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altair 8800 question

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k1atn

Experienced Member
Joined
Apr 28, 2013
Messages
106
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Albuquerque
i am having trouble finding switching power supplies to power the Altair 8800.

grant stockly said he had put an 8v 100 watt switching power supply and a +16v/-16v/5v 60W switching power supply in his kit, but i cannot find ANY switching power supplies WHATSOEVER on the net with those specs. if anyone knows where i can get power supplies with those specs it would help a lot in my running the Altair 8800 with a switching power supply.

thanks

k1atn
 
Someone with Grant's kit (or Grant!) could answer this question with authority, but my observation is that the 8v supply is provided by a Mean Well NES-100-7.5 power supply (13A at 7.5 volts, adjustable up to 8v with no problem, but you could safely run at 7.5v since the power supply's output will have less droop than the original linear supply). The second supply is probably a Mean Well NET-75-C (+15 at 2A, -15 at 0.5A, +5v at 6A). The +/-15 supplies easily meet the Altair 8800's requirements and the 5v output is not used.

Mike
 
I'm using the following to run an S-100 backplane.
Jameco: 2100857 - PWR SPLY,SW,OPEN,25W,+/-15V@1A
Jameco: 2105800 - PWR SPLY,SW,OPEN,65W,7.5V@8A

When I bought these in 2010 they were under $20 each.

Kipp
 
i want to use a PC desktop power supply, can it be done?? can i modify it to bring the 5 volts on it up to 7.5v or even 8v, and the 12 volts part of it up to 15v and or replace a regulator to get the +15v and -15v because that's what i really want to do.
 
k1atn said:
i want to use a PC desktop power supply, can it be done?? can i modify it to bring the 5 volts on it up to 7.5v or even 8v, and the 12 volts part of it up to 15v and or replace a regulator to get the +15v and -15v because that's what i really want to do.
Click to expand...

Not easily. You would likely have to change a few feedback resistors and take care to not exceed the voltage ratings of the rectifiers and output caps. Note that some of the outputs are semi regulated so if you increase the 5V output to 7.5 volts several of the other outputs may "track" upwards.
 
kyeakel said:
I'm using the following to run an S-100 backplane.
Jameco: 2100857 - PWR SPLY,SW,OPEN,25W,+/-15V@1A
Jameco: 2105800 - PWR SPLY,SW,OPEN,65W,7.5V@8A

When I bought these in 2010 they were under $20 each.

Kipp
Click to expand...

I have a "test" S100 sytem that I use for prototyping and various testing activities before putting the cards into my IMSAI. These are the same supplies I use for that setup and they work fine. I believe both have output adjust pots that I might have tweaked a bit but they work great.
 
I've got the Mean Well NES-100-7.5 supply, a fine +8 supply. All cards with non-margninal regulators will work fine down to 7 V, and they'll run cooler.
 
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