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Repairing power packs

power packs power supplies help

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#1 simbalion OFFLINE  

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Posted Sun Apr 29, 2012 10:26 AM

Yesterday I was playing with my Atari 800 and I accidentally bumped the end of the power cord that goes into the computer. Much to my horror, a few moments later the computer just stopped working! After doing some testing, I came to find that the power supply seemed to be drawing power, but not putting anything out. The 800 fired right back up with my spare power pack. Now, a month ago I had ended up with two earlier versions of the power supply, ones that state 400/800 on them. One had bad cords and the other was DOA, so I found that those use screws under the rubber pads to get them apart. Sure enough, the DOA one had a blown fuse, but the fuse in the messed up one was perfect, so I swapped the fuse with my meager soldering skills and got the DOA one working again.
Now, the other power pack that I suspect has a blown fuse is not made quite the same. It appears to be glued together and I am wondering, how do you get these things open short of destroying the case? Also wondering where these fuses can be found? I'm thinking Ace at least, but not sure.

#2 bob1200xl OFFLINE  

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Posted Sun Apr 29, 2012 11:45 AM

From what I understand, Atari power packs (9vac @ 3.4a) are glued together. Maybe some old designs have screws, but new ones do not. People crack them open, change the fuse, and tape them shut.

Bob

#3 firestorm OFFLINE  

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Posted Sun Apr 29, 2012 12:01 PM

My power pack for Atari 800 PAL was riveted, and when power cord got broken near the age of the box I had to cut off heads of rivets to get in opened. After the fix I just glued it back.

#4 Fox-1 / mnx OFFLINE  

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Posted Sun Apr 29, 2012 1:30 PM

When putting it together again, using nuts and bolts saves you some trouble to open it next time when the fuse needs to be replaced again..

#5 poobah OFFLINE  

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Posted Sun Apr 29, 2012 4:46 PM

I never did understand the fuse permanently sealed in side the case deal.

#6 Fox-1 / mnx OFFLINE  

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Posted Mon Apr 30, 2012 7:25 AM

If it breaks you need to buy a new power supply (from Atari). Sounds like a plan to me.

#7 kurtm OFFLINE  

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Posted Mon Apr 30, 2012 7:27 AM

I never did understand the fuse permanently sealed in side the case deal.


The fuse is for protection only. They never expected people to replace fuses, it was just included to prevent serious problems in case of failure.

#8 simbalion OFFLINE  

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Posted Mon Apr 30, 2012 12:43 PM

Hmm. Maybe my friend has an idea of how to crack the case open without much damage. He's done it before. Yep, the two early power packs I found were held together with phillips screws under the rubber feet. Both of those have the Atari logo on them and then under that it says. "For use with 400/800 systems." If I can get another output cord, I can revive the second one.

#9 AtariGeezer ONLINE  

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Posted Mon Apr 30, 2012 1:52 PM

I had to crack one open 2 weeks ago and wasn't hard, I just used a knife with a strong tip using it as a chisel, making a puncture in the seam about every 16th of an inch. Afterwards it was easy just to pry the case apart...

Jay

#10 atari8warez OFFLINE  

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Posted Mon Apr 30, 2012 2:16 PM

It appears to be glued together and I am wondering, how do you get these things open short of destroying the case? Also wondering where these fuses can be found? I'm thinking Ace at least, but not sure.


Yes they are glued and impossible to open without cutting. Just cut along the edges and when you're finished re-assemble by applying hot glue. If you're creful and patient you can do a pretty good job, although Fox's suggestion sounds good too in case you need to re-open the case in the future.

Edited by atari8warez, Mon Apr 30, 2012 2:21 PM.


#11 atari8warez OFFLINE  

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Posted Mon Apr 30, 2012 2:20 PM


I never did understand the fuse permanently sealed in side the case deal.


The fuse is for protection only. They never expected people to replace fuses, it was just included to prevent serious problems in case of failure.


Well they sometimes blow-up simply by inserting them into the drive (in case of an 1050 PS) while the drive Power switch is in the ON position. I had one or two blow-up this way. Nowdays I always check to see the drive power switch is in OFF position before inserting the plug.

#12 kurtm OFFLINE  

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Posted Mon Apr 30, 2012 2:21 PM



I never did understand the fuse permanently sealed in side the case deal.


The fuse is for protection only. They never expected people to replace fuses, it was just included to prevent serious problems in case of failure.


