Wednesday, 28 November 2012

Dual Boot R-Type 1 & 2 Arcade PCB - Day 3

 Dual Boot R-Type 1 & 2 Arcade PCB - Day 3

Here's the circuit I would need to correctly select between two Rom chips - using a single hi/low "game select" signal:

(I made a mistake with my first Rom-select design (The NOT & AND gate thingy) in the first post)..

The /CS (chip select) line on the Roms activates the chip when it goes low..! 

So here, I use two sections of a 74157 to pass either the hi/(active)low /CS signal (or) a 5v signal.

This should correctly disable the unused Rom chip with the positive signal while passing the /CS to the other one.


Just programmed the 27C040 ROMs for C0-3 & N0-3, wired up the A18 address pins to the previous orange wire patch and observed the following:

* R-Type 1 is still fully functional (as expected).
* R-Type 2 has some visual errors, which are related to the extra electronics & board modifications...
** Minor erroneous background tiles.. Not bad, but a few wrong (similar in nature to RT1 prior to the logic/board mods).
** All sprites are a block of solid colour.

So it looks as if I will have to add those multiplexers to switch the modifications in & out.. cool. :)

Also have to do something with the audio Rom.. And since I'm going to use those multiplexers, I think I'll go with the new Rom selection logic above (and be switched with all the other board signals).

Friday, 16 November 2012

Dual Boot R-Type 1 & 2 Arcade PCB - Day 2

 Dual Boot R-Type 1 & 2 Arcade PCB - Day 2

Just performed a simple test of the double sized RT1 & 2 Roms!! :D

Copied all the MajorTitle-RType1 & MajorTitle-RType2 Rom images into a folder & wrote a batch file that did this:

copy /V rt_h0.bin /B + rt2_h0.bin /B combined_h0.bin /B
copy /V rt_h1.bin /B + rt2_h1.bin /B combined_h1.bin /B
copy /V rt_l0.bin /B + rt2_l0.bin /B combined_l0.bin /B
copy /V rt_l1.bin /B + rt2_l1.bin /B combined_l1.bin /B

copy /V rt_n0.bin /B + rt2_n0.bin /B combined_n0.bin /B
copy /V rt_n1.bin /B + rt2_n1.bin /B combined_n1.bin /B
copy /V rt_n2.bin /B + rt2_n2.bin /B combined_n2.bin /B
copy /V rt_n3.bin /B + rt2_n3.bin /B combined_n3.bin /B

copy /V rt_c0.bin /B + rt2_c0.bin /B combined_c0.bin /B
copy /V rt_c1.bin /B + rt2_c1.bin /B combined_c1.bin /B
copy /V rt_c2.bin /B + rt2_c2.bin /B combined_c2.bin /B
copy /V rt_c3.bin /B + rt2_c3.bin /B combined_c3.bin /B

copy /V rt_sp.bin /B + rt2_sp.bin /B combined_sp.bin /B

This copies the R-Type 2 Rom data to the end of the R-Type 1 data & produces files twice the original size.

Which I then burned to four 27C020 EProms (2MBit - instead of the original 1MBit ones)

I added a two pin connector to a capacitor near the main program Roms (H0, H1, L0 & L1),
with this you can select the Hi/Low nedded for the A17 pin that toggles the top & bottom half of the memory (and between the games).

I bent the previously N/C address pin A17 (pin 30) out of the socket on each of the four Roms, then joined them all together with patch wire.. (Bydo Orange!)

With the pin inserted in the ground position, the lower half of the Rom is used & we get R-Type 1:

However when the pin is attached to 5 volts - the top half of the Rom is seen by the board & we should get the beginnings of R-Type 2...?

And............... :O                We do!!! :D

Once the 27C040's arrive.. I'll do the rest of the Roms.. then.. Game on!!

For a Dual-Boot R-Type arcade pcb!! ^_^

Once all the graphics & audio are in working order, I'll evaluate how far I have to go to make the R-Type 1 board modifications (from the original conversion) compatible with R-Type 2..

As I mentioned a couple of days back, I can use TTL Multiplexers to switch the patched & non-patch board signals using the same hi/low signal that selects the Rom halves.

