[Elecraft] Instability on 7MHz with KPA100

[g3pjt]

Hi

I have a problem with instability on 7MHz with the 100 w amp

On 7MHz in all modes the K2/100 delivers 100 + watts according to power
meter ( external too) on some frequency which I haven't been able to find
yet. The power control does not work.

When I first start up it is OK but after a few words the K2 goes into
oscillation.

On all other bands it seems to be OK and the K2 behaves normally.

If I take the KPA100 off the top of the K2 and place it alongside with all
the leads connected the oscill does not occur and on  the whole K2 behaves
normally on 7MHz. ( and on all of the other bands too)
No obvious compnent problems and has worked OK until this morning
(K2, SSB,NB,160M)

Ideas?

73 Bob G3PJT