[Amps] Do 8875's die fast after weakening?
jim.thom at telus.net
Thu Mar 19 21:53:48 EDT 2015
Date: Tue, 17 Mar 2015 21:56:45 -0400
From: "Carl" <km1h at jeremy.qozzy.com>
To: "Kim Elmore" <cw_de_n5op at sbcglobal.net>, <qrv at kd4e.com>
Cc: amps at contesting.com
Subject: Re: [Amps] Do 8875's die fast after weakening?
The 8873, 8874, and 8875 are all identical internally and just the external
anode determines the plate dissipation.
The MLA-2500 cooling is adequate for the 1000W CW INPUT the amp was designed
for since that was the FCC rule at the time. Tune up for 700-800W key down
output and the tubes last forever; PEP SSB will be around 1000W.
There are 3 flavors of the 2500, the original has a single HV and the
Continuous Duty switch changes the fan speed.
The 2500A (not marketed as an A) has a dual voltage HV and the B version is
the same minus 10M/12M.
As with most Dentrons there are often minor differences even during a
The 100 Ohm 25W input swamping resistor must be in place for 70-100W
exciters, many took them out when tubes were cheap so they could get over
1500W out......real stupid IMO.
## I thought the B version...or some later version had a band switched or relay switched tuned
input, with the usual pi nets for each band ???
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