[SignalOne] TDA2030A Installed...

[jerry]

...but probably not for long.  This is the second one.  The first one 
was killing the +15V supply
with excess current.  I'd turn up the volume, and the radio would go 
*click-click-click* as the +15V died.
   Then when I tried it on my lab supply, it went *pop* and let out its 
magic
smoke.  I probably should have remembered to turn the lab supply down 
first :).

   OK, second one.  They're easy to change because I made proper 
connectors for them.  This one
works.  It doesn't kill the +15V.

   HOWEVER - the minute you start running actual audio through it, the 
current goes up, the power
dissipated goes up, and it quickly gets hot to trot.  I'm talking over 
200F on my infrared thermometer.
Burn you hot.

   I don't think I can trust it enough to button up the case.  Either I 
seriously upgrade the heatsink,
or I go with the LM380 solution.

   Whups!  There was a sudden *click*, and the audio went away!  I turned 
its little volume control up, and the audio came back, but now the 
supply current has gone way up.  Weak audio, lots of current, bad mojo.

SO - I guess the TDA2030A is a bust, and I will be looking at an LM380 
solution.  Or maybe... Where is it written
that a transceiver has to have an audio amplifier?  It works fine with 
my amplified computer speaker...

I put everything back together with the low-level audio connected to the 
phone patch connector.  OK, we have good
audio.  But no S meter reading.  I sat down to troubleshoot the S meter 
this morning - looked at the output transistor on the AGC/Detector 
board.  Base-emitter junction's a little wide at about a volt.  But then 
I remembered - if you turn the AGC off at the front panel, there is no S 
meter!  One click, and the S meter was back.

There does seem to be one lingering effect of this adventure.  Transmit 
power is down. Whereas before I easily got
150W on the low bands, now it struggles to do 80W.  And I have to turn 
the OUTPUT control further up.  It's behaving like it did before I 
replaced the 300V current sense resistor.  Ohmed that out - 98 ohms as 
installed.  So that's not it.  I readjusted the tube bias and ALC, going 
back & forth between  the "100mA quiescent" resistor and the
"zero volts on Q5 resistor".

Still no joy.  Then I looked back at the power supply - sure enough, the 
34V is not right.  Kind of looks like the
6V regulator ( with voltage divider ) that  I put in - has popped.  Time 
to remove that, and install the TL783
high voltage regulator that I got for it. It should be more reliable, 
because it's made for the higher voltages.

I am keeping notes on all of this stuff in the manual I printed, from 
the PDF on hamanuals.com.  I made a comb-binded copy, and added 20 blank 
sheets at the end for notes.

                  - Jerry, KF6VB