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Charlie_

Problem with "new" Mega STE power supply

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I received a NOS Atari power supply for my Mega STE from Best Electronics. It works but I see lines moving across the screen.

The original supply from the system does not suffer from this problem. I attached a video. Any ideas what could cause this?

 

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I hate to be one to auto-blame the caps, but this case it probably is due to an AC line noise filtering cap.

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Problem solved.

Turns out there needs to be an isolator between the center screw hub and the power supplies PCB.

There are 5 screws that attach the PCB to the metal under frame. Four at the corners and one in the center.

I used a Mead notepad cover, cut it the size, poked 4 holes for the corner screws and slid it under the PCB above the hubs. Installed the 4 screws and left the center screw out.

So far, so good. Computer is performing excellent.

Only thing I am concerned about is the notepad cover I used. Is it a suitable isolator in the long run?

 

 

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3 hours ago, Charlie_ said:

Problem solved.

Turns out there needs to be an isolator between the center screw hub and the power supplies PCB.

There are 5 screws that attach the PCB to the metal under frame. Four at the corners and one in the center.

I used a Mead notepad cover, cut it the size, poked 4 holes for the corner screws and slid it under the PCB above the hubs. Installed the 4 screws and left the center screw out.

So far, so good. Computer is performing excellent.

Only thing I am concerned about is the notepad cover I used. Is it a suitable isolator in the long run?


I recently bought that PSU also, and Bradley’s instructions say to remove the center screw hub, as it makes contact with leads on the bottom of the PSU. 

I took a drill to the center standoff on the metal mounting plate for the PSU, solved that problem. 

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2 minutes ago, Bikerbob said:

Interesting.. this is for a PS-5341???

 

James

Yes. Apparently there is a 4 post and 5 post  version. I guess if your using the insides of a 4 post version on a 5 post frame you need to remove the center post or isolate the board from the center post. 

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I have some lines on one of my PSU.. or at least thats what I think it is, and I am planning to re-cap.  The other seems really good.. but if the MB serial is any indication its older than the first one.

 

So I know yours is new old stock.. not sure how to know .. when old is OLD.

 

James

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1 hour ago, Bikerbob said:

I have some lines on one of my PSU.. or at least thats what I think it is, and I am planning to re-cap.  The other seems really good.. but if the MB serial is any indication its older than the first one.

 

So I know yours is new old stock.. not sure how to know .. when old is OLD.

From what I understand, the five post version, which is what mine and the OP's are, is in the first revision of the Mega STE.

 

But seriously, I just took a drill bit to it and removed the center post entirely and filed it down a bit to make it smooth. Works like a charm.

 

On mine, what would happen is the 5V and 12V lines would "pulse" - I wasn't sure if recapping it would help, so I just went ahead and replaced it. I don't mind replacing caps on motherboards but getting near PSU's for that purpose freaks me out a bit... Mains power is no joke.

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On 7/15/2019 at 2:26 PM, robdaemon said:

From what I understand, the five post version, which is what mine and the OP's are, is in the first revision of the Mega STE.

 

But seriously, I just took a drill bit to it and removed the center post entirely and filed it down a bit to make it smooth. Works like a charm.

 

On mine, what would happen is the 5V and 12V lines would "pulse" - I wasn't sure if recapping it would help, so I just went ahead and replaced it. I don't mind replacing caps on motherboards but getting near PSU's for that purpose freaks me out a bit... Mains power is no joke.

I will confirm I think you are right.. I pulled the psu from my 1991 MegaSTE and it is the 5 post model.. this is a serial with only 4 digits.  Later one i have with serial in the 5 digits 40K - 4 post model.

 

I just picked up a capacitence and ESR meter - I will check my PSUs before ripping them apart.

 

James

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well I ordered an ESR/capatence tester and also all the caps I need to redo both of my megaste's. I am going to test the one that generates the lines first.. not the values.. then test the other.. before I change any caps.. So that I can see what I get once I am done.

 

James

 

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