(Topic ID: 225496)

Stern Electronics Club (1977-1984).

By Mitch

1 year ago

Topic Stats

  • 2,359 posts
  • 196 Pinsiders participating
  • Latest reply 11 hours ago by treborlicec
  • Topic is favorited by 100 Pinsiders


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Topic index (key posts)

7 key posts have been marked in this topic

Post #227 Various gate tips. Posted by cottonm4 (1 year ago)

Post #269 Hi quality thoughts from Cotton about inlanes. Posted by cottonm4 (1 year ago)

Post #279 Playfield touch up tips. Posted by klr650 (1 year ago)

Post #309 Stern inserts suggestions. Posted by cottonm4 (1 year ago)

Post #310 Seawitch gate flap solution. Posted by frunch (1 year ago)

Post #1033 Bally drop targets on the classic stern, even mix and match. Posted by cottonm4 (8 months ago)

Post #1958 Star Gazer podcast episode link. Posted by DRDAVE (77 days ago)

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#363 1 year ago
4 weeks later
#592 11 months ago
Quoted from TomT:

What are you guys using as a replacement speaker in the early Sterns?

You could try one of these:


1 week later
#647 11 months ago
Quoted from JoesCoinOp:

Help needed! Looking for the pictured chip. This is from my Stars, game plays fully but some of the chimes coils are not firing. Was told to replace the chip, anyone know where I can order one?

Was the 74L154 chip actually diagnosed as faulty? They rarely fail.

#650 11 months ago
Quoted from JoesCoinOp:

I don’t know anything about board work but I tried the board in a HG and the pops were dead but when hit the saucer kickers would fire.

If all pop bumpers didn't work on the Harlem Globetrotters then the drop target resets wouldn't be working in your Stars.
Your solenoid driver board has double sided tracks making it more difficult to remove that chip without the right equipment/skills.
I'd suggest you open a tech support thread in the "Tech: Early solid state" subforum where we can help you diagnose the actual fault.

#652 11 months ago
Quoted from JoesCoinOp:

Put the board back in Stars and confirmed the drop resets are not working, no chimes either but pop, slings and flippers work fine

With the limited info, it looks like there's a breakdown in the signal on the solenoid driver board from pin 4 of connector J4 to leg 21 of the 74L154 chip. That signal is used when selecting chimes and the drop target reset solenoids.
It could be corrosion on that pin causing poor connectivity, a cracked solder joint on the back of the board where that pin is, damage to that trace signal running to the 74L154 or the 74L154 chip itself. If you have a multi-meter or logic probe we can further diagnose it but it's better done in the tech subforum if you want to follow up.

3 months later
#1129 7 months ago
Quoted from cottonm4:

Where can I get them?


1 month later
#1438 6 months ago
Quoted from Mitch:

What's the factory playfield flipper coils and what's the factory backbox flipper coil?

Flipper coils are listed in the manual:
Playfield: J-25-475/34-4500
Backbox: J-25-600/34-4500

Quoted from Mitch:

Also need some pics of the piece in the backbox that holds the ball on the flipper when you remove the backglass

See here:

Quoted from Mitch:

and a pic of the gate in the backbox as mine is missing.

You'll find pictures in the Catacomb club thread including measurements for making one up.
[Edit] found some links:


1 month later
#1557 5 months ago
Quoted from cottonm4:

From Hot Hand to Dragonfist, they will all fit.

Trident came out before Hot Hand.
The Trident I had as a teen had the earlier screw studs mounting lockdown bar.
I think the lockdown bar changed during Hot Hand production?? My Hot Hand also has the screw stud lockdown bar (I seem to remember adjusting the screws about a year ago to get the lockdown bar to fit more snuggly).

[Edit] Trident lockdown bar receiver shows it needs the earlier screw stud mounting lockdown bar.

Hot Hand showing it has the later lockdown bar receiver for the metal slot latch mounting lockdown bar.

1 month later
#1830 3 months ago
Quoted from Flynnyfalcon:

So I’m in discussion with my tech guy trying to solve my issue, but thought I’d also ask the considerable brains trust on here, hoping it’ll speed things up.

I suggest you open a tech support thread in the Early Solid State Tech sub-forum:

Post pictures of how your transformer is wired and the three connectors that are plugged onto the rectifier board clearly showing the wire colors/positions.

Quoted from Flynnyfalcon:

Some basic research has me thinking the in-line filter may be stuffed

The inline EMI filter is before fuse F6 so that fuse doesn't protect against a filter fault. A problem with that filter will hopefully trip a fuse in your house fuse box.

#1841 3 months ago
Quoted from cottonm4:

The only difference that I can find is that the F-4 fuse on the rectifier board is rated at 5 amps for the 16B-3 and F-4 fuse is rated at 7 amps on the 16B-6. I don't know why Stern bumped the 16B-6 to 7 amp fuse.

Yeah, transformer upgraded for higher solenoid current. You might notice most if not all MPU200 games have stronger flippers compared to the MPU100 games.
Most MPU100 games had 25-500/34-5050 flipper coils while the MPU200 games used 25-475/34-4500. Galaxy even lists 25-450/34-4500
Plus a number of MPU200 games had 4 flippers.

Quoted from Redketchup:

I want to put a Catacomb in a dracula cab?

Is this a scratch build from a Catacomb playfield only? If yes, what are you doing for the head lightboard with the bagatelle artwork?

