So, here's an odd tale.
That nice TMC SSB Adapter in my post on the rack, when in the rack pops the breaker
in the outlet strip. It's the TMC MSR-4, but it has another nomenclature that the unit is more often
found as...btw.
Anyhow, I thought this rather odd. It worked fine on the bench, connected to the Variac (tm General Radio).
Brought it back to the bench, worked fine.
I thought, hmmm, the inductance of the variac is absorbing
the turn on rush! But, that did not make any sense, since I didn't
see that much current draw on
turn on watching the AC Ammeter (that everyone has) connected to the load side of the variac.
Someone on-the-air suggested replacing the outlet strip. Which, I suppose made sense, and I did. No go.
I also grabbed an iso transformer on the theory that it was an inrush current thing. BUT...
Anyone figure it out yet?
I did, a few hours ago.
The chassis was
HOT!!
Yep 118vac right there...
Plugged into the GROUNDED outlet strip - BAMM!
Plugged into the ungrounded Variac? Nothing...
Good thing not much around the bench IS grounded - this from many years of working on
stuff.Ok - so what was doing it?
Leaky AC mains input caps?
Bad power cord?
Shorted power transformer? (whooo, really hope it's not THAT!)
What??
Long story short, this is a TMC unit, laced up wiring harness and all. The unit only dumped
AC mains onto the chassis when the power switch was on. So that left everything after the
power switch. No choice but to trace the wires from the power switch out, and start disconnecting
wires until the ZERO OHMs to ground went away or was found.
The pictures below show what i discovered!
Did this come
from the factory like this??Or did someone go in there to "fix" something??
Look closely at the picture with the little mirror. Can you see it?
Hint: the leaf that is closest to the mirror carries the AC mains coil activating
voltage! See it yet? What's in the picture is NG.
The other pix is the relay itself.
The reason they went with the relay and not a wafer switch is that they needed (for what
I do not know) to be able to remote the USB/LSB function. This setup permitted a single momentary
button switch to toggle between upper and lower.
So, the lesson here is that one should never
assume that anything is automatically
wired right and free of defects. Let the trouble shooting lead to exactly what it is...
An odd tale.