Digitrak debugging advice needed

[John Severyn]

My Digitrak has been operating normally for almost 2 years. :<)

But recently it started failing to initialize.. i.e. continues to give me 3 blinking dashes, once in a while OFF will be displayed for a fraction of a second, then back to 3 blinking dashes. A full power-down and restart would sometimes cure the problem...... but no longer. Now I get 3 blinking dashes with an occasional OFF, then back to 3 blinking dashes........for several minutes, then the display goes blank. Unit is connected to a 396 that seems to be operating normally. A power-down, power-up will result in the same problem sequence as above.

I will pull the Digitrak from the panel and check the aircraft wiring this weekend. But do you have any good advice on the failure to initialize?

Thanks,
John Severyn
Livermore, Ca.
N79LH RV-9A

[TrutrakTech]

John, sorry for the late replay, you've caught me at Sun n Fun. Luckily for you (not so much for me), I'm stuck in the hotel room quite sick today. One thing to examine closely will be your CWS (control wheel steering) switch. If this wire/pin sees a ground at ANY time, it will engage CWS mode and not allow the AP to do much of anything. A good test would be to completely disconnect that circuit from the AP connector and see if it functions correctly then. Thanks!

[John Severyn]

Hi Lucas,
I do not have a CWS. So that is not the problem. The weather turned really hot and I did not crawl under the panel to inspect the wiring. It is possible that is the problem. Yep, I suspected you were at Sun-in-Fun so no problem.

Get well. I will report more in a day or two as the temps are getting cooler and I will have the patience to work upside down under the panel. But I will definitely check the internals of the backside connector to see if the CWS pin is clear, and that all other wiring is proper.

Take care,
John Severyn
Livermore, Ca
N79LH RV-9A

[John Severyn]

Lucas,
I have pulled the main Digitrak head. The CWS pin2 is open (as it should be). When connected to the servo in the aircraft, all I get is the blinking dashes, then a very short "OFF" (396 has a flight plan and is connected). Then it returns to blinking dashes. After a few minutes, the display goes dark. I can reset power, but the above sequence just starts again.

Are there any other bench checks I can do? I'm an EE with digital hardware design experience and a fair home bench setup with scopes, bench supplies etc. I could even connect a stepping motor (instead of pulling the servo), but I suspect it is something internal to the AP head.

It has done this more often when the cockpit is warm. Over the winter it performed perfectly, then became more intermittent as the weather warmed. Now it does not care what the temp. Cold or warm, it will not initialize.

What could cause the head to "fail to initialize"? Are there any other tests I can do here on my bench? If not, I probably will need an RMA for repair. Suggestions are appreciated.

Best regards,
John Severyn
RV-9A N79LH
Livermore, Ca.
DT S/N 104920

[TrutrakTech]

John,

Ok, since the CWS pin is clear, let's go ahead and have you send it in to take a look at it. Just give the office a call and they can give you an RMA#. I'll be back on Tuesday. Thanks!

[John Severyn]

Lucas,
Thanks. Will call the office.
John Severyn

[John Severyn]

Lucas,
Thanks very much. My RV was down for a few weeks and I just did the condition inspection and re-installed the overhauled Digitrak. It works perfectly! Thanks for the help and the very speedy repair.

Best regards,
John Severyn
N79LH RV-9A

[TrutrakTech]

Glad we could help out, John!