Progress with 5400, still Zero Power Out

[Robert S. Capon]

Dear Heath Gurus:

Thanks for the great advice.  About five of you nailed it on the head by
suggesting that (smoke or no smoke) the final was probably still good and
that I should follow the 13.8 trace for an open.  Sure enough, there was an
open.  It turns out that there is a home-made transformer, consisting of two
perf boards connected by two brass tubes, with toroids on the tubes.  I
thought the tubes were structural, but it turns out that they also provide
13.8 volts.  I would have cleaned/soldered/checked them better if I had
known.  Anyway, I was able to fix the connection, and both finals are getting
13.8 volts at the collector, along with proper biasing (key down).

Still, no power output.

Two of you suggested multple problems (Mike Bryce and Dave Wood).  Even with
one transistor down, these guys suggested that the PA board was not getting
RF, or I'd see some output power.

Sure enough, after I fixed the voltage problem on the PA, no RF at the input
to the PA Board (output of RF Board).

The heath troubleshooting guide suggests checking for RF at multiple places
on the RF Board.  I have RF at three places early in the chain, including the
input to a transistor in the final strip of three transistor (0.4 V RMS at
base of Q402.)  However the next stage (emitter of Q401) has no RF on the
input or output.  The schematic provides voltages for Q402, and the
transistor is dead, showing 0 volts key up or down.  There is a diode just
before the transistor, D404.  The diode has 11 volts and 0 volts to Q402 (key
up), and has 11 volts on the Q402 side when the key is down.

So there is RF on the base side of one stage, the transistor is not
functioning, and the next stage is not showing RF.

Again, I'd appreciate any ideas on how to narrow the problem down further.
Troubleshooting isn't my strength.  Again, the RF board is working perfectly
on receive.

73,

Rob, W3DX

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