HR500 relays wetting current?

[Geert Jan PE1HZG]

Hi,

I used my HR500 at the Jamboree-On-The-Air last week and it was a blast.
A SB220 would "work also", but the size and weight of that one (have to carry the thing to the scouting location!) as well as the automatic antenna tuner - the HR500 was very nice.

Unfortunately at the end of the event a defect seems to have developed. Leaving the amp idle, sometimes, the receiving signals just sink away. Giving the amplifier a good tap made receive signals come back but they would fade away after a while.

I think what I have seen is a common problem. When switching small signals with relays, one needs to feed a few mA "wetting current" to "clean the contacts". And the receive antenna signals won't do for that.
Tapping the amp will shake the contacts a bit hence the temp improvement.

Looking at the schematics I don't see a provision for wetting current. My question, has anyone else seen this and perhaps already fixed it? It is easy to add some resistors to add a few mA of DC current through the relays but I hope someone has thought of a way I didn't think of yet. So, your insight appreciated.

Also, the relays used in the HR500, is a wetting current specified? I'm not sure I have the right specs for the relays.

73,

Geert Jan PE1HZG

[jcve...@gmail.com]

Hi Geert,

We have not seen anything relates to 'wetting current' with these relays. You probably have a bad relay which we have seen. One is the bypass relay on the ATU (Y17-Y20) which are a  RZ03-1C4-D012-000C another is the relays on the rear panel which are TE  PB114012. These are the only relays that the receive signal would pass through. 

When the problem happens, try bypassing the ATU and see if it happens, then try switching between the antennas. That might help reveal which relay is at fault.

73,

Jim WA2EUJ