Bulletproofing Stern SDU-100-C Solenoid Board

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semicolin
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Bulletproofing Stern SDU-100-C Solenoid Board

Postby semicolin » Sun Jan 05, 2020 8:59 pm

Had some time this afternoon, so I took some time to bathe the solenoid board from my Meteor in the fountain of youth.

It takes about an hour to future-proof a Stern solenoid board. This should be the standard of care when bringing a new machine into the shop, although I'll admit I've been neglecting this machine in anticipation of a future overhaul.

Here is the before:
DD62E145-6718-46D8-BCE8-1E2DE03D8466.jpeg


The board is in relatively good shape. No burnt diodes, lifted traces, or bodge wires. Let's try to make them unnecessary in the future as well.

First thing that should be done is replace those crusty old electrolytic capacitors. These are original to 1979, and although they haven't failed yet, they're well on their way. Pulling out C23, C24, and C26 reveals on the ESR meter that they're badly out of spec. You don't need a fancy meter to do this procedure. Just trust me and replace these capacitors before they fail. They're definitely on the way.

C24 is a small capacitor to the bottom right of the big heatsink. Stern's early revision boards used an electrolytic, but later changed to a tantalum capacitor. If yours looks like it's in a metal can, swap it, otherwise, ignore it.

It can be a challenge to fit new caps into the board, as modern capacitors are much smaller than the originals. C26 was original an axial package, but that's no longer available. I fit in my replacement by drilling a small hole through the board and soldering directly to the wide trace, but you may wish to run a small wire instead. Once you've fitted new capacitors, it's time to make sure your board still works, and adjust the display voltage. Return it to your machine, reconnect the connectors, screw down the board (important!) and make sure everything is working as it should.

After confirming that everything is working, power down the game. Connect your multimeter's clip leads to TP2 and TP8, range it to DC voltage, and power back up. Your meter may read a couple of hundred DC volts now. With an insulated screwdriver, adjust RT1 until you get 160VDC. This will prolong the life of your plasma displays. Careful prodding around in here: you'll definitely feel it if you come in contact with any live parts in this section.

289CF48F-7263-4E01-A258-EDDF57533D5B.jpeg


Next step is to add in some jumpers. Bally/Stern were just starting to learn best engineering practices when designing these boards, and they didn't have modern computers to lay out and optimize their circuit designs. They made several errors that left their boards vulnerable to bad pinning, broken wires, and stray voltages. Both C23 and C26 need better paths to ground, and for some reason the 5V bus generated on the solenoid board needs to go all the way back to the MPU board before coming back to the solenoid board on the same harness. I'm sure in 1979 they thought they had a good reason, but forty years later we know better. Three jumpers need to be added to the board. Here's a photo:

AEF5A9C7-A2B5-4C05-8F31-A08171D918AC.jpeg


All that remains to be done is a complete replacement of the header connectors. I find it easier to remove the polarizing key pins from the strip before soldering rather than clipping short afterwards. Here's the final product, and hopefully, it will manage another forty years without requiring repair:

D672E33F-6E6F-4261-96D8-49B478590F57.jpeg


There are other changes that can be made as well. The LM323K regulators are obsolete and generate significant heat. There are replacements available that completely replace that whole section. I'll start using them when I run out of my supply of the original component.
Last edited by semicolin on Sun Jan 05, 2020 9:51 pm, edited 1 time in total.

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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby semicolin » Sun Jan 05, 2020 9:47 pm

There are lots of different parts that are suitable for repairing these boards, and I'm sure you can find cheaper places than the below links if you spend some time looking. I like to buy quality parts that will last a long time and will be a close a fit to the original as possible. Great Plains Electronics offers kits but they're often out of stock. If they are, here is what I recommend, available as of Jan 2020. This might change over time:

Parts:
C23: Nichicon UVR1E153MRD6 15000µF 25V
C24: Kemet T322B225M020AT 2.2µF 20V (the rounded side of the component is the positive end)
C26: Rubycon 450BXW150MEFC18X45 150µF 450V
.100 header strips: Sullins PREC040SFAN-RC
.156: header strips: Molex 0026481241

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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby Guard » Sun Jan 05, 2020 9:59 pm

All you folks that do this stuff impress the heck out of me....
PINS- Hit The Deck/ Buccaneer/Sure Shot/Fire Queen/ Volley/ Tee'd Off/ Rollergames/ Star Trip/ Flip Flop/ Combat/ Flash Gordon/ Capt.Card/Bluenote/ Pat Hand /Strange Science/Card Whiz/ Genesis/Jolly Roger / Bally Beat The Clock/ Spanish Eyes/ Outer Space/Bronco/ Stern POTC
Projects- Jacks Open /Stratoflite/ Tri Zone/ Hang Glider
RIP- Sinbad/ Supersonic

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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby semicolin » Sun Jan 05, 2020 10:25 pm

Guard wrote:All you folks that do this stuff impress the heck out of me....


Aw shucks! It's really not that hard once you get the hang of it. A well-lit work bench, a steady hand, and a good soldering station are all you need to get started. Hrm, that gives me an idea for another thread...


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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby steamfitter » Mon Jan 06, 2020 6:36 am

Great post Colin , i like that you put the part numbers that will make my future order a lot easier .

