Tag Archives: tech

Troubleshooting Counterforce drop targets

Chris refers to the Gottlieb drops as the Cadillac of drop targets. I’m not so sure, but they do play well. Drop targets are an annoying mechanism to work on, especially those with added features like trip coils.

Williams drop targets have a failure mode I call slo-mo drop targets. You smack one with the ball, and instead of clicking down, it sinks slowly into the playfield. This comes from dirt. If they’re really dirty, you can hit one, the ball can move far away, and then it sinks. It’d be cool if it happened on purpose.

I got this Gottlieb Counterforce. And it had slo-mo drops. I’ve never seen this in a Gottlieb game. There’s nowhere for the dirt to hide. So, while shopping out a bunch of stuff wrong with this game, I did the drops.

I replaced all the targets (which didn’t match). I followed PAPinball’s guide, which is very good. I didn’t expect this to fix anything, but I hoped it would. It didn’t.

Toasty coil sleeve in my drop target bank.

I cleaned the coil sleeves for the two reset coils, which didn’t really help. So I removed the bank and did a deeper (but still half-assed) cleaning. When I was done, I still had slo-mo targets. (This sleeve is cooked, but it still works OK. Perhaps I’ll replace the coil, but for now, it’s working fine.)

It became pretty clear the problem was with the reset bar not sinking. If one target was already fully down, any other target would drop quickly. But if no targets were all the way down, you’d get slow action because the drop target had to push the reset bar down. So once the reset bar was down, targets would drop quickly.

On this mechanism, there is some freedom to adjust the coil in the bracket. Coils can be twisted slightly relative to their plunger and the reset arm. The coil needs to be square to the bracket, and both coils need to be at about the same depth. The coils can be adjusted slightly so the reset bar doesn’t over-extend the targets out of the top of the playfield, but they need to be square to the mechanism to work correctly.

Now, as drop target banks go, this one has all the bells and whistles. There are seven drops, but there are seven trip coils on the top, too. These are triggered by the computer when it wants to drop a target. In Counterforce, these are triggered by rollover switches and standup targets scattered all over the playfield. Each drop target has a sense switch, but it also has a lamp voltage switch used for “when lit” indicators for the trip switches, and also for the big falling-bomb gimmick.

On my game, one of the trip switches didn’t trip. This appears to have been a coil that was open. The coil was A-18642, but research indicates there are a couple other usable substitutes, one of which was in Chris’ parts bin. So that’s what got used. (Pinball Resource can identify the substitutes, if necessary, but they also have the correct part number.)

I was able to identify that this coil was open by using a multimeter. In the diode setting, I was able to measure the diode of the bad coil — but not of the good coils. For the good coils, when I try to measure the diode, I measure the coil instead. So that was my indication that the coil was at fault.

So far, so good. Resoldering these coils is kind of a pain because there’s so little clearance in this mechanism.

My Counterforce is still torn apart waiting for other parts, but the drops all now work correctly.


  • Make sure the reset arm drops completely, and freely. If not, look for a twist in the position of the reset coils.
  • The reset coils should be positioned so that the coil stop stops the plunger before the drop target goes up too far and shears off the foot.
  • Find the criteria for remote-trip coils and verify they’re all working.

This all applies mostly for Gottlieb drop targets. In any case, I haven’t generally had problems with them once they were rebuilt in home use.

On Williams games with the horseshoe mechanisms, the problem is the horseshoe mechanism. Those things are terrible.

On Williams games with optos, and I suspect those with leaf switches at the bottom of the column, they get dirty and sluggish. I cleaned my BK2K’s targets once and they’ve been great, even after the game was operated for six months at the PPM.

On old Stern games, there’s only one spring that drops the target, so it can be twisted by the spring. If you can get that adjusted correctly, they work great, and can be swept by a good shot. I love these.

Old Bally games are similar, but I don’t have as much experience with them.

I have seen two different drop mechanisms on new Stern games. On my WPT, there’s a service bulletin to enlarge the catch shelf for targets that has cured most of my woes. On my Simpsons Pinball Party, I had a loose connection — otherwise it’s been quite reliable.

