TS-440 completely deaf

Discussion in 'Radio Circuits, Repair & Performance' started by KC0REL, Feb 11, 2020.

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  1. KC0REL

    KC0REL Ham Member QRZ Page

    I got a TS-440 from a friend for free, with the hopes that I can fix it and eventually use it on the air as a backup rig. The first issue I've found is it doesn't seem to recieve. No band noise or signals from the internal speaker, nor from the headphone jack. I even tried to use the data hookup to my computer and see if audio comes out there, but apparently the interface I use with my 450 is different than the one I need for the 440, so results there are inconclusive. I do have access to an oscilloscope, and I'm looking for where to start tracing the audio signal to try to see where it's gone bad.

    Also the goop issue seems to be non-existent on this rig, I don't see any evidence of it inside, so I'm assuming the previous owner removed it, thought I plan on looking closer at a later time.
  2. K7TRF

    K7TRF Premium Subscriber QRZ Page

    With a completely or mostly dead rig I'll generally start by checking every power supply which can be done with an oscilloscope or with a DVM. Download the service manual and follow the schematic starting from the main power connections looking for voltage regulators or labeled supply buses and check every one.

    If you have good supplies and you've checked the obvious functional stuff (e.g. not stuck in transmit mode, same symptoms on all bands and all modes, etc.) then you've either got the choice of tracing receive issues from the audio end or the RF end. If there's absolutely no audio, not even hiss then I'd probably start from the audio amplifier and output wiring as it's unusual for the audio chain to be completely silent. You should also check to see if you have S meter movement at times when you hear no audio that can help you identify if the issue is in the audio output sections of the rig or earlier in the processing chain.
    KC0REL likes this.
  3. N5CM

    N5CM Ham Member QRZ Page

    Make sure the squelch control is turned fully counter clockwise. Upper right most control, inner knob. Sounds crazy, but if the squelch control is turned up too far, you will hear nothing at all.
  4. KC0REL

    KC0REL Ham Member QRZ Page

    Squelch setting doesn't fix the issue. Looks like I need to figure out how to read a service manual lol
  5. G4COE

    G4COE Ham Member QRZ Page

    See this thread. It would be advisable to pick up as many clues as you can before 'delving n' guessing'.

    You really need a circuit diagram which are abundantly available, looking at the antenna input on the RF board, you'll come across a choke and a protection diode across the signal line, would it not be a good idea to check these?

    From the above link have you tried seeing if the attenuation switch and unplugging the antenna has any affect on the noise.

    KC0REL likes this.
  6. N2ZD

    N2ZD Ham Member QRZ Page

    I’m not sure about the 440, but some Kenwoods use a small glass bulb as an antenna fuse right around the input of the antenna jack. Start with that.
  7. NE4EB

    NE4EB XML Subscriber QRZ Page

    Does the radio transmit? Put in in CW mode and see if you have power out.

    If yes, chances are most of your regulated DC voltages are available. Check the receive side for the proper DC voltages being delivered to the stages. If those all look good, it's time to use the 'scope on the input to the audio stages. Then progress through the audio chain to see where it stops.

    Most service manuals will give typical signal levels for the various stages with a known RF input at the antenna jack. If you don't have a signal generator, put the radio in AM mode and tune to 10.00 mhz. Most locations in the US can hear WWV well enough for that to be useful.

    Sounds like you might be new to troubleshooting circuits. Can you follow schematic diagrams and locate the test points in a service manual? Do you know how to read what an oscilloscope is displaying? We all start somewhere so being unsure is OK, we'll try to help.

    What you are attempting can be one of the most rewarding aspects of the hobby.
  8. KA5IPF

    KA5IPF Ham Member QRZ Page

    It's not a fuse, it's a surge suppressor to ground. The TS-870 did use a bulb as a fuse. I don't know about the 890 or 990 but the rest didn't. Easy to check if it was the problem on the 870.
  9. W4FBI

    W4FBI Ham Member QRZ Page

    If you want, I'll repair it for free (yes, free). I've repaired over 100 TS-440's.

    Just a little bored here in retirement, and have no units in backlog to repair.

    You just pay for shipping.

    This is not a scam - call if you want: 843-839-3656

    Alan, W4FBI
    Myrtle Beach, SC

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