On Mon, 07 Mar 2016 21:55:56 +0100, Dimitrij Klingbeil wrote:

P.P.S. If you decide to sweep the LC part in circuit instead of out of
circuit (because the transformer is difficult to solder out etc...), you
can use a small voltage source (a 9 V block battery) connected to the
power supply's "AC" input. This will precharge the circuit enough to get
the parasitics down. It won't start the power supply controller, but it
will reverse-bias various diodes and also the base-collector junction of
the main switching transistor. That will make these semiconductor parts
non-conducting (at small signal levels) and prevent them from rectifying
the test signal from your sweep generator, and messing it up in various
ways through leakage paths. It's an easier alternative to removing the
switching transistor from the circuit.

Dimitrij

Sorry, Dimitrij; as you were. Legg has spotted I was mistakenly referring
to the wrong diagram in fact. They look very similar and when you don't
have the physical hard copy manual in front of you then errors like this
are far more easily made, I regret to say.
Sigh. I've had enough for today, I'll take yet another look at it again
tomorrow.