Hi, Andrea

Yes, you are right! Sorry about the confusion here.

It sounds like your rig should only make 10W at that low plate voltage.
It could be that they reduced the power of the original FL-50
to 10W in the FL-50B for use by the Japanese "fourth class amateur radio
operator", who did not need to pass a telegraphy examination.
This was easily done by reducing the plate voltage through a change
in power supply transformer.

73,
Ed



Andrea Baldoni wrote:
Edward Knobloch wrote:

: Here is the link to the review with the 480V voltage measurements
: of the FL-50:
: http://home.alphalink.com.au/~gfs/yaesu/Yeasu7.htm
: Page one of the review says the rated voltage is 500V.
: (500V at 100mA for 50w input). This would provide
: a reasonable 250V buss for the low level stages.

Thankyou for made me note this. I saw that page many times without never
noting the voltage chart. Hovewer, it's for the 50 and not 50B, even if
they have probably mostly the same circuit.

: D8 and D9 of the FL-50B are connected as for a voltage doubler.
: If this were a standard full wave supply,
: with half DC voltage taken from the transformer center tap,
: they would not be present.

In full wave rectifiers with center tap, we have only two diodes BUT the gnd
is in the center tap. Well, you could use the center as GND and have a
positive supply from the diodes, or also the opposite (inverted): put
diodes on GND and have the center tap at positive. So, with a 120 0 120
transformer, we have a +120V (*1.41).
If we ignore the center tap, we need 4 diodes to have a full
bridge and the transformer is like a 0 240, so +240V.
In that schematic, we have the two cases superimposed at the same time:
the center tap is not connected to GND at all, instead is used to form
another supply, the +160. It is a (inverted) full wave
rectifier with center tap and two diodes, D8 and D9. The +350 is a 4 diode
bridge, reusing D8 and D9 again but ignoring the center tap.

As I stated, I never see that way before, but do you agree with my analysis?

: You might look at the label on multi-section capacitor C81 itself,
: perhaps there is an error on the schematic which shows only 350V
: for that first section.

I'll look and report. Anyway, I suppose the problem is not there.

Ciao,
AB