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  1. Yaesu-FT-980
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BFO CVC ALIGNMENT

 

Hi, friends,

I tried to do the aligment described on pag 23 of Tec Supplement. BUT, I have not succefull on it.

I turned the TC01 to obtain the voltage on TO04 6 V, with USB mode and IF SHIFT control fully counterclockwise, and when I switch to LSB and IF SHIFT fully closkwise, it go down a little, 5,5 v.

The document refers it should be 3-4 V.

Any idea?
 

Hi Jose, I made the same experience some months ago, when I retuned the whole rig. I don't remember the precise values but I remember a similar behaviour.
Nevertheless no problem at all arose from CVC despite the discrepancy resulting from Tec Supplement: the frequency range covered by CVC is wide indeed, and the result was that the CVC PLL turned always in lock for USB (ful ccw or cw) and LSB (full ccw or cw) settings. This may be quickly checked on the rig with a counter reading the CVC signal frequency varying the USB/LSB/ccw/cw settings.
I also noticed that the equipment with low serial numbers (the first production lots) were modified by Yaesu in the CVC: perhaps the Tec Supplement refers to the previous HW version?
At the end of the day, despite what is declared in Tec Supplement, the main goal is that the CVC PLL will be able to lock with a Vtune value high enough to preserve good phase noise characteristics from CVC. The final check on frequency value, varying USB/LSB and full ccw/full cw, will dispel any doubt on the correct behaviour of this RX part.

I had various problems with my FT980, mainly due to internal coax connections/pcb tracks/electrolytic capacitors. I spent many hour on it but I'm now proud owner of a fully efficient regal rig.

Best regards
Enrico IK2XEI
?
 

My BFO likewise tunes similarly: max to 6V, but min is only 5.something (I forget) volts. Works fine. This is even after replacing the original trim-capacitor with a much better one.


--
-Mat Breton, N8TW
 

Very thanks Enrico for your reply.

Really radio works on USB and LSB, but I always should to move the IF SHIFT control for best tuning. It is a testimony that something is not ok on CVC circuit. If I am listening on USB and switch to LSB, I should to retuning the IF SHIFT control and viceversa.?

Best regards. CP6CL

Dr. José Carlos León Ortega

UDI- Universidad para el Desarrollo y la Innovación

Tel. (591 3) 3422525
Santa Cruz - Bolivia



On Friday, October 8, 2021, 11:48:11 AM GMT-4, <e.tallone@...> wrote:


Hi Jose, I made the same experience some months ago, when I retuned the whole rig. I don't remember the precise values but I remember a similar behaviour.
Nevertheless no problem at all arose from CVC despite the discrepancy resulting from Tec Supplement: the frequency range covered by CVC is wide indeed, and the result was that the CVC PLL turned always in lock for USB (ful ccw or cw) and LSB (full ccw or cw) settings. This may be quickly checked on the rig with a counter reading the CVC signal frequency varying the USB/LSB/ccw/cw settings.
I also noticed that the equipment with low serial numbers (the first production lots) were modified by Yaesu in the CVC: perhaps the Tec Supplement refers to the previous HW version?
At the end of the day, despite what is declared in Tec Supplement, the main goal is that the CVC PLL will be able to lock with a Vtune value high enough to preserve good phase noise characteristics from CVC. The final check on frequency value, varying USB/LSB and full ccw/full cw, will dispel any doubt on the correct behaviour of this RX part.

I had various problems with my FT980, mainly due to internal coax connections/pcb tracks/electrolytic capacitors. I spent many hour on it but I'm now proud owner of a fully efficient regal rig.

Best regards
Enrico IK2XEI
?

 

Heads up: here is a description for replacing the original trimmer capacitor. See the file "?Wireless Article - FT-980 BFO-Shift Oscillator Fix - Part 2.docx? " in the repair folder in files section.


--
-Mat Breton, N8TW
 

Mat,

should you return the IF SHIFT control when go from USB to LSB and viceversa?

Dr. José Carlos León Ortega

UDI- Universidad para el Desarrollo y la Innovación

Tel. (591 3) 3422525
Santa Cruz - Bolivia



On Friday, October 8, 2021, 02:05:41 PM GMT-4, Mat Breton N8TW <i.m.n8tw@...> wrote:


My BFO likewise tunes similarly: max to 6V, but min is only 5.something (I forget) volts. Works fine. This is even after replacing the original trim-capacitor with a much better one.


--
-Mat Breton, N8TW

 

I replaced the trimmer in two FT-980s.?? It can be done especially if it may be broken.? The original trimmer was of poor quality.

Dave K4JRB

-----Original Message-----
From: <[email protected]>
Sent: Oct 8, 2021 2:23 PM
To: <[email protected]>
Subject: Re: [Yaesu-FT-980] BFO CVC ALIGNMENT


Heads up: here is a description for replacing the original trimmer capacitor. See the file "?Wireless Article - FT-980 BFO-Shift Oscillator Fix - Part 2.docx? " in the repair folder in files section.


--
-Mat Breton, N8TW

?
 

Hi Jose,

When properly set, the IF Shift "function" should not be affected by switching from USB to LSB and back. The audio passband should not "change" by shifting the SSB mode.

Note: you can "observe" the passband by running the audio into an PC-based FFT program like Spectran, while making sure the AGC is off.

I tried tried to describe the shift function in the repair article "Wireless Article - FT-980 BFO-Shift Oscillator Fix - Part 1.docx?".?It is quite ingenious how they apply the oscillator twice, one each side of the 3rd IF, to ensure that errors and drift cancel each other and don't affect the passband.

You can also see how i used the PC-FFT software to "watch" the passband as I used the IF-width and IF-shift knobs, and switched mode, to ensure that this stage was functioning properly.

Hope this helps!

--
-Mat Breton, N8TW

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