Updated 8/12/22

Next in line for my Arcade Machine Repairs is this Hankin cocktail machine with Moon Patrol game by Irem.

At first glance it looks like an LAI cocktail cabinet (which in turn looks a lot like an Atari machine) but it does have a couple of rather faded Hankin manufacturers stamps inside, next to the monitor.

The cabinet could use a lot of TLC but it seems complete inside at least. Powering it on briefly the monitor silently comes to life with a faint raster which is a great start but there's no image or sound from the game PCB. The next step is to check the power supply Voltages.

2/1/22

It's time to get moving with this Moon Patrol Cocktail machine to see what's working and what's not. Opening the front panel to gain access to the power supply and the game PCB, the good news is the power rails (+/- 5V and +12V) are all present at the screw terminal outputs from the Kaga power supply unit.

That's where the good news ends as there is no sign of activity from the game PCB (actually a 4 board stack) and the boards look to be in poor condition with many ICs on each board having rusty pins. There's also plenty of old bug droppings and nests inside the machine and on the PCBs themselves.

Abandoning all hope of an easy fix, plan B is to remove the game PCB and set it up on the bench, check the monitor with my portable test setup and go from there. I'll need to make up a test lead to suit the Moon Patrol pinout, also allowing the board stack to be spread out to gain access to the inner PCBs.

But first a run around the PCBs and the inside of the machine with a brush and vacuum cleaner to remove any loose dirt and bug droppings.

Now checking the monitor it looks pretty good. The colours could use some adjustment but the image is stable so for the moment I'll leave it be. Once the game PCB is fixed (assuming that is achievable) I'll give the monitor a final adjustment and test, meanwhile 'if it isn't broken...'

This Moon Patrol Hankin Cocktail machine has been sidelined for a while with many of the ICs on the 4 board PCB set badly affected by rust and no sign of life when tested on the bench. I wouldn't say it was unrepairable but the time involved and likely cost of replacement parts would probably outweigh the value of the machine.

I usually prefer not to admit defeat with a repair but in this case a more effective solution would be to source another PCB set which would be a better starting point, either working or readily repairable. Given enough time something usually comes along and sure enough, we now have another PCB set to work with.

This one has recently been removed from another machine, was thought to be working and does not exhibit any rust issues on its components. The PCBs appear to be original Irem ones but a mix of blue and green solder mask having been swapped around at some point and have obviously seen quite a few repairs in their day.

I don't make a point of re-doing old repairs just because they're a bit messy as long as they are working correctly but will keep those in mind if there are any current issues. Having already made up a test lead for the original PCB set it is straightforward to run this set up on the bench and here s the result:

The game is running but there's a strange graphics issue with the player moon buggy and bonus score sprites which are reversed left to right. Suspecting they may be stuck in cocktail 'flip screen' state I try selecting a 2 player game but the graphics are wrong for both Player 1 and Player 2 screen orientation.

Reading up on the game documentation which is readily available online, the function of the 4 PCBs are Sound, CPU, Character and Scrolling Video. The player Moon buggy and bonus scores are characters while the parallax scrolling scenery is handled by the scrolling video PCB.

Removing the 4 tier standoff spacers allows the Moon Patrol PCBs to be set up on the test bench and turned over like pages of a book to access the required board, just inserting some non conductive bubble wrap between stacked boards to prevent shorts. Here the character PCB is shown face up for fault tracing.

Looking at the character PCB there are two EPROMs which must contain the sprite data for the moon buggy and various enemy craft. The Moon buggy sprite appears to comprise two 'tiles' and these are displayed in the correct order (so the higher order addressing must be working) but each tile is reversed left to right.

That would suggest the low order addresses which select the pixels in each row of the sprite bitmap must be counting the wrong way. This gives us a starting point to troubleshoot the problem, looking at the addressing of the two EPROMs on the circuit diagram for the character PCB.

