The G07 Kid

I spent much of this weekend digging in on  some Electrohome G07 monitor chassis repair. I have a bunch of games in the bavacade that use this monitor chassis to power the glorious CRT tubes for these 1980s miracles.

All told I have at least 7 cabinets that have a G07 chassis. There may be more, but I’m not sure what chassis all my cocktails are using given I never checked, and there are four total: Rally-X, Pleaides, Galaxian, and Moon Cresta.* Along with the Wells Gardner K4600 (at least 6 cabinets have this chassis) the G07 is the most common in the bavacade. That means part of making this hobby sustainable is figuring out how to work on these models given chassis repairs are a big part of keeping games online. I’ve slowly been getting better, but I remain very much an amateur. But even hacks like me have their moments, and this week was one of them. I got two of the three non-working G07s running again, leaving me with just one non-working chassis that I can use as a donor chassis for parts given all the games with G07s are now fully operational. YES!

Trusting the process means a lot of troubleshooting, and this weekend I was pretty happy to have committed a bit more and pushing myself to do more extensive diagnostic testing of the various components for things like resistance readings, diode readings, checking if transistors are good, voltage test points, etc. All of this was Greek to me just a couple of years ago, so starting to get my head around this basic troubleshooting before replacing anything is long overdue and pretty rewarding.

I already talked about the first successful G07 repair this week in my “bavacade Repair log from 6-29-2023,” noting “I was able to repair the Condor G07 chassis that was dead by doing a cap kit, swapping out a new B+ filter cap as well as a horizontal width coil.” The cap kit was done almost a year ago, but I never got it working. Turns out the recent replacement of the B+ filter cap is what brought it back to life. The horizontal width coil was broken, so I soldered a newer one off one of the other two non-working G07 chassis, figuring better to replace the broken one while the board was out. When I re-installed the chassis in Condor it worked, but there was a slight undulation that was annoying me. So, as a test, I tried it in Robotron and the waviness was gone and it worked perfectly, so that’s where it lives right now.

This means I needed to repair one of the other two chassis for Condor, and then I was golden. The two G07 chassis I had both blew the F901 fuses (2.25 AMP @ 250V ) next to the B+ capacitor, which is the biggest capacitor on the board. After discharging the B+ filter,† I replaced the fuses, which needed to be soldered in, and then tested the G07 that came from Pole Position (I defaulted to this one because I had desoldered the horizontal width coil from the other chassis for the first fix). Initially I thought the Pole Position chassis had an issue with the flyback and/or the horizontal output transistor (HOT) given the symptoms when it originally occurred a few weeks back. But after re-soldering the fuse and re-installing in Robotron to confirm as much, there was a total vertical collapse of the heart

That’s a new one, but I’ve read about it on forum posts innumerable times. I figured I’d have to deal with it sooner or later, so I embraced the challenge to broaden my experience—learning is painful! OK, so the first thing I did was look at some of the basic troubleshooting for this, and from what I read it is possibly linked to a few different things, such as an open circuit somewhere, which requires testing each resistor in the 400 series circuit to ensure there are no infinite (OL) ohm readings. It’s also been linked to the x401 and/or X402 trasnsitors, so you wanna check the values there. I’ve read a few cases where the IC501 chip was bad and needs to be replaced, but that seems less likely. That said, the following G07 repair video did have that issue, and it does a great job walking you through common troubleshooting as well as demonstrating how to test the transistors, which was very helpful:

I tested the transistors, and they were both reading at .570, which seems normal. I then tested all the 400 series resistors and some were lower than the specs, but none were open, so not sure they are the issue. I also compared the results on a working G07 and they were fairly similar, here are the results I got for this chassis:

FR401: 69 Ohm
R401: 99 Ohm
R402: 18K Ohm
R403: 3.3K Ohm
R404: 4K Ohm
R405: 12K Ohm
R406: Vertical linearity trim pot
R407: 4.2K Ohm
R408: vertical Height trim pot
R409: 51 Ohm
R410: 6.4 Ohm
R411: 13K Ohm
R412: 13.5K Ohm
R413: 580 Ohm
R414: 3.1K Ohm
R415: 2.6K Ohm
R416: 8K Ohm
R417: 67 Ohm
R418: 1.3K Ohm
R419: 1.9K Ohm
R420: 6.6 Ohm
R421: 5.5K Ohm
R423: 2.4 K Ohm

Some of the readings are low, particularly for R404, R411, R412, R416, R417,R421, and R423, but I got similar low values for another chassis that works just fine, so I “resisted” replacing any resistors just yet given I didn’t find any open circuits, just issues with value range (assuming a low resistor value would not cause the total collapse, but I’m not positive on this). The next test would be the IC501 chip, but I was not entirely sure how to test this chip, still a blindspot for me, and I don’t have a spare regardless, so I let that sit.

