Swan 1200-X

Discussion in 'Amateur Radio Amplifiers' started by N8SAN, Jun 28, 2017.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Better still, sell it, save up a bit more, and buy an amp that uses tubes still manufactured and intended for transmitting.:)

    That 8950s, or even 6DQ5s, 6DQ6s, and a zillion other tubes could "be used" for transmitting, is really just a coincidence; they were intended for high powered pulse operation at about 16 kHz. That they "work" and can produce gain and power up to 30 MHz (or higher) is coincidental, since that's not what they were designed to do.
    AF6LJ likes this.
  2. AF6LJ

    AF6LJ Ham Member QRZ Page

    The weak point in the 8950/6LF6 tubes is the anode. The cathodes can deliver high peak currents before saturation.
    You are right they are not transmitting tubes but if they are respected they will last.
    (but I wouldn't suggest this amplifier for a beginner's amp) (I also know there is considerable sticker shock when one is looking for a pair of 8950s, let alone four of them. )

    He could maybe $250 for the amp, save another 300 and wait and an SB-220 will come along that would be in working condition.

    He could also find an SB-200 for somewhere in the $300 range.
  3. N8SAN

    N8SAN Ham Member QRZ Page

    This is really cool to me! And why it probably looks like I'm beating myself up trying to get more outta this old amp! But I like this stuff! It wasn't intended to work, but it did!

    I can't argue that, but I pretty much got this amp for free. I bought a working GREAT shape, less the VFO cover TS-820s and this amp for 300. So you could argue I got the amp thrown in, or the amp for 150 and the Kenwood for 150, either way a good deal in my book. So I'm not into it for more than a diode and an RCA female union.
    So really that is why I'm working to use it. And as it sits, 500 on 20m isn't that awful for what I have into it.
    Doing things like this makes me learn how these things work and have a better understanding of all this.

    This is interesting. I see a set of NOS 6LX6/6LF6 but I'm not smart enough to know if that is the same thing, why are there two sets of numbers? I see that that series of numbers are used together so I assume they are the same thing.

    They are all 4 GE....that should be ok then? Only if I was mixing Sylvania with GE or RCA?
    These will have the same output as healthy 8950's?

    No arguments here, but like I said before, I don't have much into it and I'm learning! :D this is the part of the hobby that drives me. Making antennas and learning how these things work and keeping em going, even if it doesn't make sense! o_O
    KD2ACO likes this.
  4. AF6LJ

    AF6LJ Ham Member QRZ Page

    Changing the tubes to another type. (8950 to 6LF6) is not a beginners project. The amplifier must be modified.
  5. N8SAN

    N8SAN Ham Member QRZ Page

    Oh for sure. Obviously from the depth of this thread I'm by no means an expert, but isn't it just changing the heater wire from parallel to series on two of the 4, 1 for each pair? As was said early to drop the voltage in half? Then I'd have a set of 4 NOS tubes that will otherwise match the 8950.

    I'm SURE I'm making this sound simpler than it is...... :)
    Last edited: Jul 10, 2017
  6. AF6LJ

    AF6LJ Ham Member QRZ Page

    You have to do all or none.
    There is enough electrical difference between the two tube types that you can't run mixed sets.
  7. N8SAN

    N8SAN Ham Member QRZ Page

    Oh! I didn't mean only doing two to the other tube.
    There's a set of 4 6LF6 available. All GE.
    I wouldn't run two different types.
  8. N8SAN

    N8SAN Ham Member QRZ Page

    AF6LJ likes this.
  9. N8SAN

    N8SAN Ham Member QRZ Page

    I found a thread talking about this same subject and someone suggested 6LR6's or 6KD6's my question is, are the 6LR6s the same output as the 6LF6? Again, I do understand that filament voltage is different but if they have the same output as the 8950 and 6LF6 it just gives me more tubes to hunt for.
    AF6LJ likes this.
  10. AF6LJ

    AF6LJ Ham Member QRZ Page

    Again these can be used with modifications.
    Socket rewiring is necessary.

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