Discussion in '"Boat Anchor" & Classic Equipment' started by WA6MHZ, May 23, 2014.
Super! I LOVE FrankenAmp. Glad to be helpful. 73
Lotta work to put a pair of 572Bs on the air when an AC line power source is available...
Pat, I think you've lost it! You've created a 2-piece SB-200 without a LOAD control, when an SB-200 can be found for $300 working fine with its own internal AC power supply.
572Bs, like many similar tubes, don't need much if any air cooling. They cool by radiation. Frankly, a 3-500Z probably doesn't need any, either, except to keep the pin seals cool. If we used heat sinks on the anode seal and the two filament pin seals, a fan would be superfluous. The "glass" doesn't need cooling.
Very Cool Pat........
Speaking of FrankenAmps..
How about someone build a 3-500Z amp that is oil immersion cooled.
I really worked the amp hard into the DUmmy load, "hello rat hello mouse hello rat!" over and over for about 10 minutes. At the end, the tubes were red hot, but held up with full power out. I'd bet I can even run some RTTY on this! The fan is indeed cooling it down though it would be even better with a Hole in the cabinet.
In a portable situation, this is an ideal amp. Every problem with the HA-14 was addressed and conquered (except for the NO LOAD control) hafta use a tuner to compensate for that. All the metering that the SB-200 had has been restored. Cooling has been added. The HP-240 weighs 12 pounds and is easy to transport thanks to the 2 handles. cabling is OK but could be better. I still need to sheath the HV cable and add a ground braid between the 2 units.
I am anxious for it's debut at a Demo event like our Operating day we have at Frys. We sure will start cracking pileups with this!! Might even get an answer to a CQ! So the Homebrew contest for 2014 is all wrapped up! I even have a powerpoint program about the whole affair. maybe I oughta show that one at Hartford instead of the radio Restoration program!
I wouldn't run RTTY at full power, that transformer isn't rated to take that.
The one thing in your favor is that transformer had a little over a hundred hours on it before you got it.
A SB-200 is very heavy Steve!, this probably weighs only 15 pounds together. I have tried hauling around the SB-230, it is very heavy! The trick will be to find a TUNER that does 500W. Most of the small ones are 300W max. and a 1.5KW matchbox is just an overkill.
But I had to build this Steve as the HA-14 was worthless as it sat without a PS except to put on the shelf in display.
This was FUN Project to build, its always fun to build something, and lately I have run out of ideas for new things to build. Will see if anything at Hartford inspires me to build again.
Also I already have 2 SB-200s now and a SB-230. I needa SB-220 like Sue has.
well, a guy (gal) has to have an expensive, time-consuming hobby, eh?
The wonderful man who taught me disk cutting 30 years ago (unfortunately SK last year) did make a transmitter with a metal 6L6 inverted in a bucket of transformer oil (in the 50's!). He said it was good for about 80 watts CW!
An old Johnson 275 watt Matchbox would handle that power level easily, and seems like it would be just about the right physical size.
Tried to tell him that.....
An SB-200 weighs about 35 pounds all up, per the manual. Most of that is power transformer. The total weight and size of the HA-14, power supply, tuner and various other stuff will be considerably more - but it's broken up into multiple pieces.
Now that is a hobby..........