From: Greg Menke Subject: Re: TECH: Possible Gottlieb "upgrade"?? Newsgroups: rec.games.video.arcade.collecting Date: 14 Oct 2002 17:56:01 -0400 "Rob Carroll" writes: > Hey, advanced techie guys... tell me what you all think of this. > > First, the inspiration: > Got a Reactor. Lost +5V... after digging, I think it's the transformer (and > not the bridge rectifier as I originally thought). ANYways... I'd love to > replace the whole power supply with a modern switcher. > > The problem: > LM379 on the sound board needs 30VDC. I suppose I could leave the original > PS in the game to supply the 30, since that circuit is still working, but > I'd prefer not to. > > Additional consideration: > If/when the LM379 finally shits the bed, they're tough/impossible to find. > > The idea: > Replace the LM379 with an LM380 which was, according to some Google searches > I've done, once considered a viable replacement, but was then discontinued. > They're available again - datasheet at www.national.com. LM380 only needs > 12VDC. That way I can do away with the original PS completely and use a > modern switcher. I think the pinouts are *slightly* different, but that's > no biggie. > > What say ye? Have I unwittingly stumbled onto something? http://www.ionpool.net/arcade/gottlieb/reactor.html has the manual pdf for Reactor which includes the schematics for the power supply. Have you tested for 12vdc coming thru fuse F11? If its there, then your xformer may be OK but the series pass regulator may be dead (I'll bet a penny on that as you said only the +5 was dead). Assuming this is the case then the following might help; Look for resistors R13 and R14 burned- they do run a little hot- replace them with 5 watt wirewounds while you're at it. The 5v regulator side uses one of the big TO-3 transistors on the heat sink and a 2nd TO220 next to it. Somebody had done a number on my Krull's ps, to the point where both of those were blown out. Considering the ratings of the 2N5879, I wonder what must have caught on fire when he/she did it. Thankfully, both parts are easy to find; Q11 2N5879, Q12 TIP31B (both have NTE crosses and you can use a TIP31A which is easy to find). Its possible U11 might be bad as it seems to be run right up at its upper limits, but mine was OK. Its cheap to replace anyhow. If you have an NTE distributor (All Hail Baynesville Electronics in Baltimore), all of these should be easy to track down. Digikey/BG Micro/Mouser & the other usual suspects should yield the parts fairly easily. Let me know if you have trouble finding the parts. After replacing the transistors, run the board without the P3 or P4 connectors attached and use a 1.5 amp fuse instead of the 6.3amp for F11- that way if you've messed something up, you won't catch anything on fire. You might consider mounting a fan to the heatsink- shifted over a bit so it blows on the other parts too- that power supply generates a good bit of heat. I assume you know all about cold solder joints on the connector headers seen on these boards- about half of them were bad on my Krull- if you've not done it, now's the time to freshen all of them. wrt modifying the sound amp to use a more civilized voltage, I think your best bet might be to track down a Krull sound amp, it looks plug compatible- Gottlieb introduced them because they got sick of the +30vdc too. Mine was mounted by sticking a wirewound IC socket thru the adapter board into the sound board, standing the board off but yielding a good fit (and providing wonderfully convienent test points). At that point, you could switch to +16vdc (like Krull)- but make sure its only the soundboard that uses it. You could probably get away with +15 from a switcher, but I'd check the datasheets. I don't think theres anything particularly magical about the amp used- all the sound effects and distortion stuff happen before the amp anyhow, so your LM380 might work OK. Good luck, Gregm