ARC-5 Transmitter make-over

[ka1tdq]

I picked up an ARC-5 transmitter at Deerfield and just finished converting it for 75 meter AM work.  There isn't much original left except the chassis and variable capacitors.  I even removed the tube sockets and put in a pair of 6L6's for the finals.  a 6L6 is also used for the VFO.

I'm still finishing the power supply/modulator so I have yet to fire it up, but is should work! 

[AJ1G]

Looks nice!  Those aluminum cases shine up nicely, don't they?  I have a couple of hanger queens that would be prime candidates  for this type of conversion.   As I said in a related post on WU2D's thread on ARC-5s would also be nice to be able to use the finals as a linear of even a class C stage to add some strap to the little Elecraft K1 on CW.

Keep us posted on the details.

[ka1tdq]

Yeah, a class C amp for a QRP rig using a pair of 807's would work nicely!  I attached a photo of the top of the rig and yes, aluminum does shine up nicely even after being beat up for 70+ years.

Jon
KA1TDQ

[W2PFY]

I even removed the tube sockets and put in a pair of 6L6's for the finals.  a 6L6 is also used for the VFO.

Neat, I never heard of anyone doing that conversion.

[ka1tdq]

I guess the next step after this would be to put a couple FET's in there and make it a class E ARC-5. 

I've attached a photo of the power supply/modulator (wiring unfinished).

Jon
KA1TDQ

[WU2D]

Oh the Humanity!

Beautiful Jon, 6L6 MOPA. That tank is great in any oscillator circuit and the Hartley is very stable in the Command sets. Try a 6AG7 in the 6L6 spot for fun and see if you notice any real difference.

Certainly doing an ECO with a 6L6 is going to work just fine but that is a heck of a power oscillator but really not that different from the 837 ECO PTO in the ART 13 and that setup is plenty stable as a power oscillator.

I have done an ARC-5 20M conversion with a beater unit using a 12A6 ECO into a 12A6 doubler into the 1625's and that is basically a TCS setup. All kinds of output. For 10M a 12A6 at 7 MHz into a 12A6 doubler into a doubling pair of 1625's works for a modest mobile rig. For AM, tripling and using the finals straight through would work OK on 10M for more output power. You would have to regulate the oscillator screen no doubt when running the VFO at 9.8 MHz.

My first AM rig was a converted TCS with the 12A6's replaced by a pair of 6AG7's with the 1625's in parallel externally modulated by another pair and a better transformer.

Mike WU2D