[TenTec] Corsair II PBT Question

Bob McGraw - K4TAX RMcGraw at Blomand.net
Fri Oct 26 20:58:10 EDT 2012

It's been a while since I had one to repair.  I do recall that the carrier 
oscillator alignment must be made to very accurate results.  I try to obtain 
something better than 1 Hz accuracy, ideally to 0.1 Hz.  Same true for the 
Paragon BFO's and the Omni VI series BFO's as well.

Since these aren't well compensated, let the radio warm with covers loose 
for at least 30 to 45 minutes before adjustments are made.  Then put the 
covers back on and wait a suitable period and measure the frequency again. 
Be sure to use test equipment and test probes that do not load the circuits. 
I typically use a 10X low capacity scope probe on the input to my counter.

And yes it could be the 2.4 KHz filter has changed.  Without doing a sweep 
of the filter, hard to exactly say.

Bob, K4TAX

----- Original Message ----- 
From: "Barry N1EU" <barry.n1eu at gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Friday, October 26, 2012 7:38 PM
Subject: Re: [TenTec] Corsair II PBT Question

> Be sure to perform the carrier oscillator alignment (BFO) for SB-N and
> SB-R before you do the PBT adjustment.
> 73,
> Barry N1EU
> On Fri, Oct 26, 2012 at 5:12 AM, K4MT <k4mt at yahoo.com> wrote:
>> My Corsair II has a problem with the PBT adjustment. I can not get the 
>> SB-N and SB-R to sound the same.  When I adjust coil L4 the closest I can 
>> get is with the slug all the way to the top which raises the frequency f 
>> the 15.3012 crystal.  I measured the frequency range of the 15.3012 
>> oscillator and it varies from 15.3012 with the PBT control full CW to 
>> 15.2969 full CCW,  I found that SB-R audio quality is very tinny. I was 
>> wondering since the crystal reads 15.2969 with PBT CCW (no voltage on the 
>> varactor) means the crystal is too low in frequency. Tentec  wants 30 
>> shipped so before I order one I was wondering what the experts on this 
>> group think.
>> I have aligned the carrier oscillators so that is not the problem. It is 
>> the same on all bands and all crystal filters ( I have 2.4, 1.8, 500 and 
>> 250). Do you think the 15.3012 crystal is out of specs or is it something 
>> with the 2.4 9 MHz filter?
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