AL-1500 2x mod

[Jay Mojave]

Great info here. Neighbor has a Commander 1200 amp using a single 3CX800 and it was acting erratic. Doing a "Easter Egg Inspection" we found two connections in the Pi network NOT soldered. Went home and got my 150 watt soldering iron, all fixed. But the tube looked like it got real hot and the Teflon chimney looked like it was just starting to burn. Found the internal Fan clogged with hair, ook, gook, goo, and dirt. 27,000 Q-Tips and a bunch of acetone the fan all cleaned up and pretty. I suspect the stock internal fan is not big enough for big straps or even ham guy QSO's.

Added a 5 inch muffin fan on the of the amp to suck air out of the amp, as that's were the hot air from the tube was exhausted. Adding the fan was a big help in keeping the amp cool for SSB and RTTY. Yeah the stock fan isn't cutting the mustard!

Jay in the Great Mojave Desert.... "Next Gas 150 Miles"

 

[Mr Fix it]

I have read a fair amount about the amp online but haven't seen anyone mentioning the blower as "weak". I have seen where they complained about the noise but haven't seen it as a "weak" point. I have seen a lot complaints about the meter lights.

Did you have a personal bad experience with a blower on one?

Keep in mind that the Eimac specs are for a 50c ambient Room intake temp , that’s 122 degrees Fahrenheit.

Specs change with cooler intake temp. Good tool to check to see what you actually have for pressure is a magnehelic gauge.

Adding any sort of back pressure to exhaust would require a increase in blower size , hence why radio station pa’s and other commercial pa’s generally have oversized blowers.

Some , especially broadcast pa’s also tend to be housed at a higher elevation , which as the spec sheet states also requires a increase in blower size.

Extensive work must be done to the rest of the pa to handle a doubling of output. And for 3 dB is it really worth it.

The 8877 is not a cheap tube now a days, a new 3x6 from econco can be had for about 1200 bucks .