The higher address bits arrive via a 74LS273 at location 6L while bits 0 to 5 come from a 74LS283 at location 6H. Interestingly there is another 74LS273 at location 6K which appears to provide colour data as well as two signals, HREV and VREV. These are used to invert the Address bits 0 to 5 using 74LS86 Exclusive OR gates.

When tested, the VREV signal was low while HREV was high. This seemed to fit with the fault symptoms so I carefully (and briefly) used a short piece of wire to link this signal to ground, to see whether it affected the appearance of the sprites.

Sure enough, the pieces of the Moon buggy jumped back together and remained correct for a while, the output of the IC now latched in the low state. After a short time the fault returned but looking at the corresponding input (which comes from object data bus bit 1) the activity seemed fairly normal with correct levels.

So it appears the 74LS273 in location 6K is at fault with one output sticking in the high state. Unfortunately I don't have a suitable replacement on hand so will have to order some and wait till they arrive before proceeding.

Meanwhile, having the (almost) working PCB set on the bench is too good an opportunity not to test the other, rusty PCBs one by one and identify the problems with each of the four PCBs. So, substituting each board, one at a time here are the symptoms:

Sound PCB - game still runs, no sound. Board seems dead. CPU PCB - no output or activity apparent, board seems dead. Character PCB - game still runs but characters are missing, board seems dead. Scrolling Video PCB - game doesn't seem to run, stationary garbage on screen.

So, pretty much as expected all four PCBs with major issues. I certainly wouldn't hold up the repair of this nearly working set to try and troubleshoot any of those other PCBs, best to just put them aside for a rainy day...

15/11/22

It's time to get this Moon Patrol machine up and running, the original PCB set having gone in the 'too hard' basket due to severe corrosion on many of its components. I'm now working on a replacement PCB set which only seems to have a minor graphics issue with sprites appearing 'backwards' left to right.

Tracing the cause to a HREV signal which appears High but should be Low, I've ordered a replacement for the 74LS273 in position 6K with the incorrect output level. That part having now arrrived and duly replacing the IC in question (also installing a new socket), the fault initially seems cured.

After a while though the problem intermittently returns, the new component having improved the situation but still apparently unable to maintain this signal at a Logic Low level. That seems to indicate an excessive load on its output, either due to a short between PCB tracks or a fault on a following IC input.

Inspecting the traces around the relevant area I can't see any obvious defects so the next most likely cause would be a faulty 74LS86 at location 8F which has the HREV signal at its input Pin 1. Fortunately I already have spares on hand for that IC so replacing it, adding a new socket and re-testing the fault now appears to be fixed.

Incidentally, in addition to its cocktail two player 'flip screen' mode this PCB appears to have the ability to continuously reverse or 'flip' the entire image if required to suit a particular monitor, controlled by a DIP switch setting.

Adding control inputs now to my bench test lead, all game functions and sounds appear to be working correctly so it's time to install the game into the cocktail machine and check its operation.

When powered up the game runs in attract mode but after warming up a bit the monitor which previously seemed to work well starts to play up. The Blue signal is dropping out and the image becomes very jittery. With a bit of careful prodding it seems it might just be an issue with the connections, either way the monitor needs to come out for a look.

It looks like an earlier model Kaga monitor with the dreaded '3 piece' chassis but the EHT stage was still working and it does have a frame which unites CRT and Chassis, making removal / replacement and servicing much easier as the interconnections do not have to be unplugged in order to remove from the machine.

The present issue is no more than a bunch of broken solder joints on the RGBS input connector, easily cleaned up and reflowed. The monitor lives on.

Back in the machine and just needing a few adjustments. The wiring loom which uses an adaptor from its generic connections to the Moon Patrol specific pinout was losing about 0.6V from the +5V supply, I've cleaned the edge connectors to reduce this loss but the Voltage at the power supply still needed to be increased slightly to compensate, using its internal adjustment pot.

