FT707 Unstable frequency display

[M0KCM]

Can anybody offer guidance...?
I have a Yaesu FT707 which is my main shack rig. Last night the freqeuncy display started drifting +/- 3 khz from the receive freqency.  The actual rx frequency does not alter as the ssb speech is still perfect through the speaker.  On tx the display remains constant on the tx freq.
(I saw this once but in reverse, constant on rx, and moving on tx).
changing modes does not help, and the warmer the set gets, the more bands it affects.  from cold only 10 metres, then eventually all bands when it is warm.
Using the external vfo (fv707dm) keeps the frequency display static.
Any ideas would be most appreciated.
I have the full service manual for part identification if that helps.
thanks
ian sweatman M0KCM
ian@sweatman.co.uk

[ON6AB]

Hello Ian,

I also had a 707 with drift problems.
I first tried operating the rig without the top and bottom covers, which improved the situation drastically.
I finally ended up with drilling some airholes in the top cover and mounting a litlle computer fan under the bottom cover just under the VFO, also over some holes.
Doing so drift was not gone, but much less.
If you look at the FT707 I find it strange there is not a single ventilation hole in the cabinet.
If you go for the holes in the top, remember it will take down the resell value of the rig...
Anyway, my experience with it was that the temperature compensation of the VFO is not as it should be. There's a lot of tricks that can help, but the only real cure is to tacklle the VFO itself. But then again, you're on your way for a lot of trouble..
Nice rig though! reasonable receiver(much better than the FT757 or the TS130),good audio and solid construction.

[W9GB]

Contact Yaesu for any service bulletings for this VFO problem .. likely heat related.

73 de w9gb

[M0KCM]

remove the covers and the problem will go..... yeah right!!! okay so i remove the top cover only, and guess what, the fault is immediately cured.
I did not sleep last night cos my "baby" was poorly, but now she fires on all cylinders.

Thanks for the help.
ian m0kcm