Dave this is interesting because a similar problem was the subject of
discussion recently on the Orion Yahoo reflector. Here's what that author did:
--- In firstname.lastname@example.org, "jskalski" <jskalski@...> wrote:
The process that I used to fix the 565 was:
> Checked front panel to see that ANT 1 was selected.
> Checked to see that TX was lit and on for VFOA
> Menu items TX showed transmit enabled, Tuner enabled, Loops off.
> Tested with and without Tuner enabled. Tuner would find a match but no
> Took off top and bottom covers and checked voltage regulators that were
>onboards and all were ok. 12v was available for final unit.
> There was output at the TX 9mhz board out that fed the PA unit.
> There was output at the XTVR output jack when that was enabled.
> So at this point I was left with the PA unit and the cabling that supplied
>itand the antenna relay. The antenna relay I assumed to work because the
>I kept the back panel on but unscrewed the heat sink/ PA enclosure and
>unplugged the coax from driver and output to tuner. I had checked the voltages
>to the LM358 keyed and unkeyed mic and they seemed to be ok prior to
>I lifted two legs from one of the 2sc3133 driver transistor and hmmm
>There was a short. Tested the other driver in the same fashion and it told me
>that "no component was found"....open.
>That was encouraging. I replaced both 2SC3133 drivers with 2SC1945
>transistors. They have the same foot print, pin out and similar gain.
>3133 is rated at 14dB and the 1945 is rated at 14.5dB.
>I have some 2SC3133's somewhere but can't put my fingers on them at the
>When I put the transistors in and replaced the wiring, I turned the radio on
>and nothing burned up. That is always a good sign :)
>I set the radio to 5 Watts and keyed the microphone...success...
>The output meter is bouncing around once again when I talk.
>Now, I have a question for those that know what they are doing.
>There is an associated trimmer pot probably for the bias adjustment.
>What should it be set at while the transmitter is idling?
>Where is the test point that the voltage is measured?
>Hopefully this info is helpful for others in the same situation.
I hope it helps.
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