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FT817ND Front Panel PCB replacement - Blinking display

 

I have just replaced the front panel PCB on a friends FT817ND (Lot82).
I had called Yaesu UK and the told me that the board was compatible (CS1909409).
 
It was a straightforward replacement except for desoldering the AF-SQL/RF pot. 
I had to snip the pins of the old connector to remove it but I do not believe that I damaged the pot and it seems to test ok.
On powering up the LCD screen display blinks and there is no audio.  I am able to change frequency, mode, etc and all buttons and dials seem to work.  However, the  AF-SQL/RF pot does nothing.
Searching the web I am told that this is clasical of the PLL not locking.
 
I plugged in the original board and this seems to lock (PLL wise).  I have no screen (reason for replacement) but using 'FT817 Commander' software I can 'see' the frequency, mode etc and all seems to be well on the receive front.  Audio is working.  The radio shuts down when I try to transmit but this may be RF getting in somewhere it shouldn't (the whole radio is out of its container).
 
I obtained all the parameters from the service menu on the original board and programmed it into the new one hoping that this was the answer.  No difference.
I presumed that I would have to do a full alignment and I started this.  I did not get very far:-
 
Reference Frequency Adjustment - No problem - freq and voltage fine.
 
VCO VCV Adjustment - voltage wrong and not adjustable as PLL not locked.
 
PLL "Unlock" Display alert - unplugging the Ref Unit the voltage is 5mV on J2002 (pin1) but no change in the display.  The voltage is 25mV with the unit replaced.
 
2nd Local Adjustment - No problem
 
3rd Local Adjustment - not possible as no transmit
 
And thats as far as I got.
 
Am I missing something?  Is this board really compatible?
Is there something specific that I need to alter (pot,menu item etc) to allow the PLL to lock.
 
Any help gratefully received. Thanks.
 
Best wishes,
David G7IBO
 
 

David,

1) Do you have a copy of the service manual? That's pretty much essential for what you are trying to do.

2) Given that the PLL, as noted below, seems to lock with the original front panel, that could indicate that the unlock signal (UL) on pin 18 of J4002 on the panel, sent from pin 33 of J1008 on the main board, is not getting through.

3) The PLL adjustments are covered on pages 16 & 17 of the service manual, and the circuit is very briefly described on page 12.

Good luck,

Robin, G8DQX

On 14/12/2024 14:47, David via groups.io wrote:

I have just replaced the front panel PCB on a friends FT817ND (Lot82).
I had called Yaesu UK and the told me that the board was compatible (CS1909409).
 
It was a straightforward replacement except for desoldering the AF-SQL/RF pot. 
I had to snip the pins of the old connector to remove it but I do not believe that I damaged the pot and it seems to test ok.
On powering up the LCD screen display blinks and there is no audio.  I am able to change frequency, mode, etc and all buttons and dials seem to work.  However, the  AF-SQL/RF pot does nothing.
Searching the web I am told that this is clasical of the PLL not locking.
 
I plugged in the original board and this seems to lock (PLL wise).  I have no screen (reason for replacement) but using 'FT817 Commander' software I can 'see' the frequency, mode etc and all seems to be well on the receive front.  Audio is working.  The radio shuts down when I try to transmit but this may be RF getting in somewhere it shouldn't (the whole radio is out of its container).
 
I obtained all the parameters from the service menu on the original board and programmed it into the new one hoping that this was the answer.  No difference.
I presumed that I would have to do a full alignment and I started this.  I did not get very far:-
 
Reference Frequency Adjustment - No problem - freq and voltage fine.
 
VCO VCV Adjustment - voltage wrong and not adjustable as PLL not locked.
 
PLL "Unlock" Display alert - unplugging the Ref Unit the voltage is 5mV on J2002 (pin1) but no change in the display.  The voltage is 25mV with the unit replaced.
 
2nd Local Adjustment - No problem
 
3rd Local Adjustment - not possible as no transmit
 
And thats as far as I got.
 
Am I missing something?  Is this board really compatible?
Is there something specific that I need to alter (pot,menu item etc) to allow the PLL to lock.
 
Any help gratefully received. Thanks.
 
Best wishes,
David G7IBO
 
 

Hi Robin,
 
Thanks for the response.
 
Yes, I was trying to follow the alignment procedure from the service manual as far as I could.  I have a number of manuals but I'm using the one which covers all FT817, FT817ND, and FT818 which I presume is the most up to date (2019 - E137790K).  The older version doesn't seem to be any different (2005 - E137790B) which seems to be the one you are refering to. 
 
The unlock signal (UL) is on pin 15 of J4002 and goes to the CPU on pin 17.  It arises at pin 1 on J2002 of the PLL unit and actually passes through pin 36 of J1008 on the main board.
I have tested continuity throughout its length and it seem to be fine. 
With the old front panel (which locks) this line is at 5v whereas with the new one it is at 25mV (essentially 0 v).  So I think the signal is getting through, but unfortunately the correct signal is not being produced.
 
I think that I need to look at two sets of lines related to the PLL.  What I presume are frequency related FSTB, FD, FCK, and those that are phase related (maybe) PSTB, PD, PCK, and I guess in addition the VSTB (voltage?).  I am not clear on what these all do but I can compare them in the locked and unlocked state to see how they differ.  At least I may have more info to go on - how to interpret it or fix any problem is another matter.  I'll keep trying.
 
Regards,
David
 

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