[time-nuts] Using a common power supply among few time standards

[jimlux]

On 2/7/20 7:01 PM, Taka Kamiya via time-nuts wrote:
> I recall S-100 scheme had an issue of per-board regulator failing short and dumping 8V into bus killing rest of the system....

More like the 5V regulator (most likely a trusty 7805 in a TO-3 package) 
shorting, applying 8V to all those TTL parts on the board, which die, 
and put 8V on the address and data lines.  However, I'm not sure that 
was a particularly common failure.  In many years of working with a lot 
of S100 systems, I never had that problem.

> I am thinking of making use of 28V (aircraft power supply?) regulated power supply, and have local linear regulator to created needed voltages.  One concern is, should I need large amount of 5V then loss will be tremendous.

Probably a better solution is multiple bulk supplies off line AC then 
regulate down. Or a DC/DC from 28V to 8V, then good linear regulator to 5V.

There's really no way around it, although you can do things like 
synchronize all your PWM converters, so if you do get spurs, they're in 
consistent places.


   I just came across an article that discussed magnetic field 
sensitivity of LPRO-101.  The author ended up relocating the transformer 
off-board.  (in a different case)  A very timely information as this is 
what I am actually working on.
> Further comment will be appreciatedTakaTime-nut in training
> ---------------------------------------
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
>   
> 
>      On Thursday, February 6, 2020, 6:51:38 PM EST, jimlux <jimlux at earthlink.net> wrote:
>   
>   On 2/6/20 3:14 PM, Will Kimber wrote:
>> Hi,
>>
>> Usual (best?) is supply slight over voltage and use LDO/RC filtering in
>> each unit as Bob suggested. But that would require either supplying
>> 24v/12v/5v/-12v (with some margin 10%?) or converting some single supply
>> of 24v or 48v  in each unit to required voltages at each piece of
>> equipment.  The later requires switching supplies to get all voltages.
> 
> 
> Well that was the strategy used on S-100 boards. Bulk 8V unregulated
> supply regulated down to 5V on the board.
> 
> 
> 
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