Good info Rick. If anybody ever removes the Corsair's LPF-TR board in the
future, please take plenty of photos to document the process and we can
post on tentecwiki.org. Actually, this goes for any
complex dis-assembly for any of the TT radios.
73, Barry N1EU
On Wed, Jun 8, 2016 at 7:44 AM, Reeve Family <reevefamily@cogeco.ca> wrote:
> Regarding Marco's IS0KYB posting about the Corsair II weak receive
> condition.I had the exact same issue with my Corsair II that I have owned
> since new. Like Marco I suspected the problem to be diodes related to T/R
> switching, however the problem turned out to be in the High Pass Filter
> circuit on the LPF-TR board (80969). Symptoms were identical to what Marco
> is indicating, and I found that receive strength was normal if I connected
> the antenna to the 'RX ANT' connector on the rear panel, which effectively
> bypasses the SWR and LPF-TR boards (and the High Pass Filter).
>
>
>
> My original TEN TEC manual has notation showing "OPTIONAL HIGH PASS FILTER
> NOT INSTALLED" . However once I got the LPF-TR board removed I discovered
> that the "Optional" High Pass filter was in fact installed contrary to the
> notation on the schematic. Trouble shooting eventually led me to
> disconnecting and bypassing the High Pass Filter and receive performance
> issue was resolved. I did this by opening the circuit at the input to the
> High Pass Filter and bypassing it with a capacitor between Q2 collector and
> the RX connector to avoid interfering with operation of Q2. It has worked
> fine ever since and no noticeable issue without the "Optional" High Pass
> Filter.
>
>
>
> The biggest challenge in all of this was getting the LPF-TR board out of
> the
> chassis which required careful removal of the Band Switch shaft while
> ensuring that all of the Band Switch wafer sections were in the correct
> position when reinserting the switch shaft.
>
>
>
> Like Marco, I would also like to know of a suitable PIN diode replacement
> for the TR switching on the board as TEN TEC did not include details of
> those components on the LPF-TR board schematic. Fortunately mine is still
> fine after 28 years but I suspect one day I will need to replace those
> diodes.
>
>
>
> Hope this helps.
>
>
>
> 73,
>
> Rick VE3ORY
>
>
>
>
>
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