ABI Boardmaster Keyboard

My boardmaster 4000 didn't come with a keyboard so ever since it arrived I've been on the look out for one. You cannot really make the most of the system without it, anyway it is a rather unique 65 key serial 3 pin connector keyboard.

I wasn't bothered about having an original one and didn't think it would be much of an issue getting a old ps/2 keyboard running on the system as two different people have made adapters. Unfortunately the first one wasn't ever released publicly and the other one is available but at a price of $100 or $125 if you want a used ps/2 keyboard too.

As much of a bargain as that is I went looking for an alterative, ABI didn't help matters by using a top quality cherry made keyboard. As now in 2016 you've got keyboard collectors (yes that's a thing apparently) buying them up. Not only are they driving prices up but they butcher them by pulling off all keycaps, don't ask me what they do with them I have no idea.

While waiting to hear back from a keyboard collector who had one (minus all the keycaps of course) I came across this keyboard listed as a 'vintage studio keyboard' on ebay. As it had the correct layout and number of keys I took a chance on it and ended up winning it dirt cheap.

After receiving it and cracking it open I confirmed it had the correct cherry pcb. As this keyboard was used for different equipment I had to make a few changes, two 74LS08 needed to be populated along with a 1k resistor and a couple of jumpers needed to be changed to change it to serial from parallel. Also the data on the 8749 mcu had some incorrect character data compared to the original keyboard.

A big thanks to my friend Equites on ukvac who was willing to dump the 8749 in his original keyboard and I now have a fully working boardmaster keyboard for less than £10.

While searching I came across this pdf datasheet which has all the info you'd need to replicate the keyboard if anyone else happens to need one and aren't lucky enough to stumble across a cheap one on ebay. :)

Burnin' Rubber (Bump 'N Jump) repair

This was bought in a job lot and listed as untested, I thought there was a good chance it would work after making a jamma adapter for it but no such luck.

Powered it on and got nothing but a black screen, I could coin up and there was music so it was mostly working. Checking with a logic probe I had sync but no red, green or blue, all three pins were floating.

I decided to check the bottom pcb with the trusty hp logic comparator, this was a little tricky as the top board covers most of the bottom one. I was able to flip the top pcb to the right being careful not to short anything to the jamma adapter. I eventually found a bad 74LS74 at B11.

Bad 74LS74 removed.

New one fitted.

 Repair complete.

ABI Boardmaster 4000 repair

Another new toy to play with, this is a very useful bit of test equipment that can test chips not only out of circuit but also when they are still in circuit. I bought this knowing it had some issues but they are very rare and sought after so you cannot be too picky.

First I wanted to fix the lcd backlight which would flash on for a second then go off, this is a common problem with these things. It also made it hard to read the self test fail messages so looking on UKVAC forum there is a thread explaining how to wire a generic laptop inverter in place of the old one. I was impatient though and did not want to wait 2 weeks or more for one to arrive from China. The two surface mount capacitors looked like they had leaked which I've seen many times repairing Sega Game Gears.

I replaced them with high quality radials and the screen was now nice and clear and made it easy to read the 14! fail messages. I won't go over all the error messages again here but if you want to read more check this thread on UKVAC.

Twelve of the error messages gave part numbers to six different relays which from reading in circuit with a multi meter I could see were bad. The other two error messages didn't point to any parts but I was able to find them by metering every relay, it turned out to be two on the out of circuit testing pcb.

After replacing the eight bad relays...

the repair is complete.

Suitable replacement relays can be found here. - Thanks trm.

Taito AA017751 cocktail power supply repair

I am very slowly restoring a Taito black & white Space Invaders in between other projects. The time has come to rebuild the power supply, I fully recapped it including all the tantalums. One of the resistors was burnt out but there's no documentation online for this exact power supply, so I had to hope that the reading of 33 ohms was correct and replaced it with another 33 ohms.

I then tested it in the cabinet and the 12v, 18v and -5v were all spot on but the 5v was putting out 8.5v! luckily I didn't have the board hooked up at the time or it would have gone up in smoke.

Adjusting the 5v pot made no difference to the voltage. I went looking for documentation online again, backflipper on ukvac pointed me to a schematic in the moon alien manual but after looking it over my power supply is very different.

Then I found a very old newsgroup post by John from John's Jukes (www.flippers.com) that mentioned he had schematics for the AA017741 power supply. I sent an email and got a reply and a copy of the schematics almost instantly, thanks again John. The layout is slightly different but otherwise looks the same as the 51 version.

I looked over both the schematics and the board again and I narrowed the problem down to the TA7089P voltage regulator. A chip that hasn't been made for years and can be hard / expensive to find.

