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Yaesu FT-736R unstable 440 module

Posted: Sun May 09, 2010 2:18 pm
by xe1/ve3oqc
Would like to know if anyone would have the answer to this.
I just purchased a FT-736R however after a few minutes to an hour if I am on 432.144 the frequency will drop down to 432.109 and stay there. When I change the frequency with the VFO it will not move until I cycle the VFO and when it does move it moves in 29khz increments. The VFO indicates that it is changing frequency normally (the readout moves) but is in fact not. :?
The 2 meter side is good,output,on frequency etc. , the other noted fact is that when initiated the 440 module is 1.5khz low, now could this be a catastrophic failure occurring in the PLL board or is there something else I should be looking for.Or maybe it would make a good paper weight? Tapping on various components on the boards does not reveal any mechanical faults.
Any ideas from the Yaesu experts out there??? :x

Glenn,XE1/VE3OQC

Freq shift

Posted: Fri May 14, 2010 2:40 am
by KB3LMV
Hi Glenn
I'm no expert on FT 736 but it almost sounds like a Cap breakdown is causing your 35 KC freq drop or a cold solder joint,as it only occurs in UHF modeIt might be worth a call to Yaesu tech support in LA and pick theit brains.
Good Luck & 73 4 Now
Paul KB3LMV

440 Board

Posted: Mon May 17, 2010 11:37 pm
by xe1/ve3oqc
Hi Paul, thanks for the advice.
Upon further checking it is not the RF unit, what is causing the problem is the PLL is unlocking. I had the board out and it appears that one section is bad, or the components in that area are weak. :?
I have changed out the RF unit for a ¨New¨one and the problem still persists. It is however NOT the same problem as you would encounter in the 2 meter side when the cap is bad.
I have a PLL board on the way and will change that out.

Glenn, XE1/VE3OQC

440 module

Posted: Fri May 28, 2010 12:49 am
by xe1/ve3oqc
:lol: Found that it was the PLL board that was bad. Replaced it with another and the radio is perfect.
The symptoms were the same as on the 2 meter side posted in another site, however after changing caps,and such it turns out to be the PLL. What part exactly I don´t know,perhaps a chip??

Glenn,VE3OQC