was to get the Everdrive & Ballz-cart open :/

Meh... security screws! :(

Luckly there's a tutorial on youTube on how to melt the end of a biro and push it into a screw (while molten), to make a poor-mans security-screwdriver.. \o/

My first attempt didn't go too well & biro plastic got stuck around one the screw heads, but since I was practicing on the donor cart - there was nothing a hack saw couldn't handle.

Had to desolder three components: a 74HCU04, Ceramic Oscilator & the DSP1 chip:

Care had to be taken when mounting the chips to te Everdrive pcb.. there are several surface mount resistors right next to the IC pin holes!

And - The DSP1 chip has to mounted on the back side of the board & the Logic & Clock on the front!

And the other (front) side:

Reassembled the cart WITHOUT security screws! ;)

Happy days! <3

We have: Pilotwings..

And more importantly..

Retro-tastic :D I haven't had a Snes for over 21 years! I'm old.. :/

Oh.. also worth a mention.. I received an RGB SCART lead with the Snes I bought, but upon plugging into my later-day LCD TV, the screen would fade to black as soon as the picture became busy / too bright.

The solution was to desolder three capacitors that were in-line with the R,G&B wires in the SCART plug.
(I left the Cap on the Sync wire & that seemed cool.)

Recycled Master-System Cartridge

Recycled Master-System Cartridge

Recently received some freebee Master-System cartridge PCB's from steveBM1 over on Jamma+, a very kind fellow indeed!

Went and fitted a 32 pin chip socket to one of the boards and naively burned a 27C020 (256k / 2Mbit) Eprom with Wonderboy 3 game data (love that game - still remember the cheat password: WE5TONE)

But no boot.. :'(

Later learned that Master-System Roms have custom logic inside to page in the blocks of data for games bigger than 32k.

Apparently you can re-use carts that have a second 'mapper' chip, so for now I thought I might try a 32K game burned onto a 27C256 chip.

But............. The 27C256 has 4 less pins than the 27C020 (it's 28 pin, rather than 32)

From experience with the R-Type conversions, I knew that all the lower 26 pins are the same between the two chip types.  So I burned a 32K Eprom with Teddy Boy and inserted it into the lower end of the socket.
I had to then fit 2 wire bridges to bring the 5v line down to the top two pins of the 28 pin Eprom.

I also had to cut one trace that led from the third pin - to the edge connector (Shown below).

And here is the finished board in full:

And again from below:

And you know what..? It worked! :D

Just have to wait for a RGB SCART lead to turn up, my TV won't tune in well enough to get a good picture on RF.

I'll also have to research this mapper-chip stuff.. might be able to build some logic to do this.

Friday, 26 July 2013

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 ...  

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!"

Thursday, 4 July 2013

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..