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Model II power supply advice

D

dhoelzer

Veteran Member
Joined
Oct 20, 2012
Messages
523
Location
New York
Hello!

First, I'm by no means a purist. I love my vintage computers, but they are like my antique cars; I don't care if the parts are original as long as it's reliable. This is why I'm happy to rip stromberg carburetors off of my GT-6 and replace them with twin SUs. They're both carbs, they're both british but the SUs are way more reliable and easier to work on.

That said, I've taken apart my Model II. My god, the engineer who "designed" how this case fits together should be shot. Every single screw requires either an 8 inch screw driver or five other things to be removed before you can get at it! Anyway, I've been having some spotty memory issues and spotty start up. The thing has never been apart so I'm sure that the 35 year old capacitors could use replacing.

Now that I have it apart I'm looking at the size of some of these babies and thinking seriously about replacing the entire module with this: http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_323812_-1

Based on the tech reference for it, the typical load on the original supply would be 4+ amps on 5 volt, 2.25 amps on 12 volt, 1.3 amps on 24 volt and .1 amps on -12 volt. I believe the above power supply can meet that capacity with no problem. All I'd need to do is mate the connectors to the rectangular 15 pin connector.

Is there any good reason that you folks can give me why I shouldn't? I think I'd shed a few pounds in the process as well, which would be welcome since the case "flexes" under its own weight when you try to move it as it is.

Thanks folks. Any input is appreciated.
 
dhoelzer said:
Hello!

Is there any good reason that you folks can give me why I shouldn't? I think I'd shed a few pounds in the process as well, which would be welcome since the case "flexes" under its own weight when you try to move it as it is.

Thanks folks. Any input is appreciated.
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I have replaced the 12 volt part of my Model II power supply with the same type of power supply as you want to use to improve the quality of the video part of
my Model II. It is a good and very stable device, I think you can save use it to replace the main power supply.
 
If it means another Model II is up and running, I say more power to you. More power...get it? :)

Please document your modification and share it when working. I'm sure it will be helpful to others in the future.
 
Will do.

pski said:
If it means another Model II is up and running, I say more power to you. More power...get it? :)

Please document your modification and share it when working. I'm sure it will be helpful to others in the future.
Click to expand...
 
Hello again!

The power supply arrived from Jameco last week and I finally had a few minutes to go downstairs and fool around. The short story is that it works wonderfully. I'll have to post some pictures.

To make my life easier, I used a saw to remove the portion of the original power supply board that had the original power connector that runs to everything else in the chassis. That done, it was just a few minutes soldering to put some 16 gauge wire onto it and tie that into the power supply. A few self-tapping sheet metal screws and everything's buttoned up just fine. The screen is rock solid and not a single memory error to be seen.
 
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Great news! Looking forward to the pictures. It's nice to know there is a modern almost drop in replacement for the MII power supply. I imagine this unit would have no issues powering a full card cage.
 
It shouldn't I forget the amp rating but it should be more than sufficient.

I was actually pleasantly surprised to find that the display is powered off it the connector rather than something pulled off of windings on the transformer. That's been the sticking point with doing the identical drop in on a PET, for instance.

pski said:
Great news! Looking forward to the pictures. It's nice to know there is a modern almost drop in replacement for the MII power supply. I imagine this unit would have no issues powering a full card cage.
Click to expand...
 
Full replacement. I bought a supply for $35 that supplies all four required voltages. You can see the link to it in the original post. I haven't bothered with a wiring diagram since the tech reference manual is very well documented and I simply reused the connector from the original power supply.

JonB said:
You didn't say if the Jameco supply was a partial replacement (12v only) or full. Have you got a wiring diagram?
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