Tags: Amateur Radio, Elecraft, K3

Posted: June 8, 2012

Elecraft K3 service

My main radio is an Elecraft K3, and it has a hard life! It’s never enjoyed the luxury of a permanent shack setup, but has always travelled around. It’s been to various contests, Antarctica and back twice (including 5 different bases, 2 refuges and 3 islands) and Ascension island, to name a few.

While on Ascension it would occasionally show “ERR12V” and then refuse to transmit until I reset the power. After seeking the wisdom of the Elecraft mailing list on my return, this was put down to a dodgy PL-259 to BNC adaptor I had been using. The problem went away but then resurfaced more intermittently at Halley.

Eventually this mail from Wayne, N6KR, appeared on the list – the problem was due to corrosion on the pins that supply power to the PA.

Now that I’m back in the UK and the K3 has caught up with me I ordered the replacement parts and decided that, since I would more or less have to dismantle the thing to change the relevant pins, I might as well give it a service and some general TLC while I was at it.

I must admit to being slightly daunted by the prospect of taking a soldering iron to my beloved (and very expensive!) rig. Fortunately, I’d originally built my K3 from a kit (you can choose to buy a kit or the pre-assembled radio). The knowledge gained from doing that, and the experience of building the K1 and KX1 made me decide to give it a go; without that behind me I’m not sure I would have wanted to do the job myself. Even so, I decided to put aside a whole Saturday for the job to ensure I wasn’t rushed at any stage – I was quite willing to take the whole day to ensure I was happy I’d done the best job I could.

(At this stage I should apologise for the quality of the photos that follow—I’m afraid proper lighting wasn’t the first thing on my mind.)

The patient checks in.

The first stage is to take the lid off the K3, and remove the sub receiver. With the sub-receiver out of the way, take off the fan panel and remove the patch lead that goes from the back of the sub-receiver to the tuner board (seen here with some yellow tape on it.)

Once that patch lead is out of harm’s way you can remove the screws holding the PA in place and gently start to work it upwards. The K3 scored first blood at this point, with a small cut on the finger as the board came free… After the PA is clear, gently ‘walk’ the KPAIO board off its connectors.

Here you can see the discoloured pins on the KPAIO board.

I was originally hoping to get away without removing the back panel, but it has to go in order to gain access to the bottom of the pins on the RF board.

I don’t really have any action photos of the next stage, but the idea is to remove the 6 power pins circled in the photo above while leaving the rest of the pins in the connector intact. I removed the plastic surrounding the pins with a combination of a sharp knife and some cutters (this was by far the most painstaking part of the whole operation!) and then removed the pins one-by-one with the soldering iron. Once the pins were removed, I tidied up and inspected the area with a magnifying glass before replacing them with the new gold-plated pins.

Next up, repeat exactly the same steps on the PA board. This is somewhat tricky, because there are some very vulnerable-looking toroids on the bottom of this board and no good way to support it while you’re working on it. I ended up fitting some motherboard stand-offs I had lying around at the three points where the PA would normally be attached to the K3, and using those to keep the components on the bottom of board clear of the table while I worked on the top.

The final part of the operation is the KPAIO board. Identify the two connectors you need to remove and use your side-cutters to snip all of the legs as close as you can to the plastic. Then remove each pin from the board one by one. My main worry when doing this was the tiny U6 – I didn’t want the heat I was putting into the pins right next to it to free it from the board so I was careful to avoid working in that area too much without giving it time to cool down.

With the old connectors removed I tidied up the board and inspected it under a magnifying glass again (especially around the SMT components) before soldering the replacement sockets in place.

That done, it was time to put everything back together and test.

Not without a certain degree of apprehensiveness, I connected the rig back up and flicked the switch. Happily the magic smoke stayed on the inside, and the W2 reported a solid 100W on key down, with the temperature of the PA remaining stable. To complete the test I hooked up an antenna and worked Switzerland and Slovenia on 20m CW before declaring the operation successful.

The real test will come in the IOTA contest… Hopefully the K3 will go the distance!