Dave,
If you "jack up" the the type of 8V regulator used in the K2 by adding a
diode in series with the regulators ground lead, have you found any sign of
oscillation at the regulator's 8V output terminal? Also, if my memory is
working properly, the regulator's ground lead is connected to its heatsink
tab which would require that an insulated thermal pad be added and
non-conductive (DC) hardware used for mounting the regulator.
In my opinion the reverse connected diode which you mention as a protective
device should always be used with these three terminal voltage regulators.
FWIW the regulators made by Motorola or ST which I have purchased from
Farnell in the past have always produced the correct output voltage be it
5V, 8V, 10V or 15V, both positive and negative.
73,
Geoff
GM4ESD
David Lankshear G3TJP wrote on Tuesday, June 03, 2008 at 10:00 PM
From postings on the reflector, it would seem that more than a few of K2 8v
regulators are on the low side, including mine.
I've just ordered a couple from a local supplier to see if they are any
better, but if they are not, I will "jack up" the ground lead of the 8v
regulator by connecting a diode in series with it - i.e. interposed between
the regulator's ground lead and the ground it was connected to. A silicon
diode like a 4148 (or 4001 to 4007) will effect about a 0v6 increase in
output voltage and a schottky or germanium diode will give about 0v2 to 0v3
increase.
Of course, this "jacking up" compromises the regulator's inbuilt short
circuit protection but in a stable environment like the K2 it can either be
accepted that it is unlikely to ever be called to work into a short circuit,
or a reverse connected diode can be introduced between output and ground as
protection.
73 DaveL G3TJP
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