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Spy Hunter Fixes (or, I can’t follow simple directions from anyone)

A few years (!) ago I bought a Spy Hunter. It played blind.

I got this game as a sweetheart deal, and I got a great price because it wasn’t working. It belonged to a friend who used it for party rentals. I knew it had been well maintained. Must be a loose wire or a fuse or something.

I talked to Chris, who said that if I pulled the boards apart, everything would work until the game got moved. Well that sounded pretty annoying. So, as I am wont to do, I bought some parts—in this case, a set of new interconnect cables—and put them in the cash box for some other day.

Well, that day was in late 2019, when I conned GMike and I into taking a look at it. Still no video, and no obvious reason for no video. So we replaced the interconnect cables. This is a pretty large pain in the ass, because the MCR III system is such a convolution. Power comes in one end of the board stack, I/O comes in the other end, and all the spring tension on the connectors is so tight, they’re nearly impossible to take apart.

GMike and I got the boards apart on the dining room table, cables replaced, back together—same thing. I texted the previous owner and got the scope out and handed it to Mike, who confirmed the video pins weren’t videoing. I have a pattern generator for the monitor, which proved it was OK. The text conversation went back and forth a few times until I realized the video signals weren’t connected to the CPU, but to the Super Sound I/O board which, for some reason, has a connector with exactly the same connector as the CPU.

So we moved the connector over and played some Spy Hunter.

Next problem: bad power switch. I think it had just mechanically failed and wouldn’t stay off. Unfortunately we had to change the QD connectors from .25 to .187, but they work just as well.

Last problem: no saved settings. There are two types of difficulty setting in Spy Hunter. One is DIP switches and controls how long the “unlimited cars” time is. The other is in software, and coincidentally, also saves high scores and bookkeeping.

The battery had long since been replaced with a supercapacitor. But when the power was shut off, whether or not the card rack was connected to the power supply, the available voltage dropped to nothing quickly. So, GMike put a new cap in it. That would at least hold voltage with the power off. But with the boards connected, voltage would drop.

Chris suggested replacing the 6116 on the CPU, or the capacitor and diode on the power supply related to the battery. I had the cap and diode, so I replaced them. I would have done the 6116, but it’s so difficult to get the card rack out, I put it off. I got some 6116s from Chris on a visit to his shop, and actually ordered an NVRAM so that I’d only have to go at this once.

Tonight, though, rather than put the NVRAM in, I wanted to get the 6116 to work. It’s so difficult to get the ribbon cables off, I stopped trying, and learned to work with the boards connected (very carefully). Actually, the Spy Hunter is in the garage, and the available low-static workspace I had was a pinball machine in the house, so I just took it inside. Where it’s warm.

I got the stack apart and couldn’t find the 6116 on the CPU board. So I looked around and saw that it’s actually on the video board. I put in a new chip, and no change. (OK, one change: the video connector is so hard to get on, I missed pins and corrupted the video. Other than my heart breaking that I just broke the game, no problem.)

So I put the NVRAM in. It barely fit in the stack. Plugged it back in, and the sprites were either missing entirely or corrupt. Uhoh. Had I changed the wrong 6116? Yep. The correct 6116 to change is on the CPU board, at 5G, and this was documented by the vendor. I had missed it because the original chip had a weird part number. So, on my third reassembly of the day, I put the right chip in and reinstalled, and things appear to be working!

(So I can’t really say that the NVRAM didn’t fit. I mean, if you put it in the wrong place, it doesn’t fit. That isn’t helpful. However, the NVRAM will not work as video RAM. That’s also not helpful but is something of a fun fact. I guess.)

I finally increased the difficulty from default 3 up to maximum 9. It’s a more interesting game. At 3, there are a lot of times where there are no spy cars to attack. At 9, there are spies almost all the time. It’s great.

I re-checked the voltage, and with the power off, it stayed around 4.80, a big change from the various broken parts. So far, the cap appears to be working.

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