CW offset frequency on TS-430s

Discussion in 'Radio Circuits, Repair & Performance' started by N7IV, Sep 14, 2015.

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  1. N7IV

    N7IV Ham Member QRZ Page

    Our local high school radio club received a donation of a nice (if elderly) TS-430s. The radio appears to work well but the CW offset frequency is 2.5 KHz instead of 800 Hz. Since my new 14 year old hams only have CW privileges on HF (except for 10m) this is a big problem.

    There must be an easy, internal adjustment to fix this problem in an otherwise excellent old radio.

    Joe, N7IV
     
    WA0PTZ likes this.
  2. KA5IPF

    KA5IPF Ham Member QRZ Page

    Make sure the RIT is turned off. Start with a full reset and then make sure all the push buttons except the Power are out.
     
  3. N7IV

    N7IV Ham Member QRZ Page

    Thanks for the input. The RIT was/is off and all the pushbuttons are out. Right now I'm betting on the CW crystal being problematic.

    Joe
     
  4. KA5IPF

    KA5IPF Ham Member QRZ Page

    Better hope not, they are on the unobtanium list.
     
  5. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    I would think that International Crystal could produce a proper crystal for CW operation. According to my service manual, on the TS-430S, that frequency is 8.8307 MHz. I can't tell for sure, but the crystals appear to be HC6/U.

    To find out if the CW crystal is the problem, either a counter or a well calibrated general coverage receiver could be used to measure the frequency.

    Glen, K9STH
     
  6. KA5IPF

    KA5IPF Ham Member QRZ Page

    The CW offset is set by X6, a 9 MHz xtal. There is no 8.8307 xtal, that frequency is set using a varactor. See step 2 on Pg 40 for CW offset.
     
  7. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Is the frequency of the CW crystal 9.0000 MHz? If not, what is the frequency of the needed crystal?

    Anyway, International Crystal should be able to supply the needed crystal. Not dirt cheap! But, at a reasonable cost.

    Also, there may be standard "clock" crystals available. 9.000 MHz is a "standard" clock crystal frequency. If so, then the cost of those crystals is usually less than $1.00 each. The reason those crystals are so cheap is that there are literally thousands of them made at any time.

    Glen, K9STH
     
  8. KO6WB

    KO6WB Premium Subscriber QRZ Page

    Glen's assessment of the required frequency is exactly right. It needs to be 8.8307MHz.
    You get that by adjusting VR1 on the CONTROL UNIT. It's in the service manual found here; http://www.qsl.net/sp9hzx/img/servmants430.pdf
    Page 31-32 are the PCB and circuit diagram where the adjustment is on page 40.
    Just like has already been stated. There are two crystals that are used in the circuit. One is the LSB crystal at 8.8285MHz and the one for USB at 8.8315MHz. VR1 is used to pull the frequency of the USB crystal to obtain the 8.8307MHz frequency.

    Hope this helps
    73
    Gary
     
    Last edited: Sep 16, 2015
  9. KA5IPF

    KA5IPF Ham Member QRZ Page

    VR1 adjusts the RX frequency. The CW TX freq (offset) is set by the 9 MHz xtal.
     
  10. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Again, is the exact frequency of the CW transmit crystal 9.0000 MHz or is it slightly different?

    In any case, getting a replacement crystal is not difficult from sources like International Crystal. The crystal may not be stocked by Kenwood. But, that doesn't make it "unobtainium"! In many cases, replacement crystals from ICM are better than the original units.

    Glen, K9STH
     

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