On Sat, 05 Dec 1998 19:35:26 -0800 dan hearn <dhearn@ix.netcom.com>
writes:
>
>Chris, I owned a DTR200L for several years and made a number of mods
>to
>improve it. Sold it about 6 months ago before moving to Spokane from
>Dallas.
>It has a number of good features. Excellent appearance and sheet metal
>work.
>Ceramic coil forms, hypersil HV xfmr. It desperately needs grid
>current
>metering and a grid overcurrent trip ckt. The fil voltage was over
>spec so
>had to put a res in series w fil. I rearranged the hv grounding to
>allow
>grid current metering. I installed a step start circuit on the
>plate/fil
>xfmr. I am relating this from memory as the new owner has my revised
>ckt and
>notes. I believe I replaced one of the panel lamps with a toggle sw
>to
>select grid current metering. I changed the value of some of the
>doorknob
>padder caps in the pi net output for 80/160m. Like nearly all ham
>linears,
>the ability to handle 80/160 antennas which are off resonance, is
>limited.
>There is no tuned input, as you know, and it would be nice to have one
>but
>that would be difficult to implement so I never did that. Mine would
>do
>about 1200w out with the low plate voltage the PS supplies. Oh by the
>way,
>the tuning cap on mine had been arc'd by the previous owner. I had a
>surplus
>ceramic vac var cap so put it in place for C1 and used a Helipot 10
>turn
>dial for it. Looked pretty nice and I don't recall having to drill any
>new
>holes in the front panel. The grid trip circuit was the one shown in
>ARRL HB
>and other places. I used a single xstr w a dpdt mini relay arranged
>to
>electrically latch shut and interrupt the PTT line. Good luck w the
>mods. It
>was fun to do, for me. 73, Dan, N5AR
>From your description I have that amp on the bench right now Dan! Its a
small world.
It has now been converted to a 6M monobander and will easily do 1500W
with 70W of drive with the original PS. The vacuum variable was junk by
the time it got here.
I have another one that is completely original that the customer wants
the grid ckt upgrades and I'll also do some tank ckt changes.
73 Carl KM1H
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