Hidden connector on Tecsun PL-660?

Many thanks to SWLing Post contributor, Andy (G0FTD), who writes:


Not sure if you’ve come across this, but earlier when I was cleaning my Tecsun PL660 and took the main tuning knob off the spindle, I discovered what looked
like 4 holes of a hidden connector behind it !

I just did a quick search around and I came across a piccy of the PCB on a blog
page here and yes there appears to be what looks like a small USB connector of some sort poking out the PCB where the VFO knob is. [Andy clarifies that he was trying to point out the area to look, but the pic appears to be from the opposite side, so you can’t see it.]

I can’t say that I’ve ever seen reference to it.

Maybe you or your readers might know ?

73 de Andy G0FTD

Thanks for sharing this, Andy. I am curious if that might be the port they use for firmware updates? Perhaps someone here can verify? I gave my PL-660 to a friend and no longer have it here for reference. Please comment if you have some info about this port.

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13 thoughts on “Hidden connector on Tecsun PL-660?

    1. Jake Brodsky

      I suspect it is more likely to be something like I2C, or JTAG pins. That’s how one might flash the code in to the display and controller in the first place.

      1. Ron F

        Unlikely to be JTAG; that requires at least 5 pins (the minimum 4 signals + 0v/gnd). I had in my mind that the uC was an NEC/Renesas 78K series, but that also requires a minimum of 5, so I’m probably mis-remembering.

        Given it’s only 4 pins it’s likely i2c, serial, or similar, or maybe some device-specific interface.

  1. Ron F

    Here’s a short sequence of pics showing PL-660 disassembly down to releasing the front panel board. As I say there, once you get it out there’s not a lot to see – everything’s hidden under a soldered-down shield.


    One day, if I ever get get some free time & have my workbenches tidy again (!), I might try seeing if there’s any activity on those connector pins at e.g. startup, after reset, etc.

  2. Bob Colegrove

    You have to remove the front cover. I have a clear shot of it, but cannot post it as a comment. It is located between the light-snooze and fast-slow switches in the upper right corner of the PCB (black molded 4-pin connector). Here is a link to a YouTube video (shows after about 9 seconds).


    Interesting that the shot in the RadioJayAllen review of the radio does not show one.


    I cannot find it located on the schematic I have.

    Bob Colegrove

    1. Ron F

      Yeah, it’s not there in all revisions – one of mine (an earlier one) is lacking it.

      FWIW, if you’re looking at that chinese PL-660 schematic that’s commonly available on the ‘net, you’ll notice it’s lacking the whole front panel board / keypad / display / uC section where the socket is mounted. The rest of it has a few other errors too, though it’s usable for repairs/mods if you know what you’re doing.

  3. Broadwing

    That’s interesting. Sort of off the subject I often wondered why the PL-880 had so many hidden features and the PL-660 had none I’m aware of? The 880 came out not to long after the 660 if I remember rightly. I still use my PL-660 for car DXing. In fact it resides permanently in the car in a nice sling pouch with accessories.

    1. Ron F

      The PL-880 is essentially an SDR receiver chip (Si47xx) controlled by a uC, while the PL-6xx are pretty much conventional analogue receivers (albeit with a digital PLL & linear IC receiver chips) with uC-controlled tuning.

      Upshot is in the PL-880 the front-panel uC can directly control the different modes/features/etc of the Si47xx chip, while in the PL-660 all it can do is tune & switch between the different analogue sections (e.g. AM, FM, a little tweaking to get Air Band, etc). Which is why the PL-880 has ‘hidden’ receiver features like (barely working) sync, adjustable DNR & muting, etc, while the PL-660’s hidden feature is basically ‘tuning/display calibration’.

  4. Ron F

    Yeah, there is a 4-pin header-type connector there, though it’s not visible in the linked pics – it’s on the front panel/display/keyboard board, in *front* of the tuning knob.

    With the 660 apart It’s mostly hidden under the display & I’ve never investigated it, but I assume it’s for updating the micro which is on the front panel board. If nobody beats me to it, I’ll see if I can upload some pics later tonight or tomorrow.


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