Kc9cdt@aol.com wrote:
> Hi Gang,
> I am taking a quick look at the inside of my OII to see if something obvious
> is wrong. My ALC light never blinks, Ever.
> My question is:
> I have the top cover off, now it looks like to get at the ALC LED and where
> it may connect, I have to tilt the front panel forward?
Hi Lee,
It's just like that with Orion I.
The ALC LED is on the A8 Keypad Board (front panel),
driven by the CPU peripheral circuitry,
with no direct connection to the RF circutry.
The CPU ALC input comes from A5 IF converter board
(under the speaker), pin 8 (ALCLED) of P1 connector.
The actual ALC signal going to RF stages is on
pin 7 (ALC) of the same connector. Both signals
are analog in nature. See sheet 2 of A5 schematic.
There are three related pots on the A5 board.
R20 (PWR) and R21 (REF) are used to calibrate
the forward and reflected power measurements.
They do not influence ALC circuts.
R179 (ALCSET) is used to calibrate the RF power
setpoint, i.e. with PWR setting of 100 the
ALCSET pot is adjusted for 100 W output into a 50 Ohms load.
This pot affects both ALC and ALCLED outputs from A5.
All of this applies to the original Orion, but
it's likely to be the same or similar in Orion II.
73,
Sinisa YT1NT, VE3EA
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