The coin mechanism is not working and not quite complete but manually operating its microswitch and testing, the game controls are all working. The setup is a bit unusual and obviously not originally intended for Moon Patrol which only requires a 2 way joystick and 2 buttons for each player in addition to the 1P / 2P Start buttons.

In this machine the Start buttons are off to the right of the Player 1 Control Panel using a pair of (recessed) Atari style Volcano buttons and not illuminated in this case. Only Left, Right and the two buttons in a row are used on each player Control Panel, the remaining switches not required for this game.

28/11/22

Continuing with the tidy up of the Moon Patrol cocktail machine, the controls are working and game plays correctly once 'coined up' but the coin mechanism is missing a couple of parts and not working. It's a mechanical, roll down type and looks to be made by Coin Controls, the main part missing is the spring clip which retains the moving side assembly and allows for coin reject operation.

Fortunately the side assembly was found loose inside the machine and had not gone completely missing. I don't have any parts for that exact mechanism but do have a spare one made by Asahi Seiko which isn't complete but still has its spring clip. That part is so similar it turns out to be interchangeable between the two mechanisms.

The other problem with the coin mechanism is a broken trigger wire from the microswitch. In this regard my spare coin mech differs slightly in design so its equivalent part would not fit. Instead I've made up a replacement from a straightened paper clip which works well as an interim measure at least. In the longer term, perhaps a correct part could be found or failing that, made from scratch using some piano wire which would be more resilient.

That gets the coin mechanism working, accepting 20c coins so the next issue is that the coin box is entirely missing from the machine. It's a unique shape with both front and back faces angled to suit so a replacement would most likely be unobtainable. Instead I'll make up something to fit, from scratch.

The original may have been made entirely from sheet metal but the recess it slides into is just MDF so I'll make the box itself from some scrap pieces of melamine faced particle board. For the front panel I'll affix a black painted piece of sheet steel, replicating the external appearance of an original item.

Although the coin function now works it seems worthwhile adding a simple credit button, utilising one of the 'spare' buttons on the Player 1 control panel. The button to the left of the joystick was not wired and did not even have a switch fitted so I'm adding a microswitch and some fig. 8 cable from there to the previously unused 'Coin 2' input wire just next to the coin mechanism.

A convenient point to connect the ground wire for the credit button is the otherwise unused NC terminal on the coin microswitch - as it is normally closed that point is normally connected to ground except when a coin is being accepted. I've used a few cable ties to bundle the wires from the credit button to the machine's existing wiring loom and spade connectors at both ends so that it can be easily removed if not required, to return the machine to coin per play operation.

8/12/22

Getting back to the new coin box for the Moon Patrol Hankin cocktail machine, I've trimmed a piece of black finished steel to fit the recess in the machine's back panel (the coin switch is fitted to the player 1 side but the coin box is removed from the rear, player 2 side) and affixed that to the front of the coin box.

The sheetmetal is also repurposed from scrap, having been cut from the side panel of an old PC case. This has the advantage of already having a textured black finish and being from an early '90s model computer used a much heavier gauge of sheetmetal than a modern desktop PC.

I've spraypainted the cut edges (from behind to avoid overspray on the front) and hand finished the lock mounting hole with a file to retain the flats on two sides which prevent the entire lock from turning in its mounting.

The coin box front panel is a neat fit in the recess and gives the external appearance of an original style all-metal box. The black finished MDF panels on the machine itself look pretty tired and could definitely benefit from a sand, fill and repaint.

That's beyond the scope of this repair though as I'm only returning the machine to working condition and leaving any cabinet restoration work for its owner.

So, after a final check of the wiring to ensure external metal parts such as coin, start and control panels are connected to mains earth and a few plays to ensure all controls are working this is where we leave the Moon Patrol, a fun 'Golden age' arcade game well suited to its classic 80's cocktail machine.

Web Resources (External Links) -

The Arcade Flyer Archive - Video Game Flyers: Moon Patrol, Irem

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