[BC] Maintaining older transmitters

[Warren Shulz]

From: Thomas G. Osenkowsky

>Designers have little opportunity to spend time with their creations. They are tasked with the next project. We, as users, have ample time to examine
>and become very familiar with the products we are charged with operating and maintaining. Most of us have come up with modifications based on our (extensive) experience. Designers do not have that luxury.

Tom,

You are right on about "designers do not have that luxury".

An example is things I changed in an aged Continental 317C3:

a)  Overload current relays (P & C overload) were a 4PDT relay with only 1 set of contacts used and the other three left to float.  As it aged out vibration of the mounting plate would translate to overload faults when none existed.  Bifurcating the 3 unused contacts stopped that issue.

b)  Filament leads with 300a on a 1/2-13 x 6 inch treaded rod heating up.  Found that a 1/2-20 fine thread made of silicon bronze reduced the voltage drop to 1/2 of the brass coarse threaded rod.

c)  Found a RF mute contact riding on the vacuum switch plate contactor at TTL level was erratic.  Along side it was a spare contact was unused.  Again bifurcated and increase current flow for a more reliable contact closure.

These examples are of things not found in the transmitter lab or in final test. Nor do the lab guys have the equipment under design connected to a phone call 24 x 7 every time it blips.  The lab engineer live with a design for a few weeks and the field guy lives with it for 20 years!

I was told by one GM about transmitter outages and I quote,

        "The problem is simple, *it can't happen again!* Temporary transmitter    interruptions is completely unacceptable. One transmitter interruption  is a problem. Two is a disaster. This needs to be treated as a  disaster. The only acceptable response from the manufacturer is that    they will fix it.  We can't be off the air for seconds never mind       minutes."

We all know the transmitter hardware while reliable is not perfect.  My fault file (reads like a bad paper back novel) on the Harris DX50 is 6 MB and twice the size of manual file of 3 MB Love it or hate it you have to face every transmitter failure like a science fair project.  Lots of documentation, photos, research, and reading between the lines of manuals and drawings provided.

Warren Shulz
WLS Chicago