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Modernised original power supply

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I'm quite new to 99's but have been curious for years.  Finally have a bunch that I'm restoring to their proper glory.


Finally finished refurbishing a power supply from the black model - replaced all the electrolytics, replaced the "boring" red LED with a "futuristic" clear blue one, re-applied heat sink compound to the transistor and replaced the 12V and -5V linear regulators with switching equivalents (no more coffee warmer).


And it still works.


I've got more 99's than power supplies, and we use 240V instead of 110V here in Australia, so am reading with interest the other thread about using a Mean Well GP25A13A-R1B as it'd be handy for my BBC Model Bs too.


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Posted (edited)

Oh, certainly!


The 12V one is a Multicomp Pro MP-K78L12-1000R3, but there's a few you can choose from that output 12W/1A.


The -5V one, not much choice (i.e. pricey) - went for a Traco TSN 1-2450 - it's also 1A (5W) output.  The linear regulator version lies horizontally on the board and is riveted in - not a big deal, just need to snip off the rivet on one side and then pull it through the other, once you've desoldered everything.  


But the replacement has to stand vertically because of the short legs - not a problem though as there's still a few mm gap between the top of the regulator and the underside of the case.

Edited by asdf87
Forgot to mention the -5V one isn't cheap!

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I use Element 14 here in Australia as they do free, overnight shipping (if they have it in stock).




I went for the open-PCB type for the 12V as I could de-solder the right-angle header pins and solder on straight-through pins if I wanted to "lie it flat".


The enclosed ones usually have pretty short legs so you are limited to how you can mount it if space is a consideration.  The -5V one from Traco is actually pretty tall compared to others I've had but luckily there is space in the case for it.

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