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Kenwood TS-2000 problem

Discussion in 'Radio Circuits, Repair & Performance' started by KC4UMO, Apr 26, 2015.

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  1. KC4UMO

    KC4UMO Ham Member QRZ Page

    This C5125 looks like it died a hard life.
    I have to did around the circuit and make sure something else is not bad.
    At this point I am only wondering what caused the failure.
    I just don't want to install another with out knowing.
     

    Attached Files:

  2. KA9JLM

    KA9JLM Ham Member QRZ Page


    Good thinking.

    In my experience, There is always a good reason parts pop.

    I would at least use a very under-rated Fuse, after you replace the transistor. Until you get it up to speed.


    Good Luck on your project.
     
  3. G4COE

    G4COE Ham Member QRZ Page

    Transistors do pop, at least you have one consolation..... only one went, a clue here perhaps? Thermal runaway I'd be betting, this could start as a slight leak that deteriorated over time, I'd be checking the bias is OK and not creeping wildly just in case it is a biasing fault.

    Run the set into a dummy load and monitor the bias current.... measure the total current taken from the power supply in TX mode with NO drive and NO PA transistors and the bias pot set to minimum current, fit the transistors and simply add the bias current to the total set consumption by adjustment of the pot for an extra 1 Amp, see page 111 of the service manual.

    Dave
     
  4. W4DNR

    W4DNR Ham Member QRZ Page

    Happy Ending ??
     
  5. KC4UMO

    KC4UMO Ham Member QRZ Page

    Hey Don, Sorry for the late reply.
    Been extremely busy here and have not found any transistors as of yet. Really have not looked hard.
    Will get to it soon :)
     
  6. KM4FVI

    KM4FVI Platinum Subscriber Platinum Subscriber QRZ Page

    I'm in the same boat! My TS-2000 has been at Kenwood East repair center with transistors on back order. They are supposed to call me back on Monday with their parts list so I can source them myself! Otherwise, I'm at the mercy of Kenwood's supply system! Thank goodness that I have other radios.

    Frank
     
  7. KA9JLM

    KA9JLM Ham Member QRZ Page


    That would be a bummer. Must be supply and demand.

    Sometimes you need to demand supply.


    73
     
  8. G4COE

    G4COE Ham Member QRZ Page

    Never changed PA trannys in a 2000 yet, changed bucket fulls of drivers - 2SC1970 & 2SC1972....... can't say about the 2SC5125's.... should it be the drivers you are in deep water, very deep water because it seems you can only get 'fakes'.

    I use to recommend Eleflow, used em' before, but the last lot had all my alarm bells ringing - never again!
    1. They wouldn't fit - 1mm too big.
    2. The leads being much thinner than the originals.
    3. The metal tabs looked different and shinier.
    4. I accidentally caught the markings.... and they smudged very easily.
    5. Some of them had very high HFE gain, this would cause instability. All the marking of fakes if you do a search on the web.

    KA5IPF. Cliff on another post was saying he blew a load, so he sent some for X-ray and said the die, was much smaller than what they should be.

    Never, never, never ever buy RF transistors from Ebay unless a reputable company you know..... or from one Pantomime company you see on the internet, faking is common with audio power transistors too - it's big business. You fit em' and blow em' you'll have a hard time proving it's not your fault. The last bunch of produced TS2000's uses FET if I understand correctly.

    I reckon the cause of driver and PA transistors blowing is thermal run-a-way more than anything.... they *seem* to set them to a ridiculous high level's, the PA trannys are well protected, Hi SWR and you get drive reduction.

    Thought I'd clod that in the works.

    Dave
     
  9. KC4UMO

    KC4UMO Ham Member QRZ Page

    I wish this one would had been the drivers. I have several NOS in stock and a few used ones.
    Looks like I am going with the 2SC2782's from RF Parts instead of refurbished C5125's from ebay.
     
  10. G4COE

    G4COE Ham Member QRZ Page

    Drat, I knew I should have saved all the dud ones...... never heard of folks refurbishing transistors before - not after I've blown em they won't.

    No Sir not for me, I'd be tempted to stay well clear not refurbished or used tranny's..... lol, I bought two 5 amp 'el cheapo' meters from Ebay - complete and utter trash.....! The numbering on the dial was anything but straight, as soon as I opened the packet, I got the ol' lump hammer out, smashed em up into the bin they went - one clout did it.

    To be honest I did expect them to be junk but not that bad a junk, you have to have you head all over the place to read the dial......

    hehehe, how do you rate this product - I did. Two day's later I got an email asking if I wanted them replacement, "No thanks. I've 'lump hammered and binned them', end of meters n' end of story!

    I'm sure if we looked hard enough we could find alternative transistors what would at least get some power out WITH reliability, if it was *my* rig maybe I'd be doing just that.

    Good luck and hope it's resolved, should I come across any info or alternatives I'll post back here.

    Dave
     

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