MAME cabinet, new display
When I finally dared powering up the video monitor I modified for my MAME cabinet, it failed immediately accompanied by a quiet *POOF* emanating from the direction where the internal glass fuse is. Great.
No idea what might’ve gone wrong, though a safe guess is it must’ve been somewhere with my wiring or board installation. After all, the monitor did work prior to disassembly and installation.. I labeled all connectors prior to disconnecting them and checked the modified cables for resistance prior to powering up; no problems there. As far as I know, the extended cables weren’t the high voltage ones either, thus the added length shouldn’t pose a problem.. But despite putting in several hours looking at the connections etc., I was still unable to spot anything. The fuse just kept burning..
Since I didn’t have a service manual for the monitor and I’m no expert enough with CRTs either, I chose to ditch the video monitor and go for something “new”. I wasn’t actively looking for anything in particular, moreover just keeping an eye out for whatever suitable might come my way. Just so as it happened, last november I stumbled upon this 21″ Sony Trinitron (model KV-21LT1E) at the basement hallways of the building I live in. It was just sitting there, abandoned for weeks on end and nobody seemed to care. Don’t ask why, but for some reason this kind of stuff seems to happen in the building more than often: People just dump their old stuff on the hallways “wherever convenient for the lazy fat-ass” without any regard to fire regulations or whatever. Barely out of sight equals out of mind, I guess.
Anyway, as the tube size seemed “somewhat there” and the telly wasn’t moving anywhere, I decided to haul it home for closer inspection. Sure enough, it turned out to be a perfectly working one minus a missing remote. There was some greenish tint on the lower left corner, but I thought it to be not that bad for the screen to be considered unusable. Could even be curable by degaussing the tube, if there aren’t any on-board electronics for this purpose.. New display, on to installation then!
Dismantling the telly for installation inside the cabinet, it turned out that one of the internal degaussing cables had been dislodged. The greenish tint was probably because there was the internal speaker pretty close next to it; with the cable out of place, the tube wasn’t degaussed properly during the power-on cycle.
Test-fitting the bare tube, it turned out rather snug fit dimension-wise. Slightly bigger view area than on the old one, but still small enough to fit the opening. As much expected, the new tube needed customized mounting solution just like the old one. After some junk box digging sessions, I settled for a square aluminium tube. Easy to machine (as aluminium always is) and there was just enough of it; a minimum of 13cm was required per mounting support, but I went with 15cm for the upper and 16cm for the lower supports. This made it easy to distinguish which part goes where.
I decided to add a threaded hole to the “tube end” of the support in order to simplify fastening. 5mm bolts seemed like the way to go. I had no idea for a recommendable ratio for between a drilled hole and its threading, so the first piece got drilled with 4,8mm bit. This was ok for a very light fastening but the threadings broke once the bolt was screwed in more tightly. The second time around, I used a 5,6mm bit for the hole and a 6mm bit for threading. Lesson learned: if you make a threaded hole, preferably pick a drill bit about 0,5mm smaller than the intended bolt size :)
I didn’t bother drawing up any schematics for the support, the cutout dimensions were just roughly sketched over the piece of aluminium. Figuring out the final shape for the first piece took maybe about an hour, but once that was completed making the remaining three took somewhat similar amount of time all in all.
As for the electron gun end of the tube, my rough estimate proved way more tight than expected. Because of the size of the electronics board and it’s angle in regard to the rear wall of the cabinet, the board simply didn’t fit in. So, I desoldered the tube socket from the board and added short extension cables to each of the pins. Currently, the electronics board simply hangs loose by the wires, not sure whether I should fashion some kind of a custom bracket for it..
Once the wiring was complete, not much else to it than bite the bullet and see whether the tube works or the cabinet burns up in flames..
Not to fear, off it goes! As the degaussing cable was now in its correct location, the green tint disappeared \:D/
For the test, I hooked up my PSOne to the screen and then spent a good while playing Metal Slug X. No burning smells or visible flames after about 20 minutes, so I guess it’s ok! Currently, as there is no remote there’s the green channel indicator constantly displayed on-screen. Have to see if I can locate a proper remote somewhere, the service manual suggests it should be RM-884 or similar.