[ARC5] [Milsurplus] Sandy Coolness for Our BAs

[Tom Lee]

If this part is like some of the TV regulators I've encountered in the 
past, the base terminal needs to be pulled up to the unregulated input 
voltage through a resistor. Depending on the input-output differential 
you seek, the resistor will be of the order of 10k or so, typically. 
Frequency compensation is also frequently required, and the base 
terminal is a convenient place to connect an appropriate stabilization 
network (e.g., C or series RC to ground).

Sorry for not providing a sketch, but here's a verbal description of 
what I think is inside that part: The input is the collector of a 
Darlington pass transistor, and the output is the emitter. The base 
terminal of the regulator is the base of the first transistor of the 
Darlington pair. Regulation is performed by a one-transistor "op-amp" 
that pulls down on the base in opposition to an external pullup 
connected to the base. That resistor will have one end at two diode 
drops above the output, and the other at the input voltage, so be sure 
to compute the power dissipated by that resistor and choose accordingly. 
As a reasonable approximation, just assume that the input-output 
differential appears across that pull up. So, if the unregulated input 
is 180V, and the regulated output is 130V, the resistor will dissipate 
(50)^2/10k = 0.25W, so use a resistor rated for at least half a watt or 
more. Your mileage may vary.

Hope that helps some.

--Tom

-- 
Prof. Thomas H. Lee
Allen Bldg., CIS-205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu
650-725-3383 (public fax; no confidential information, please)

On 5/12/2017 7:05 PM, arc5 at ix.netcom.com wrote:
>
> Ok looks like I jumped the gun on this one.  The leads look like an 
> LM317 in that there is an INPUT, an OUTPUT and a COMMON(-), but 
> there's another lead marked BASE that is not what I thought it was.  I 
> can find spec sheets on this and the other devices, but not one 
> application note or circuit diagram.  Datasheets are no help- no 
> circuits on them.  No output with that BASE lead open.  Surely one of 
> you folks knows about these things?
>
> 73 Dave S.
>
>
> Sent from my Ain't Smart Phone.
>
>
>
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