kenwood ts-50 pll unlock

Discussion in 'Radio Circuits, Repair & Performance' started by AB3LW, Aug 2, 2010.

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  1. AB3LW

    AB3LW Ham Member QRZ Page

    I am looking at a kenwood ts-50 for sale, it is being sold for parts dirt cheap. the problem is described as "common" with the pll going out of lock 20 meters and above. If its a common problem maybe someone here can tell me more before i buy it. is it a simple vco adjustment or an expensive (not worth it) repair.
  2. W5RKL

    W5RKL Ham Member QRZ Page

    If you decide to buy or have already bought the TS-50 you will need the Instruction and Service manuals. You can download both manuals at the following link

    The Kenwood TS-50 Service manual

    The Kenwood TS-50 Instruction manual

    You did not state, one way or the other, what you technical skill level is. Therefore, and with all respect, I highly recommend you take the time to thoroughly read and understand the service manual's "Circuit Description" section, including all block diagrams, frequency tables/charts, etc, starting on page 2, BEFORE you make any attempt to troubleshooting and repair the TS-50.

    These types of radios do not have the conventional mechanical band switching and variable capacitor analog type VFOs found in older PLL controlled Kenwood transceivers such as the Kenwood TS-120, TS-130, TS-530, TS-820, and TS-830. VFO tuning is accomplished through an Encoder attached to the VFO knob that, when rotated CW or CCW, communicates digital signals through the LCD ASSY to the microprocessor (M37702M4A) on the "Digital Unit". The microprocessor on the Digital Unit further communicates with the PLL Unit, Filter Unit, and TX/RX Unit. This is shown in the TS-50's service manual on page 14.

    I will say that if you take your time, do your research reading and learn how the TS-50 individual circuits operate and work together, troubleshooting and repairing a TS-50 will be an invaluable educational/learning experience for you to say the least!

    Just my 2 cents worth.

    Last edited: Aug 8, 2010
  3. AB3LW

    AB3LW Ham Member QRZ Page

    Thank you very much for your reply. I lost the auction. And i guess its just as well because my technical ability is limited. I have some experience on collins kwm-2a's from my air force days back in the seventies, and i am able to do some of the more simple repairs on scanners and such.

    So the ts-50 probably would have been "biting off more than i could chew" at this point, but i am learning and someday i'll know more.

    I am a new general and looking for my first hf rig. I can afford a brand new one, but i want to learn and enjoy the technical aspects of the hobby and sense of accomplishment of being able to repair my own rig.

    So I am now considering a sienna kit from this looks like a better learning experience than fixing a broken radio.

    I really miss heathkit, lafayette and olsens, i've enjoyed many of thier kits.

    Again thanks for your good input
    73's rich n3kvn
    Last edited: Aug 8, 2010
  4. W5RKL

    W5RKL Ham Member QRZ Page

    Hello Rich,

    Sorry to hear you lost the auction. That happens now and then.

    A Kenwood transceiver that would be much easier to troubleshoot and repair is the TS-520 series, TS-520, TS-520S, and TS-520SE. They all operate from 120/240VDC internal power supplies.

    All 3 520 series transceivers are basically the same except the TS-520 model did not have 160 meters but it did come from the factory with the 13.8VDC 20 amp DC supply which was an "optional" accessory on the 520S. The TS-520SE was designed to operate on 120/240VAC only.

    The TS-520 series transceivers had a typical input power of 200 watts on sideband and 160 watts on CW from a pair of Japanese S2001As (6146B) driven by a 12BY7 driver.

    Factory digital display using the "optional" Kenwood DG-5, was standard on the TS-520S and TS-520SE. A modification to the TS-520 can be made to bring the HET, VFO, and CAR signals out to 3 RCA sockets on the rear panel for use with the Kenwood DG-5 digital display. Power for the DG-5 is 13VDC obtained through a 2 prong socket on the rear of the TS-520S and TS-520SE and through a modification to the 13VDC power supply in the TS-520.

    A bit more complicated transceiver to troubleshoot and repair is the TS-820/TS-820S. The TS-820 and TS-820S are the exact same transceiver except for the Digital Display in the TS-820S. The TS-820 series transceivers have a simple PLL UNIT that uses the VFO and CAR UNIT RF signals with individually band switch diode switched VCO oscillators. The individual band switch selected VCO oscillators in the 820's PLL UNIT is used to mix with the 8Mhz IF signal in the RF UNIT to produce the transmit "operating" frequency. The same VCO signal is mixed with the incoming receive signal on the RF UNIT to produce the 8Mhz IF signal in receive.

    Like the TS-520 series transceivers, the TS-820 series transceivers operate from an internal 120/240VAC power supply and also from 13.8VDC with the optional DC converter.

    The 520 and 820 series transceiver models may be a good starting point to build up your technical skills in troubleshooting and repair. Again, as I mentioned in my previous response, always have the operating and service manuals then read them before attempting any troubleshooting and repairs.

    Good luck with the Sienna transceiver, it looks "different" and appears that a few owners really like it. This is the first time I've heard of the Sienna transceiver kit.

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