Vacuum tube based keyers

Discussion in 'Straight Keys - CW Enthusiasts' started by AA4OO, Apr 5, 2018.

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  1. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    QST has dozens of designs from single tube models on up....
    WB5YUZ likes this.
  2. K3XR

    K3XR Ham Member QRZ Page

    Not that I'm an expert in the field but when tracking down a problem with the HA-1 became very frustrated that I could not solve it turns out the mercury wetted relay that is used for keying needs to be in the up (base down) position or the liquid will run and make contact turned the chassis right side up .....problem solved. As N2EY indicates do the basics to restore there are two electrolytics and one wirewound resistor check the tubes if you have a tester or substitute except for the two regulators they are all 12AU7's plus the neon tube NE-2 .
  3. N2EY

    N2EY Premium Subscriber QRZ Page

    Yes, they do. But beware of a couple of things.....

    First, the termd "keyer tube" and "tube keyer" had a very different meaning in the past. Until the mid-1950s or so, it meant a tube used as a switch, not a device to generate dots and dashes. Keyer tubes and tube keyers were used to reduce the voltage and current at the key contacts, and to shape the keying waveform. The use of paralleled triodes such as '45s was common.

    The following articles from the list are about that sort of "tube keyer":

    Second, there were a lot of designs, but they're not all created equal. Some of the simpler ones depended a lot on relay characteristics and adjustment.....which is fine if you can get the exact parts.

    I should have mentioned that. It's the kind of "tribal knowledge" that sometimes gets lost.

    All true, but there's more.

    Carbon composition resistors tend to drift in value over time - almost always they go high in resistance. They don't all do it - I've found carbon comps older than me which are dead-on the right value - but it happens enough that they should ALL be checked.

    Paper-wax and similar capacitors were commonly used in those keyers, and they tend to go leaky. All should be checked.

    I don't know how tolerant various keyer designs are to component values, so it's a good idea to check everything and replace anything that is the least bit out of specification.

    The power transformer used in the 9TO keyer is the Stancor PA-8421.

    has one for $9. (Standard no-connection disclaimer)

    73 de Jim, N2EY
    Last edited: Apr 5, 2018
    K3XR likes this.
  4. K3XR

    K3XR Ham Member QRZ Page

    What the heck a chance to be a show-off the restored Hallicrafters HA-1 not my original which still have this was a hamfest find.
    DSC02537.JPG DSC02532.JPG DSC02534.JPG

    You can see replaced the electrolytics the wirewound resistor was just about on the money replaced the neon tube checked the tubes on my Eico 625 checker all checked good. The cabinet was powder coated when I had some other Hallicrafters cabinets done the HT-40 Transmitter and the SX-140 receiver . After it's all cleaned up mostly with Windex use a product from Turtle Wax called ICE it's a clear polish leaves no white residue.
    W0GSQ, VE7PJR, AA4OO and 3 others like this.
  5. WA7PRC

    WA7PRC Ham Member QRZ Page

    This is interesting:
    IIRC, after I mastered a straight key, I built one that used a pair of 12AU7s. I built it in an olde cigar box and used it w/ a homebrew paddle. The keyer worked OK but, my paddle required yuuge contact spacing.
    K3XR likes this.
  6. K3XR

    K3XR Ham Member QRZ Page

    Some of you may find this article on James B. Ricks W9TO of interest....
    KA0HCP likes this.
  7. K5UJ

    K5UJ Ham Member QRZ Page

    Last year Electric Radio ran an article on the TO Keyer and I added a bench note about restoring them. The gist of the note was that after you do all the stuff mentioned above, drill out a tube socket rivet on each socket and put in a nut bolt and star washer and crank them down. Even an ohm of resistance to the chassis from the socket ground via the rivets can destabilize the dash generation. I had a pesky problem with initial dashes starting as dots and the star washer swap fixed the problem. Keep in mind the TO Keyer is essentially a vacuum tube flip flop circuit. You have to think about it in a non-analog way, which challenged me for some reason. You have a simple vacuum tube computer in other words.

    I think it is an excellent keyer. I think to really enjoy it, you have to pair it with a Vibrokey paddle, in the gray base and black finger piece color scheme Vibroplex used for the paddles made to match the TO Keyer when it first came out.
    K3XR likes this.
  8. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    The ARRL QST archives have quite a few of them.
  9. K8JD

    K8JD Ham Member QRZ Page

    The "W9TO" keyers
    I used a Hallicrafters W9TO keyer for many years but put it on the shelf when I got the MFJ grandmaster memory keyer back in the late 70's and still use it.
    Just for fun, I got the 'TO keyer down and hooked it up but it seems to be intermittant now ! :eek:
    After too may years of storage. Needs some trouble shooting. :rolleyes:
  10. AA4OO

    AA4OO XML Subscriber QRZ Page

    Send it to me. I'll get it refreshed for ya, if you let me hang onto it for a while.

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