From: Ron Wagner 
Subject: Re: [drakelist] Schematic for T4XC convert to 6146s


Ron Wagner  made an utterence to the drakelist gang
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Peter,
First, I have not made the mod for my radio, but here are my thoughts.

The mod is easy enough, given the bama.sbc.edu and Al Parker  
http://www.thecompendium.net/radio/  web sites and a look at the HW101 
schematic.  Finding low profile "tube tester sockets" is a bit difficult, 
but I found a set after 2 years of hamfests (I only visit Dayton, Ft 
Wayne, Findley, but wished I could do more).

One especially easy way to go is to find 12JB6s and rewire the T4XB for 
them.  Very easy with the twins, not so with the 3 tube XCVRs as the 
whole thing is a maze of series and parallel filaments.

Resale is important, but personally I am not so sure that it is that big a 
deal. It will take the price down for collectors, but not so much for 
nostalgia folks.  Keep the documentation and old parts and offer them up 
with the sale.  But then again you should never sell a Drake :-)

The 6146 should last longer by virtue that they are actually transmitting 
tubes.  They do not need the max rated plate voltage to work, and should 
run fine with the ~650 volt from and AC4.

Use a fan.  I have a 24 volt DC fan which I found at Midwest Electronics 
which I have wire into the rig.  I added a diode and capacitor (half wave) 
to the filament line.  The small wires go though holes already in the 
chassis. I suggest that you pull air out of the rig to avoid pushing warm 
are into the VFO.  I mounted mine with grommets and nylon wire ties to 
avoid pain chips etc. The fan gets about 9 volts which keeps it spinning 
nicely, but not very noisy.  Mine is on the back of the final cage to 
prevent problems when I open the cabinet.

Even soft tubes work fairly well on 80, 40, and maybe 20.  The time you 
know you have tube issues is when your power is really low on the upper 
bands.  That is not to say that your rig is not in need of a tuneup, just 
that all things equal I have observed this.

The worst thing that can be done with sweep tubes is poor tune up.  I sent 
a "gentle tuneup" for the twins to the list some time ago.  I will send to 
the list again.  Be looking for it.

73,
Ron

-- 
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Visit my astronomy home page.   http://www.dma.org/~wagner
Amateur Radio Station: WD8SBB - Ron  and  KB8NRP - Joann
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