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MA-309The MA-309 is the same as the MA-216 without the SC-01a speech chip and support circuitry installed. It was used in the System80 pinball machines Super Orbit, Royal Flush Deluxe, Amazon Hunt, Haunted House, Spirit, Krull, Goin’Nuts and video game Mad Planets. It will also work with ROMs from Mars, Volcano, Black Hole, Devil’s Dare, Rocky, Striker, Q*Bert’s Quest, Caveman and video games Reactor, Qbert, Krull, Three Stooges  although the speech feature from this game will obviously not work. If someone implements the SC-01a in HDL then adding the support logic is trivial.

This code works as-is on the cheap Alterra Cyclone II dev boards available on eBay for $20 or so.  Hook up a PS/2 keyboard to it and you can trigger the sounds with it.  Disable/remove the PS/2 code and this should plug straight in to one of the real machines listed above.



The MA-55 was used in Panthera, Spiderman, Circus, CounterForce, StarRace, James Bond 007, Time Line, Force II, Pink Panther, and the export versions of Volcano, Black Hole, Devil’s Dare, and Eclipse.

This code works as-is on the cheap Alterra Cyclone II dev boards available on eBay for $20 or so.  Hook up a PS/2 keyboard to it and you can trigger the sounds with it.  Disable/remove the PS/2 code and this should plug straight in to one of the real machines listed above.


Gottlieb MA-490 Pinball Sound Board in an FPGA

Screen Shot 2015-12-14 at 10.04.56 AM

The Gottlieb MA-490 is a cost-reduced board which is just the older MA-55 with a kludge piggyback board plugged into it increasing the ROM capacity. Used in Amazon Hunt (late production), Rack’Em Up, Ready… Aim… Fire!, Jacks to Open, Touchdown, Alien Star, The Games, El Dorado City of Gold and Ice Fever.

This board is meant to be loaded onto an Alterra Cyclone II board and hooked up to a PS/2 keyboard to be triggered.  It has not been tested in a real machine but should work with a couple of simple modifications.


William System 3 sound board

Here’s the sound board used in Williams System 3 and System 4 pins from the late 70s to early 80s. It’s simpler than the System 6/7 board but similar architecture, 6802 CPU(similar to 6800) with 128 bytes of RAM, 2K ROM and a 6820 PIA driving a DAC. Curiously the ROMs for every game using this board seem to be identical so it seems they used the same sounds in all of the pins of this era.  Maybe this shouldn’t be surprising since it’s right on the tail of the electromechanical chime era.

The top level file is set up for an Altera Cyclone II mini development board available on eBay for less than $20.  There is a PS/2 interface to control the sounds which can easily be removed if you are going to attempt to use it in a real machine.  This has not been tested in a real machine yet.

Here is the code, it’s a little messy but it will be cleaned up eventually if time permits:


Bally AS-2518-51 sound board in an FPGA

Screen Shot 2015-12-04 at 11.23.32 AM

This is a Bally AS-2518-51 sound board, the predecessor of the Squawk & Talk implemented in an FPGA.  This is set up with the ROM for the 1978 pinball Nitro Ground Shaker but other ROMs are available.

Some general info about the hardware
This one is interesting because it uses a AY-3-8910 sound synthesis chip to generate all the sounds rather than driving a DAC directly from the PIA. It’s got a bit of a different sound as a result.

It has not been tested in an actual pinball.  Currently it is set up to plug in a PS/2 Keyboard that will allow you to trigger all of the sounds.  Some keys are repeats, others are blank, it was just a quick hack.  The PS/2 hack is in the top level file and easy to remove which would theoretically allow you to wire this up in a real pinball.

The target board for this is the very economical Altera Cyclone II dev board.  They are all over eBay for less than $20.

Here is the code:


Tenergy Li-ion 4400mAh Roomba 400 Battery Review


Several people over the years have found my blog posting on why not to use Lithium battery packs in Roombas.  Some people have taken the information at face value, others have argued with me in the comments and tried to claim my views on the subject are not valid.

