On 13/11/2018 10:59, Adrian Tuddenham wrote:
Dave Platt wrote:

In article ,
Sjouke Burry wrote:
On 13-11-2018 0:18, Adrian Tuddenham wrote:

Oscillating a bit somewhere?

That's what I was thinking, but why only on the left channel? Both
recorders behave the same way.


Spread in components, differences in layout causing parasitic caps an
inductances
to vary, take your pic.

Possibly there's some occasional switching noise on a digital or power
trace, which is coupled more effectively into the left-channel analog
trace going to the ADC? The left-channel trace might actually be
acting to shield the right-channel trace from some of the noise.

That could be the sort of thing that is happening - but I wonder why it
comes on after about a second's delay?

Demonstration at:
www.wrightshardware.co.uk/Other/DR0002_0276.wav
....beware loud clicks!



Any chance of cutting a couple of traces and jumpering/swapping left and
right to see if the problem swaps channel or stays the same?

The mystery ticking noise I had long ago was with magnetic tape car
cassette player, no record function, would overlay ticks on pre-recorded
tapes.
A small bit of ferrite/magnet buried in the pinchwheel rubber was the
cause there.