Guys, I'm having a strange issue with my Baby Pacman. The lamp matrix gets messed up to where the inserts still light, but the lights are not lighting in the correct order. I've traced it to the PIA that leads to the lamp matrix. After I replace the PIA, the lamp matrix works fine for a while (a day or two) then it acts up again. Rebooting the machine sometimes results in it starting messed up or sometimes it starts up normally which leads me to thinking the PIA is not being initialized correctly. I have an Alltek CPU board.

Anyone seen the lamp matrix get messed up like this before? Any idea where to look for whats messing up these PIAs?

I think it is still running baby pac code as all the playfield rules still work. I tried reseating the PIA in the socket tonight and low and behold, it started working again. The problem appears to be a flakey socket on the Alltek board. I'll contact them tomorrow.

Don't know of a guide but they are standard .1" pitch connectors. I replaced the headers on my boards with extra long, gold plated connectors and that solved most of my connector problems. You may still have to replace some of the connectors, however.

I used part number CH100-40G-0.318 from GPE. You can get the crimp on pins and housings from him too. https://www.greatplainselectronics.com/categories.asp?cat=70

If you need a crimping tool, this one works great for me. It crimps the wire and the insulation in one crimp. I was skeptical but it really works each and every time!

https://www.amazon.com/gp/product/B007JLN93S/ref=oh_aui_search_detailpage

Make sure you check the lamp matrix SCRs before replacing sockets. I thought I had bad sockets, turned out to be several bad SCRs in the lamp driver.

Do you have a diode installed on that new socket? I doesn't look like if from the picture.

I had several bulbs not working on my Baby Pac that I swore were bad sockets. Ended up being blown whimpy SCRs in the lamp matrix.

Is this the ONLY controlled lamp this isn't working? When the SCRs blow, the bulbs stop working in pairs. You should be able to tell if it is a bad SCR by looking at the schematics for your game and checking if the other bulb paired with this one is not working as well.

Look closely at the original socket. The mounting bracket is soldered to the common wire and there usually is a diode built into the socket between the mounting bracket and the contact point for the bulb in the socket. It is on the back side of the original socket in the picture you posted. I do not have an EBD but that is the way the sockets are on my Baby Pac.

See the slot in the plastic at the top as you are holding it in the picture? There is another terminal in that slot on the working sockets. From the terminal in that slot, there is a diode that connects to the mounting leg. The diode may get routed under the bend in the mounting leg (to the right in your picture). The diodes on my sockets are the small, pink glass type, not the black plastic type common on other games and modern games.

That is the way my sockets are laid out. But as aobrien points out, your sockets may be different than the ones used on my game.

Yea, now that I think about it, if the Diode was missing, I think the bulb would be lit all the time. It wouldn't hurt to take a close look at the working sockets and confirm there isn't a diode on them.

If there are no diodes on the other sockets, it's most likely the SCR on the board for that lamp.

Hey guys, I was helping a friend with an early Stern with -100 series boards that are virtually the same, if not the same as the 2518 boards. Issue is his 5v was running at 5.9v. I lifted R49 Andrew mentioned in another thread to drop it to 5.7v but that is still too high for comfort. I reflowed the solder joints around the 7805, even though they all looked good without change. I lifted legs on R50 and it was a little over 5 ohms but is supposed to be 4.7. Could this be it?

Anyone have any tips or is this simply a bad 7805SC?

Thanks Marco. The fact that this resistor drifted up to 5+ ohms isn't helping. I'll try a 2.2 ohm there and report back.

So I reconnected R49 and made R50 2.7 ohm (measured, closest value I had) and the voltage went from 5.9 to 5.7. Maybe the effects of an aging 7805?

Is there harm in making R50 (zero ohms)? I suspect not as the reference design for the 7805 has the "common" pin tied to ground. I guess my other option is removing R49 again and taking back another .2V or so.

Whats typical for a Stern PS 5V supply?

The game with this power supply problem is a Stern Magic. After getting it running again, the controlled inserts are very dim. I rebuilt the power supply board in the base cab with new resistors, header pins and fuse holder clips and they are still dim. The header pins on the lamp board are all new too.

Anyone have suggestions what the cause of dim inserts could be? Repin the cable connector on the power board? Other ideas to check?

Thanks! I'll check that!

Thanks!

Nice solution!

I thought I would post the problem I was having with my Baby-Pac, just in case someone has similar problems.

Occasionally when I powered up the game, the insert lamps would work, but not light up the correct inserts. Sometimes turning it off and back on would resolve it. I thought it was the lamp matrix PIA U10 as swapping it would appear to resolve the issue.

Turned out to be the zero cross circuit. This circuit on the CPU board is fed by the GI AC voltage (on Baby Pac, other games may have different feed) and tells the lamp U10 PIA when to switch between the 2 lamps on each lamp string. Someone had snipped the wire at the GI tie-in point under the playfield and patched a wire from the 43V DC flipper circuit from the lamp/solenoid board into the zero cross circuit. Not sure why someone would make this mod but its no wonder why the zero cross circuit had a hard time functioning only detecting the ripple on the DC supply. Removing the jumper, reconnecting the GI wire under the playfield fixed it right up. Insert lamps function perfectly each and every time I power up the game.

Not sure how common this "mod" is but I thought I would post it just in case someone else has problems with inserts not lighting the correct inserts.

Interesting, and good to know, thanks. My game had an Alltek CPU board so the mod was probably done for the CPU board that was in the game before the Alltek.

The parts you linked are 8A bridges. I thought the stock bridges were 10A.

Check out Gatecrashers repro parts. Looks like all he makes is the metal lift trim, not metal u-channel.

https://images.pinside.com/5/2a/52a32db70762186e50ce5c3a2f212eb4514cee4f/resized/large/52a32db70762186e50ce5c3a2f212eb4514cee4f.jpg

https://pinside.com/pinball/biz/directory/1228-gatecrasher

Isn't that a standard 24 pin 0.062 molex connector? You can confirm my looking at the dimensions on the drawing at GPE's site. If its the right size, you can order the housings and pins/sockets from GPE. They also sell a tool to make removing pins/sockets from those housings.

https://www.greatplainselectronics.com/proddetail.asp?prod=03-06-2242