Some of the folks over at Tenergy also noticed my article and decided to send me a battery to prove to me they have resolved the issues I was citing.  Here is a link to the battery in question:

In the interest of full disclosure, in consideration for the battery, they only asked for my honest review along with a link back to the product to allow people to find it.


At this point in time, I have been using the battery lightly for about a month.  I use my roombas somewhat sporadically.  This may actually shorten their life due to lack of cycles and a poor factory charger circuit.  So far, this pack seems to be holding up just fine.  One thing I should point out that is different about this pack from the other lithium packs I used in the past…  When the other packs ran low, the Roomba light would start to glow orange and then suddenly the roomba would die in place.  In other words, it never had enough charge left to bring itself back to the base.  The batteries low volt protection cutout would kick in and save the cells from damage.

This pack appears to work like a typical NiMH pack.  The light eventually goes red like it should and the robot stops moving but the power remains on.

As far as runtime, I’m using the pack on hard surfaces.  I haven’t paid close attention but it seems to go for a couple of hours.  One day I will time it and update the review, for now though, I wanted to post my initial thoughts.

Similarly, I will obviously need to reserve my judgement on longevity until the pack starts to noticeably deteriorate.  That could be months or could take over a year.

So far, if I had to pick one complaint about the pack, I would say that one of the retainer clips is unable to snap into place.  This is a pretty minor issue that I could probably fix with some sandpaper or a knife but I shouldn’t have to.  I’ve cleaned the area under the battery and pushed on it pretty hard but it just won’t snap in there for some reason.


For now, I will say that the price is currently $68.99.  This is marked down from the typical $90.  The Tenergy packs for the 400 are $25 on Amazon.  So what do you get for 3x the price?  I’m not sure yet.  Only time will really tell there.  The pack is certainly lighter than a NiMH pack so it’s putting a little less wear on the robot.  It seems to last similarly to some of the best NiMH packs I’ve had.  It’s not exactly an all-day battery pack however.  In the coming months, I’ll try to monitor the health of this pack a bit more closely and possibly more scientifically.

My first lithium pack for the Roomba was $150.  When it prematurely cooked, I was not pleased.  At $69, if I got a year out of this one, I probably wouldn’t complain too much but then again, if it only lasts a year, why pay any premium on it at all?  Let’s hope that I’m able to favorably speak of this pack for years to come as “the best Roomba battery I’ve ever had”.

Dead Hypex SMPS600 V3 Power Supplies


A couple of years ago I decided to build myself some class-d amps based on the Hypex NC400 modules.  I had also designed some custom billet aluminum cases but I knew they were going to take a while so I put them in temporary enclosures.  I had noticed during the summer months when the weather was warmer, one channel would click off.  I finally figured out it was thermal shutdown and so I turned the case over and put some metal objects on top to act as heat sinks.

Fast forward to a couple weeks ago, I needed to turn my equipment off to make some changes to the setup.  It took me overnight to make all of the changes and when I went to plug the amps in the next day, neither would turn on.  No signs of life at all.  No clicks, no lights, nothing.  I was a little confused that both could die at the same time.  They are in separate cases on opposite sides of the room but when I popped them open, I reached for my cap wizard and started testing out some of the caps in the power supply.  Turned out several were cooked.  Some did not even move the needle on the cap wizard.  To my suprise, even one of the largest caps, a 820uf @ 200v, had drifted far out of spec.

I decided I would just replace all of the caps on the power supply boards because I wanted to make sure they were perfectly matched and I figured they all probably have a shortened life span from the heat they incurred.  My first task was to remove and map out all of the caps.  To get to the 2 largest caps on the board, the large heatsink HS1 needed to be removed.  In order to remove that large heat sink, R2 needed to first be removed to access the screw holding D43 to the heat sink.  After I got that out of the way, then I could  remove and catalog the caps.  This board is not particularly easy to work with.  The holes are drilled with very small tolerances compared to most.  This means you really need to get all of the solder out of the holes or the new components won’t go in easily.

