Many thanks for the advice Farhan.
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I've taken the measurements you suggested and
indeed it was the driver whose output was low - only about 1 volt peak. I was
using BC549s throughout and although they tested ok when I changed them in the
pre-driver and driver stages for 2n2369s the output from the driver went up to
4.5volts peak.
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I've tried a variety of core types and none appears
to be critical. I'm using a t-50-6 in the IRF510 drain - 14 bifiliar turns to
get the 3uh you suggest. Know what you mean about winding these
things!
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The output without the lpf in circuit is 6.25watts
but I need to adjust the bias for a standing current of rather more than 80ma to
achieve this - although it may be that the balanced mod is not that well
balanced (I haven't put in any caps yet).
I'll test this and let you know. Even without the
lpf the output is quite a pretty sine-wave.
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Now where does this 6.3 volt resistor fit in? Am I
looking at the wrong schematic? Perhaps in the driver emitters? I'll try
changing the 10 ohms to 5.6 or thereabouts and see if the output goes
up.
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Lastly thanks for putting a unit on the rf
voltages. All too often schematics either don't contain rf voltages at all or
they don't specify whether they're Peak to Peak or Peak or RMS - and there's
quite a difference!
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I think I'll change the other 549s for 2n2369s if I
have enough just to see what happens.
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Good luck to everyone.
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David?