Wednesday, 14 November 2012

Dual Boot R-Type 1 & 2 Arcade PCB - Day 1

 Dual Boot R-Type 1 & 2 Arcade PCB - Day 1

Okay here's the rough plan... :/

Use several  74LS157's (Quad 2-input Multiplexer TTL Logic chips), attach all the patch wires involved in the R-Type 1 conversion into all the 'A' inputs..

Then, connect all the original connections (As in the unmodified R-Type 2 configuration) into the 'B' inputs..

Then join the outputs to the motherboard.. and a switch would be fitted to set either game A (or) B (R-Type 1 or 2).

For the main Rom's... I'll use 27c040's where the 27c020's were (and) 27c020's instead of the 27c010's.

- Then take each Rom-image file from RT1 & RT2 (place them 'end-to-end' RT1 in the lower half of the memory & RT2 in the top half (aligned to the relevant 1/2MBit boundary))

.. Then use the A/B select line used above to drive the upper address pin, which will then allow the mother-board to see either of the games data - as per-normal.
(..grounding the select pin you boot RT1 & setting it to 5v will yield RT2) :D

Then do something similar to the sound Rom /or/ Piggy back another 27512 & monkey with the 'Chip Select' lines.. etc.

Hmm.. 27c040's are quite expensive.. 20 for 60 odd quid on fleaBay!!  :O

Okay.. found 10 for £16.23 .. just hope they are fast enough (nano-second wise).

Sunday, 11 November 2012

Major Title to R-Type 1 Conversion - Day 3

The conversion of Major Title to R-Type 1


Day 3: De-Solder & Replace the N0, N1, N2 & N3 Sprite Roms..


Time to fit the remaining TTL Logic & SRAM chip..

There are several modifications to the motherboard to be carried out in this final section..
Firstly, cut several tracks on the underside of the top-board - here:

And here:

(Looks rough, but that pictures are extremely zoomed in.)

Next-up you have to add the new 74LS32 Quad OR Gate to one of the spare chip 'slots' on the board..

Quite why iRem had added 'unused' spare chip sites to their board is anyones guess.. perhaps they expected to have to bodge the boards post-production?

Either way, they are a welcome coincedence for what we want to do.. the original guide recommends using the chip-site towards the outer corner of the PCB, however my board had an iRem sticker over that one..

So I located the OR-Gate in the next site along:

Next, you piggyback the SRAM & 74LS244 Bus-Tranceiver, like so... taking care to follow the instructions on bending out the correct pins & ensuring the correct chip orientation.

Then all that remains is to just connect it all up with some patch wire.. (just he says)

..and power her up! *drum-roll*

Ta-da! One humanly-affordable R-Type 1 Arcade board \o/

Job done!

Massive thanks and the upmost respect to Paul Swan and Chris Hardy for the original conversion technique.. and for doing all the really hard-work!

And a massive thank you to the various members of the Jamma+ forum who helped make this project possible, particularly; ben76, Jenginner, PaulCan69, Lee-Lee & Vib.

It must be noted that the modification of Major Title to R-Type 2 is a little simpler than the mod above..
(Fewer board modifications are required & you don't need the extra SRAM chip & logic iirc.)

Overall, it took about 22 hours and cost about £20-£30 in spare parts (in addition to the Major-Title board).

That also assumes you already have the tools to hand!.. (I didn't and it ended up being about £150 all-in - still half the price of the original board though!) and most of the time was taken up by de-soldering & chip-extraction (pays not to rush!).. but it should be possible to reduce that given more experience.

Right, I'm off to destroy the Bydo empire..

Saturday, 10 November 2012

Major Title to R-Type 1 Conversion - Day 2.5

The conversion of Major Title to R-Type 1


Day 2.5: De-Solder & Replace the N0, N1, N2 & N3 Sprite Roms..


Okey dokey, just spent 6 hours replacing the remaining 4 Roms.. (N0, N1, N2 & N3)

Pretty much a repeat performance of before.. (shaved 2 hours off the time-tho)
(256 finger-burns & counting..)

