I spent much of this weekend digging in onย 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.
Image of G07 chassis with yoke connector
All told I have at least 7 cabinets that have a G07 chassis. There may be more, but Iโm 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. Iโve 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!
More detailed image of a G07 chassis
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.
The multimeter has proven to be the most indispensable tool of them all
I already talked about the first successful G07 repair this week in my โbavacade Repair log from 6-29-2023,โ noting โI 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.โ 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 thatโs 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,โ 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 firstย 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
G07 chassis with vertical collapse
Thatโs a new one, but Iโve read about it on forum posts innumerable times. I figured Iโd have to deal with it sooner or later, so I embraced the challenge to broaden my experienceโlearning 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. Itโs also been linked to the x401 and/or X402 trasnsitors, so you wanna check the values there. Iโve 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 โresistedโ replacing any resistors just yet given I didnโt find any open circuits, just issues with value range (assuming a low resistor value would not cause the total collapse, but Iโm 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 donโt 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.
The dark splotch on the flyback is where it burst and started leaking
At this point I decided to step away from the Pole Position chassis, and turn to the other one that wasnโt 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 voilร 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, Iโll 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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*Iโve yet to dismantle a cocktail cabinet, but that task will probably be coming soon given some work needed on my Pleiades cocktail cabinet, I donโt trust the adjustable metal legs on that game and want to get them properly lubricated and adjust with the write screws.
โ 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 โ posts, read more on this on the KLOV forums here.
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, Iโve 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 itโs very exciting. I also documented some of my work a couple of weekโs ago testing various parts I bought in the US in the โArcade Therapyโ post, so things are definitely moving along.
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 Iโd bought and brought to Italy over, but turns out I am either delusional or simply left it in Fredericksburg. Either way, because Iโm 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.
The mint Moon Cresta Cocktail machine in residence at Cast Iron Codingโs HQ
Anyway, back to the spare Make Trax and Super Cobra boards. The Make Trax spare works, but the sound is noisy. Itโs 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) Iโve attempted in earnest, and Iโm hopeful itโs the start of some basic board work.
Stargate Yellow Screen of Death
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 romsโthis board has several ROMs removed given they are programmed on the HSS kitโand 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 Iโm going to buy new chips andย burn the Super Cobra roms (a first for me). After that, Iโll try to track down the random rebooting issue, which is definitely an issue I can isolate to that board, should be fun!
Shot of Super Cobra with weird special characters in high score
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 whatโs shaping up to be an almost a 6-month wait, which Iโm not thrilled about. Iโll 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 Iโm 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 thereโs a slight undulating wave that Tommaso tells me is good enough, but itโs 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 canโt find them for the life of me (part of the quest for order undertaken this week), so Iโve been parting out one of my extra, non-working G07 chassis. Iโm 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 Challengerโs 4600 into Venture to get that game up and running) to repair. Iโm 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, โHope springs eternal in the bava heart.โ
Cracks in the Make Trax control panel overlay
Cracks in the Make Trax control panel overlay
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, โNo problem!โ Heโs the best! He removed the old one, which by all accounts from Tim is a totally nightmare, and got it sanded and cleaned up.
Sanded Make Trax control panel ready for the like-new original overlay
After that, he put on the new overlay and it looks like new! So good. Sometimes those things I bought that I thought โWill I use thisโ are now almost all in use, and that makes me happy.
Albertoโs work on these cabinets continues to blow my mind, this control panel is, indeed, like new thanks to his craftsmanship
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. Thatโs pretty awesome.
Iโm 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 Iโll 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 Iโm on the road and away from the family for a while. If Iโm not mindful my thoughts can begin to spiral. So for this re-entryโbefore blogging or jumping headlong back into workโI 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 Sidamโs Condor, Exidyโsย Cheyenne, and Nichibutsuโs 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:
Thatโs a fair amount of board work, but as of now there are no bad boards,. This will be a short-lived victory, but Iโll take it.
Next up is monitor chassis repairs.ย 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 Iโm 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. Iโve also been testing boards like Condor (looks and sounds amazing)ย 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 Iโll 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 Exidyโs 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 ofย sync. Major bummer. I started troubleshooting which lasted deep into Sunday to finally learn the monitorโs 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.
Iโve been pretty busy knocking out my to-do list for the bavacade. I created a long one after returning from the US, and Iโve gotten through most of it, so might be a good time to create a log with work done over the past month or so.
Back of pac-man painted
Pac-man Multi-game HSS Kit
High Score Save Kit for Venture
Cheyenne original ROMs
Big Blue Capacitor (Atari Power Brick)
12V Power Switch for LED Marquee Light in Dig Dug
Still to do: