For those who are interested here is what I have found out about keying an
older tube type amplifier.
In the case of the HL-2200, the relay has about 120 VDC @ 100 mills
present.
From the manual for the Flex 3000, page 6 the following information :
"(6) External Keying Line
This keying line, which can be given a delay, can be used to key an external
device such as a linear power amplifier or transverter. The external keying
is provided by a relay closure to ground, with a rating of 250 VAC, 220 VDC
at 2 A and with a 2.5 ms nominal switching time."
From a person whom I consider very knowledgeable I received the following:
"I would not recommend connecting that amp directly to any radio.. You
should always use a isolation relay, today's radios have logic that can run
at 3.3 volt levels, I would not want 120 vdc rattling around in any radio
built in the last 20 years.. There are lots of buffer relays you can
purchase or build that can handle the voltage, and a little arc will not
hurt anything.. "
So I'm following that advice and have ordered an interface from
"Hamgadgets.com"
It seems like it will key just about anything, it is rated at 400 VDC and
400 mA.
This unit uses an Optical isolator type relay, so it should be safe for the
equipment.
If anyone is interested enough, send me a note offline and I will let you
know how it goes.
Thanks for the help.
Don, kd6hq
By far if in doubt, use the buffer relay!
73
Neal K3NC
On Thu, Aug 18, 2011 at 6:49 PM, Steve Sterling <[email protected]> wrote:
Don-- I haven't seen an answer to this yet, so I'll take my best shot
although there are better experts than I am.
For my Flex 5000, the voltage limit is 50vdc, so 120vdc would smoke it.
Maybe did you mean 12 vdc?
Current is 400 ma so the 100 ma would be OK. I don't know what the
limits
are on the Flex 3000, I just have my 5000 specs.
Also, my guess (again I don't know) is that the keying line is pulling
down
a relay in the HL-2200. Relays have windings with inductance, and I would
be concerned that when the Flex unkeys, it would generate a high voltage
back-emf spike as the relay coil field collapsed back into the keying
transistor in the Flex, smoking it. So as a minimum, a back-emf protection
diode would be needed across the relay in the HL-2200 (if it really has
one).
Probably easiest to let the Flex key a buffer relay in your situation.
You
could make it work direct though with a little soldering.
Steve WA7DUH
On 8/17/2011 6:34 PM, Don wrote:
From what I have read in the manual I should be able to do a direct
connect to the keying relay circuit in an HeathKit HL-2200 amplifier.
The keying relay has about 120 VDC at 100 ma. on it. I just wanted to
check here an make sure.
Also does anyone know that device is being use to obtain the 2.5 ms
switching time?
Don
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