Posted by
Stewart Baker on
Feb 13, 2006; 8:13am
URL: http://elecraft.85.s1.nabble.com/K2-Relay-contact-resistance-tp386534p386541.html
Wayne,
Thank you for your very comprehensive reply.
The FT1000MP gets switched on about once a month, and I tend to switch between
bands and functions. This is not an excessive idle time, and I think that if
decent relays were fitted there would be no problem. All relays are not created
equal, and I have my doubts about those that were fitted to my FT1000MP.
The wiping action of relay contacts certainly makes as big difference, and I am
pleased that the Omron ones selected do that.
My experience of Elecraft PCB's is that their construction is really robust, and
providing care is taken when removing components no tracks or plated through
holes should be damaged. Despite removing/replacing components in a number of
areas, I have yet to lift a track.
Your mail has really put my mind at rest, and I will continue to enjoy my
Elecraft gear with no worries.
73
Stewart G3RXQ
On Sun, 12 Feb 2006 10:16:23 -0800, wayne burdick wrote:
> Stewart,
>
> The small relays we use all have wiping action. This was one of our
> selection criteria. We also ran them through millions of switching
> cycles just to be sure, and not a single one failed, which bodes well
> for relay life in our products. Gary, our customer support engineer,
> has noted that relay failures in the field are also extremely rare, and
> in most cases can be traced to damage during initial installation
> (e.g., melting a corner of the package with a soldering iron).
>
> Even if a relay did develop a problem, you should only replace that
> relay, not an entire group. All of our manuals include signal-tracing
> procedures that should be helpful in identifying a failing relay. In
> the case of our internal ATUs, you can exercise each relay individually
> using the rig's ATU menu entry. The T1 allows individual relay testing
> using its switch/LED user interface.
>
> If you ever do have to replace a relay, it's wise to remove *all* of
> the solder using a large (not wimpy!) vacuum desoldering tool, followed
> by solder-wicking all pins to clean things up. Even still, you might
> have to pry a bit with a jeweler's driver to get the relay off.
>
> Since all of our PC boards are double-sided, there's a small risk of
> pulling out the plating on one or two plated-through holes when you do
> this. But we anticipated this, so we make all PC board connections to
> relays on the opposite side of the board. The loss of through-plating
> is then a non-problem. We apply this rule to all large components that
> obscure their top-side traces. The rule is harder to follow in dense
> areas around ICs, but in this case you can solder the pins both top and
> bottom if plating is lost.
>
> We also strive to maximize the size of PC board pads and traces
> whenever possible. This simplifies possible rework, lowers trace
> impedance and improves reliability. Our PC layout methodology is in
> sharp contrast to most of the electronics industry, which seems to use
> the smallest trace widths they can get away with, even when PCB
> real-estate isn't an issue.
>
> 73,
> Wayne
> N6KR
>
> -----
>
> www.elecraft.com
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