sticking DowKey

[K8DI]

Well, the AM Rally was (was!) off to a good start for me, six contacts in the first hour, and I took a few minute break, and then the band was dead, or so I thought.  Went back out today and found out it wasn't the band, but that one of the two DowKey relays that take my Yaesu receiver/RCA conversion transmitter between transmit and receive is sticking in transmit about half the time. Re-keying TX once or twice frees it up. This kills receive signal strength by what, 40dB or so, but kerchunking a broadcast rig to free a relay seems like it'll eventually cause a bigger problem..

What's the best way to clean the contacts, anything else to know to make it work better?

the relays are the typical T shape with the coil on the side next to one connector. They are 24v, run on a regulated 24v supply. They are used/eBay/unknown history, although one seemed new in box when I got it. Image attached is the type I am using.

Note that my rig is well-sequenced and there's no RF during T/R relay switching, and I am completely certain that it is proper.

Thanks for any advice...

Ed
 

[Pete, WA2CWA]

Using your picture, right side of relay (on the end) is a metal cap. Remove it and now you have access to the relay contacts. Moisten a piece of cardstock paper with deoxit and rub the contacts with it. You can also use a 100 dollar bill. Don't use anything too abrasive like a file or sandpaper.

[KD1SH]

I second that excellent advice; been there done that. Stiff paper sprayed with DeoxIt, slide it gently between the contacts and rub. Works wonders.

Using your picture, right side of relay (on the end) is a metal cap. Remove it and now you have access to the relay contacts. Moisten a piece of cardstock paper with deoxit and rub the contacts with it. You can also use a 100 dollar bill. Don't use anything too abrasive like a file or sandpaper.

[KD6VXI]

A new dollar is great.  Old school 3x5 card stock works great too.

--Shane
WP2ASS / ex KD6VXI

[Pete, WA2CWA]

A new dollar is great.  Old school 3x5 card stock works great too.

--Shane
WP2ASS / ex KD6VXI

A $100 bill use gives it class 

[W1NJC]

Is the action sticking (not cycling) or are the contacts high-Z?  If it's the latter, then dolla-dolla bill or paper, etc. is in order.  If it's the former there may be some lubrication necessary but also check to ensure your control signal is of appropriate voltage (and current sourcing ability).  Measure the 28V right at the relay coil.

On the smaller 401 series DowKey relays which have +/- DC power, and two TTL control lines I have found that not driving the control lines with enough V (one low and one high) can cause intermittent operation.  Use 5V if possible on these.  3.3V should be OK.  Also make sure logic 0 is as close to 0V as possible.

This doesn't apply to your relay, but maybe someone will happen upon this thread when troubleshooting the smaller ones.