The PTT/VOX input on the rear of the Titan, when connected to ground should
key the amp when the MODE switch is in PTT/VOX position. Do this then apply
drive from the exciter. This should produce output or at least cause plate
current to move upward. Be sure there is a suitable antenna or load on the
output of the amp. If this works, then one may presume that the problem is
likely in the QSK switching circuit of the amp. If no output appears or no
increase in plate current occurs then I'd suspect the input switching relay
to be at fault or the driver for the relay. If plate current rises and no
output appears, one can conclude that the input relay is good but the I'd
suspect the output relay fault even though you "hear" the relays operate.
Now, if you are using a Tentec exciter, Omni, Paragon or such, it may be
that the exciter is keying the amp in the QSK mode but the amp is not in
sequence keying the exciter to produce drive. It may be the control cable
between the amp and the radio that is at fault. This however most likely
would cause he exciter not to produce output when the amp is off. This is
the same as not having the jumper in place between the TX OUT and TX EN on
the back of the transceiver.
Here is a discussion on how the QSK sequence takes place. When the PTT, VOX
or CW key is activated on the transceiver a command (logic low) is generated
at the TX OUTput jack of the transceiver. This signal is connected to the
KEY INput jack on the amp by one of two interconnect cables. At this point
the transceiver/exciter is not producing RF although the PTT or VOX or CW
key is closed. The KEY INput signal at the amp activates the switching
circuit in the amp to transition from RX mode to TX mode. And it sends a
signal (logic low) slightly delayed via the 2nd interconnect cable back to
the transceiver TX ENable. It is this signal that activates the RF circuit
in the transceiver/exciter to produce RF to excite the amp. Without this
loop through control and delay sequence there is great risk of causing the
amp to "hot switch" which most likely will damage the amp RF circuit or
output relay.
If you have questions.......ask.
73
Bob, K4TAX
----- Original Message -----
From: Larry Groom<mailto:lgroom@frontiernet.net>
To: tentec@contesting.com<mailto:tentec@contesting.com>
Sent: Wednesday, October 26, 2005 7:21 PM
Subject: [TenTec] I need a Titan 525 Expert!
My late model Titan amp has had a problem that at first would
show up seldom, but has now shown up regularly. It will not put
out power when the exciter is key down. I can hear the Vacuum relay
keying up, but there is no output. A friend tested the relay over 100
times
with no failure.
My question is this... Is it possible to bypass the circuit that senses
the
input RF and then allows the amp to key up? I would like to see if it
will work when PTT is grounded with the RF sensing circuit bypassed, thus
eliminating a possible trouble spot. I called Ten-Tec and they said
they'd
be happy to work on it, but that it could be a ton of things including
the
tubes
etc and I'd like to have an idea of what is wrong if I could. I wish the
problem
wasn't intermittant, that would help.
Thanks in advance for any help
73's Larry
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