For a new old stock one anyway, I went the utsource route which basically means used pulls that have had their legs sanded and dipped in solder to make them look new again. I don't like this as it makes the legs extremely fragile but they are cheap and everything I've had from them has always worked.

The TA7089's arrived after about two weeks, I fitted a 'new' one to the power supply fired it up, 5.05v on the 5v line, success!.

I replaced the 555 timer too as chances are the 8.5v killed it.

Next the monitor speaking of which, TC if you're reading this I might have a spare chassis available at the end of this project.

My cap map is famous.

 

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CPS1 B Board repair

This capcom CPS1 B board (middle board) was running but the video output would not sync, usually this would be a C or A board fault but I'd already ruled them out by swapping them.

I went around the board checking the connection between the A and B board was solid with a multi meter and found two pins not making contact near the C board. This part of the board had taken a nasty knock at some point and cracked the near by resistor array in half, but one problem at a time.

First I desoldered the connector that had the two missing connections.

Now I could clearly see the two broken pins.

Once I replaced the connector with one from a scrap board sync was restored but there was a graphics glitch, most sprites had vertical lines going through them.

I replaced the two resistor arrays next to the c board as one was broken in half and one had a leg broken off. This made no difference.

I was convinced the issue was in this area since I'd already found so many other issues there. Running the board without the C board means the game won't work but it's the only way to access that area and probe around while the board is running.

I checked every pin on the two resistor arrays and noticed one was high while the others were all toggling. A closer look I could see the through hole had come away from the trace and probing the trace it was toggling away.

A tiny piece of kynar wire to repair the trace and the repair was complete.

Repair logs

I recently bought a job lot of 16 faulty boards plus I have all my other faulty boards I've collected over the years scattered every where.

So I've been in a hurry to repair boards and get them sold just to make some space, because of this I haven't really been thinking about logging the repairs or taking pictures.

I have covered as much as I can remember but that's why there's no pictures this time.

Shinobi
No sound apart from 'mission one' when you start a game otherwise completely silent. A note on the board said 'probably YM2151' but looking at it on the scope all pins looked very active, the near by YM3012 on the other hand had four dead pins. Piggy backing a pulled 3012 from a scrap board brought all sounds back.

Street Fighter 2 World Warrior (Bootleg)
Lots of missing sounds, sounds playing randomly, noise / static and missing the colour red.
Looking on the bottom of the board there were some pins that looked like they had little to no solder on them. After soldering them properly red returned. As for the sound I suspected the yamaha chips at first as these bootlegs use fake chips. Turned out to be the surface mount OKI 6295 chip, I took one from a scrap CPS1 board.

CPS1 Motherboard
Game running but screen is blue and nothing is visible.
All four 6116 palette rams near the edge connector bad. Depending on the board some times it's 2x 6264 rather than 4x 6116.

CPS1 Motherboard
Board would always lose sound after a few minutes.
This one was a real bastard to find, I thought it was going to be a thermal problem and something was failing as it heated up. I thought the most likely candidate would be the z80 cpu as capcom fitted a standard z80 instead of a z80a. Then I tried replacing the amp, still no difference. I recapped the entire sound section still no change. I was about to give up but thought what the hell and replaced the z80 crystal even though I've never had a crystal fail on me before apart from ones that were physically damaged. To my surprise this actually fixed it.

Commando (Capcom)
Bad background graphics.
The only fujitsu ttl on the top board a 74LS30 if I remember correctly, replaced and problem fixed.

There have been several other repairs but simple trace repairs and ram replacements.

Gun Smoke (Bootleg) repair

I bought this bootleg Gun Smoke board years ago but a colour prom was missing and as I had no way to burn another it has pretty much sat waiting for a prom ever since.

Time to deploy my new favorite toy that I picked up from ebay a couple of months ago.

Stag System 3000 (cira 1991)

This beast of a programmer can program many chips but most importantly for this repair it can do bipolar proms.

I usually use it on an old laptop in dos connected by serial cable but as I had an original Gun Smoke pcb as well I decided to copy the original proms directly rather than try and find the correct files in mame. Turn the key and you're in standalone mode, copy the content of the original prom and burn it to a new blank one which took a total of about 8 seconds.

When the prom was missing the screen was all red (which I forgot to photograph) but just think of a virtualboy game.

After installing the new prom the game looked a lot better but there was no green, checked the green pin at the edge connector with a meter and sure enough 0v. Traced it back to the prom next to the new one, pin 12 had internally shorted to pin 8 (ground).

Bad prom removed.

I did the same as before to replace the missing prom by simply copying the one from my original board and burning it to a new old stock 82S129.

Green restored, repair complete.