How to install a switcher?

cwilkson

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Gonna upgrade a couple of B&W games to use switchers. I was trying to keep the games original in all the technical aspects, but I'm tired of being defeated by some hack repair that left loose solder balls hidden under components 20 years ago. It's time to make a change.

Some games use a seperate regulated linear supply. They send DC to the boards. For +5V I should be able to simply unplug that and slap the switcher in it's place.

But what about the higher voltages? Is it ok to drive +15V and +18V (and god knows what other weird voltages) using the +12V from a switcher? Those usually only supply the audio. Will I loose too much head room for my amplifiers (or PLLs, or FSKs, or whatever other esoteric audio stuff is there)? Is there anything else to worry about on those supplies other than audio?

Next, I have a lot of early boards where the transformer connects directly to the edge connector to supply AC to the board. It's rectified, filtered, and (linear) regulated on the board. I don't have those magic transformers for my loose Bronze Age boards. What's the standard practice here? Is there one? I can make it work, sure. But I'd like to do it the same way everyone else does to save confusion later.
 
When I have PS problems on these games, it's typically the +5. What I do is let the original PS run the funky voltage, and I attach a ground and +5 wire from the switcher to the connector, removing the original +5...
 
When I have PS problems on these games, it's typically the +5. What I do is let the original PS run the funky voltage, and I attach a ground and +5 wire from the switcher to the connector, removing the original +5...

Yep yep. Had do do that with a Pole Position and Dig Dug (so far).

Left the original AR PS in there for the higher voltages needed for audio, but cut traces and tied the +5 and +sense together, and ran +5 and GND directly to the test points.
 
When I have PS problems on these games, it's typically the +5. What I do is let the original PS run the funky voltage, and I attach a ground and +5 wire from the switcher to the connector, removing the original +5...
Yeah, that's what I planned to do on Death Race, which uses an external regulator. Leave the high voltage alone (15VDC or whatever it is) and use +5VDC from the switcher. How about ones with on-board regulators? Is it enough to pull the 7VAC wires out of the edge harness and solder the switcher leads to +5V and GND on the PCB? Or should I also remove the output components (power resistor and pass transistor) from the linear regulator on the board? I don't like cutting power traces....that's permanent. But I can do that if it's what is normally done.
 
Yeah, that's what I planned to do on Death Race, which uses an external regulator. Leave the high voltage alone (15VDC or whatever it is) and use +5VDC from the switcher. How about ones with on-board regulators? Is it enough to pull the 7VAC wires out of the edge harness and solder the switcher leads to +5V and GND on the PCB? Or should I also remove the output components (power resistor and pass transistor) from the linear regulator on the board? I don't like cutting power traces....that's permanent. But I can do that if it's what is normally done.

I just suggested traces because I hate cutting wires. If there's any way to isolate the +5 on the PS (lifting a resistor, etc etc) I'd try that. Pulling the wires from the connector and tape'ng them off will work just fine as well, as long as the PS (Atari) isn't try'ng to find that +5 through the board.

For boards with regulators on the board... just bypass them, find a joint or pad you KNOW is +5, and tack the +5 there, and GND to a place you know is ground. Then you won't have to worry about the regulator, you'll get get your +5 and GND, and you've avoided destroying (hopefully) anything. I had to run a Ms. Pac like that for a while until I got around to repairing the edge connector. Just tacked a +5 line, and GND line and she worked like a champ until I got off my lazy butt and fixed the edge.
 
A lot of times (like with the 7vac to a Ms. Pac-Man board), instead of cutting wires or traces, you can simply remove the fuses for those voltages. No fuses means no power. Plus, it makes it easier if ever decide to make it original again....
 
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