2465B CH1,2 compression


Jean-Paul
 

Hello all

I Swapped just CHAN 1,2 switch hybrids from another scope with Maxtek Hybrids, 1994 that is 100% OK.

Chuck Harris was indeed correct, U500 IS BAD causing the distortion. Was orig TEK dated 1991.

Need to get a 155-0236-00 Channel Switch IC

Bon Journee,


Jon


Jean-Paul
 

Dear Chuck as always perfect information and exactly right.

I will go through swapping the hybrids, later this week.

Kind Regards

Jon


Chuck Harris <cfharris@...>
 

Hi Jon,

The calibration routine compensates for the gain of the
CH1 and CH2 preamp/attenuators, and adjusts a bias level
to aid the transient performance, but there is nothing
in the stored calibration data that would prevent a scope
from displaying a waveform with pretty good fidelity.

-Chuck Harris

Jean-Paul wrote:

Dear Chuck rebonjour,

I thought so, and tested CH2 out at rear panel BNC, direct from CH2 preamp hybrid, it was perfect.

Before I pay $120 or more for the channel switch hybrid, I will swap out from a know working scope.

My other point: In the CAL procedure is there a vert CAL that somehow affects bias or other voltage dependent parameters in this hybrid? If yes can this be an off CAL symptom: I am using a swapped A5 at the moment with definitely wrong CAL parameters.

I really need a parts donor 2465B!

Jon






Jean-Paul
 

Dear Chuck rebonjour,

I thought so, and tested CH2 out at rear panel BNC, direct from CH2 preamp hybrid, it was perfect.

Before I pay $120 or more for the channel switch hybrid, I will swap out from a know working scope.

My other point: In the CAL procedure is there a vert CAL that somehow affects bias or other voltage dependent parameters in this hybrid? If yes can this be an off CAL symptom: I am using a swapped A5 at the moment with definitely wrong CAL parameters.

I really need a parts donor 2465B!

Jon


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

Jon







Roger Evans
 

Bonjour,

I had exactly the same symptoms on Ch1 and Ch2 with Ch3 and Ch4 OK. Fixed by buying a new U400, I think about 50 - 60 Euros about 3 years ago.

Best wishes,

Roger


Jean-Paul
 

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

Jon