K2/100 Completed

The KPA100 is now completed and after thorough testing I’m glad to report I’m getting 115 watts out of the K2. 

I have to admit towards the end of the build I was beginning to get a bit tired, I’d taken a lot on but it has been worth it, to build a pristine K2/100 in the such a short period of time cannot be bad. 

I’ve had some ups and downs especially with the PLL oscillator testing which really threw me, but I’ve fulfilled my ambition which was to build my ultimate kit.  

There’s no question if you want a bit of a challenge and something to do during those long winter evenings this is a great kit to build. You have excellent instructions and the knowledge of back up from both Elecraft and the forums should you run in to any difficulties.

Problems associated with these or any kits are normally self administered, e.g. cold solders, soldering bridges or missed components. Rarely do you get a component failure and if by chance you do, Elecraft will simply ship out another to you.

The instructions are extremely good but you must follow them carefully, you cannot jump ahead or miss out pages; you will find yourself open to mistakes which take forever to find and then repair.

I have only one correction in the instructions, that is to include the connectors P3 and P6 in the original build of the K2. These small two pin connectors are  used for connections to the KPA100, they would not effect the K2 if added before hand and it would mean you don't have to remove the bottom cover of the K2, which can be a difficult process.
It’s a real shame when you see the light at the end of the tunnel then you realise you have to open up the K2 bottom cover just to add two pins!

I'm not sure whether to add the SSB option in the near future, knowing me I suspect I probably will, also at some stage I will need an automatic antenna tuner, the SWR on the K2 is very sensitive and using a manual ATU is proving interesting to say the least!

Well I'm at the stage now where I'm going to enjoy my new toy, I will use the K2 as my main radio for the next month, just to get used to it and to see how good it really is. 

I must admit looking at the shack now I'm beginning to build up quite a few pieces of kit. Not sure what my next project will be but I suspect some kind of antenna, I have a nice rotator sitting in my shed doing nothing, maybe I should attach it to a moxon or a yagi!!

KAF2 Installed in to the K2

I’ve now completed the installation of the KAF2 in to the K2 and what a difference on receive, I was pretty impressed with the standard set up but by activating the KAF2 the background noise literally melts away.

I have the optional CW filters fitted to my Yaesu FT1000 MP V and it is extremely good at fishing out those quiet stations hidden by QRM or some other interference, but the K2 matches up and in certain circumstances beats it hands down.

It’s not necessarily the filters, it’s the background noise, with the KAF2 installed in the K2 there simply is none!

Attempting a simple test I matched both radios to a fairly strong 30m CW signal with all the filters switched in. I have to be honest I was amazed at the difference.

The background noise on the Mk 5 was certainly louder although clarity of the CW station was good, it was just you had that what I can only describe as a fish bowl echo to deal with.

The K2 did not have the fish bowl echo; it was just very quiet with excellent clarity, even more incredible was that I could reduce the filters on the K2 and it still beat the FT for clarity and background hiss. No question the K2 wins that particular department.

What's interesting is I can remember when I first bought the FT1000 MP V and being so impressed by the receive capabilities, especially against the old FT 990 I had at the time.  The MP V is a fine radio and I must admit I didn't think its receiver would be beaten by a kit radio costing quarter of the price. Still, I wouldn't sell or swap my FT for anything, the K2 may beat it on receive but that's about it!

The KPA 100 is now under construction and I’ve now reached the first alignment procedure, no big issues yet, but now I have to start connecting the amp up to the K2 and start doing some testing, so things may liven up! Once the alignment has been completed I can start winding the toroid’s and hopefully begin to see the light at the end of the tunnel.

A footnote to my K2 receiver opinions, I've just come off air an hour after writing the earlier post:
I had a QSO with JA4FKX/QRP (Nan, near Osaka) he was transmitting 5 watts using a Yagi. I heard him closing with an Italian station and I thought "what the hell, let's give it a try" So I called him on the K2 with 5 watts going through the cobweb. He came back giving me a 549!  
Distance between us: 9602 kilometers or 5966 miles. 
Don't you just love amateur radio!

Rework Eliminator and KAF2

The audio filter KAF2 has now been completed but not yet installed. 

The kit was fairly easy to build and only took me a day to finish. Besides the KAF2 I have also built the Rework Eliminator which alleviates the pain of removing components from the K2 when installing the various options, it’s a sort of plug in and play which a lot of K2 owners recommend for obvious reasons. 

