From: "David Austin" 
Subject: [drakelist] Relay not pulling in (TX4C)


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Hi all,

Another plea for help! I have replaced relay K1 with a 2.5K solenoid as =
per the updated T4XC circuit, as I discovered the old relay (old 15k =
solenoid version) to be open circuit. Of course I also added the =
necessary 1.5K resistor in series. All as per advice from Garey - K4OAH =
(for which many thanks Garey).

Now, when I go into tune mode, the relay will not pull in. There is only =
30V across the solenoid, and should be nearer 40V I believe from my =
calculation (assuming plate resistance =3D 11.5K). I suspect the VOX =
control tube is not conducting fully. Voltages (in Tune mode) on V10 are =
as follows:

Pin 6 plate:    215v (manual says 170v)
Pin 7 grid:    -2mV (manual says -100mV)
Pin8 cathode:  +880mV (manual says -660mV)

R70 measures spot on 82ohm
Have checked all outputs on AC4 and these all seem to measure fine.

Any thoughts on where to look for likely problem? Could diodes CR13 or =
CR14 have blown and if so, what would be effect? Could anything have =
been taken out when the solenoid blew (can't see anything vulnerable) or =
could the solenoid originally have blown due to failure of other =
components in this area?

Hoping someone might give some pointers!

73 to all
David
G4GTP

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Hi all,
 
Another plea for help! I have replaced =
relay K1=20
with a 2.5K solenoid as per the updated T4XC circuit, as I discovered =
the old=20
relay (old 15k solenoid version) to be open circuit. Of course I =
also added=20
the necessary 1.5K resistor in series. All as per advice from Garey - K4OAH (for which
many thanks=20
Garey).
 
Now, when I go into tune mode, the =
relay will not=20
pull in. There is only 30V across the solenoid, and should be nearer 40V =
I=20
believe from my calculation (assuming plate resistance =3D 11.5K). =
I suspect=20
the VOX control tube is not conducting fully. Voltages (in Tune mode) on =
V10 are=20
as follows:
 
Pin 6
plate:    =
215v (manual=20
says 170v)
Pin 7
grid:    -2mV =
(manual says=20
-100mV)
Pin8 cathode:  +880mV
(manual says =

-660mV)
 
R70 measures spot on
82ohm
Have checked all outputs on AC4 and =
these all seem=20
to measure fine.
 
Any thoughts on where to look for =
likely problem?=20
Could diodes CR13 or CR14 have blown and if so, what would be effect? =
Could=20
anything have been taken out when the solenoid blew (can't see anything=20
vulnerable) or could the solenoid originally have blown due to failure =
of other=20
components in this area?
 
Hoping someone might give some=20
pointers!
 

---