It could be the bypass caps at the encoder inputs of the MCU, but more
probable is either noisy series diodes at the Channel A and B encoder
outputs or a noisy tuning encoder. Looking at mine, it appears to be a
mechanical encoder vs an optical unit. Another thing to check are the bulk
decoupling capacitors on the front panel display board. If the MCU isn't
properly bypassed because of degraded 'lytic caps you could be experience
ground bounce. It shouldn't be too bad to find, but I have had repairs in
the past that have started out as "a ten minute job".

Pete

"Lars Brandt" wrote in message
...
Hi ,
Is there anybody have experince of a Lowe HF-150? On mine there is a
"crunchy sound" from the speaker when you turn the tuning knob.
It has been so from the beginning.When I have my fingertips on the upper
part of the case the crunchy sound reduces.
Is this phenomen normal for the HF-150 or it should be quite when you turn
the tuning knob?
Shall the tuning knob be connect to earth?
Thankful for all help
Lars