Legal limit amps....

[Mr Clean]

I just picked up this Drake L4B last week for about $800 with two new 3-500z tubes. I use it primarily on 80/40/20m SSB, wired for 220v it peaks at 1.3kw on 80m SSB with a 100 watt drive and I'm seeing a 1.1kw PEP on 10-15m AM. 80/40m CW is showing over 2kw and 10m CW is at 1.7kw.

The unit to the right of the amp is the matching L4PS power supply.

Nice looking box! Love the pic of the tubes.

 

[W5LZ]

An important consideration with amplifiers and their power ratings is -when- that amplifier was made and how they did things at that time. The 'old way' of rating an amplifier was using input power to the amplifier, doing the math, and coming up with a number. The 'new way' is by measuring the typical output power. That means the old way of doing it is usually 'off' by about 50% give or take a bit. That means that you can count on maybe half the rated power at the output of the amplifier.
The normal, 'stock' SB-220 never did legal limit as it's measured today. It can't for several reason, typical for any amplifier made during that period of time. It can certainly be made to do legal limit and more, but only by @#$ near rebuilding it.
And except for very few instances, any HeathKit product was build by an amateur builder. that means that every connection made is a possible problem, and who knows what else!
- 'Doc

Did you know that there used to be such a thing as 'liquid solder'? And would you believe that unless it gets really hot that it will work about as well as regular solder? It will. I built a HeathKit DX-60 once upon a time, and my parents didn't trust me much with a hot soldering iron. Considering my age, I don't blame them. It worked, the DX-60, I mean. I ain't saying anything about the VFO I built later, that was embarrasing.

 

[74IN]

I live only 35 miles away from Benton Harbor MI, so I've seen alot of the good stuff.

TV's, stereos, etc.

I miss that type of DIY thing.

I'd be very happy with a KW that glows.

Just me and nostalgia, I guess.:laugh:

 

[Captain Kilowatt]

Did you know that there used to be such a thing as 'liquid solder'? And would you believe that unless it gets really hot that it will work about as well as regular solder? It will. I built a HeathKit DX-60 once upon a time, and my parents didn't trust me much with a hot soldering iron. Considering my age, I don't blame them. It worked, the DX-60, I mean. I ain't saying anything about the VFO I built later, that was embarrasing.

You mean the gray colored stuff in a tube? You used it like glue. You actually "glued" a DX-60 together with that stuff? :w00t: I have heard of it being used in car radiators but never RF radiators.

 

[Capt'nCrunch]

Great Amp - Super Value - a Classic

got a SB-220 years ago from a friend. It has the following mods from Harbach Electronics: RM-220 Replacement Rectifier/Metering Board,PS-220 Parasitic Suppressor Kit,FM-220 Replacement Fan & Motor (moves a lot of air quietly, runs real cool); FB-220 Replacement Filter Capacitor Block, SK-220 Soft-Key,SS-221 Soft-Start. With all of this, it's like a new amp at less than half the price. This baby just hums along. It runs abt 1300 watts PEP on ssb and about 1 KW on CW, and it'll do it all day long. Power is a bit less on 10M and 12M. Yes, it loads up nice on 17M (15M position)and 12M (10M position), but you may need the rigs tuner in line. It's a real work horse. It lacks 160M and a QSK vacuum relay, but other than that, it's everything you could want in an amp. It doesn't have a standby switch, but with the 3-500zg tubes (no warm-up time) it's not really needed. In my opinion, if you want to run QRO, and don't care about 160M, this is the best bargain in ham radio. They were built from kits, so construction quality can vary. The assembly manuals, which include schematics, are readily available. The stuff from Harbach also comes with good instructions and schematics, so if you know how to solder, there's almost nothing you couldn't recover from.