--- In firstname.lastname@example.org
, "AD6HF" <ad6hf@...> wrote:
> I'm now trying to get the Pa operating with no success.
> I've been following Robby's excellent Build and test notes.
> PTT is ok I read 12 volts on both side of RFC 1 when PTT is
> T 2 reads 12 volts on the primary side and only 2.5 volts on the
> secondaries. No voltage is read on r31 and r32 I rewound t2
> to the instructions but no change does any have any suggestions?
When I had some issues in this area, they turned out to be due to
poor solder joints, especially on the transformer leads (and in one
occasion, on the FET leads).
Check the voltage at the drains of Q5 and Q6. Each should read 12
Vdc. The drains are the rightmost lead on each MOSFET (see the
topside diagram at
Each should see 12 Vdc via the center-tapped secondaries of T3 and
RFC1. If you are not getting 12 Vdc there, but, as you stated, you
are getting 12 Vdc on RFC1, suspect the transformer leads in T3.
If you are getting 12 Vdc at the T2 primary and at the drains of Q5
and Q6, but no readings across R31 and R32, check for the following
approximate voltages (all WRT ground with PTT-I high):
R25 hairpin - you should see your 12 V rail (could be as low as
R26 hairpin - you should see 0.7 Vdc
R27 hairpin - you should see 1.8 Vdc
R29 or R30 hairpin - you should see 2.5 Vdc (which is what you saw
on the T2 Secondaries)
See the added testing instructions at
73 de robby wb5rvz