Jim Palfreyman wrote:
OK folks, I've rechecked the voltages and here's the details.
Firstly, changing the oven temperature screw was a mistake. Read a
previous thread to see why I did it. It was logical given my
experience with 10811 ovens. I've owned up to it and begged
forgiveness from the great Flying Spaghetti Monster. It never answered
so it must have made me do it. Please drop that now. :-)
When I first powered the unit up it had bad and leaking NiCd batteries
and made a horrible sound. I removed those and I presume something was
damaged.
The "input" voltage to the 2N1701 is normal (according to the front
panel meter) and is close to 26V. The "output" voltage is 25V and not
18V as the manual says. I have the manual now and anyone (with more
experience than me on old fashioned power supplies) who wants to
comment I am happy to email the circuit diagram and eagerly await
comment!!!
Now that I have looked at it and also read the relevant description
text, all I can conclude is that the circuit actually behaves as
intended. Just look at the text on battery current limitation, which
includes a pasus on behaviour when batteries is removed.
The battery charge limiter will actually act as a current limiter to Q1
so the regulated voltage varies in level accordingly. With no batteries
installed, it does drift upwards in voltage as a result.
So, the "regulated" voltage is infact designed to vary around. The
"regulated" aspect of it is damping of the rectified voltage ripple but
the DC level is allowed to wander around.
If voltage is below 20 V, the relay disconnects so that the batteries
does not discharge further. Neat.
Cheers,
Magnus
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