Noisy amp blower fan

[AE1PT]

So here it is 3AM. Finally ran the 220VAC line from the tech bench over to where the OP is and plugged in the 'new' amp. It's an Amp Supply LK-500BZ. Fine business, as it pumps 1.8KW into a dummy load with 100W of exciter input on a two tone audio signal. 500/1000W out @ 30/50W in, respectively. Output is clean as can be. Next task is to make a couple more LMR-400 Flexi jumper cables--and continue building a base tune/load chart for the bands.

I got started on this on 75M. Then the fan kicked in to a higher speed. It's noisy enough just on standby--but turns into a real nuisance after the 3-500Z's warm up a bit. Like obnoxiously loud. The fan is not bad--just a suck design. Anyone have any experience with these amps--and a suggestion for a better fan?

[n2ize]

Are you saying that it is not the fan itself that is loud but the airflow system used to cool the tubes is noisy by design ? In other words if you swapped out the fan for a different one it would still be loud ?

[N8YX]

You may find the following discussion to be of interest:

http://www.eham.net/ehamforum/smf/index.php?topic=79809.0

[ad4mg]

So here it is 3AM. Finally ran the 220VAC line from the tech bench over to where the OP is and plugged in the 'new' amp. It's an Amp Supply LK-500BZ. Fine business, as it pumps 1.8KW into a dummy load with 100W of exciter input on a two tone audio signal. 500/1000W out @ 30/50W in, respectively. Output is clean as can be. Next task is to make a couple more LMR-400 Flexi jumper cables--and continue building a base tune/load chart for the bands.

I got started on this on 75M. Then the fan kicked in to a higher speed. It's noisy enough just on standby--but turns into a real nuisance after the 3-500Z's warm up a bit. Like obnoxiously loud. The fan is not bad--just a suck design. Anyone have any experience with these amps--and a suggestion for a better fan?

Amazing, I have the same amplifier, LK-500ZB. I haven't noticed that the fan is all that noisy. 1800 watts is squeezing that baby, and a little hard on the power supply. The PS in those things wasn't all that hefty. Mine will output 1300-1400 watts on 40 and 20 meters with 100w in, but the tubes are the originals. I have an unused pair of Eimac 3-500's I should install in the thing.

Guess I better get the HF antennas back in the air first. They've been laying on the ground for a long time now...

[AE1PT]

Oh, I have no intention of ever running this thing that hard as a practice. Nice to see what a decent set of 3-500Z's and a Harbach kit can do for one though... :-D

I went through 3 different muffin fans when I rebuilt my SB-200 about four years ago. The first two came from Mouser, the last from Digi-Key. The big difference was the last was a 220VAC model. Whisper quiet, and a very nice CFM rate.

[KG4CGC]

I wanted to think of something helpful AND practical but all I can see in my mind are insulated ducts running in and out of the wall behind the amp bringing air in and exhausting it back out.