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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