Dentron MLA-2500 manual

The MLA-2500 is a good quality SSB linear amplifier with 600 watts total plate dissipation and a 1KW DC CCS input rating, covering the traditional ham bands from 160 to 10 meters plus a bit extra for MARS.

The output band-change circuit is a PI-network that switches extra capacitance into the plate side of the circuit on the 160M and 80M bands as well as doing the same on the load side for 160M, 80M, and 40M. This allows a compact tuning capacitor design which still maintains generous spacing between the capacitor plates, at the expense of expanded frequency coverage on some bandswitch positions.

The power supply is a full wave voltage doubler producing about 2400VDC (no load) with a total filter bank capacitance of 25uF.

The MLA-2500 will produce an input power of 2KW PEP ("full legal power" -as defined under the old rules). This interpretation obviously means SSB only, as averaging the 1KW DC (old rules) power input for SSB has been generally taken to mean 2KW PEP input. CCS DC input for CW, data, and SSTV is to be limited in the real world to 1KW, due to power supply limitations and cooling arrangements. Since the amplifier was designed to be compatible with the old rules which measured "power" by averaging DC input to the final amplifier rather than by measuring peak output power, this amplifier should be considered to be capable of about 1200W PEP output on uncompressed-voice SSB and about 650 watts output on CW and data without exceeding the component ratings.

Eimac data gives the pair of 8875 triodes an output rating of 1174 watts (CCS).

No rating is given by Dentron for AM operation of this equipment. AM operation is hard on both the power supply and tubes of SSB-type amplifiers. Our reccomendation for AM is to run no more than 180W carrier output, or 950 watts DC input. Power supply ripple will be about 2.6% under AM carrier conditions.


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front cover
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contents
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page 1
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page 3
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schematic page 1
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schematic page 2
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entire schematic
zz8875.html
Eimac ratings for the 8875 triode