AMPLIFIER RM HLA 300 plus,
in which the initial MODIFICATION was made to give up to 600W...

Modification Details:
Instead of the original transistors (at 13.8V) I mounted a matched BLW97 (4x 175W power each) supplied 
with the 28-30V voltage. In/Out transformers and feedback resistors also modified.
Thanks to this modification, the amplifier gives from 450 to 600W of power, depending on the HF band. 
The power measurement system and protection have been adjusted. 
Temperature stabilization/compensation of the transistors-base currents reworked as it should be 
done at the factory (one diode in heat-sink-silicon mounted on the transistor from each pair).
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NOTE(!) - this project still needs to be refined, i.e.
currently the amplifier requires two power sources (13.8V for the control circuit and 28-30V 
for the PA transistors). In my opinion, it can stay like this, but you can add a voltage regulator 
from 28V to 13.8V for greater convenience.
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You should also spend a little longer and choose the right matching capacitors on the 
inputs/outputs/adjustment of transistors and possibly resistors in the "feedback" to 
get 600W on all bands (I have no time to do it as I spend now most of my efforts on designing 
the LCD/LED service kits - see SP2AND/bitStork projects).

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Preferably collection in person with a demonstration of the output power on an artificial load.
I cannot give a guarantee due to the nature of the PA item.
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Condition:
The device is functional, but needs to be completed thus sold as "for parts/repair"!
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Regards,
Andy SP2AND
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