The SB-200 on 6: A MONUMENTAL Project!

Discussion in 'Amateur Radio Amplifiers' started by WA6MHZ, Oct 2, 2012.

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  1. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    I just don't want to throw more money down a rathole. I could order a brand new set of 572Bs from RF Parts, but I might as well go with the GI-7Bs for that much money. I started out with what I THOUGHT were 4 good spares I had received with a FL-2100B. Evidently the guy just put the dead tubes back in the box instead of pitching them.

    And I am NOT just some novice Service tech. I have been working on these kind of things for 40+ years now, and a Paid RF Technician with thousands of hours of bench time for the past 30 years!
  2. N2EY

    N2EY Premium Subscriber QRZ Page

    That's fine but if an HF amp is working on HF, why convert it? The whole point of this conversion was that the HF parts were almost all gone already.

    It's not so much about the time. It's about the money.

    No, it's not a repair or service project at all. The goal is NOT to make the amp work the way it was intended when designed. The intent is to build something different, from a basket-case hangar-queen.

    It's a one-off customization, not a repair, not a service job. And that's a big part of the problem.

    73 de Jim, N2EY
  3. N2EY

    N2EY Premium Subscriber QRZ Page

    Maybe. You don't know if the 572Bs that light up are good, bad, or what, because you haven't really tested out the "DC stuff" in the amp yet. That stuff has to work right regardless of the tubes used.

    Did you see the 15 step process I wrote?

    Maybe. But this isn't a service or repair job where you have something that once worked but now doesn't. It's really a one-off design job using available components, many of which are used and of unknown quality. Completely different thing.

    When I see more design time going into the colored lighting of the sticking meter than going into calculation of the L and C values of the input and output pi-networks, I have to wonder a bit.

    I am convinced the project can be made to work if done right. But it has to be done systematically.

    73 de Jim, N2EY
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Time to start over with known good tubes.

    I have a pair of 6L6GTs that I know are 100% good...:eek:
  5. W1QJ

    W1QJ Ham Member QRZ Page

    WOW!! I don't normally agree with this fellow, but he's finally hit on a subject we agree on and I got to give credit where credit is due. He's 100% right on this one. I've got a migraine going through this fisaco of a conversion, rebuild, repair, et al. If that was my amp I would throw it in the dumpster right now and start anew. I learned my lesson about this years ago. In my quest to add more HF 6 meter amp conversions to my list I tried a Dentron MLA-2500 by first converting the tube to a single 3CX800. I did not get past making a sealed air plenum to mount the tube etc, when I saw I was already in the red with time and money needed to move further forward. I cut my losses and decided it is not a good idea. The project still looms in the pile of rubble. If you want to spend time troubleshooting and fisxing broken things, buy some non working radios like a KWM-2 or something, troubleshoot and fix them and then they are worth something. It's like the stock market, you got to know when to get out.
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Lou W1QJ I understand you met with my old friend and neighbor Wayne N6NB at the VHF conference in Philadelphia recently.

    At least, Wayne told me that.?

    How's the VHF amp business going so far? Are you stocking anything yet for delivery?
  7. W1QJ

    W1QJ Ham Member QRZ Page

    INDEED I did Steve! In fact Wayne was the very first fellow I met. He was sitting at the bar with 2 other fellows when we came in. Since my buddy already knew everybody he introduced me and when Wayne heard my name and call he immediately told me he was set out on speaking with me on your recommendation. We had a great chat from moment one. Later on he showed me his rover station with his trailer etc. Very neat and workable set up. Wayne is quite a fellow and a pleasure to speak with. I'm glad you had him look for me. The only other people I knew there was K1JT,K2LIM and his friend. I know them for some time snce they have been customers. Some of the ARRL folks I knew by callsign but not personally. Being an HF'er for so many years this VHF/UHF conference was a whole new thing. I am used to going to Dayton DX hospitality suites and discussing major rare Dxpedition stories and pile up battles etc. The talk I heard here was how one fellow worked another fellow on 122 Gigahertz at 3.8 kilometers. I met many interesting people in the circles of VHF/UHF community over that weekend. BTW, is Wayne now back in CA.?
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Lou, Wayne is back. He lives about 60 miles from me but we do see each other and I've been part of his west coast VHF contesting roving team.

    What Wayne has for 10-band operation 50 MHz through 10.3 GHz in his van, he has eleven more stations exactly like that all built and ready to roll, so anyone with an SUV or van with roof racks can pick up a "station," install it, and be on the road with ten bands in about 1-2 hours.

    Glad you got together!
  9. N2EY

    N2EY Premium Subscriber QRZ Page

    Wayne's been at the rover thing a long time.

    I still remember his QST article from August, 1971 - "The Cabover Kilowatt". He took a pickup with cabover camper and put a crankup tower on one side of the rear bumper and a generator on the other side. Developed a 4 band (20/15/10/6 meters) folding quad to go on the tower, which could also hold the center of an 80/40 inverted vee. He could drive up to a remote location and have the whole thing set up and ready to go in under half an hour. 1000 watts input on 80/75, 40, 20, 15, 10 and 6 meters (this was long before WARC-79)

    With 1960s technology.

    Here's the best part:

    The way he achieved high power in the confined space of the cabover shack was.....the Heathkit SB-200. He had two of them in there - one for 80 through 10, the other converted to 6 meter operation.

    So it can be done - and was being done, 40+ years ago.

    He was K6YNB back then.

    73 de Jim, N2EY
  10. N2EY

    N2EY Premium Subscriber QRZ Page

    Why? The problem isn't in the basic idea, it's the implementation. SB-200s have been converted to 6 meters for over 40 years now.

    In any event, if the project is abandoned, the SB-200 could easily be dismantled and the valuable parts sold off. The power transformer alone is worth some bucks if cleaned up. Filament choke and some other pieces the same.

    Of course the likelihood of that actually being done is rather small...

    73 de Jim, N2EY
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