[Boatanchors] Trials...and cussssin...

[W4AWM at aol.com]

Hi Brian,

I had a similar, although not as disasterous occurance several months ago 
with an Apache I was restoring.  I got it working well on CW and it appeared to 
work on AM as well.  The next time I tried it, I noticed that the modulator was 
drawing all kinds of current and the power tranny was grunting like mad.  I 
killed it before anything happened and then after some visual checks, fired it 
up again,  WHAM!  It blew a fuse. I pulled the modulator tubes and the both 
checked good, but tried a NOS pair just to make sure, promptly killing another 
fuse.  I pulled the modulators again and fired it up.  Everything was fine so 
it had to be something associated with the modulators.  All the caps checked 
good as did the resistors.  Then it dawned on me to check the diode they were 
using for bias.  The meter said it was good, but a voltage check said it wasn't. 
 I replaced the diode and got a within range voltage reading. I reinstalled 
the modulators and lit it up again.  The fuse held but it was still drawing a 
good bit of current. I got on the bias pot and brought it to where it is 
supposed to be and it has worked fine ever since.

Those filters may have been ready to go anyhow and with the constant current 
draw in the phone position, that could have been the straw that broke the 
camel's back as they say. It is possible that one of the modulators was shorted 
internally causing a big current draw. Check the tubes and before reinstalling 
them, check the bias and other voltages.  Then try again.

Please post your findings so we can all benefit from your experience.

73 and good luck,

John,  W4AWM