Hi gang.
My Dentrol DTR-2000L was cruising along nicely in the CQ WW SSB
contest this weekend, when it suddenly developed an interesting (?)
anomaly.
During some transmissions, the plate current would rise to an unusual
level, but then, the amp would function normally under drive.
Sometimes, the plate current would NOT go back to zero when the PTT
line was 'dropped', but idle at a value above 250 ma.
Pushing and releasing the PTT would finally reset the plate current to
zero, though I have no idea what was causing this anomaly.
This morning, while operating on 15m, there was a sudden eruption of
sparks from within the amplifier RF circuit that 'synced' with
modulation, and the amp 'hummed' and 'buzzed' until I switched it to
stand-by.
Upon inspection, I discovered that the plate blocking capacitor was
the 'culprit' and a further analysis of this situation leads me to
believe the following:
A. The plate blocking cap was beginning to 'break down' under use.
B. The 'eruption' of sparks and noise occurred due to the cap leaking
high levels of current from the DC supply into the output tuning
circuit and RF was arcing within the cap.
C. I will have to disassemble the RF deck and inspect the entire area
for any additional problems that might not be otherwise obvious,
including bandswitch problems.
D. I NEED A NEW PLATE BLOCKING CAP.
Anyone who has one or two or more that would be willing to part with
them for a nominal fee, please contact me off reflector.
Hope this is going to be a quick and easy fix ...
73
Don
N8DE
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