Start of my Stern Hot Hand restore

[Mr Pinbologist]

G’day guys, since I’ve been on a bit of a “get some of these bloody projects up & running” binge lately I thought id drag my Stern Hot Hand out of storage last weekend and set it up to start on it… same deal as with Flash, Cosmic Princess and Stellar Wars etc, get them running and play them for a while before doing the full resto treatment.

After getting it up on legs and bolting the backbox on (after cutting off some stripped leg levellers and recutting the threads in a couple of the legs that is!!) first job was to replace the cut off connectors (it was hard wired and I had to cut the wires to dismantle the game when I bought it two yrs ago). I left enough of the wire on each pin of the board to help identify which wire was which when I got around to redoing the connectors.

[Mr Pinbologist]

Next job was to rebuild the hacked power transformer board, replacing all of the bridges and the diodes for the high voltage display supply, as well as replacing the pin headers. I ended up running out of the correct length headers and had to ‘make do’ with what I had on hand, hence the gap in the top left connector on the board in the 2nd pic. But hey, its my own machine and not a clients pin and I wanted to see this thing up and running without having to buy anything yet if possible! I added heatsinks to the bridges, the larger two were cut up pieces of a larger heatsink from a dead plasma TV panel driver board that I had raided from my ex boss.
2nd pic is the finished board still sitting on my bench.

After that was done I started on the solenoid driver board, replacing the cap for the 5 volt regulator circuit, doing the ground mods as per Clays repair guides, and rebuilding the dead HV display regulator section, I replaced all of the transistors and diodes, I didn’t have a 2n3584 for the regulator transistor so I used a BUX85 initially.. then replaced it later on with a BUX84 (more on this in a moment). It seems I must’ve bought a bad lot of BUX85 transistors as every single one I have used in a Bally HV section so far has failed!..  these were ones I bought from WES components and they just weren’t lasting long.. I mean about half an hour and they would fail (they are higher voltage versions of a BUX84). I’m now using BUX84s I buy from Element14 and haven’t had a problem since.

I had already repaired some of the displays when I originally bought the game, replacing display glasses in three of them as well as some transistors and all the 100k resistors that often fail.

Next I started on the MPU board.. it wasn’t too bad as far as corrosion goes, but on powering it up it only came on with the LED stuck on.. I unplugged all the connectors leaving only J4 in, incase one of the other boards was locking it up, still no go. I knew the reset circuit was working as I checked it with a logic probe. Next I thought id try reseating chips, and when I got to the game ROMS.. about a third of the pins broke off of U2.    Shows over for the MPU for the moment, I have a new EPROM coming from Ken (skybeaux) he is doing one that combines the two ROMs into one, that plugs into the U2 socket.

[Mr Pinbologist]

Well after that little setback I decided to borrow the Alltek MPU from my Stern Stingray to see this game up and running for the first time in who knows how many years. Booted up straight away but had a continuous tone coming from the speaker, which I eventually worked out was the sound circuit that generates the falling pitch sound when the ball hits the bumper on most of these boards/games, ended up being a 0.1uF cap (C10) on the sound board causing the problem.

By this stage most of the game was working, except for a couple of solenoids. I had the game in solenoid test going over the board with the logic probe, when the power transformer board started to arc up and smoke poured out of it.. not good! After that I had no feature lamps and no displays. 

If you look at the 3rd pic of the damage, it had arced up between the fuse holder for the display circuit (and blew the fuse) and the ground track for the bridge for the feature lamps. Once again I decided to repair this board just for originality sake, and because it was my own game (id have replaced the board for a customers pin). I cleaned up as much of the carboned up mess as I could with my Dremel, and cut away completely the ground track for the bridge. Instead of reinserting the ground lead of the bridge back into the board I placed a couple of layers of heatshrink over it and resoldered it to the top of the board, right away from the hv fuse and the burnt area. Last pic shows the bridge ready to go back in.

[Mr Pinbologist]

Ist pic shows the board repaired for the 2nd time.. all good now, it has been left running for several hours now with no problems.
As I mentioned earlier I had to repair the display regulator circuit again, the BUX85 I had fitted failed. This happed while I was testing other game functions as well.. so once again I replaced ALL of the transistors and diodes, this time using a BUX84, which saw the HV regulator functioning normally again. To make matters worse, when the reg failed and sent 230 volts thru the NEW display glasses I think it damaged one of the new glasses.. some segments in one display intermittently flickering now. Well at least the Hv reg is running reliably now.

2nd pic shows a couple of the shorted coils I removed.. a sling coil and a drop target coil. I also need to replace the knocker coil. The Sling coil (a J26 1500) has been replaced, my recently deceased Vortex pin came to the rescue here as it had some Stern coils in it. I had one bumper not working which ended up being the drive transistor emitter lead not soldered properly.

