Maybe not very likely, but perhaps check the 0.015 ohm current shunt resistor
to make sure it's not open or that there's not a bad solder joint on the
board? I.e. make sure there's power to the finals first before going further.
73, Al
On Mon October 26 2015 9:54:09 am Bill ACITO, W1PA wrote:
> Number 1 is fixed. As pointed out/suggested – loose crystals. I should
> have know this from my Omni-A/D/C experience.
>
> >>No RX 160 and 80: freq counter bounces around on 0.180 to 0.190 Mhz on
> >> these bands. I assume I should be looking at the wafer switches and
> >> oscillators? All other bands are fine on RX.
>
> Now on to #2:
> On transmit I see no power, and no current draw.
> What’s the best way to diagnose the PA module? Voltage checks on the
> transistors themselves? Check the bias circuit? Should I just replace all
> four?
> Has anyone successfully substituted for the MRF-458’s, and if so, what did
> you use? Do any other rigs use the same PA module (80565) that I can swap
> with? the 561 Corsair II?
>
> >>No power out on TX -- zero. Scope says I have good output from the
> >>low-level driver board, which changes with the drive control. Do the
> >> finals fail open? Do they both go together?
> >>Any easy way to check if it's the drivers or the actual finals in the PA
> >> module? I also read that there was a common T/R diode fail that impacted
> >> ALC? What were the symptoms of this fail?
>
> Bill W1PA
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