[ARC5] BC-230 first run

[J Mcvey]

All of the aircraft radios were designed for electrically short antennas 5-12 ohms plus a boatload of capacitive reactance . They spec 90 to 150 pf .Try putting a 100 pf transmit cap in series with the 5 ohm load. It will probably load up that way.  The original dummy load has a 100 pf cap in it.I made one with a wirewound resistor and  variable cap to tune out the inductance of the resistor and provide the series capacitance. Sounds crazy but works!
 

    On Sunday, March 27, 2016 10:34 AM, Glen Zook via ARC5 <arc5 at mailman.qth.net> wrote:
 

 I am not really familiar with the transmitter.  However, is it designed to work into a 5-ohm load?  That is almost a dead short where r.f. is concerned.
You indicated a dummy load of 5-each 1-ohm resistors in series.  I would try 5-each 10-ohm resistors to get the load impedance up to 50-ohms. Glen, K9STH Website: http://k9sth.net

      From: AKLDGUY . <neilb0627 at gmail.com>
 To: ARC-5 List <arc5 at mailman.qth.net> 
 Sent: Sunday, March 27, 2016 5:38 AM
 Subject: [ARC5] BC-230 first run
  
Need some suggestions because I may have overlooked something.

BC-AO-230 with 4 x 6AQ5 in adapter sockets with 12.8 VDC on the
heater line and 320 VDC plate supply. All 4 heaters light up and look
normal. To protect the modulator and final tubes in case the VFO
failed to start or bias wasn't developed, I connected 5 x 10V batteries
in series to the bias line (battery -ve to junction of R100 and R104
via a diode).

I heard the VFO on a monitor receiver, so disconnected the batteries
and sure enough, about 70 V bias was present at the same junction
so the VFO was operating and no tube showed any sign of distress.
Freq was reasonably stable and the note was good. Freq: 6200 KHz;
6200-7700 KHz coil set inserted. All coil windings have continuity.

No matter what I did, I could get no output from the final into a dummy
load of 5 x 1 ohm carbon resistors in series. No indication on the RF
ammeter, nothing but a steady 25mA final plate current with a meter
plugged into the meter jack. No sign of dip when tuning the final tank
capacitor through its range. The coil wiper contact is good and several
settings don't work.

Mike (ex-taxi radio) not yet connected but its PTT switch operates a
12V relay to switch on the B+ to the set.

Have I overlooked something?

   
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