A post for board electronic parts number would be awesome . The hardest part for me in board repair is finding the right part , i've ordered stuff i'll never use :FP:
Pins: Black Hole , Flash Gordon, Black Jack
Jukebox :1972 Seeburg Olympian sps160 , 1986 seeburg SCD-1
Projects : fireball (home edition ) , seeburg LPC-1 , Meteor , star trek , James bond 007 , Black Jack

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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby semicolin » Mon Jan 06, 2020 5:14 pm

steamfitter wrote:A post for board electronic parts number would be awesome . The hardest part for me in board repair is finding the right part , i've ordered stuff i'll never use :FP:


Ping me any time and I'll tell you what you need. Or post it right here!

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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby steamfitter » Mon Jan 06, 2020 7:31 pm

semicolin wrote:
steamfitter wrote:A post for board electronic parts number would be awesome . The hardest part for me in board repair is finding the right part , i've ordered stuff i'll never use :FP:


Ping me any time and I'll tell you what you need. Or post it right here!


Thanks
Pins: Black Hole , Flash Gordon, Black Jack
Jukebox :1972 Seeburg Olympian sps160 , 1986 seeburg SCD-1
Projects : fireball (home edition ) , seeburg LPC-1 , Meteor , star trek , James bond 007 , Black Jack

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Bulletproofing Bally/Stern Displays

Postby semicolin » Wed Jan 08, 2020 12:37 am

Bonus bulletproofing: Bally/Stern were notoriously cheap for tolerances when choosing components. Some of the resistors on their display boards that were rated for 1/4W often had to dissipate more heat than that.

When one of these resistors fails, it can take out the board entirely. They're getting harder to find every day, and they aren't cheap either. This rework takes about ten minutes per board and costs about fifty cents.

The first thing that should be done when reworking a machine's displays is to strip out R1,3,5,7,9,11(and R56 on a seven-digit unit). Replace all of them with 100K 1/2W resistors.

3DC0A060-D2D0-4A3D-A32B-E265B3433F7B.jpeg


11B400E1-DB6D-47AD-9698-9087306686D4.jpeg


FEE969D3-9343-475F-AA1D-DB438258A667.jpeg

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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby Sparky » Wed Jan 08, 2020 8:04 am

Gold.

I have about 40 displays and 12 solenoid drivers on shelves... About time I got to them. LOL
Stage 5B. All except for NIB crap.

viewtopic.php?f=3&t=4742&p=40349&hilit=stages#p40349

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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby semicolin » Wed Jan 08, 2020 9:43 am

Sparky wrote:Gold.

I have about 40 displays and 12 solenoid drivers on shelves... About time I got to them. LOL


Now I know who to call when I need spare parts.

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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby Sparky » Wed Jan 08, 2020 10:27 am

semicolin wrote:
Sparky wrote:Gold.

I have about 40 displays and 12 solenoid drivers on shelves... About time I got to them. LOL


Now I know who to call when I need spare parts.


You have NO idea.... LOL Many have said that I should create my own used parts business.

But, I am not in it for the money. I just want to keep shit running.
Stage 5B. All except for NIB crap.

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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby sylvain » Wed Jan 08, 2020 10:18 pm

Those original 100K 1/4W under-rated resistors on displays burn even faster
if the Solenoid Driver High Voltage Regulator section becomes short
or adjusted too high for a while (e.g. HV outputting > 200+ VDC).

I usually adjust the voltage down to 175VDC to preserve the displays.
This also helps lowering the power dissipated by those resistors.

I agree that 1/2W is the way to go, when replacing those resistors.

-Sylvain.
Looking for Bally Star-Jet, Capersville or The Wiggler, Williams Magic City, Grand Lizard, Swords of Fury, 1986 Pinstar Gamatron, and a few others.
Collecting & repairing electro-mechanical and solid state pinball machines with quality and care for over 35 years.
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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby DrDude » Thu Jan 09, 2020 12:21 pm

sylvain wrote:Those original 100K 1/4W under-rated resistors on displays burn even faster
if the Solenoid Driver High Voltage Regulator section becomes short
or adjusted too high for a while (e.g. HV outputting > 200+ VDC).

I usually adjust the voltage down to 175VDC to preserve the displays.
This also helps lowering the power dissipated by those resistors.

I agree that 1/2W is the way to go, when replacing those resistors.


Agreed on all counts, Sylvain: Drop the HV section to 175v ALWAYS. And modern 1/2W resistors are the same size as old-school 1/4W, so they fit just fine.
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Re: Bulletproofing Stern SDU-100-C Solenoid Board

Postby semicolin » Thu Jan 09, 2020 2:20 pm

DrDude wrote:Agreed on all counts, Sylvain: Drop the HV section to 175v ALWAYS. And modern 1/2W resistors are the same size as old-school 1/4W, so they fit just fine.


I bring them down to 160VDC and they're still bright. You should see some of the new Stackpole 1/2w minis! They're even smaller; like a combination of a through-hole and surface mount component. No real reason to use them unless you're trying to save space, but the actual package itself is only 2mm x 6mm. I ordered them by mistake once and they were small enough that I couldn't read the colour code.



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