WW1L: Project to replace 8877 with SSPA

Friday, August 5, 2016

Project to replace 8877 with SSPA

The past 6-7 years on 6m I've used a converted Ameritron AL-1500 (8877 tube) amp to get 1.5Kw out on 50 Mhz. It's been fairly reliable, but when it isn't, things get expensive fast. Used tubes run about $550 from 'MRI Pulls'. 8 Caps in the power supply will run about $250.00 relays cost $25/35 depending...and the list goes on.

Recently the Plate Choke on my AL-1500 gave up, and it's taken about a month to resolve all the little issues left behind in it's wake.

I love this amp and I hate it all at the same time. I've never really liked working with High Voltages like the 3600 volts in this amp.

So...I've been kicking around the idea of retiring this amp from full time use, and building my own Solid State Amp (instead of tube).

I've decided to start out building and then combining two of the BLF188XR Pallets from W6PQL (as kits they cost about $473 each) His manual on assembly looks very easy. One of these pallets can output about 1200 watts, two combined will do 1500 watts with a LOT left over....allowing them to run cooler when running the max legal limit. So TWO it is.

These devices draw about 30 amps at 50 volts DC when putting out 1200w. So that's 60 amps needed to power them.

A friend of mine mentioned that the HP DPS-1200fb (computer server power supplies) are available on Ebay for about $25-30 each (new) and even cheaper used. These supplies can output 12 Volts DC @ 100 AMPS! When powered from 220v AC they only draw 7.8 amps at 220v for full power output.

Wiring 4 of these DPS-1200fb's in series and floating them can make 48V DC at 100 amps available. (4 x 12v = 48). With a slight modification and some tweaking these can be brought up to about 51V combined total.

So that takes care of the 50V @ 60 Amps the two pallets would draw and still only be taxing the power supplies at 60% of their max.

So this is plan. I've already ordered the power supplies, some power cables, and PDU's for distribution. I also ordered a 4U 19" rack server case that I'll chop up to suite my needs for mounting these power supplies together.

I already have a 16U 19" floor mount rack system not being used. SO that'll house these power supplies and the amps and everything related to them when this is completed.

My End goal tho, isn't to stop with combining 2 of the BLF188XR's. I'm planning to run 4 of them combined. This means when running 1500w out TOTAL (legal limit) they will all individually be running NICE AND COOL.

I'll update this post later today with Photo's and links of the various bits I'm talking about.

For now I just wanted to get this started. I plan to work on this project for a while. Hopefully taking my time, and doing a really nice job of it. This is something I'd like to have running and usable for the rest of my days if possible. If I do it right, I think that's realistic.

Here are some images related to what I'm talking about:

The SSPA from W6PQL ($473 each when sold as Kit):