[Drake] T4X sticking relay

Fri, 4 Jul 2003 11:04:35 -0400

This may or may not be helpful, but in the errata sheet for the T4XC, Drake
noted
that the block diagram showing the 6EV7 as the VOX, is to be changed to read
6FQ7.
73
Tony, W4FOA

Watch your thoughts; they become words.
Watch your words; they become actions.
Watch your actions; they become habits.
Watch your habits; they become character.
Watch your character; it becomes your destiny.
                         -Frank Outlaw

-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of Rick Wells (W2RW)
Sent: Friday, July 04, 2003 10:52 AM
To: [email protected]
Cc: [email protected]; Barry L. Ornitz
Subject: Re: [Drake] T4X sticking relay

The coil in my T4XC relay went open some years but I have never been able to
find a replacement.  It had a 15k ohm coil.  Had to replace it with a unit
with somewhere around a 2500 ohm coil and it has since never been reliable
with pull in and drop out.  I believe this is due to the higher current it
draws through the triode switching circuit.  6EV7 maybe if I recall?

73,
Rick, W2RW

----- Original Message -----
From: "Barry L. Ornitz" <[email protected]>
To: <[email protected]>
Cc: <[email protected]>
Sent: Thursday, July 03, 2003 9:25 PM
Subject: Re: [Drake] T4X sticking relay

> 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     [email protected]
>
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>
>

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