Used masking tape as there wasn't much clearance between the chips being removed and the surrounding components.

Also had one dead EPROM in the batch.. but for $7 for 10 second-hand on eBay, it's all good.
(Getting a UV Eraser box soon.)

Once the ROMs were installed, all the game sprites have all appeared on screen & it's looking positive. :)

The backgrounds are still a little broken, but I'm assuming the tracks that are to be cut 'n' patched and the extra logic is Rom addressing related.. and should sort that out.

Hmm, in addition, the back-ground tile layer seems to be missing.. We'll have to see if that comes online once the extra SRAM chip is fitted.

Here's a video of the sprites in action:

Okay.. on to the SRAM & TTL logic chips... Er.. well, maybe not tonight. The frikin' cat's stole my chair.

Major Title to R-Type 1 Conversion - Day 2

The conversion of Major Title to R-Type 1


Day 2: De-Solder & Replace the C0, C1, C2 & C3 Roms..


After sorting the Program & Audio ROMs, I thought I might attempt to remove & socket the four background graphic ROMs on the top CPU board.

Following the advice given by a fellow member of Jamma+, I went straight for the wire cutters... as there was no real need to salvage to original ROMs. (Especially as they were of the PROM type and could not be erased to be re-written.)

The pins were snipped along the edge of the four PROMs as far away from the PCB as possible.

Before de-soldering I've found it's always a good idea to flow some new solder into the joints, just to make sure theres some flux running through to the other side of the board.

Since we are talking about a circuit board more than 20 years old.. I would advise using lead-solder with multi-core flux.

I then used a heated de-soldering pump to remove 90% of the solder.. It's a cheap pump (~£15 in Maplin) and to be fair is a good tool - but the tip is prone to cracking around the tips-edge! :(

Looks like a combination of heat-stress & cheap alloy..

Word of advice - keep the receipt, as you're probably not going to get more that a couple of jobs done before it's knackerd (I'm on my second) - Maplin seem cool with replacing it as they dont sell spare tips.

Finger burning time.. Grabbed each pin (by-hand) from underneath and applied my soldering iron (quickly) in such a way as to touch/heat both the pin & the surrounding pad.

The pins should pop right out (with 128 little finger burns) without tearing any of the pcb contacts off the board.  Not using too much heat, or for too long is important!

Might also be a good time to recommend you use a temperature controlled iron.. ;)

Goodbye Mr Golf game..

I then ran a flux pen over the pads and used de-soldering braid (wick) to suck-up the remaining blobs of solder.

Application of flux really helps you get a good solder flow & you get a satisfying little sizzle when you apply the heat. :)

But.. dont forget to clean the flux off with an isopropyl (rubbing) alcohol soaked cotton bud, as flux is quite corrosive and could potencially eat thru stuff over time.

Not bad for a first attempt..

Just have to fit four 32-Pin DIL sockets & were good to go..!

NOTE: I thought i'd be clever and use turned-pin sockets... Talk about square peg in a round hole! (literally) I spent over an hour just trying to fit the chips into the sockets! while listening to Rom pins going "tink-ta-tink-tink" and have two pins bend under a chip! :(

I know these sockets provide the best connection - but mate this is b*ll*cks! For the other four chips I'm seriously thinking about using the cheaper sockets! Much less stress on the chips and me.

Below is a video of the progress so far: The first part is how the board behaved with just fitting the chips.. (graphics are still a mess), and the second part is how it looked after moving the 3 jumpers on the CPU board (to reflect the change from 1 to 2MBit Roms):

As can be seen, the backgrounds are starting to take shape & it's actually quite playable!

(This was actually the first time I'd performed a major de-soldering job on a double-sided board, it took best part of a day.. and was quite nerve racking.)

Friday, 9 November 2012

Major Title to R-Type 1 Conversion - Day 1

The conversion of Major Title to R-Type 1


A top bloke ben76 over on the Jamma+ site brought my attention to a modification devised by Paul Swan and Chris Hardy to convert an iRem Major-Title arcade PCB to run either R-Type 1 or 2.

