Ten Tec 645 Manual/Schematic needed

Discussion in 'Straight Keys - CW Enthusiasts' started by W4KJG, Jan 31, 2016.

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  1. W4KJG

    W4KJG Subscriber QRZ Page

    Hey all,

    Moderators: I didn't know where best to post this. I would ask you to move it, if there is a more appropriate place for it.

    I recently got a Ten Tec 645 "Ultramatic" keyer to go with my vintage Ten Tec transceivers. It needed some TLC, which I mostly completed. I've got it working to the point of exasperation!

    It works reliably to about 10-12 WPM, and then it gets really flaky.

    I haven't owned an Ultramatic keyer in probably 30 years, until I bought this one. Yet, I believe I have a pretty good sense of how they should work and how they should be adjusted.

    I'm now at a point where I need some assembly drawings or photos before I want to go much further in dismantling it for cleaning and repair. I removed the PC board for inspection, and so I could trace out where the keying and power cable should connect. I'm not sure how the keying/relay/pressure assembly is assembled. I don't want to take out a screw and have a dozen parts free falling onto my workbench.

    I've searched high and low on the Internet for a manual. The various Ten Tec/RKR/BAMA, etc., sites don't have any schematics or manuals. I've found one manual, but it is credit card only, in a foreign country where I wouldn't trust sending credit card info.

    I don't think the keyer problem is my "fist." I can't tell exactly what it is doing, but after certain keying pauses and sequences, it seems to be adding and subtracting dits and dahs, and it seems to get slightly confused between dits and dahs when starting a new string of characters after sending a string of perfect characters. For instance, if I call CQ CQ CQ de K8KJG K8KJG -- and, after about a second pause, a new sequence of CQs is completely indecipherable for the first several characters unless I pause, and start re-sending the CQ.

    I suspect it may just be dirty contacts on the DIT/DAH paddles, but I'm reluctant to take it apart without knowing how the keyer/relay area is actually assembled. That is where I assume the issue is located.

    I can tell that a previous owner has made some component/PCB modifications. It also came without a power/keying cable. This all seems to be OK.

    So -- does anybody know where I can find a manual. Best yet, has anyone else run into this problem, and, if so, did you find a fix to the problem?

  2. K7MEM

    K7MEM Ham Member QRZ Page

    Overall, a keyer is a pretty simple. You should be able to take it apart and put it back together pretty simply. The circuit is also relatively simple and you should be able to reverse engineer the whole circuit. The best I can tell, from some old pictures, is that it uses a few old TTL IC (3 - SN7400, 1 - SN7476, and 1 - ???). Specs for all of those chips are readily available on line.

    I had to reverse engineer a old MFJ 482 memory keyer. There were schematics available for the 484, but not the 482. After I worked out the whole circuit and got it running, someone saw my request and sent me a PDF of the manual. Maybe you will get lucky too.

    As far as the sending issue, it sounds like you have discovered the "Ultimatic" mode. Most hams are familiar with the Iambic Modes A & B, but there was also a "Ultimatic" mode. Hence the name of the keyer. But it was never very popular. Usually there was a jumper or switch that allowed you to switch between the various operation modes.

    Here is a link to a PDF document called "An ultimatic adapter for iambic keyers". In the article, the author describes the "Ultimatic" mode. You may want to see if that description matches what you are experiencing. It may be that it's working correctly.
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    I think You have to cut a jumper in those to get above 13 WPM.

    The jumper was for when you get your extra, It is like cutting a ribbon. 20 WPM was a great test.

    13 WPM is a speed that most can copy. For 13+ you cut the green wire, unless it has been modified for no code. That wire is red. I think. o_O

    Last edited: Jan 31, 2016
  4. K7MH

    K7MH Ham Member QRZ Page

    I have only torn down the single lever TenTec keys like the KR20A but I would just carefully disassemble it. Take some pictures as you go if you need to. I always do if it is a key(er) I have not worked on before.
    Clean anything and everything that is a metal to metal contact that the signal passes through.
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    That is a great idea. :)

    You can even make a schematic with the use of a good camera.
    Last edited: Jan 31, 2016
  6. W4KJG

    W4KJG Subscriber QRZ Page

    Thanks guys. I believe it is now operating properly. It was due to my memory not remembering how the controls and switches worked. I'm thinking it was at least 40 years ago when I last had a dual paddle Ten Tec Ultramatic.

    I found a manual for the Ten Tec KR50 which appears to use the same basic circuit and controls. It just has some extra features, like a built in power supply, side tone, reed relay keying, etc.

    After reading the setup instructions for the KR50 I'm now in business using it in the Ultramatic mode that my brain still remembers, and that my old brain prefers over iambic. It complements my Argonauts and my Ten Tec 540 (Triton IV) perfectly.

    I still would like to find a manual, or at least a schematic. There are two posts that connect to the 7476, and possible to one of the 7400s. A 150 Ohm resistor is in series with two parallel 1000 Ohm resistors. The appear to be meant for easy replacement. In reading the KR50 manual I'm thinking they may be for changing the weighting limits.

    Anyway thanks. I'm away from the farm at a house we own in an HOA. I'm about to go up and install a 44' doublet in the attic. Then I can test this thing out for real with my 3000-4000 milliWatt monster Argonaut 505.:D
    W0GSQ and KA9JLM like this.
  7. W4KJG

    W4KJG Subscriber QRZ Page


    I'm still looking for a manual for my old Ten Tec Model 645 Ultramatic dual paddle keyer. I pretty much had it again figured out a few years ago. I've recently wanted to use it again, but ...

    When I've known/remembered how to use it, I've loved it.

    The dual paddle and speed knob on the front panel are pretty self explanatory. I'm able to deal with the two adjustments through its scull on the top panel.

    The three 3-position switches, and the three potentiometers on the rear panel obviously interact in some 1970s witchy way that I don't understand. I'm beginning to think the designer was sleeping in the devil's bed and after they built a couple of these things they destroyed all paper traces of it.

    Does anybody have a schematic and setup instructions for the Model 645 Ultramatic keyer???


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