You simply break off the required circuit and plug it in to the area the option will sit within the K2, this acts as a cover until you are ready to install the option kit in to the circuit. This means when you purchase an extra option you do not have to unsolder any pieces of kit, you can just remove the eliminator and install your new option at will without the hassle of any soldering, a very simple but vital piece of kit. 

My only problem was that the Eliminator turned up late and I was well in to the build of the K2, so I thought better to wait until I’d completed the radio before installing, just means I have to dismantle the main box again and have a play on the circuit boards , but I think I can live with that

K2 Completed

Well the K2 was completed on Sunday afternoon virtually one month to the day from first receiving it in the post.
By Sunday evening I’d had my first QSO with a French station F3MB (Jean in Bordeaux) who gave me a good 589 report. 

 Safely positioned in the Shack!

 

The building of the transmitter went a lot easier than the receiver but I still had a few issues along the way. Sunday morning on the first power test I thought I might have a serious problem as it was only pushing out half a watt no matter what power output I was selecting, something was not quite right.

A quick search on the Elecraft K2 forum and I had the information for a basic power trace of the problem and within the first couple of power checks with the DMM I found a cold solder joint on one of the transistors. A quick touch of solder and a few more checks which produced no further issues I put the K2 back together and hit the tune button, all was well and I was getting good power out in to the dummy load.

My only concern is that I'm having to use a manual ATU which is a bit of a pain when trying to remember each tune and load settings for the different bands. So its either invest in the K2 auto ATU or buy myself something like an LDG auto ATU, well see what happens.

Looking good next to the old OHR 100A

Now I’ve got the two other options to build; the 100 watt PA and the audio filter which hopefully won’t take me too long. I’ve also got the chance to buy the SSB, 20 watt ATU, and 160 meter option from my fellow K2 builder down the road from me. The SSB and 160 might suit but the 20w ATU wont be much use.
I'll see, I may well be "elecraft'd" out by the time I've built the PA and filter!

Success Alignment 2 Completed at Last

After two weeks of having my PLL oscillator problems I finally cracked it and thankfully the “Alignment test part 2” is now completed. I have to give a huge thanks to Don Wilhelm from the K2 forum, without his help I would still be tearing out what little hair I have! 

As usual with these things it was something small, a resistor or to be precise a resistor network that wasn’t playing ball. After replacing various components we narrowed it down to this resistor pak and in the end I replaced the pak for two separate 10k resistors as suggested by Don and it worked. 

From removing and replacing the pak a number of times I managed to damage one of the patches off the PCB but thankfully it wasn’t required so I was extremely lucky. 

 The PLL oscillating area is the top right of the PCB, you can see in the picture below where I've replaced the resistor pak with two 10k single resistors, that finally did the trick and got it running. You can see the 6th patch is damaged but luckily is now not used.

 I must admit I was beginning to lose hope and my confidence was getting low, I really thought I wasn’t going to get the old K2 working. It’s an amazing feeling when it all comes together and you realise you are not  a solder wavering madman who mucked everything up. 

The good news is I have had a listen to 40 meters CW and the radio sounds great, the filters are really good and first impressions are that it needs a slight tweak here and there but all in all it’s a very good receiver.

K2 PLL Issues But I'm Getting There!

The problem with alignment continues but the good news is that as I go along checking each part, measuring the capacitance or the resistance I'm getting to know how everything works. 

The interesting fact now appearing to me is I'm no longer scared of this kit, it's actually quite fun to learn and slowly understand how each individual part works in conjunction with another.

I think I know the problem with the PLL testing, for K2 owners its D17 one of the varactors. At the moment when I switch to PLL testing I get a good 12099.00 Khz reading and when pressing the plus button it stays as it should, but when pressing the minus button it drops to 00.450KHz , way out. 

So I kept plugging away trying to find the problem and by chance found with the DMM probe that if I touched D17 instead of the one good reading of 12099 it reverted to 00.450 so that both plus and minus was then out. By touching D17 again I got the 12099 back up. Definitely a varactor problem and a new one has been ordered and I suspect once replaced should hopefully fix the issue. 

You find yourself checking your soldering, (is it any good and up to spec?) are there any bridges? Have you made some gigantic cock up somewhere? And all your confidence vanishes as the hours go by and you find yourself getting nowhere and even dare I say think about giving up!

But then you realise that hundreds of kit builders have gone through the process where somewhere along the line they've come across a problem and find themselves scratching their heads wondering what the hell to do.

Inevitably it something simple like one component that refuses to play or a simple soldering issue and once its rectified, bingo, the kit works and you wonder what all the fuss was about! 

