Got Signal?

Two things about ham radio that make it such an interesting adventure are (1) home-brew & kit built gear, and (2) buying used home-brew or kit built gear and recognizing therein that the quality of what you buy is only as good as the quality of the builder's desire to make it work.
     At which point it goes without saying that buying used home-brew or kit build equipment is either the result of an estate auction or the builder finally giving up on undoing all the shoddy work that went into building whatever it is that's up for sale.
     And all that explains the SB-200 amp sitting on my desk, basically unusable, that has held the floor down under the desk for the past three years. I spent $275 on it being here, not counting shipping costs. It was a hard luck case of sorts when I got it, but at least it came from a place where the seller had taken the time to test the amp before boxing it up to sell. As the advert said, “Good output on 15m and 10m, fair on 40m and 80m. You fix or use as-is and save! Tubes are good!”
     Which is exactly what I got.
     The box had been built before the day of solid state transceivers and thus needs modified for radios that were not designed to switch relay voltages of 130VDC. Back in the day of tube radios, this was no problem. But new transistorized radios won't take that sort of power switch arrangement. Thus, I had to add a board to use with the Icoms. And I had to rebuild the power supply, which fortunately was available as a kit. After all, the amp was sold by Heathkit from around 1964 through 1978 as part of the Heathkit SB-series of transceivers, receivers, transmitters & accessories.
     I went through a bunch of Heath gear when I first got into ham radio back in 1969, starting with the SB-310 shortwave receiver, which I soon modified to give me 15m ham receive coverage. I used a DX60 transmitter, a home-brew T/R antenna switch and a TenTec KR40 keyer for my entire time as WP4DKA. Then I built a SB401 transmitter and tried to use it with the '310 for a while. I also ran a used DX100 transmitter, a behemoth of drifty VFO, chirpy signal CW/AM gear that disappeared into some void between 1973 and 1975 when my first son was born.
     All that stuff had been replaced by a TenTec Argonaut somewhere along the line and the Argonaut went on the shelf when I built my last piece of Heath gear, an HW101 that died during a blizzard around 1977 or 1978.
     So now, surrounded by Icom radios – all of which are very nice, easy to use and, so far, high quality & trustworthy gear – my decision to get a used amp was driven more by idiocy than reason. Idiocy because I just want to have a strong signal when I get on 75m every Friday night with the ex-radio hippies and late-night-radio leftovers of the once thriving Ohio Valley Teratology Net. And maybe talk to my cousin in Pennsylvania who lives in a RF noise hole and has to run a kW to get a signal over to Ohio mid day on Saturday or Sunday afternoons, something that hasn't worked for a while 'cause my signal is buried in the noise at Keith's location.

But back to the amp.

First thing I did was buy a power supply rebuild kit from Harbach Electronics, which set me back $75 and a couple days of patient building. I later added in the low voltage keying board so I wouldn't fry my Icom radios running the amp. (I have yet to hose the amp up to the radios 'cause, well, that's the rest of the story.)
     In the process of getting the amp running I've had to redress some cabling and give a serious long look at the tank circuit and the tubes in the RF deck. What I eventually found was disheartening.
     Whoever had this amp last modified the hell out of the band switch circuitry.
     First, the high end of the HF section was wired backwards, so the 10m tap fell into place before the 15m tap. And someone had moved the tap on the 10m section of the tank circuit to what can only be guessed at being 11m, although the placement is more suitable for something higher in frequency than 11m.
     Confused work there.
     Then the padding cap that get switched in to the tank circuit on 75m is on the 40m position of the band switch, which makes 40m tune way the hell off somewhere else.
     This misplaced padding cap position was tossed in because the point and switch contacts on the 75m position of the switch is, for want of a better term, gone.
     So what I end up with is an amp that won't work on 40m and barely makes sense of 75m, should I be nuts enough to use it only there. Which I could, I will admit.
     But I bought a five band amp and I want a five band amp.
     So now I'm adding on the bill the $35 it costs to replace the mangled switch section (not counting what it would cost me to have someone take the switch out of the box and take it apart so a new section could be laced into place).
     Then there's the quality of craftsmanship that's missing from the ass of the amp, on the input section to the tubes. And there the list is simple.
     First off, all the bypass caps have long enough leads on 'em to snag a fingernail.
     Then there's the strange wiring of the input circuitry, some of which is part of the build instructions but about which I have serious disenchantments.
     That's 'cause one of the tubes runs hotter (as in the plate gets redder) than the other. And that may be caused by something not done up right or completely failed in that section of the box.
     So there's that.

All in all, it looks from the figures and frustration that I could just as easily have bought a higher-priced, probably better-constructed, used amplifier. I could have bought a fresh off the factory floor amp, if I had been interested in buying one of the cheaper – and notorious by their cheapness – amps that run tubes familiar to anyone who's been playing radio since 1969.
     Which brings up the other part: I have another amp, a Heathkit Warrior HA-10, that I got more or less as a “please take this off my bench and make it go away” deal.
     Took that one apart – it was way easy to do – and built it back up again. Used it for a long time over the solar maximum of the late 70s and early 80s. Worked the world, seriously, with that amp, a TR7 and a home brew three-element beam on top of a 40 ft tower.
     Then we moved to the new digs and that was the end of ham radio. At least until the past couple years when it became possible to remotely control antenna switches, antenna tuners & similar bits and pieces that make it more fun.
     Which brings us to today: two Icom radios and a used SB-200 that needs serious therapy.

By the time I clean up the wiring mess in the tank circuit area, rebuild the entire input section at the tube sockets & replace or repair (if possible) all the broken bits and pieces, I'll have spent almost as much in resurrection as I did making the box appear on my porch.
     But that's the way it's gonna have to work, if I want the amp to work.
     I've done it before.
     It ain't easy, however.
     Every single component in the radio has to be vetted. Can I trust this piece? Is it the right value now, if it ever was? And what about all these improvements to the design that have shown up since the beast went out of “production” a bit over thirty years ago?
     That is a good question. The hot tube may be part of a design feature that was discovered by a ham in Holland. Another guy in the US collected a pile of useful mods and improvements that sound interesting. But mods are like Communism. They sound good on paper. But . . .
     Will they work?

And truth be told, as my 65th birthday approaches, I am less than enthusiastic about sticking my hands inside a piece of radio gear, let alone guide a soldering iron in there among the plastic and wire.
     The plate voltage for the amp is around 2.3kV. Twenty-three hundred volts.
     I took 750V across my arms once. I remember screaming.
     I doubt I'd remember anything if I crossed 2.3kV. They' sweep up the ashes and thrown me in the oceans so I could swim with my family every summer.
     I don't have the steady hands that I once had either. Two hands to plant a screwdriver tip in the head of a screw. That kind of thing.
     So there's that to consider.
     But I spent my money and, goddammit, I want the amp to be amplifyin'!
     And I'm tired of hearing W9BS tell me I'm weak and that I need a signal.