The lamp driver board seemed to be working initially until I discovered some strange goings on in attract mode..
the ‘4 players’ lamp flashed in attract mode which I thought was odd, I started a game and racked up 4 players and watched the player lamps.. all ok until#4 when it didn’t come on.. hmmm.. time to check some connectors! Looking at the schematic, it showed plyr #4 going to J2 pin7, whereas MY J2 didn’t have a wire!! I found it pushed into another position on the connector, one problem solved.

Next problem was the tilt light coming on at the end of a game. To cut a long story short, this ended up being a strange hack I found on the back of the board (4th pic). Someone had put this jumper on the back which effectively linked the ‘tilt’ lamp output with the ‘game over’ (I think, not 100% sure now). Just why this was done is beyond me.  

3rd pic shows the board being tested on my test rig. No other repairs were needed to this board.

[Mr Pinbologist]

At this stage the game is pretty much running (after a few setbacks and some swearing, lol), except that the mechanics, ie flippers are badly worn (1st pic) and bumpers need to be rebuilt. I have replaced the slingshot kickers which were both broken, given the pf  a quick clean and put some new rubbers on so I could play a few games.

I might rebuild the flippers but nothing else will be done at this stage, with the exception of repairing the original MPU.  
For the time being I’ll relive my younger days and play it for a while. I’ll probably have to trawl thru 40 something pages of resto threads to find this one to add to it when I eventually get time and money to devote to restore this game.. and as usual it’ll get the FULL treatment.. Cab repaint, pf touchup and restore, AND some pretty extensive backglass work..

Watch this space!!

[pinnies4me]

Boy, looks like a big job ahead. Thanks for the post, enjoyed the read!!

[femto]

Yes thanks for this post. I really enjoy reading these type of post.

[Mr Pinbologist]

Hi again peoples, just a quick update;

I got the original MPU up and running today when the new eprom arrived that i bought from Ken (skybeaux)  

I did all the modifications, required to run the single 2732 eprom in the U2 socket, only to find that i had some more work to do to get the board to boot up on the bench! I ended up having to replace the mpu chip U9, plus the U11 PIA chip (and their sockets) as well as U12 (the 555 timer IC). After all this was done i could get the board to do six blinks of the LED (no 7th without the +43 volts connected).

Fitted the board into the game and it booted up fine and into attract mode with all the pf lamps flashing as they should.. then.. when i closed the lamp insert door... no displays   at first i thought the display regulator had shat itsself again, but it was ok. Hmmm...

Anyway to cut a long story short, replacing U19 (4011) on the MPU fixed the problem!!

Only thing left to do is to fit the remote battery holder, i didnt have one on hand so i'll grab one tomorrow.

I still need to rebuild the flippers so it can be played properly, i intend to enjoy it for a while before doing the full resto.

[goodolddays]

Good work there Mitch .. sounds like it was a bit of a pain but you got there in the end .
Wish I had your level of experience with these electronic pins .

[Strangeways]

An underrated title. I used to own one of these years ago. Backlgass was shot, but it had contact protecting the playfield. I sold it maybe 7 years ago, and it has never had a problem. A fun game, but as with all games from this era that are neglected, they need work. Glad to see you working on it Mitch !

Where did you score the lamp tested from ? I've been on the hunt for one for a while !

[Mr Pinbologist]

An underrated title. I used to own one of these years ago. Backlgass was shot, but it had contact protecting the playfield. I sold it maybe 7 years ago, and it has never had a problem. A fun game, but as with all games from this era that are neglected, they need work. Glad to see you working on it Mitch !

Where did you score the lamp tested from ? I've been on the hunt for one for a while !

Thanks Nino, do you mean the test rig im using to test the lamp driver board in the previous posts? i built that myself. It also tests Bally/Stern 6 digit displays (im about to modify it to do 7 digit ones as well) Gtb system1 driver boards and displays (it even has a gtb display rejuvenator function for the dim fluorescent displays!) as well as power supply outputs of regulated +5volts and + and -12volt outputs for bench testing other boards, like Bally/Stern MPUs and Gtb sys1 MPU boards etc.

It has been a work in progress for a few years now, i've been adding onto it on and off for those few years, as a result it aint pretty inside 
And in case anyone asks yes i do have schematic diagrams for the individual test circuits somewhere. I remember sending Daniel (ddstoys) some schematics a couple of years back

[Strangeways]

That's right - you designed it. I might have to ask you for schematics as well 

[chuppa21]

Good stuff!

[bossninja17]

Reading this is a bit like a good horror story to me - scares me to think about all the stuff involved but engrossing and I keep reading to the end.
I only owned EMs up to fairly recently. Then I got a Nugent (thanks Greg EB) which was problem free. It got my confidence up to buy a pretty damaged Flash thinking I might be able to learn how to work on SS machines by getting Flash up and running. I bit off more than I could chew and thank heavens for Ken! I would love to know how to do the magic with driver boards, MPUs, diodes, etc.