Do you know if the control board has a microcontroller on it or is it just
hardwired logic? If it is hardwired logic you should be able to trace the
circuit out on the board and figure out what is going on. A pain in the behind
I know but that is the price you pay for being a ham scrounger. If it has a
microcontroller, ASIC or other proprietary ICs than unless you can find some
dcumentation you are out of luck. At that point I would probably try to figure
out what the control board is trying to do by looking at the RF board and then
replicate that functinality with my own circuitry. The control board then goes
in the trash.
73
Jim, W4KXY
-------------- Original message from Keith Morehouse <w9rm@yahoo.com>:
--------------
> I have a commercial 220 MHz PA manufactured in the mid
> 1990's by a company in Washington called II Morrow.
> They were bought out by UPS and later by Garmin. It's
> a 28V linear PA mounted on a plain black heat sink,
> using a single push-pull Phillips DU28200 MOSFET (or
> PolyFET SH703) for 150W rated Po. It has a single
> large multi-pin connector handling A+ and a control
> interface. I bought it off E-Bay a year or so ago and
> I'm pretty sure it was one of several that were sold -
> probably to other hams.
>
> Does anyone have any info on this PA or been
> successful in getting one running ?
>
> Here's the issue - Internal to the PA is a control
> board, handling (I assume) the PA bias and (I'm told)
> power fold-back from a external detector/VSWR sensor
> plus a simple interface to the systems original
> exciter. There are no switches or controls on the PA,
> only red and green LEDs, which I figure is a status
> indication. On the control board (among other stuff)
> is a big power relay which switches the A+ directly to
> the PA board. When A+ is applied to the connector
> with the other 8-10 control lines unterminated, the
> red status LED flashes for a couple of hundred
> milliseconds.....and nothing else happens. The power
> relay does not pull in to supply A+ to the PA module.
> I'm pretty sure one or several of the control lines
> need to be manipulated to convince the control board
> all is well and have it power up the PA. None of the
> control lines have any solid voltages on them so I
> grounded them one by one through a 1K resistor to see
> if a logic low might bring it to life - nope. I don't
> think I want to try a logic high unless it's a last
> resort...
>
> Before someone says 'Just bypass the relay', I'm
> concerned that doing so will result in improper (or
> no) bias being supplied to the MOSFET. I don't think
> these devices are still available, so, again, that's a
> last resort. Any info or suggestions would be
> appreciated.
>
> Jay W9RM
>
>
>
>
>
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