Heathkit SB-230 Amp

Discussion in 'Amateur Radio Amplifiers' started by WA6MHZ, May 26, 2012.

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  1. WA7PRC

    WA7PRC Ham Member QRZ Page

    I cringe every time I hear about an amplifier being heavily modified but, it's your sandbox. At least, we know you're talented enough to do a first-class job.
     
  2. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    The only other choice it to build one from the ground up, and I need a SB-200/230 transformer to do that. And a power tube if I don't use 572Bs. I would prefer not to bother the SB-230 as it is in perfect working condx now. Wish I had found an Xtmer at Dayton, but I didn't have time to COMB the swapmeet that carefully.
    Now I am a little scared to Molest this 230, as it is a RARE antique! SB-200s are a dime a dozen, but a working 230 is a FIND!
     
  3. K9STH

    K9STH Ham Member QRZ Page

    Try a pair of the Russian GI-7bT tubes for your 6-meter amplifier. They are pretty easy to tame at 50 MHz and are not that expensive.

    Glen, K9STH
     
  4. WA7PRC

    WA7PRC Ham Member QRZ Page

    There are many options, in both the amplifer & power supply deck. Various Russian tubes are useable to WAY beyond 6m. It's been said that, in terms of IMD, a single larger tube is better than two (or more) smaller tubes.

    If you envision separate amplifiers for HF/VHF/UHF, you can use a separate common PS (assuming you'd never use two amplifiers simultaneously) to reduce cost. HV relays with lockout OR control logic makes it work.
     
  5. AG6K

    AG6K Guest

     It's commonly assumed that all commercial amplifier designs are virtually perfect -- but this is not the case. The only amplifier design that even came close to being perfect was the Collins Radio 30S-1.
     
  6. W2VW

    W2VW XML Subscriber QRZ Page


    Unless you need to change the blower bushings.
     
  7. N3JBH

    N3JBH Ham Member QRZ Page

    I thought this was as close as a amp ever came to being perfect "The Nearly Perfect Amplifier" (1/94 QST)
     
  8. AG6K

    AG6K Guest

     Which is what I just said. . . . The only useful and beneficial things that were lacking in the 30S-1 were high-speed T/R switching and step-start. A low-VHF-Q parasitic osc. suppressor was used --- but you would not have known it without talking to one of the Collins engineers on the project (W6HW).

    - a slice of history pie - The Jan/1994 QST article was written because QST staffer Paul Pagel, N1FB told me that because my previous articles elicited many responses from QST readers, another article might be well received. I wrote about useful and beneficial things that amplifiers need to have. I read the manuscript to friends on the air, asked for suggestions,.I made changes, sent it in, and the manuscript was accepted for publication, Few changes were made by QST's copy-editor. Quite naturally those QST advertisers who were selling amplifiers that lacked a number of the useful and beneficial things were definitely not happy. Also, engineers? of amplifiers that lacked some of the useful and beneficial things apparently suffered immediate and profuse incontinence upon reading the article. QST caved in to the distraught ones. As a result, QST and I parted ways. This turned out to be a good thing because the Internet was expanding rapidly and the things I wrote were no longer subject to censorship to please some fat-cat advertiser.
     
  9. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    The parts are ordered for the 6M conversion, but there are a few hitches. NO value given for the cap in the Cathode circuit

    [​IMG]

    See this handdrawn schematic in the mod

    http://www.newsvhf.com/n6cw.html

    I see the input capacitors are changed to two 2000pf Silver Micas. WOW are those expensive!!!! They get $7 each for those from Digikey, but I ordered them anyway.

    I am ASSUMING the variable cap in question between the 2 coils is about 50pF, so thats what I bought.

    The next problem is the 70pF SM cap across the LOAD cap. The original circuit shows a big war surplus cap. Can't buy those anymore. Is that really needed?

    [​IMG]
     
  10. AF6LJ

    AF6LJ Ham Member QRZ Page

    I'm sure you could use any 70 (68 or thereabouts) PF cap that will handle the current.
     
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