[UK-CONTEST] K3 working again

[Chris G3SJJ]

Good point about the cable ties Ian. Yes, the 14 pin DIL socket is a source of potential failure for such a key component. A weak design point I would 
say.

73 Chris G3SJJ



On 10/11/2011 08:54, Ian White GM3SEK wrote:
> Chris G3SJJ wrote:
>> Firstly thanks for all the comments and suggestions. Here is the story
>> for any other K3 owners who experience the problem. Initially I was
>> hesitant to accept that the fault might be a poor contact on a
>> connector pin, however I called in at the local Maplin store and bought
>> a £3.50 can contact cleaner. Spread the ESD mat out and wired myself up
>> to it! Removed both KSYNC3 boards and the KREF3 board, examined the
>> surface mount soldering carefully and then sprayed the pins on the PCB
>> connectors.
>>
>> On re-assembly the fault was still there! That is, no rx /tx and PLL1&
>> 2 display showing either 7.4 or 0.0. By chance I happened to tap the
>> TXCO, which is the metal can component on the KREF3 board, and the
>> fault cleared. The pins were quite sloppy in the DIL carrier so I bent
>> them very slightly to make a more solid fit. I have had the radio on
>> soak test now for several hours now and it is very stable.
>>
> I had exactly the same problem about a year ago. The wire leads on the
> oscillator module are too thin to give a completely reliable contact in
> the DIL socket, so in a few unlucky cases it eventually loses contact
> and throws up an ERR PLL.
>
> Bending the pins was not a complete solution here, as the fault came
> back after a few weeks. What finally did the trick was tinning the wires
> with solder to make them just a tiny bit thicker. The pins went into the
> socket with a much more solid feel and there have been no further
> problems.
>
> Related to that, the oscillator module was retained in the DIL socket by
> a single wrap-around cable tie. The nylon tie provided in the kit was
> too stiff and was causing one end of the module to tilt out of the
> socket. It is better to use two very thin ties of a softer material,
> inserted under the DIL socket from opposite ends so the module is pulled
> down flat.
>
>> A tip - Instead of trying to get the scope probe down the TMP mini coax
>> sockets, I used a spare patch lead supplied with the 2nd rx kit.
>> Plugged one
>> end into the socket and clipped the probe on to the other end.
>>
> Long medical forceps are a godsend for handling those TMP plugs deep
> down inside.
>
>> A satisfactory conclusion all round!
>>
> Fingers crossed for you, Chris.  If it happens again here, that DIL
> socket has already had its final warning.
>
>
>