1 month later
2 weeks later
#2194 40 days ago
Quoted from Whridlsoncestood:

On ali all greatest letters on left shot flicker still. On dragon fist it’s a few around the blue bonus inserts.

The "greatest" inserts on Ali are the very first lamps to be refreshed during the zero crossing routine. If on Dragon Fist you're talking about the 1000-8000 blue bonus inserts then same story. The SCRs driving those LEDs will find it most difficult to latch since the DC voltage is at the lowest point in the lamp refresh cycle and the current isn't yet at the right level for the SCR to latch in certain conditions. The types of LEDs used will probably be a factor but lower value resistors may likely be needed on those first lamp outputs in order to draw more current to help the SCRs latch.

#2197 40 days ago
Quoted from cottonm4:

I currently have some other problems going on with my Dragonfist at the moment, but when it was working, there were no flickering LEDs. I am using a Bally LDA and a set of Hans's adaptor sets are mounted. For the blue and green bonus inserts, I am using 4-SMD units/bulbs from Comet. I am 100% LED in this pin with the exception of 18 yellow feature lights which are still incandescent.

I have done nothing special. How/why did I get lucky and miss this flickering issue?

As mentioned in my previous post, the blue bonus lamps are the first lamps to be refreshed during the zero crossing service routine - they are the ones most likely to suffer from flickering. Your using 4-SMD LEDs which draw more current than the single/twin SMD LEDs others are using. This results in more current through the SCRs allowing them to better reach latch current hold threshold.
Once you get the game working again it might be interesting to swap some of those blue 4-SMD LEDs particularly at 1k - 4k bonus to low cost non SMDs or single SMD and see what happens.

Your feature lamp voltage maybe a bit higher than others possibly due to the way your transformer is tapped resulting in slightly increased current draw.

You might be lucky that the batch/manufacturer of SCRs on your lamp driver board have lower than normal hold latch current characteristics. Spec for the 2N5060 and MCR106 SCRS state that holding current is 5ma "Max" meaning the worst case SCRs need to see at least 5ma before latching. In other words you might have SCRs capable of latching at lower currents. This is why when some people swap SCRs it fixes their issue.

#2214 38 days ago
Quoted from Shapeshifter:

Ok, not expecting many answers on this but here goes!

My Catacomb will 100% of the time award an extra 20000 points each time a drop target set completes.

I just looked up your MPU board picture you previously posted and notice you have RA28G ROMs meanwhile RA32 are the version in the wild and what I've twice recently seen.

We need you to get your ROMs dumped! They might be special with other differences!

FYI, Alltek is running Catacomb code matching the RA32 code.

#2217 38 days ago
Quoted from Shapeshifter:

Thanks - so it's basically early code?

Potentially yes. Looks like the German Stern ROM list for Catacomb may have started at version 25 - see page 3 of the below pdf.

It would be great if they could be dumped and the code preserved for the community.


#2218 38 days ago
Quoted from cottonm4:

It was a blown fuse on the rectifier baord. A 4amp fuse on F3. It is working fine now. But my big question is why did the fuse blow in the first place?

Did the old fuse blow violently or was it just open circuit? Got a picture?
Do you have LED displays?

#2220 38 days ago
Quoted from Shapeshifter:

Wonder which version is most fun to play?

The question is whether there's other differences in your version.

#2223 37 days ago
Quoted from cottonm4:

I would say it blew violently. There is quite a gap between blown electrode?/wire.

It looks like it was a new fuse that blew so it had already been recently replaced?
Suspect it will probably happen again till the cause is found.

#2243 34 days ago
Quoted from HHaase:

Just to confirm, it looks like I'm able to register switches on the upper header, but not on the lower header.

I can trigger all coils, and the flipper relay, by grounding their respective tabs on the solenoid driver board.

Measure the voltage at test point TP3 on the solenoid driver board. If you don't read 5 volts, you've lost voltage to the solenoid logic and predriver circuit on the solenoid driver board. Usually happens due to a bad connection on the 5 volt loop wire at connector J3 that runs from pin 13 to 25.
See the section from the solenoid driver board schematic below:

SDB_TP3 (resized).jpg

1 week later
#2297 23 days ago
Quoted from HHaase:

I think I'm just going to rebuild the whole circuit for that coil on the SDB, from the 3081 on down.

The transistor usually only blows when there's a problem with the diode on the coil preventing the back EMF being blocked, otherwise most other issues should cause the solenoid fuse under the playfield to blow, not the transistor. Check that fuse and make sure someone hasn't overfused it. Should be a 1 amp slow blow. Banded side of the coil diode should be on the yellow wire. Measure the DC resistance of that coil, it should probably be in the 9 - 10 ohm range.

#2305 20 days ago
Quoted from brandsilence:

Need a little help with a Dracula flipper rebuild.
I just noticed that the switch stack on one flipper appears to have an extra switch... the tabs on the switch base aren't connected to anything

Quoted from djblouw:

Here’s kinda what is should look like

Quoted from chuckwurt:

I think that extra switch it to drive the upper flipper.

Quoted from brandsilence:

That’s s good guess, but the upper flipper was working before I tore the playfield down, so who knows!

As djblouw and chuckwurt showed/mentioned, that extra switch is for activating the upper left flipper.
It looks like somebody's bypassed that second switch so the upper flipper activates the same time as the lower flipper. The consequence is the left flippers will be weaker than normal because there's more current strain on the transformer the moment you flip.
Those flipper mech switches should be setup so the EOS switch opens first, then the secondary switch closes to activate the upper flipper.

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