[TenTec] Cautionary Tale: Orion 13.8 V connector (long)

[Dick Green]

Hi,

 

I want to warn everyone about a problem I encountered with the 13.8 VDC
power connector on my Orion I. Over time, stress on the cable can deform the
pins inside the connector, resulting in intermittent contact and/or a high
resistance connection. If the resistance gets high enough, the voltage
inside the radio will drop below spec when transmitting, causing the Orion
to crash and reboot. There can be other odd symptoms before a crash occurs,
such as the LCD backlight flickering and audio artifacts in QSK operation
(I'm sure that will get the attention of many on this reflector -- see the
end of this mesage.) In my case, the high-resistance connection also caused
burn marks inside the plastic connector on the hot side. This made me wonder
if the problem could present a fire hazard.

 

In my opinion, the connector arrangement is flawed because one end is
rigidly fixed to a PC board inside the radio and the other end is attached
to the cable. Repeated wiggling of the cable will cause the split male pins
in the cable end to compress, while the female pins at the radio end expand.
Eventually, they begin to lose contact with each other. Pulling a lot of
current through the resulting high resistance junction causes the pins to
heat up, leading to discoloration of the metal and burning of the
surrounding plastic. I believe heat plays a role, making the symptoms
intermittent. As you transmit, the connector heats up from drawing high
current across the high resistance junction, the female pins expand even
more, the resistance increases, and the voltage drops below spec. 

 

I've had my Orion for about 3 1/2 years. It's been moved around a few times
and was taken on a trip once, but I wouldn't say the cable has had excessive
stress put on it beyond what would be normal in most shacks. I considered
ordering a new PC-mounted connector and power cable from Ten-Tec, but
decided to install a more rigid system. I ended up soldering the cable
directly to the PC board in place of the connector. I passed the cable
through a rubber grommet to keep it from abrading against the sharp edges of
the rectangular connector hole in the chassis, and used a small cable tie to
clamp the cable down so it can't move inside the radio and put stress on the
solder junctions. I suppose it's a bit of a kludge, but is superior
mechanically to what was there before. The downside is that the cable is
permanently attached to the radio. I can live with that, but others may not
like it.

 

Many mobile rigs have the power cable pass directly into the radio through a
strain relief, and the connectors are a few inches down the cable away from
the radio. I believe this arrangement puts less stress on the connectors.
Also, I've seen much higher-quality connectors used for mobile rigs, which
probably aren't vulnerable to the problem I encountered. Although it would
result in a little pigtail hanging out of the back of the Orion, such an
arrangement would be superior to the current design. If that's not
acceptable, I'd recommend a completely different type of power connector.

 

The story of how I discovered the problem follows. Some may find it
interesting or helpful for diagnosing their own connector problems. 

 

I operated CQ WPX CW this weekend. In the weeks before the contest, I had
noticed some mild flickering in the LCD backlight on transmit, which I had
not seen before. I meant to look into the problem, but didn't get around to
it. 

 

I had great runs on 40m to Europe during the first two hours, about 235
contacts, and then the rate dropped off. I turned on the CQ repeat loop and
the Orion spent at least an hour or two calling CQ. The Orion was driving an
Alpha 87A amp, which needed about 70W of drive to put legal limit power on
my 2-el 40m beam (SWR about 1.5:1 at the bottom of the band.) I noticed that
the LCD backlight flicker seemed to be getting worse. All of a sudden, I
heard a loud pop in the headphones, several relays inside the Orion snapped
loudly, and the firmware rebooted. I've never seen that before -- usually a
crash kills  the radio and I have to cycle power. But the Orion came back up
by itself and appeared to be working normally again, except for the LCD
backlight flicker.

 

About 20 minutes later, I had another crash-reboot. Again, the radio
recovered by itself. Pretty soon, the Orion was going through the
crash-reboot sequence every few minutes. I was forced to switch run
operation to my FT-1000D. I had loaded the latest V2.062a firmware before
the contest (I like to live dangerously) and thought perhaps it was the
culprit. I backed up to a previous V2 release, but the crash-reboot sequence
kept happening. I even backed up all the way to V1.363b5, but that did not
cure the problem.

 

I use an Alinco DM-33MV switching power supply with the Orion because I find
the fan on the stock Ten-Tec 963 power supply to be horrendously loud when
it kicks on -- even when I'm wearing high-isolation headphones. I checked
the voltage on the Alinco and found that it was slightly low -- 13.6VDC. I
increased the voltage slowly, and found that at about 14VDC the LCD
backlight flicker nearly disappeared. At 15VDC it went away entirely. The
higher voltage seemed to somewhat reduce the frequency of the crash-reboot
problem, but didn't cure it. Then I swapped out the Alinco for the Ten Tec
963 supply. That supply puts out about 14.22VDC when idle, and the LCD
backlight flicker was completely gone. However, the Orion would still crash
and reboot every few minutes. I was beginning to think  the finals were
shot, or perhaps an internal voltage regulator was failing.

 

Later in the contest, I realized that if I reduced power to 30W the Orion
would not crash. This drove the 87A to put out 500-750W, depending on the
antenna, which was acceptable for S&P work. That's how I limped through the
contest.

 

Late in the contest, I caught a break that saved the radio a trip to
Tennessee. To battle fatigue, I decided to change my sitting position. I
have a wireless keyboard that lets me push the chair away from the desk and
put my feet up with the keyboard on my lap. I reached over to grab the
Orion's VFO pod, and suddenly the Orion crashed again -- without
transmitting. I discovered that if I pulled on the cable, the Orion would
crash. It didn't take long to realize that the pod cable was resting on the
power cable. I wiggled the Orion's 13.8 VDC connector, and the radio
crashed. I pulled the connector and saw ugly brown burn marks on the hot
side. The split male pins were compressed all the way. I tried cleaning the
male pins and spreading them. This solved the backlight flicker problem, and
greatly reduced the frequency of the crashes, but did not eliminate the
problem. Back to 30W.

 

After the contest, I popped the Orion's covers and, using an ohmmeter, found
that no matter what I did to rehabilitate the male and female pins, the
cable would lose continuity if I wiggled it. That's when I decided to
replace the connector, as detailed above. After doing so. I ran a CQ loop
into both 80m and 40m at 100W for 15 minutes each and experienced no
crashes. I also duplicated the 40m scenario, 70W into the 87A into the 2-el
40m beam, and had no crashes for over 20 minutes. It'll take another contest
to be sure, but I believe the problem has been solved. 

 

QSK Audio Artifacts: There was some barely noticable LCD backlight flicker
with the Alinco set to 13.8 VDC, so I increased it to 14.22 V, same as the
963 power supply. Now the flicker is gone. In the course of playing with the
input voltage, I was surprised to hear the tail-end clicks in the QSK audio
significantly reduced when the voltage was increased to the point where the
LCD backlight didn't flicker. This may explain why some people hear more QSK
audio artifacts than others. 

 

The moral of the story is: check your 13.8 VDC connector. Make sure there
are no burn marks and that the pins are making tight contact. Be sure to
rout the cable in such a way that there is minimal stress on the power
connector. If you're really worried about it, devise a better connection and
let me know what you did.

 

Sorry for the long story, but hopefully it will be useful to someone out
there.

 

73, Dick WC1M