4x 820uf 200v (C1, C15)
16x 220uf 35v (C3, C4, C5, C6, C7, C8, C13, C14)
4x 22uf 63v (C22,C26)
2x 470uf 50v (C9)
12x 100uf 100v (C10, C11, C12, C19, C20, C21)

After that, I ordered the caps for about $40 shipped and replaced them when they showed up.  So far so good.  Everything seems to be working again.  Lesson learned.  Even though these amps use a very small amount of power and run very cool for their power outputs, cooling is still super important.  I would suggest having plenty of cross-ventilation in your cases.  Make sure you leave adequate distance between the amp and power supply.  Also make sure your NC400 module is attached to a larger and thicker piece of metal to properly cool it.  Apparently a smallish piece of light gauge aluminum is not adequate when in an enclosed space.  If you need to replace your caps, ONLY use 105 degree varieties and use the ones rated for the most amount of hours at that temperature.

NC400 & SMPS600

Sharp Image SI-727R-DS Repair Log

This monitor has been on my desk for months because I’ve been avoiding it but I’ve decided that it’s taking up too much space so I’ve decided to start digging into it again.  I’m going to document my repairs here in hopes that it will help someone else out to see my troubleshooting process.

The symptom of the issue is no picture.

The problems are several.  The monitor is switchable between standard and medium resolution hence the “DS” in the model name which stands for dual sync.  When I attempt to run it at 15k, things seems somewhat stable.  There is no picture but when I test B+, it will sit there right around 130v which seems pretty reasonable.  Testing with the high voltage probe I get about 130v on the anode which tells me something in the flyback/HOT area is not working correctly but I don’t have a schematic so I’m flying blind on it.  When I hit the base on the oscilloscope, I get a reasonably nice looking square wave that seems to be at the correct frequency and looks happy.

Oscilliscope reading (base)

So that makes it appear that the driving waveform is ok.  When I hit the collector, I get this:

Oscilliscope reading (collector)

That does not look good.  Theoretically I should be getting voltage spikes that go well of the screen when the HOT grounds the flyback.  The scope is set for 50 volts per div and I’m barely covering two of them so something is clearly wrong here.

When I switch over to medium resolution (25k jumper) things get much worse.  The B+ pops on and starts at about 140v, then it keeps climbing and the monitor starts getting noisy to the point where I’m concerned and then I shut it down.

I’ve tested the flyback with a ring tester and it looks good but perhaps there is a different problem with the flyback that cannot be diagnosed with that tool.  I know for sure the HOT is good, I have several of them and they all test the same.  When I pull the HOT out of circuit, both the 15k and 25k mode act the same and give the same B+ voltage of roughly 130v.  The only difference is the waveform reading on the base of the HOT.

Mattel Aquarius Composite Video Modification

During the holiday season here I had some time to tackle some of the projects that have been on my todo list for ages.  One of these projects was improving the video output from my Aquarius.  Last time I hooked it up, the picture was pretty horrible.  It may have been a flaky RF switch box but an RF modulated video signal isn’t really ideal in the first place.  Searching around, I found some schematics for the Aquarius so I thought this project would be a piece of cake.

Here is the offending RF modulator

Here is the offending RF modulator

It appeared to be a simple matter of removing the RF modulator from the board and then grabbing pin 1 and feeding it to a RCA jack and feeding pin 3 to another for sound.  When I did that though, I got video like this:


Wrong colors, smearing, illegible text.  Yuck!

Wrong colors, smearing, sync loss, illegible text. Yuck!

It was at this point that I realized the project might not be as easy as I first thought.  I decided that the problems was a weak signal so I set out to try to amplify it.

I was a little puzzled as to why such a weak signal worked fine for the RF modulator but not for the TV.  When I looked at the signal on a scope, it looked fine:

This is the unloaded signal straight out of the TEA1002 chip with the two resistors in place.

This is the unloaded signal straight out of the TEA1002 chip with the two resistors in place.

