[TenTec] Orion - No Transmit Power

[Rick W]

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 orion565 at yahoogroups.com, "jskalski" <jskalski at ...>  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 
>outputon  meter.
> 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  
>tunerworked.
>
>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 
unplugging
>the cables.
>
>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
>moment.
>
>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.
>
>Happy holidays.
>
>Jim n2go
I hope it helps.
 
73,
Rick
VE7TK
Website:  http://www.ve7tk.com