I C 8 P O F
Commander HF-2500 Linear Amplifier
mods, improvements & hints
This amplifier was one (*n1) of the best workhorses in the Ham RF_PA arena some decades ago,
and has still lot to say nowadays even if that Eimac 3CX800A7 tubes are very expensive.
But as for every thing on this world, sooner or later it may happen a failure
and improvements are added as the daily use suggest.
In the following pages I describe my experiences and solutions with this fine equipment.
- links to the
- Band switch and voltmeter repair.
Hint: how_to lighten the Commander 2500 heavy bandswitch change see at pic 12.
- LOAD Pi- failure and improvements.
During an RTTY contest in 40 meters the relative PI_ part has so much overheated
that the toroid support has melted and the teflon wire had the cover broken in some curves.
The poor ventilation of the PI_ toroid has been improved...
The fault has been repaired.
follow this link...
- Commander 2500 40mt RTTY affair.
The only weak point of this fine amplifier.
From time to time I replay to emails asking about the operatings of this PA.
There is nothing special to explain, only one major attention has to be carried when operating RTTY on 40meters.
Running a maximum of 400 watts output during long runs in rtty is a safe practice (but not key_down 24h),
with few short bursts on the 800 watts level.
Detuning the LOAD capacitor in RTTY (from its full power setting) reduces the IG current and gives few watts less output
and keeps the PA heat somewhat lower.
Use a digital thermometer on the exaust air and you will notice at once the difference.
- 30 meter band added
The story and the article
- Tubes cleaning for better ventilation comes asap....
Any improvement or suggestions will be appreciated,
Write to my email on ic8pofATyahoodotcom (copy,paste and correct)
*Note1 : after so many years of use in every possible condition I can say that this amplifier has one major project missing: RTTY on 40meters.
Due to the very small surface occupied by the 7 turns on the L2 toroids, the generated heath is too much even on a 3/4 power and with an auxiliary ventilation ,
and few other bugs that most be corrected during every day use.
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