| redrabbit |
It is based around an obsolete LH0041.....but wait, don't leave....
The topology is apparent when viewing the LH0041's easy schematic......easy enough to be could be built discretely ??
(xept for the 741 ??)
PSU schemo is on page 5.
http://cache.national.com/ds/LH/LH0021.pdf
I bought 15 of these devices on E_ay.
I'm building one psu tonite, using an 1N825 for thr 6.2v zener (temp compensated, 1/4 watt). Is this wattage sufficiant ?
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| redrabbit |
I built one last night.
(Heatsinks not yet applied,)
But at my local surplus store, found some 1N4579A 6.4v ref diodes @ .0005% tempco.
So if I understand what's going on...I altered R1, R2 values to work with the 6.4v reference.
What I think happens is:
that R1+R2 should equal 15k, (which coinsides with the 15k's on the neg. rail.)
And based on the value of R1 vs 6.4v reference , using the datasheet formula should give me the positive output.
Are my assumptions correct ?
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Does anyone have a copy of an older National Linear Applications Handbook ? I believe there's more info on this circuit in there.
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Powering Up:
No load.....I get a stable +15.38v, -15.34v
6k load (per rail) very close to the above voltages.
100 ohm load (per rail)....+15.35v (stable), -14v (erratic, not stable, transistors get warm with this load only.)
Transformer: 36v CT @1.2 amp
w/2200uf smoothing caps.
Layout:
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| redrabbit |
I built another one, this time using the exact components as in the datasheet schemo. (the ref diode I have is 1/4 watt.)
Similiar results, with a 100 ohm load, neg voltage drops to 14v.
Any idea why this would be?
Could it be that this kind of psu is not meant to be pushed like that?
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