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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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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?

 

 

IMG_20190712_192010311.jpg

IMG_20190712_192500106.jpg

IMG_20190712_192521682.jpg

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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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I'm replacing the P/S in my Mega STe with a new one from Best. I've drilled out the center post and cleaned the base. 

 

(1) The original P/S had N toward the switch and L toward the back. The new Best P/S has L toward the switch and N toward the back. I just checking to see if you guys put the Brown wire toward the front and the Blue wire toward the back. Basically the two wires are in the opposite position.

 

(2) Did you attache the fan to the new P/S?

 

Bill

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Posted (edited)

Its up and running, so #1 is answered. Still don't see anyway to re-attach the fan though.

 

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Edited by Bill Lange
Adding pics

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1 minute ago, Bill Lange said:

Its up and running, so #1 is answered. Still don't see anyway to re-attach the fan though.

I was told that I had purchased Bests last Atari NOS power supply. So I'm guessing you have the "Best" version of the power supply? Can you post a picture of it? Does it not have the same pins to plug the fan in like the original does? 

 

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Its a new Best power supply. The differences are there is no (obvious) place to attached the fan. The two wires from the switch to the board are reversed, brown toward the front and blue toward the back on the new one. I also had to drill out the screw mount in the center of the cast so as to not short the board. I  already have it back together, but if I take it back apart I'll take some pics.

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Just now, Bill Lange said:

Its a new Best power supply. The differences are there is no (obvious) place to attached the fan. The two wires from the switch to the board are reversed, brown toward the front and blue toward the back on the new one. I also had to drill out the screw mount in the center of the cast so as to not short the board. I  already have it back together, but if I take it back apart I'll take some pics.

Glad you have it working! Does it get very hot with no fan? 

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Not yet. I pinged Best to ask if I was supposed to re-attach it. I'll let you know what he says.

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