Kenwood TM-D710G go box

Discussion in 'Mobile Radio Systems' started by KD4MAX, May 14, 2018.

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  1. KD4MAX

    KD4MAX Ham Member QRZ Page

    I was just participating in a 2m net tonight, running off battery power, sending and receiving just fine. Then, my radio (Kenwood TM-D710G) went completely silent. I couldn’t hear anything on either receive side, turning up the volume, using the built-in speaker, headphones or an external speaker. I couldn’t even hear key beeps from pressing buttons. I turned the radio off and on multiple times, but nothing changed. I don’t even hear the power-on chirp. The display seems to function normally, and I see things happening when I receive and transmit APRS packets. I just don’t hear any sounds.
     
  2. KB0MNM

    KB0MNM Ham Member QRZ Page

    Kevin- Regarding that silent TM-D710G in APRS mode: Have you done any of these steps(?) : 1. Checked the manual regarding the default remote-control password ( was it at default? ). 2. Attempted to revert the radio to factory settings by way of the Kenwood program? 3. Checked the external speaker wiring for an errant short-circuit ( hint: a multimeter will often read around 2 ohms for an 8 ohm impedance speaker, yet .2 ohms or so-maybe in the meter leads would be shorted ). 4. Looked at your receipt for length of warranty? ( please follow the other steps first ! ). One thing that comes to mind is that the volume and squelch knob plastic might have become 'stripped' from the shaft underneath. These knobs would take a while to re-order, so be very cautious about testing by removal of the inner volume knob- if you misplace it, the new one may take months to arrive... ( Yes, I once had a TM-D700a with a lost knob... same size as less sophisticated mobile ).
     
  3. KD4MAX

    KD4MAX Ham Member QRZ Page

    1) I haven't checked for a remote control setting; I've never used it. It just went silent mid-operation.
    2) I have done a full reset since posting the above - nothing changed.
    3) I haven't checked the external speaker, but I don't receive sounds from it, nor a pair of headphones, nor the internal speaker.
    4) I bought the radio less than two months ago from Ham Radio Outlet.

    As to the knobs -- both knobs, both VFOs, simultaneously? Probably not. ;)
     
  4. KB0MNM

    KB0MNM Ham Member QRZ Page

    Kevin, While the remote control might allow someone else to change settings in your radio- because you did the full factory reset the radio should produce audio ( except if the audio section is damaged ). The TM-D700a that I owned had two separate audio jacks ( as in channel 1 and channel 2 ), yet I think that it only had one internal speaker. So you may have an external audio jack that silences the internal speaker, but if you have two- the problem may indeed be the audio amp chip or other device(s). Since you just purchased the radio, you should be able to contact Kenwood ( www.kenwoodusa.com, I think... ) about a warranty claim. Your radio may have what we refer to in the trade as 'infant mortality' ( as in something that went wrong in manufacture, and slipped past the Kenwood quality assurance folks ). If that is the case, they can find it without much charge to you. Before you re-connect an external speaker, consider using an AM/FM pocket radio or other device to verify that it is not shorted. Do this before disturbing the wiring in your go kit- in case the short is intermittent in nature. Of course, the ohm-meter check should be done first. Then you can be assured that the repaired radio will not need repair a second time, which might be hard to justify to Kenwood.
     
  5. KD4MAX

    KD4MAX Ham Member QRZ Page

    Jon,

    Thanks - I can certainly check it out with an HT to see if signals are getting out.

    I'm not sure that I have a device to check the external speaker (yes, there are two ports on the radio), but I can connect it to another device and see if it works there. It's just an MFJ box speaker.
     
  6. KD4MAX

    KD4MAX Ham Member QRZ Page

    @KB0MNM - I didn't check the transmit (no antenna on the Kenwood at the moment), but I did plug the MFJ speaker into my phone, and it works just fine.

    I got a couple of numbers for Kenwood, but one was just to order parts and the other was a canned recording telling me an address to ship it. I may try to talk to someone at HRO again, now that Hamvention is over.
     
  7. KB0MNM

    KB0MNM Ham Member QRZ Page

    You did not specify which model external MFJ speaker, yet may want to see if it has an impedance between 4 and 8 ohms. If I remember correctly, the Kenwood audio should work with speaker impedances as low as 4 ohms. I can attest this because I used the external speaker made by Yaesu which included a red noise reduction push button in the lower left corner. This may have been their model 4. Again, check for KenwoodUSA as a web site to get info. 73
     
  8. KD4MAX

    KD4MAX Ham Member QRZ Page

    Sorry, I should have specified - it's an MFJ-281 http://www.mfjenterprises.com/Product.php?productid=MFJ-281

    In any case, it's just one (silent) piece of the puzzle. The headphones I had been using only seconds before radio failure were working fine, when all audio simply ceased.
     
  9. KB0MNM

    KB0MNM Ham Member QRZ Page

    The problem may not necessarily then be with the headphones. Many technicians have found that there are very - very small differences in the sizes of 'mini' and 'submini' jacks from different vendors, as there are with plugs. The issue is that the plug can sometimes bend the switch contacts of a jack such that no audio would later be produced by the internal speaker ( and only opening the radio and examining each internal part of that speaker jack will find the issue ). That said, if your plugs were truly the right size- the jacks theoretically would not have been damaged. Since the radio is under warranty- I would let a trained tech at Kenwood or an authorized facility look at the audio section. Since you state that you can see packet activity on the bargraph display, the receiver should be good *except* for the audio and/or automatic gain control circuits. How those circuits might have responded to your headset would be a mystery. If the problem is just in the jacks, the repair *may* be relatively quick. Because of surface mount components and spares- this *may* be true... The new RoHS soldering means that circuit board rework by inexperienced techs usually fails.
     

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