Uk fm motorboating on high channels while on tx

[damo666]

Radio Make and Model:Binatone route 66
PCB Number:
PLL Number:
lc7136
Test gear available: rf sig gen, audio sig gen, dmm, scope
Symptoms:
motorboating on higher channels on tx

What is working:
everything

What has been tried: nothing at present, but think it could be decoupling prob

Did it suddenly happen ?:
unsure, as bought 2nd hand has spares/repair
Anything else that may be of help?:Hi. I have an old Binatone uk fm cb that motorboats when i tx from channel 35 to 40 but not on the lower channels. It motorboats gradually worse as i go from 35 to 40, but doesn't do it when i turn the rf power down. In addition to this, it only motorboats for about 5 secs, the s meter fluctuates then it settles. Any ideas on what the fault could be please? Cheers.

[Uncle Ray]

Gday Mate , sounds like the vco is not locking. Get the service diagram and re-align the vco and asscociated cans.
Good luck !

[damo666]

Hi Uncle Ray, cheers for the reply. I also thought that a maligned vco could've been the problem. But surely, if this was the case, wouldn't it motorboat regardless of the rf power output. Ie - if i turn the power up to 5 watts out it motorboats continuously, but if i reduce to 3 watts it doesn't motorboat at all. I'm thinking along the lines of a voltage regulation problem perhaps?

[damo666]

Problem now remedied. No further assistance is required. Cheers.