There could also be an issue with soldering joints at the yoke connectors on the board but the solder was fine, but still might reflow those. Beyond that, I tested the resistors for R406 and R408 which adjust the vertical height and linearity, and they adjusting values accordingly, so I was hitting a brick wall. I even checked the diodes in the 400 circuit, but all seemed good.

At this point I decided to step away from the Pole Position chassis, and turn to the other one that wasn’t working. First thing was desolder the horizontal width coil from the chassis I just abandoned and solder it to this one. I already added the new F901 fuse, so with the width coil added and the fuse in I tested it out. The last time it had not powered on at all, whereas this time it powered on and immediately there was smoke coming out of the flyback. It had blown. This, oddly, was very reassuring because at least I knew exactly where the issue was, and I also had an extra flyback that worked. So, I replaced the flyback and tested the game again and voilà this time it worked perfectly, whew! All the work on the other one with no results but a lot of learning, and this one was a simple replacement part swap, I’ll take it every time.

I need another width coil and a working flyback, but once I have them I might even take another shot at the last non-working G07, but given no games are effected I can finally move on to the last chassis repair I need to do, the K4600 for the Centuri Challenger, so until then!

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*I’ve yet to dismantle a cocktail cabinet, but that task will probably be coming soon given some work needed on my Pleiades cocktail cabinet, I don’t trust the adjustable metal legs on that game and want to get them properly lubricated and adjust with the write screws.

† Capacitors are designed to hold a charge, and when you blow the F901 fuse that charge has nowhere to go, which makes these big capacitor dangerous to the touch. Whenever removing this board do not grab it from underneath before discharging the G07 cap. You can do this by using an insulated screw driver that is connected to a ground via an alligator clip to ensure the charge has somewhere to go. To ground it, make sure the screw driver touches the + and – posts, read more on this on the KLOV forums here.

bavacade Repair Log 6-29-2023

This is just a quick update to document some of the work happening recently in the bavacade. It has a been a bit of catch as catch can given how busy the last month has been with the Reclaim open conference the and coming virtual event in July. That said, I’ve been sneaking in work here and there in the mornings, and as usual it adds up. I already blogged about the Yie-Ar Kung-fu custom cabinet project, and will be a summer long endeavor, but it’s very exciting. I also documented some of my work a couple of week’s ago testing various parts I bought in the US in the “Arcade Therapy” post, so things are definitely moving along.

Arcade Therapy

More recently I have been testing some spare boards I have, namely a spare Make Trax board as well as spare Super Cobra board. This was also part of my attempt to start organizing all my parts and spares in the basement and get some semblance of order. I find testing and labeling when things worked saves me a ton of time, and some of the metadata on the boxes noted that these boards were questions marks. Also, I was looking to test a Crush Roller board in Make Trax I was sure I’d bought and brought to Italy over, but turns out I am either delusional or simply left it in Fredericksburg. Either way, because I’m obsessed I bought another Crush Roller board I found for a decent price in Germany along with a spare Moon Cresta board. The latter board is for the cocktail cabinet in Zach Davis is minding for me in Portland, Oregon, and I want to install and test the high score save kit on this one before shipping it back once I am in New Orleans next month.

Anyway, back to the spare Make Trax and Super Cobra boards. The Make Trax spare works, but the sound is noisy. It’s as if the sound pot is not working correctly and there it is too loud and scratchy, so will need to track that down a new potentiometer (pot) and see if tracing the audio gives me any insight. This board will be the first real PCB work (besides my botched Stargate repair attempts) I’ve attempted in earnest, and I’m hopeful it’s the start of some basic board work.

