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
NI4L wrote:
> Lets talk about this amp....
> Not much mentioned anywhere on this amp. 8877. What about the
> upgrade,Peter dahl trans, cap, dioides,new tank circuit that will handle
> the new p/d trans.
> anyone tried this? what about the non existing grid circuit protection?
> any help on this subject would be greatly appreciated.
> chris
>
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