Re: 2465B CH1,2 compression

Chuck Harris <cfharris@...>

Channel switch hybrids, and trigger hybrids are the two most
common hybrid failures on this scope, in my experience.

CH1 and CH2 are the only channels the readout steals time from,
CH3 and CH4 are left alone.

Some strange channel dependent failures can be traced to the
transistor array chips used to condition the CH5 readout stuff,
but probably not in this case.

I would try a different channel switch hybrid first. It is
always good to have a scope on hand to swap parts.

-Chuck Harris

Jean-Paul wrote:

Rebonjour a tous:
Same low SN B062 2465B
has extrême CH1,2 compression on lower part of display.

CH 3, 4 are perfect and normal.

Photo Album: 2465B CH1,2 compression

Taken with 100 kHz triangle on CH 1 and CH2,
position upper nearly linear position lower screen, extreme compression and non linearity.
Transient response is also severely affected as position of traces is moved.

1/ all PSU voltages normal,

2/ using substitute A5 so no CAL data is valid.

3/ Is there an adjustment or bias eg on U400 channel sw ?

4/ Pulled U400, cleaned the hybrid contacts, no change

is there a place to test signals into U400 from CH 1,2 preamp U100, U200?

Assume U400 155-0236-00 is bad and replace (VERY costly!)

Many thanks


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