I think the limited DC arc is the cleaning mechanism, but it would be
good to give AC a try. A typical rig relay failure point is the RX side
of the TX-RX relay, which is often available from the external connectors
Dave.
On 2/17/26 10:04 AM, Richard (Rick) Karlquist wrote:
I am wondering if it makes sense to use 60Hz AC for the wetting current,
to avoid pulling an arc when the relay opens. With AC the ARC is
extinguished in at most 8.3 msec.
73
Rick N6RK
On 2/17/2026 9:10 AM, Leeson wrote:
Many years ago, Dave Pruett, K8CC (SK) was working for Chrysler-Jeep,
and he mentioned to me that auto manufacturers specified a minimum
current to maintain the contacts in every switch, relay or connector,
typically 10 mA. Without this current, there is potential for surface
oxide or sulfide to develop on the contacts, resulting in a failure
and safety risk.
He told me those with a maintaining current level were termed “wet
contacts” while those with too little (or no) current were called “dry
contacts.” This came back to mind as I’ve recently experienced a spate
of relay and connector failures, all of which were situations without
a “wetting current” (also termed “fritting current”).
I refurbished my old IC-730 for my grandson who recently upgraded, and
both the T/R relay and the preamp relay weren’t working on receive.
ICOM’s bulletin shows how to add resistors to provide a wetting
current for the preamp relay, and I made a similar fix for the T/R
relay. Then I had a failure in my remote antenna rotating system,
which I finally traced to a dry contact failure in the RJ45 connector
on the cable that included a wire to the solid-state relay that
controls the rotator primary power. With the dominance today of CMOS
circuits that don’t need input current, it seems this problem has
become more common with control circuits, as well.
Cleaning the contacts with contact cleaner or a mild abrasive can
temporarily fix things, but the problem can return without a real
wetting current. In addition to providing this small current through
resistors, there is a suggestion to discharge a capacitor through
relay contacts on closing. Some relays have wiping contacts, which can
help remove surface contamination. Apparently, even 1 mA is enough to
do the job. I hope this info can be useful.
Online references include these:
“Wetting current,” https://en.wikipedia.org/wiki/Wetting_current;
P-T de Boer, PA3FWM, “Relay contacts and ‘fritting’"
https://www.pa3fwm.nl/technotes/tn17a.html;
“Wetting Current,”
https://resources.pcb.cadence.com/blog/2023-wetting- current;
D. McCarty, “Wetting or Sealing Current,” https://www.isemag.com/
columnist/article/14266765/wetting-or-sealing-current.
For the ICOM upgrades, see A. Copland, GM1SXX, “IC-730_relay_fix.txt,
“ www.f6hoy.com/wp-content/uploads/2022/01/IC-730_relay_fix.pdf and
"Preamp Relay Circuit Modification for IC-730" on mods.dk.
Dave, W6NL/HC8L
On 2/17/26 6:40 AM, Jamie WW3S via TowerTalk wrote:
I seem to recall someone mentioning a way to clean relay contacts by
applying voltage ? Looking for a way to try to clean up some sealed
relays in a 2x6 antenna switch
Sent with [Proton Mail](https://proton.me/mail/home) secure email.
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