Well they sometimes blow-up simply by inserting them into the drive (in case of an 1050 PS) while the drive Power switch is in the ON position. I had one or two blow-up this way. Nowdays I always check to see the drive power switch is in OFF position before inserting the plug.


I was mainly pointing out there is still a point to putting a fuse in, even if it's not designed to be user replaceable.

#13 31336haxx0r OFFLINE  

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Posted Mon Apr 30, 2012 2:50 PM

An alternative route may getting a modern switch mode power supply and solder a 5 pole DIN connector to it. I know it's not a repair, but may come in handy if you're out of original PSUs. Like this one http://www.pollin.de...20_5_V_1_A.html .

BTW, that connector on that linked PSU looks like it would fit a 7800? :ponder:

#14 Fox-1 / mnx OFFLINE  

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Posted Mon Apr 30, 2012 3:39 PM

An alternative route may getting a modern switch mode power supply and solder a 5 pole DIN connector to it


Without modifying the 800 this won't do as it needs AC, not DC.

#15 31336haxx0r OFFLINE  

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Posted Mon Apr 30, 2012 4:05 PM

Really? I always thought it needs DC? Sadly, I've never seen an 800, so I can't tell.

#16 mimo OFFLINE  

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Posted Mon Apr 30, 2012 4:25 PM

Pal UK 400/800 power supplys are DC

#17 31336haxx0r OFFLINE  

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Posted Mon Apr 30, 2012 4:50 PM

If the rectifier(s) can sustain a load high enough, you could feed it with DC even if it needs AC. You'd need to have an input voltage of at least 5 Volts plus the dropout voltage fo the regulator. I strongly recommend against this mode of operation without knowing the ratings of the rectifier!

#18 BillC OFFLINE  

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Posted Mon Apr 30, 2012 5:04 PM

If the rectifier(s) can sustain a load high enough, you could feed it with DC even if it needs AC. You'd need to have an input voltage of at least 5 Volts plus the dropout voltage fo the regulator. I strongly recommend against this mode of operation without knowing the ratings of the rectifier!

The other issue is that the RAM chips on the 16K boards for the 400/800 use +12V.

#19 Fox-1 / mnx OFFLINE  

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Posted Mon Apr 30, 2012 5:11 PM

Pal UK 400/800 power supplys are DC


I find that hard to believe. Dutch PAL 800's are using AC and I can't think of a reason why it would be different in the U.K.

#20 31336haxx0r OFFLINE  

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Posted Mon Apr 30, 2012 5:17 PM

Woah, didn't know those RAMs need +12V! :o If the power circuit uses a voltage doubler approach, you'd indeed need 12V AC. If not, you may be fine by feeding it 16V DC.

#21 feather OFFLINE  

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Posted Mon Apr 30, 2012 6:06 PM

Yes, even the +5V, -5V and +12 V.

Posted Image

#22 bob1200xl OFFLINE  

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Posted Mon Apr 30, 2012 6:36 PM

It's hard to see what the power switch setting may have to do with blowing the fuse, but I have certainly done it by plugging the power pack in with the power pack on (even with the Atari switch off).

Not a good plan - turn off all the power.

Bob




I never did understand the fuse permanently sealed in side the case deal.


The fuse is for protection only. They never expected people to replace fuses, it was just included to prevent serious problems in case of failure.


Well they sometimes blow-up simply by inserting them into the drive (in case of an 1050 PS) while the drive Power switch is in the ON position. I had one or two blow-up this way. Nowdays I always check to see the drive power switch is in OFF position before inserting the plug.



#23 kurtm OFFLINE  

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Posted Mon Apr 30, 2012 10:02 PM

If the rectifier(s) can sustain a load high enough, you could feed it with DC even if it needs AC. You'd need to have an input voltage of at least 5 Volts plus the dropout voltage fo the regulator. I strongly recommend against this mode of operation without knowing the ratings of the rectifier!


Doesn't work. I have a 9v DC brick that looks almost identical to the 9vAC ones (for an Indus GT). I thought my 800 died at one point because I was using the DC brick.

#24 31336haxx0r OFFLINE  

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Posted Tue May 1, 2012 3:58 AM

Yes, know I've seen the schematic it's clear they use some interesting approach at generating -5V.

#25 mimo OFFLINE  

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Posted Tue May 1, 2012 4:27 PM

You are all absolutely correct, I'm really sorry. I convinced myself some how that the psu was dc





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