The AM Forum

My Dow Key started acting persnickety. When I would switch back to receive, the receive would be weak. I'd click the PTT again and it would clear up. I shot some Deoxit D5 in it and it seems to have cleared it up.

I assume this is normal since we're switching 150 watts of carrier; therefore, contact cleaning is a regular chore I would assume is required. Is this the best way to clean the contacts, eg. spray alone? I know better than to use a file since that will simply ruin the contacts.

tnx.

Philip

Philip,

I wouldn't think the contacts on the receive side of the dow-key to be much of an issue. But with that said, both the receive thingy & the transmit thingy can be removed, cleaned, adjusted, etc. Please keep those files out in the garage ;D

So, if your dow-key relay is like mine, there is a little cover/peek hole on one end. Make sure the receive side is screwed in enough for good contact. Don't get carried away and not leave enough adjustment for that little arm to move from TX to RX.

Craig,

Deoxit is a conductive spray.  The last thing one wants to do is slobber it around inside the contact area, since this could increase chances of arcing and carbon tracking.

I would clean with a plain, non-lubricated spray first.  Then if you want to use Deoxit, use a cotton swab and apply it carefully to just the contacts.

I've used a trick from an old timer (w2wme) using a newish dollar bill. Gentely place it between the contacts, and draw it through.

Can't hurt to try.


klc

Question;  Will you get better results if one uses progressively larger bills i.e. 5s, 10s, 20s or even better, one of the new 100 dollar bills?

Fred

One would think so, but not. The $100, Franklin, will not work, as it expects the electrons to be of a + charge. The $50, Grant, will grind the contact down, untill they give up. The $20,Jackson, will not always work if the equipment is a Apache, Mohawk, Chippewa, Seneca, Cheyenne or Comanche. It will only work to the west of the Mississippi River. The $10, Hamilton, faces the wrong way, and $5 Lincoln, didn't finish the last job (although it wasn't his fault). So you see, only the $1, Washington works. That's why our leaders want all of ours.


klc

remarkable !

The spray may do the job but if it comes back, I would suggest investing in burnishing tools.

When I used to repair electronic organs and piano keyboards, often times sprays would not do the job and I think while more dangerous than today's sprays, they were better at removing crud..............

I used to use a 3/16" wide strip of crocus cloth, drawn through the closed contacts once on each side. But as fine as that stuff is, it may remove contact plating. Using rough paper is probably a better idea.

It is strange to have anything other than simple dry switching corrosion here. A strip of croakus cloth or even blue jeans (heavy cotton duck) should polish without stripping the silver plating. You may want to consider a T/R sequencer if you don't already have one. Essentially, you want to dry switch the relay, for transmit. It basically means, Switch antenna relay prior to keying transmitter, and unkey transmitter before releasing antenna relay. The usual setup has the transmitter relay power up the transmitter and also power the antenna relay. IN some rigs, the same relay does both with multiple contacts. usually, the antenna is switched over before the RF builds up, but is changed before the RF has decayed. So you end up hot switching the RF for going from Transmit to receive. Using two relays allows the sequencing to be set up with simple diodes, resistors, and capacitors in the relay coil circuits.

Kevin is on the right track here! The contacts on the receive side will tend to get some oxidation with age. the transmit side gets a "wipe" everytome it closes, not to mention that the power from the transmitter helps burn the oxidation off of them.

I usually take a dollar bill and dip it in a good contact cleaner or a 50/50 mix of mineral spirits and lacquer thinner and drag it between the NC (receive) contacts on mine. I usually find I have to do this every 5 years or so.

Frank

Dollar bills are made with 100% cotton rag.  Good quality Bond paper is equivalent and won't have the grease and dirt from a hundred hands on it. ;)

p.s. BTW, I was taught to the dollar bill trick when I was operating TTY and crypto gear in the Navy.