Friday, August 28, 2009

Orion Surgery

My Ten-Tec Orion transceiver was 5 years old in February. It's getting to be an old timer -- in computer years, at least. It needed a few chores done.
  1. The LCD panel was flickering. Internet scuttlebutt says this may be because of impending failure of filter capacitors that were undersize (in terms of ripple current handling).
  2. With the current version 2.xx firmware, the LCD contrast is close to zero after a hardware reset. This can be a serious problem, depending on room temperature. Contrast is normally set via a menu adjustment -- that requires you to navigate through the LCD display. The display could be so faint that you couldn't make the adjustment. There is an internal bias control that should fix this.
  3. Finally, I have been seeing the "RIT freeze" problem that others have noted. At times, the RIT control loses the ability to make any adjustments. Many people have reported this problem, but the cause and cure have not been well understood. It seems that you can fix it temporarily by grabbing the RIT/XIT encoder control and twisting hard in odd directions -- as if there were a bad solder joint on the PC board. A recent report suggests the trouble is actually with one of the board-to-board connectors making unreliable contact.
All the above have been discussed on the helpful Ten-Tec reflector, which I recommend to other Orion users. I have been saving up these problems for some time now. Hopefully, I only have to disassemble the Orion once!

Making a long story short, I pulled the rig out of my operating position, unplugging many cables, unscrewed many screws, and finally spread out the works on my bench. The RIT fix requires disassembling the front panel and the LCD/computer board. That's a fairly big operation, particularly since a wrong move with a tool could lead to a very costly repair job.

I located and replaced 3 electrolytic capacitors on the A9 board with higher voltage, low ESR units, per the helpful analysis of N6IE. Soldering was tricky, to prevent inadvertent short circuits and to get enough heat into the ground connections, which were not thermally isolated from the big ground planes on either side of the board. (That could have been avoided by a better PCB layout!) OK. That's problem #1 done.

The email instructions say that to solve #3, you need to look for bent or misaligned connecting pins on the computer / LCD board. I looked very carefully, but saw no misalignment or other problem. Still, it's possible there was some oxidation or dirt. I cleaned the pins and the sockets as best I could. So problem #3 might be resolved.

The LCD bias issue (#2) turns out to be easy. There is a control on the LCD/computer board that sets the default bias for the display. You just adjust it for a good display with the LCD menu set at the default 50% level (and of course with the power on and the rig having a chance to warm up).

Accomplishing all this, I reassembled the Orion and put back all those screws, and put the rig back in the operating position. Everything appeared to work, except no transmit power. Oops! There are a lot of reasons why this could happen. Fortunately, I did not smell smoke, and that eliminated some of the more expensive possibilities. Still, I'm not sure how much bench testing and repair I would be able to do, if this turned out to be a non-trivial problem. Thinking of where that shipping box might be, and how much Ten-Tec charges...

So, what did I really do in that repair process? I changed out the capacitors, true, but the fact that everything works in receive mode indicates that the power board was probably working. The other thing I did was to unplug many internal cables, disassemble the LCD boards, and reassemble. There could be a loose connection or a misplaced cable.

The problem was "fixed" by opening up the box all the way again, and carefully reinstalling all the cables and screws. We have transmit power for now. I hope it stays that way!

The triple repair job is done. The LCD is behaving much better than before, and at least for now, the RIT/XIT controls work smoothly.

One thing I hadn't counted on was the trouble of reconnecting my ratsnest of cables to the Orion. I have a linear, a transverter, computer audio and controls, and other gadgets that need to be connected. All these just got hooked up over several years, and of course I had nothing documented on paper. Figuring out how to reconnect took a while, but it should be better next time. Now the cables have labels on them. Documentation is still pending...
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