January 3rd, 2024. Trouble Shooting a Mystery

Bill, N2CQR on a recent trip to San Fransisco missed seeing the Persian Lamb, AKA Yvonne dAngers. Sorry Bill, but the photo I have is not suitable for a blog. Having seen her show I can attest -- they are real!

 A trouble shooting mystery! Recently I built an external Digital -VFO and Controller for the Ten Tec Triton II. I am very pleased with the results. But I had not totally completed the project as the final piece was to install the back apron which contained the LO Output to the Triton II and the Power Input to the box. 
 
For several weeks I operated the unit with leads temporarily soldered to the electronics. Another reason: I misplaced the bag with the stock of RCA connectors. In between visits to the ER and Hospital I vowed to "get'er done." as Larry the Cable Guy would say. We did that and screwed the small apron assembly to the back of the homebrew box. The two RCA Jacks and the small aluminum panel are shown below.


The final piece was to tighten all of the screws as many of the holes are tapped and do not have nuts. Powering the assembly up I get the reading for the 15M Band and none of the other band selections work. 

Some "noodling" suggested that when I tightened everything, I torqued something where wires would be touching. I started by removing the newly installed back panel and everything worked! That led me to a faulty conclusion that the torquing was coming from the back panel. 
 
I next removed the Arduino/Si5351 Board as I used a row of pin headers to install all of the wiring going to the Keypad, Encoder and LCD to see if there were wires that were so close that they would touch if the board was torqued. 
 
I carefully powered on the assembly to see if 15M came up on the screen. It didn't -- but somehow I smoked the Arduino, Si5351 and the LCD when some power wiring got crossed. There is the Mushroom Cloud, #30 wire wrap wire glowing red and the stench of burning plastic. To say it was a disaster would be kind. 

So at the next break from the ER/Hospital I replaced the burnt wiring and found  a new Arduino, Si5351 and LCD. A bit of programming and a careful re-installation of the power wiring showed the unit to be operational again.

This is where I stopped to think about why installing the back panel resulted in the 15M reading and simply removing the back panel made it work properly. 
 
The back panel has but three connections, the LO source, the +12 Volts and Ground. Nothing on the Board, the Encoder or the Keypad is grounded to the case. Yet connecting that back panel was grounding the case.

If 15M was being called when you grounded the back panel then the culprit had to be the Keypad.

Shown below is the back of the Keypad and how I mounted it. The Keypad front panel hole is just slightly bigger than the Keypad itself. Around the periphery is but a small lip area with very small mounting hole in each corner. 
 
I would not be able to use the mounting holes. So I got a piece of scrap PC Board and cut out a hole so that it would fit over the L Shaped Header and then using holes in each corner of the scrap board literally fabricated a Compression Clamp. The L Shaped header is soldered on the front side of the keypad and I did clip the pin leads so the would not short to the front panel.

Here was problem #1! I used the non-copper side as the front panel as its color was close to the Triton's color so no painting but the back side was copper and through mechanical connections -- the Front Panel was part of a circuit now connected to the back panel. Removing the Keypad I found that Pin #1 although cut off was ever so slightly longer than the rest. 
 
The compression mounting caused a connection between Pin 1 and ground. As long as the back panel was not connected you were OK because nothing else is grounded to the case. Connect the back panel and you have a complete circuit. Now you can install the back panel and all works.



The OL is back in the hospital and I can't tell you how much even something like a mystery troubleshoot can offer a break from the grim reality at the ER and Hospital. Then of course there are the YL Nurses with the Tattoos. I am now prone to wearing my beret all of the time.
 
73's
Pete N6QW



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