But then when I put a resistor across the signal to load it down, it squashed down to nearly nothing.  Apparently the RF modulator doesn’t have much of a load at all since it has no 75 ohm cable termination to deal with.

I unsuccessfully tried a couple of single transistor emitter-follower circuits such as this NES Video Booster circuit that I found.  While it improved the signal, it didn’t entirely fix the problem.  My friend suggested a purpose built video buffer chip such as the MAX4090.  Oddly, he had a roll of 200 of them laying around that he never found a use for.  I hooked it up on my breadboard to check it out:

Breadboarding an SOT23-6 packaged chip was a small challenge but certainly not impossible.

Breadboarding an SOT23-6 packaged chip was a small challenge but certainly not impossible.

That's more like it!  (Ignore the moire pattern from my cell phone cam)

That’s more like it! (Ignore the moire pattern from my cell phone cam)

Success!  That worked pretty well.  I started with the reference circuit found in the MAX4090 datasheet but found that it worked best with only the one cap installed on the output.  I omitted all of the resistors from the circuit and the decoupling cap on the vcc.  Just in case though, I designed my PCB off of the reference schematic:

MAX4090 Breakout Board Schematic

MAX4090 Breakout Board Schematic

Here's my Kicad layout for the breakout board.

Here’s my Kicad layout for the breakout board.

Here's the breakout board installed in the Aquarius.  Fits where the RF modulator was.

Here’s the breakout board installed in the Aquarius. Fits where the RF modulator was.


This is how it should have looked from the factory the day it was shipped!

In case you are wondering about the red +5v line, I got that from the bottom of the board.  The 5v regulator line is very clearly marked on the solder side over near where the three wires from the regulator go under the metal shield.  I just followed it as close to the former location of the RF modulator and grabbed it there.

S.T.U.N. Runner Random Resets


The opportunity finally presented itself for me to buy a full-sized arcade game.  I suppose I could have picked a smaller one but I kind of bought it on a whim.  The game?  S.T.U.N. Runner.  It’s a sit down “cockpit” style racer with no gas pedal.  It’s a game that I used to play all the time whenever I would see it back in the early nineties.  This particular copy was obtained from the B&I Amusements auction when they shut down in 2013.  I was pretty disappointed to see them go but I thought this was a reasonable souvenir.

The game was not perfect when I got it.  The cabinet and plastics were not bad at all but the monitor was so dim it was totally unplayable.  A recap and rejuv made the monitor really nice again.  There was some other random small issues such as a cracked handle on the steering yoke.  Luckily there is a stockpile of over 5,000 of these at Suzo-Happ.  The Dallas battery powered RAMs which kept high scores were also shot.  Luckily a new comparable part is still manufactured.  I ironed out a most of the small issues but then another one popped up.  The game started resetting randomly.

At first I sort of ignored it because I figured it was just a ghost in the wires or something but then it started making the machine unplayable.  I finally got so frustrated that I ordered a new board set off eBay.  I figured that whatever was making this happen HAD to be on the board.  I put the new one in for a bit and it seemed to fix it for a bit but soon it started again.

Surely the only other culprit could be the power supply, right?  Wrong.  I tried a different one and the problems still continued.  All the was left to look at were the connectors and wires.  I started furiously blasting all the molex connectors with DeoxIT.  After waiting the recommended two minutes and powering it back up, I was hoping to see the end of the resets but did not.  As a last ditch effort, I decided to start unplugging harnesses because I figured something external had to be killing it.

Turns out that not much experimentation was involved after all.  I unplugged the harness going to the volume control and service switch.  I put my son on the game to playtest it for me and he decided he wanted sound again which doesn’t work without the volume obviously.  I plugged it back in live and what do you know?  It reset, right there.  Eureka!  I pulled the service switch and volume bracket and stuck my VOM probes on the switch.  It read overload at first which was fine but then all the sudden started bouncing between 100-300 ohms.  No wonder this poor game was confused.  This switch started conducting if you sneezed on it.

The date ended with me blasting the heck out of the switch with DeoxIT and me needing to list a perfect second board set on eBay.  :-)

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