With the original PCB of R-Type 1 costing upwards of £2-300 a conversion of the much cheaper golf board is very attractive.. and just had to be attempted.

Major Title runs on an iRem M84 pcb, while R-Type 1 runs on an M72 board and R-Type 2 on an M82.

They all appear to have quite similar hardware, give or take a tile-layer.. and there appears to be some memory and addressing differences.  The work of Paul & Chris bridge these gaps by way of a new set of program ROM's and a set of physical board modifications & additions to be carried out.

The original modification guides can be found below:

Major Title to R-Type (M72) Conversions
Major Title to R-Type 2 (M84) Conversions

Major respect to these guys, this couldn't have been easy to fathom at all! A serious understanding of the hardware and game code must have been needed to pull this off! Hat's off to you indeed! with guide in hand, several ingredients are needed:


  • 1 x iRem Major Title arcade board:

  • 1 x 27512 EPROM
  • 9 x 27C010 EPROMs
  • 4 x 27C020 EPROMs:

  • An EPROM Programmer capable of writting the above:

  • 9 x 32-Pin DIL socket
  • 1 x 28-Pin DIL socket

  • 1 x HM62256-12 (or equiv.) SRAM chip:

 And a pair of 74 series TTL logic chips:
  • 1 x 74LS244 Tri-State Octal Buffer / Line driver chip
and an:
  • 1 x 74LS32 Quadruple 2-Input Positive-OR Gate chip 

Day 1: Replace the L0, L1, H0, H1 & SP Roms.

The first step was to burn a new set of program ROMs, as these were socketed it seemed like the first port of call..

Four 27C010's were programmed with the data for the L0, L1, H0 & H1 chips (which contain the code for the V30 CPU).
At that point I decided to power up the board, just to see how far it would work..

Happy days indeed! :D

While the sound & graphic data was garbage (the rest of the ROM's still held the Major Title data), R-Type can clearly be seen to be running!

The next easy step was to replace the 27C512 (SP) EPROM holding the sound code:

Once this was done, the sweet sound of R-Type filled the air! :)

Next stop, de-solder the remaining chips and fit the sockets..

Tuesday, 6 November 2012

1943 (bootleg) - Repair Log

1943 (bootleg) - Repair Log

Just got back from the pub with a fellow member of J+ ..who has kindly set me up with this fixer-upper 1943 bootleg pcb (Nice to meet you dude! & Thanks again mate!)..

Initial reports were of no-display & partial audio response, a quick look over the board revealed some cracked solder joints on the primary capacitors (the big fekers in the far left) - and a suspect patch wire near the Jamma connector..

Cleaned her up, eyeballed the soldering & removed the patch wire which seemed to wire the second coin button to a severed track (that would have carried the 1st coin switches signal).. 

Installed a new patch that connected the coin-signal to the service switch (which is how I coin up all my other boards) & powered her up... but.

Nada.. Ziltch! :'(  ..Got nothing initially. 

But remembering how my bootleg copy of Twin-Cobra behaved, I took a risk and turning the 5v voltage up (slowly!) on my adjustable supply ... :S (always tense time doing that!) ...

And wouldn't you know it.. Bling!!! At 5.9v she woke up out of her slumber. ¦)

Forgot how basic this game looks after hanging around Twin-Cobra & the R-Type's!!

Its got a very distinctive Red, Green & Blue palette... But come on, what other game has a Tsunami as a power up?!! Oooh Yeeah... :o)

And the twin sound chip setup in this game is mental! :D Esp. when the continue music plays over the top of the background tune! It gets crazily busy!!

The stories not over though...

Playing further into the game I noticed that the back-ground tiles above the sea (& below the clouds) had some corruption as they passed by certain regions of the screen.

However, the corruption clears up when the tiles reach the bottom of the screen!

This feels like a RAM issue.. and not all of it, perhaps just the chips responsible for the middle section of the frame-buffer!?! :/ Hmmm..?

Edit: aha.. It's not all of the BG-Tiles that are broken.. There is one island that scrolls by intact!! Rom then? (or both?)

But it's bed-time now... I'm going to have to tackle Level 2 another time.