Dave: I owned a 2000L for several years which I modified with excellent
results. I sold it about 6 years ago when I moved from Dallas to Washington
state. I have no schematics or notes on the changes since those were given
to the buyer but here is what I did as I can best remember.
1. The filament voltage on the tube was quite a bit higher than it should
be. I connected a resistor in series with the filament to set it to the
right value. The resistor value was quite low and it had to be considerable
in wattage.(when I bought the amp from a friend, the filament of the 8877
was open).
2.The filament winding for the tube is on the plate xfmr, bad practice since
the large core will supply lots of energy at turn on with a big filament
current surge.
3.There is no soft start circuit in the primary and one is desperately
needed to protect the tube, diodes, and caps. I installed a series resistor
in the primary. Rather than using a relay as is customary, I removed one of
the pilot lites on the front panel and installed a toggle switch which
manually shorted the resistor after turn on. Obviously, you have to remember
to return this switch to the non shorting position when you shut the amp
off. I don't particularly reccomend this approach but it allowed all of the
parts to be inside the amp. The relay approach is foolproof.
4. I felt that the amp needed a grid current meter so I modified it so that
that could be done with the front LH meter.
5. I am not positive, but, I think I installed a latching grid current trip
circuit.
I believe those were the things I changed. 73, and GL with the mods. Dan,
N5AR
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]On
Behalf Of Dave Meitzen
Sent: Saturday, January 22, 2005 11:32 AM
To: Amps@contesting.com
Subject: [Amps] Need Info
I bought a Dentron 2000L 8877 amp
I understand there is a list of recommended upgrades. Can anyone help me
with info sources?
Thanks
Dave aa9tt
http://www.aa9tt.com
Various amps
http://www.aa9tt.com/Fun_Stuff/Amplifiers/amplifiers.html
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