[Drake] T4X sticking relay

[Barry L. Ornitz]

Jim Barrie, WA8SDF, asked:

> Need the group's advice. The relay in my very early model 
> T4X has started to stick... after transmitting, I have to 
> hit the PTT switch a couple of times to get my R4C  back on. 
> I suspect the relay for the antenna isn't releasing...  I 
> can hear signals, but they are very weak until I cycle he 
> PTT switch, then I get full audio.

You are correct that the problem lies with the relay.  This is 
a relatively common problem with high-impedance DC-coil relays 
like this.  One approach is to purchase a new relay.  I think 
Mouser stocks them.

But in most cases, you can cure the problem by simply 
reversing the leads to the relay's coil.

What happens is that over time the DC current magnetizes the 
relay's iron core, making it stick.  Naturally this does not 
happen with AC-coil relays.  If you have a very old, 
powerful,  tape-head demagnetizer, you can use this on the 
core.  However, since there is more than adequate "pull" from 
energizing the relay, reversing the leads will tend to 
magnetize the core in the opposite direction and let it work 
properly again.  In another 20 to 30 years, you may have to do 
this once again!    :-)

Actually I first saw this problem with a friend's T-4x in 
1972.  I have never seen this problem with my unit which I 
have had since early 1966, but then again I am not too active 
in using the radio.

        73, Dr. Barry L. Ornitz     WA4VZQ     ornitz@tricon.net