A friend of mine who has just completed his K2 took 18 months and had various issues, he is I might add is a true experienced home-brew builder, having built many transceivers and other more complicated pieces of kit and I dare say was building other kits along with the K2 (hence the 18 months). 

Yet he had similar PLL problem besides others issues. An interesting thing he said to me was that he knew builders who had lot less experience and had sailed through the kit with absolutely no problems. It's the luck of the draw.

However, he is now happily singing its praises and telling me what a superb rig the K2 is and that I will get there in the end and no doubt I will, but it will not take me 18 months I can assure you!

K2 Alignment Testing Begins

The build with the K2 continues on and I am now at the second alignment testing stage. With the front and control boards completed I’ve reached halfway through the RF board with most of the components for the receiver now fitted.

The alignment testing consists of a number of actions to prove all is working correctly, these are the 4MHz ref oscillator, RF alignment, AGC threshold and IF filter alignment.

Sadly though I’m stuck on the oscillator test and am unable to get signals within the approved spec.  Searching the K2 forums this is a well-known problem and normally means some soldering/bridging issues or a component problem or perhaps a component misplacement.

So at the moment I’m running checks within the oscillator circuit searching for what may be at fault. One thing I did suspect was the toroid’s which have the correct windings (I've double checked), but don't seem to have a decent amount of tinning on them and I suspect I will have to remove and re-tin. I've never had the issue of toroid winding, in fact I find it quite therapeutic although hand winding five of them in one afternoon does tend to cut your fingers up!

I think with a bit of time and patience I’ll get there, normally with problems like this it’s some minor issue that the builder has missed and when the problem is found you can never believe that such a small error could cause the issue.

The good news is that the forum provides plenty of support and talks you through each check in detail so you are bound to find the cause in the end. Also by chance a fellow ham just down the road is building a K2 so if needs be we can get together to discuss. 

Hopefully in the next post I'll have moved on and perhaps start to see light at the end of the tunnel!

K2 Smoke Test Completed

Well I’ve done the initial smoke test and thankfully all is working, but I had a few issues along the way. 

 Note the egg box in the background, an ideal area for placing parts

Naturally when you get your kit you are very keen to get going and build as quickly as possible, the simple rule you must follow is to take your time and check every component as you go along. You must check it’s the correct item, and when installed is soldered correctly with no bridges.

I did the classic of installing a component (the socket for U1 a large chip) and missed one solder point. Naturally I thought I had checked, but obviously no doubt due to haste I missed it.

 Consequently I carried on and installed the LED Backlight assembly and the LCD over the socket, so two separate items were covering this costly mistake. On the first smoke test I got no LED backlight or LCD readout.

It took me a whole morning to find the problem and then I had the difficult task of creating an opening to raise the LCD followed by removal of the back light to actually get to the problem which then took only seconds to fix, a simple solder.

It felt more like a surgical operation rather than a repair. Mistakes are bound to happen, but the morale of the story when building this kit is check, check and double check! 

 With initial testing done the main board has now to be completed with RX and TX components

However, all is now well and with the smoke test completed I can continue on but at a slightly slower pace.

K2 Front Panel Completed

The front panel is now completed and so far the build is going well, a few minor issues where there have been some solder dry joints and bridges but nothing major. With the Easter break upon us I’ve had a few work free days so that I have managed to make a good start and things are progressing nicely and hopefully I’m ahead of schedule.

My old vinyl record disc anti static mat makes and Ideal building pad and attached to my anti static wrist band I happily work away with the radio playing some background rock music and drinking vast amounts of coffee! 

I picked up an interesting tip for checking dry joint which is to hold up a bright torch behind the PCB board and check each joint; pinpricks of light will appear if the solder is dry or incomplete.

 Resistance tests on each completed PCB board were a little worrying as my experience with a DMM is not great but a quick lesson on the web got me started and the tests were not as bad as I thought. 

 It’s noticeable that if I work too long I make silly errors, so I must pace myself and remember that mistakes can happen when you have been over doing it!

K2 Build Begins

Inventory completed, I’ve cracked on and made a start on the Control board which is the first of the three PCB boards that have to be completed. 

So far so good with no initial problems, I’m using some thinner solder wire than previous builds and it definitely makes a difference, I only wish I’d done this for the OHR100. 

I’ve managed to install all the capacitors, resistors, diodes and begun work installing the transistors. Hopefully by tomorrow I should have the Control board completed.

I've managed to take over the conservatory at the back of the house which is a small well lit room  and ideal for building purposes as it's out the way and I can leave everything in place knowing it wont be disturbed. With the radio turned up I am left to my own devices and can happily solder away!