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Kenwood TS-830S Deafened Receive Repair!

Discussion in 'Radio Circuits, Repair & Performance' started by N9PCT, Mar 20, 2019.

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  1. N9PCT

    N9PCT Ham Member QRZ Page

    I just completed the repair of my TS-830S after an unfortunate incident a few years ago. I'm simply looking to document my procedure here and have no specific question, but would welcome advice from those that know these radios better!

    I am a graduate student at Purdue University and a member of the club, W9YB, and approximately four years ago we installed a 160m dipole. Long story short we found out that this antenna couples with our 40m dipole. We discovered this when another member was running 1.3kW of 160m and I was tuning around 40m on my TS-830S. The input transformer was blown almost immediately upon his key-up and my radio has been deafened ever since.

    At the time K4EAA had a large list of radios to get to and I could not find a replacement transformer (L41) so the radio sat until recently when I decided to look again and stumbled upon KD7DNY (kd7dny.com) who makes reproduction hybrid parts. I ordered a new L41 straightaway and this is the result.

    Here W3AXL and I find the reception baseline before repair. The 1kHz tone is lost at -90dbm at 28.8Mhz



    I first disassembled the radio and found L41 on the RF board in the main top compartment. L41 has a yellow/orange top.

    [​IMG]

    [​IMG]
    I removed the RF board per instructions on K4EAA's website. It seems the RF board has had some modifications done to it over the years... not sure what any of them do, but I put everything back exactly as I found it. Nothing else except L41 was broken, so I'm not looking to "fix" anything else. I'd appreciate any insight on what these mods may be though.



    I flipped the RF board over and using liberal flux and solder wick, desoldered the original L41.

    [​IMG]

    Here are the old and new L41 transformers. The new one is in black. Huge thank you to KD7DNY, without whose help this radio would not have lived for another several years.

    [​IMG]

    The new L41 went in without complaint once the thru-holes were wicked of old solder and fluxed.

    [​IMG]

    The whole underside of the board and as much of the top side of the board as I could get to was cleaned with 91% isopropanol.

    After reinstalling the board and re-soldering the wires that were previously added, I reassembled the radio.

    Here's a video of the same test that was initially done by W3AXL and I. The radio now will clearly receive a 1kHz tone at -130dbm! Apologies for the dirty AF pot - It's on the list of things to clean.



    While I was in the radio I noticed the HV caps were original, but not leaking. Figured I should "quit while I'm ahead" and ordered a new set of HV Caps from VE3PVS for $30.

    You Kenwood Hybrid gurus, what else should I do to this radio to keep it up? I have considered upgrading the 6146B tubes to 6146W tubes as recommended by K4EAA. My tubes work but are somewhat soft and appear to be pretty old.

    I also noticed that, even though my radio is a "gold label" model, my two CW filters are missing. They must have been removed and sold. Are these filters available any more? What filters were installed, and where can I find them? I would like to bring this radio back to full operational capability.

    [​IMG]

    Extremely excited to have my radio back. Thanks again to KD7DNY and to K4EAA for the parts and knowledge.
     
    Last edited: Mar 20, 2019
    K6RBK and K7TRF like this.
  2. KA5IPF

    KA5IPF Ham Member QRZ Page

    Nice that those old parts are available again. The filters are still available on the used market but there is a very good chance the radio didn't come with them. The Gold/Silver label myth is just that. In the later runs the marking were Gold. If it had filters they were dealer/owner installed. Oh, and make sure the trap coils are good. Usually when L41 goes one or both trap coils are damaged also. I usually replaced all 3 at once.
     
    N9PCT likes this.
  3. KQ9J

    KQ9J Premium Subscriber QRZ Page

    Brings back memories. I had to replace that input coil on my TS-530SP about a dozen years ago. I couldn't blame that on any specific cause...just turned it on one day and no receive! Found a parted out 530 on ebay, changed the coil, and fine ever since.

    Hopefully your post will help other amateurs keep these beautiful hybrid Kenwood rigs running! They are classics :)
     
    K7TRF likes this.
  4. N9PCT

    N9PCT Ham Member QRZ Page

    Thanks for the info - I'm probably going to remove the RF board again and clean the band selector switches and I can check them then. I'm not familiar with where they are located though, or where replacements could be found. Is there any published info on this? A quick Google search didn't return much.
     
  5. K7TRF

    K7TRF Premium Subscriber QRZ Page

    They're on the RF board near L41:
    upload_2019-3-20_8-59-34.png

    Perform the alignment step 20 - IF trap adjustment, in the service manual. If each of those adjustment coils (L22, L3, L4) help to null the 8.83 MHz signal injected into the antenna terminal then they're doing their jobs. If one or more do nothing while trying to perform the IF trap adjustment (turing the coil slug does nothing to help null the injected carrier signal at the IF frequency) then it's likely you burned out that coil.
     
    N9PCT likes this.
  6. K7TRF

    K7TRF Premium Subscriber QRZ Page

    P.S. You probably already know this if you're aligning a TS-830, but the Kenwood service manual refers to levels out of their SSG (Standard Signal Generator) that are listed in dB (no suffix) and not dBm. Their SSG is referenced to a 1 uV signal which is very unusual but something some of the Asian manufacturer's did back in the day.

    So for instance in that IF trap alignment step where they tell you to inject a SSG signal at 8.83 MHz at 80 dB they're talking about a 10mV signal (-27dBm) from the signal generator. IOW every level referenced from the Kenwood SSG is referenced to -107dBm = 0dB (SSG).
     
  7. KA5IPF

    KA5IPF Ham Member QRZ Page

    Just as a note. The problems with the bandswitch are usually not the contacts but the rivets that hold the contacts to the PCB and trace.
     
    CX3CP and KA9JLM like this.
  8. N9PCT

    N9PCT Ham Member QRZ Page

    I read this article from W0NTA describing the bandswitch cleaning process. In it he soldered some contacts to the trace because of rivet problems.

    http://www.w0nta.com/Rebuilding the bandswitch.pdf

    I figure I'll give them a good inspection and if the rivets are making poor contact after cleaning, perform a similar repair.

    As far as the SSG goes, I see what you mean and I didn't know that was the case - thanks. Since we don't have one, I'll just have to suffice with our R&S CMU200.
     
  9. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Yeah, that's kind of the point of my post. None of us have the Kenwood 'SSG' so just use a 50 ohm RF signal generator and set the dBm levels appropriately with the understanding that when the manual says X dB from the SSG that's X dB above -107 dBm.
     
    Last edited: Mar 20, 2019
  10. N8YX

    N8YX Ham Member QRZ Page

    If you can't find the OEM filters used, put a set of Inrads in it. They have better shape factors than the stock accessory units.

    My 'SSB/CW' '830 has both 500Hz Kenwood filters fitted and this arrangement works well in digging out weak CW signals. The other - a TS-830'M' (which I built from an -S) has no CW filters installed (by design) and must make use of the VBT control to narrow down the receiver passband when operating CW.

    It's about a 5 minute job to swap the rigs in the lineup if I'm doing serious CW work on the upper HF bands, which is where the position is used.
     

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