Monitor Meltdown

Spent this week straining my back moving CRT monitors like it was the 90s again.

First was revisiting an Electrohome G07 that developed an exciting new failure after I recapped it and replaced the flyback transformer a few months ago. It would just energize but not show any picture. I checked the horizontal output transistor first since it hadn’t been replaced and they’re a common failure point. It was in fact blown so I threw a new one in, which yielded this…

It’s a start, but we need more than a quarter of the picture. I started by checking transistors X401 and X402, which metered fine. Then, worked my way through the resistors in the 400s and everything was within tolerances there. Then I reflowed some dubious traces and all the header pins. Still nothing after all that effort, which left me a bit stumped.

I decided to swap out X401 and X402 just because, and after swapping X402 got a screenful of Badlands again. So! Lesson learned, testing a transistor with a DMM doesn’t necessarily tell the whole story.

Second part of the CRT adventuring comes from the basement of one of Portland’s late bowling alleys. Hollywood Bowl closed recently after over 50 years, another casualty of the explosive redevelopment of NE Portland. Earlier this year there’d been some rumors, but they’d insisted their lease was intact for a long time to come and they had no intention of shutting up shop. Apparently someone threw enough money at the situation to break through and now we’re losing one of Portland proper’s last bowling alleys to make way for… A hardware store. What a waste.

My disappointment with that turn of events didn’t prevent me from touching down on the site like a starved vulture when it came time for the fixtures to be auctioned off. This past Wednesday I secured a few banks of Brunswick lockers, the big lighted ‘Entrance’ sign from the parking garage, and a few other small things. While I was there I noticed a big pile of overhead monitors in a corner of the garage that had been on the auction catalog initially but were pulled… I inquired about them and was told they were destined for the dump. Sooooo I did what any self-respecting scrounger would do and loaded a few up while retrieving the stuff I bought.

They’re Brunswick Frameworx system 27″ overhead displays, designed to be hung over the approach area of the bowling lanes and display scores and those dopey animations that play when you get a strike. The guts are a Ceronix model 2793 chassis and a little Brunswick board that gets fed off the 36V output from the isolation transformer and does some conversion of the signal from the scoring system, as well as controlling power to the monitor via a relay.

The Ceronix chassis is a standard CGA deal and it didn’t take a whole lot of modification to get the thing displaying the image from an arcade board.

I had to bypass the Brunswick board by removing its 36V power connection, and bypassing the monitor power relay and connecting the AC output from the isolation transformer to the Ceronix power input directly.

Then I took the video input harness that goes between the Brunswick board and Ceronix chassis, clipped off the Brunswick end, and fitted a Molex connector to mate it to an arcade wiring harness.

Hooked up my Cyberball 2072 board to test and dial in the adjustments.

Not too shabby for a freebie!

There is a service bulletin from Brunswick regarding these monitors, and the Ceronix chassis in particular. From reading old threads on Bowltech it looks like these chassis were prone to a manufacturing issue that led to weak or absent solder traces. Repairable, but definitely worth being aware of. It’s also likely that most or all of these things still in service will have had the defective components repaired or replaced by now.

Crimp, seat, repeat

The ‘Gallag’ Galaga bootleg board I was planning on dropping into my project Midway cocktail cab shit the bed at some point during handling. I got it staged for installation, partially wired up, and then found I couldn’t get a useable video signal out of it. I could get a few frames of the attract screen when it wasn’t uncontrollably rolling, but even then everything was tinted red. I thought the G07 monitor chassis might be to blame, but swapping that out with a known good one didn’t elicit any change. Time for plan B.

Earlier this month the Gorf control panels I bought came in the mail. They were cheap, match the original equipment for the cab, and are a two axis joystick with single button configuration which works for a ton of games. This past Friday I picked up a pair of 60 in 1 multi game boards locally for a pretty decent price. Finally, I had a generic JAMMA standard harness from a cut corner Dynamo cab I salvaged parts from several years back when the High Score arcade in the Dimond Center closed.

I started combining all of these bits and pieces, got stuff laid out on Friday and was able to get video from the multi board. Good sign…

I used connectors salvaged off of the super hacked up Galaxian harness that came with the Gallag bootleg board to interface the JAMMA harness cleanly with the Gorf control panels. I picked up a ton of tools and pins to use with Molex connector bodies over the past few weeks. My end goals are making everything I build from here on out very modular, and cutting out butt splice and blade connectors as much as I can.

Ended up having to special order the .084″ MLX style connectors that are common in the golden age arcade games since they’re obsolete and weren’t carried by URS electronics. I was able to get the .062″ and .096″ standard and KK stuff from them though. I’m told I’m their #2 consumer of Molex products now… That’s a little scary.

Getting things squared away. I was testing intermittently here to make sure I had my inputs wired up correctly, and noticed the colors were distorted on one side of the monitor, but only when the cabinet was closed. At first I though it was due to the speaker coil being close to the tube, or maybe the isolation transformer… Turns out though that if you drastically change the orientation of a monitor some funky stuff can happen with magnetic fields and you’ll get odd results. Fortunately, degaussing will fix it, and in this case the built in degaussing coil on the G07 was enough to solve the issue.

The finished product, more or less. I need to clean up the AC wiring a little bit still, there’s a lot of slack in there from the pigtails I built for the power switch and ventilation fan.

The cab is totally playable at this point, I’ve got it booting straight to Galaga. Might try to find either a Galaga or Gorf top glass, but that’s pretty low priority since this thing is a total Frankenstein regardless of any changes. The things I 100% need to do are get a set of the plexiglass filler pieces that go behind the control panels, and wire up lighting behind them, and a set of strike brackets for the latches that hold down the table top.

Might also try to shore up the far side of the table top from the hinge since it’s bowed a bit which allows a lot of stress to be placed on the glass on that edge. Happy with the results so far though and looking forward to getting some competition going on this one since I know Galaga strikes some nostalgic chords for a lot of people.