If it goes well, the second project will be Super Cobra, which has an issue with the high score save kit. There are weird special characters in the high score save (HSS) kit and free play is not working. When I substituted the original roms—this board has several ROMs removed given they are programmed on the HSS kit—and Z80 chip from the working board the special characters went away. That said, there was then a strange rebooting issue with the game that did not happen with HSS kit in, so I’m going to buy new chips and  burn the Super Cobra roms (a first for me). After that, I’ll try to track down the random rebooting issue, which is definitely an issue I can isolate to that board, should be fun!

As far as other work, I am making headway on monitor chassis repair. I had the spare Hanterex Polo in Cheyenne sent in for diagnosis given the original is stuck in the US on what’s shaping up to be an almost a 6-month wait, which I’m not thrilled about. I’ll keep pushing on the US repair, but in the meantime if the spare board is fixed here in Italy I can finally get this game back online. If that happens, then I’m just one G07 chassis and one K4600 chassis away from having everything running. I was able to repair the Condor G07 chassis that was dead by doing a cap kit, swapping out a new B+ filter cap as well as a horizontal width coil, and the chassis is working pretty well, but there’s a slight undulating wave that Tommaso tells me is good enough, but it’s annoying me, so I do think I need to replace all the adjustment pots, especially for vertical linearity and vertical hold.

In fact, I was certain I bought spare G07 pots, but I can’t find them for the life of me (part of the quest for order undertaken this week), so I’ve been parting out one of my extra, non-working G07 chassis. I’m also waiting on some 1.25 AMP fuses that should come today to try and get the chassis that came out of Pole Position working again. I think this chassis has either a bad flyback or a bad voltage regulator given there has been a recent cap kit done already. I might also need to swap the B+ filter cap. If that works, it will be put in Robotron, which leaves only the K4600 chassis for Challenger (I put Challenger‘s 4600 into Venture to get that game up and running) to repair. I’m not sure what is up there cause I swapped flyback and there was a recent cap kit, so a bit perplexed, but hopefully we some poking around and testing that will be the final piece of the puzzle. This is where the chorus sings, “Hope springs eternal in the bava heart.”

Finally, I have the Make Trax cabinet totally stripped and with Alberto to add wheels because every game will be on wheels sooner than later in the bavacade. The cabinet, overall, is close to mint save the control panel overlay which cracking. When Tim and I were getting Reclaim Arcade up and running I came across an original control panel overlay for this game and snagged it, it was one of the things that came over with the container so I asked Alberto iof he could remove the old one and add this one, and as he says to everything, “No problem!” He’s the best! He removed the old one, which by all accounts from Tim is a totally nightmare, and got it sanded and cleaned up.

After that, he put on the new overlay and it looks like new! So good. Sometimes those things I bought that I thought “Will I use this” are now almost all in use, and that makes me happy.

I think the next game to go on wheels will be Elevator Action, so will start taking that one apart, and that will mean 16 of the 30 games in the bavacade will be on wheels, and that means I am have crossed the half-way mark, which is encouraging progress! It also means I will have stripped almost every game down to just the cabinet if I manage to get wells on all of them. That’s pretty awesome.

Arcade Therapy

I’m back from a trip to both Fredericksburg, Virginia for Reclaim Open and after that Long Island, New York for some extended family time. All of that coming off several days in Lisbon, Portugal, so I was feeling the effects of being on the road for a bit. I have a lot to say about Reclaim Open, and that will begin here shortly, but before that I need to ease back onto the blog, so I’ll highlight some of my recent work in the bavacade.

Turns out the arcade work can also do double-duty as a kind of re-entry therapy. My bipolar gets pretty acute when I’m on the road and away from the family for a while. If I’m not mindful my thoughts can begin to spiral. So for this re-entry—before blogging or jumping headlong back into work—I took some time to tinker on a few games. I usually lug a bunch of arcade parts, repaired boards, chassis, etc. back from the US, and this trip was no different.* On top of the random parts, I also retrieved a few game boards I had shipped during my last trip to the US in February (including Sidam’s Condor, Exidy’s  Cheyenne, and Nichibutsu’s Moon Cresta). On top of that, I took a few with me from Italy, namely a Moon Patrol bootleg board with sound issues, a Bagman with sprite issues, and my back-up Yie-Ar Kung-fu board. So, in short, a lot of boards to be looked at, and below is the tale of the tape for board repairs:

• The Sidam Condor board had a boot issue and missing star field caused by a bad 74LS32 chip. Mike ordered a MN6221AA melody chip and replaced that.  The last problem was that the foreground was shifted to the left, cutting off the “F” in Fuel on the left hand side of the screen. This was fixed by replacing chip 74LS00 at location J4. Seems like pin 6 of that chip was stuck at a logic high and never moved.
• Moon Patrol bootleg- dead sound cpu, replaced but still no sound. Traced sound all the way back to the amp. The problem was the folks who made this bootleg pcb switched the +/- speaker wires on the edge connector. Simply swapping the wires at the speaker fixes this.
• Yie-Ar Kung-Fu – there was nothing wrong, no graphics problems, sound or control issues. This means power is the issue creating sprites, need to test this hypothesis once that cabinet is put back together, more on that custom project setup shortly
• Bagman – the Z80 cpu was bad, but Mike did not report any sprites issues after it was fixed. I had recurring sprite issues and assumed it was a board/chip issue, but turns out it was power, as it always is. +5V DC needed to be raised a tad.
• The issues with the Cheyenne board were linked to the 440 Multi-kit. Turns out the the sound portion of the Exidy kit was causing the no sound condition.The logic portion (the kit) had a problem coming from the GAL chip. Specifically, addresses 14 and 15 were missing and these addresses get generated by the GAL chip.  The game boots and plays fine, but opted to remove the 440 Exidy kit and re-install original Cheyenne chips, now to fix that Hanterex Polo to get Cheyenne back up and running after nearly 10 months of that game being offline.
• Moon Cresta was a strange issue, it was working fine until Zach and I tried swapping out the main CPU chip for a high-score save kit. Once we did that the game just threw garbage to the screen. Turns out the chip (and or high score save kit) needed to be soldered directly to board given the socket was not making contact with the chip’s legs— which seems odd. That said, the board is working again without the high score save kit, so might need to solder the HSS kit directly to board, we will see.
• The non-working spare Dig Dug board was the final one Mike worked on, and that board had a bunch of missing chips, so that was a full blown salvage mission, but it works a treat.

That’s a fair amount of board work, but as of now there are no bad boards,. This will be a short-lived victory, but I’ll take it.

Next up is monitor chassis repairs.  I have two G07 cap kits (Robotron and Condor) I need to do, as well as a K4600 capkit for the Centuri Challenger. After that, the final project is the Hanterx Polo, which has been drawn out way too long, so I’m trying to resolve that sooner than later.

The other work happening has just been some random testing of parts and boards I brought back, such as testing a 15-pin Williams power brick for Make Trax: it works fine. I’ve also been testing boards like Condor (looks and sounds amazing)  Bagman (working again and power adjustment fixed the power-induced sprite issue), Dig Dug (works perfectly), and Zach reported back Moon Cresta is all systems go. So Cheyenne, Moon Patrol, and Yie-Ar Kung-fu are the last boards to test, but two out of the three will need to wait until the games are back online. That leaves Moon Patrol, and I’ll be testing that here soon.

This weekend I fell down a repair rabbit hole. I picked up a degaussing coil in the US, and brought it back to add the final touch to Exidy’s Venture (one of my absolute favs) which had a bit of discoloration on the CRT. The degaussing fixed the issue, but soon after the game was freezing and eventually it seemed the monitor was cutting out. When I adjusted voltage the screen came back, but this time with mono-chromatic colors and it was out of  sync. Major bummer. I started troubleshooting which lasted deep into Sunday to finally learn the monitor’s fine, but one of the chips that controls the color and sync (chip 13C) needed to have the solder re-flowed. I did that and re-seated everything and the game started working again and looking better than ever. That was a small, but rewarding, win.

It all becomes pretty consuming for me (which is true of most everything I do), but I find that focused attention and tinkering to solve small, elusive problems can be just what the doctor ordered when trying to return to a much needed work/life rhythm. Arcade therapy! But not so much playing the games these days as fixing them which is a really pleasurable, if unexpected, consequence of getting into this hobby.

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*I even found all my Dungeons & Dragons maps and guide books feared lost, but that is a post for another day.