[Boatanchors] DX-35 Problem(s)

[Jim Wiley]

Just a shot in the dark, so to speak, but has this thing ever worked, to 
your knowledge?  It is not unheard of  for a kit rig to have never 
worked properly, and been given up as a "lost cause" because the 
original builder was unable to find the problem - a not uncommon problem 
with beginners who are unfamiliar with servicing their equipment.   
Carefully check the wiring, stage by stage.  Is it really wired the way 
it is supposed to be?   If that isn't the problem, then voltage checks 
are in order.  You say you have minimal test equipment, so you may have 
to be creative. 


You should have at least a basic VOM - if not, get one.  A minimalist 
instrument can be found at hardware stores, Sears, etc. if there is no 
electronic parts vendor in your area. Caution - DO NOT attempt to 
measure the PA plate voltage with a cheap instrument - many of them are 
not intended to measure much more than 300 volts or so, and will be 
damaged by the 600 volts typically found in vacuum tube transmitters for 
the PA plate stage.


Do you have a general coverage receiver?  If so, use it to listen for 
the signals from the DX-35.  If it is self-oscillating, you may be able 
to hear it somewhere (anywhere) in the HF range.  


Pull the PA tube, key the transmitter and see if you can hear signals.  
If so, are they on or about the correct frequency? Are you using crystal 
or VFO control?  If crystal, then you should be able to hear the exciter 
stages in your receiver on exactly the frequency marked on the crystal.  
If VFO, then you should hear signals on or close to the frequency  
marked on the VFO dial - but calibration errors may cause the frequency 
to be off by several kilohertz. . 


Before you re-install the PA tube, try temporarily removing the screen 
voltage from the PA tube (simply disconnect the lead to the screen at 
the PA tube socket). Once this is done, reinstall the PA tube,  fire up 
the rig and see if it will "dip" (tune to resonance with the PA plate 
tuning control).  You should also hear a stronger signal in the receiver 
at "dip".  If it passes these tests,  then try adding a little screen 
voltage (reconnect the PA screen, but through an extra resistor - 
perhaps 20K / 2-watts or so - this value is not critical), to see what 
happens.  Does it "dip" now?   


Does the PA indicate grid drive?  Can  you see grid current in when the 
meter switch is in the grid position (I am assuming it has  one, I am 
not all that familiar with a DX-35, I had a DX-40 some years ago) .  If 
you have grid drive, can you vary it with the exciter or oscillator 
tuning controls? 


Let us know what the results of these tests are. 


- Jim, KL7CC