I've recently acquired a 2465B. The instrument powers up okay but the display has a vertical wobble (about the 50Hz mark..) which affects both the trace and the alphanumerics. I'd think it's power supply, but is there anywhere to look first?

Thanks,
Richard

no idea what the "50 Hz mark" means.

does wobble change with any setting eg time/ div? vert pos ?

Refer to the service manual J119 A1 board check every power supply V and ripple

bon chance

Jon

50Hz - I'm in the UK, our mains frequency is 50Hz and can affect things if the power supply smoothing caps are not too good....

First things first:

When you get a new piece of test equipment, you should
always measure the power supply voltages, and check the
ripple. When doing the ripple measurements, you will
need a scope, and you must jumper the two scope's ground
jacks together.

Second, the vertical and horizontal amplifiers can create
jitter due to the instantaneous heating of the parts in
their respective hybrids. This jitter can be balanced
out using the jitter adjustments as described in the
calibration section of the manual. The adjustment won't
bother the calibration significantly.

If the ripple isn't coming from the power supply, nor the
jitter, you can determine if it is mains related by
placing the trigger in the LINE position. If the ripple
stops drifting, it is MAINS related.

I don't usually find the big electrolytics that filter
the rectified power line to be a problem with the 2465,
but some do. I almost always find the filter for the
+15V supply to be bad. It won't cause ripple, though.

-Chuck Harris

Chuck, great to see your excellent notes on general troubleshooting...long time, How are you doing?

Agree on the bus and 15 V PSU caps notes. The bus caps are ample for 50 or 60 Hz mains.

Could the " wobbly" traces be the readout multiplexing, eg as sweep rate changes, the readouts move slightly to prevent burnin?

Bon courage

Jon

The OP should send some scope photos or post a video to clarify the problem....

Unfortunately I'm not able to check voltages right now, the instrument is in my shop and my tools are in my workshop - a few miles away.....

Tests reveal that the wobble is in the vertical amplifier, horizontal is stable. It looks like 50Hz noise. Focus & Intensity controls work as expected, Sweep & Channel voltage selection work, most other controls seem to work properly.

I will check the power supply over the weekend and report any findings.

Richard

Trace it back to the imput to see where it comes from.
Does it do it if the input is set to ground or 50ohms?

All four channels are affected, grounded or not. The Alphanumerics are similarly affected.

Hi Jon,

I am well.

The 2467's have the feature of moving the readout to prevent
burning the rather unique MCP (Micro Channel Plate) CRT,
but that feature is disabled when the firmware is used with
a 2465B configured motherboard.

-Chuck Harris


On Thu, 16 Jun 2022 23:01:46 -0700 "Froggie the Gremlin"
<jonpaul@...> wrote:

Chuck, great to see your excellent notes on general
troubleshooting...long time, How are you doing?

Agree on the bus and 15 V PSU caps notes. The bus caps are ample for
50 or 60 Hz mains.

Could the " wobbly" traces be the readout multiplexing, eg as sweep
rate changes, the readouts move slightly to prevent burnin?

Bon courage

Jon

The OP should send some scope photos or post a video to clarify the
problem....

Hi Richard,

I cannot think of any way you could have 50Hz mains injected
into the vertical amplifier (after the channel mux), and not
have it injected into the horizontal amplifier.

Check the vertical jitter adjustment. It affects everything
vertical.

-Chuck Harris

i'll check the vertical jitter adjustment but it won't be until later in the weekend.

Richard

Dear Chuck fine to hear from you!


Perfect answer re the jitter adjust and 2467 MCP intentionally slightly wobbly....

Bon Soirée

Jon

PS here in Paris, just received a fine 7L5!

开云体育

An update since I've done some investigation. The power supply test point measures 10.0047 volts which is pretty close to spec. The vertical jitter control does not improve the display but it does worsen the vertical jitter in either direction. There is evidence of knob twiddler activity around the vertical jitter pot. The power supply is dust-filled and has not been re-capped.

That's all for now, I'm busy for the next few days so I'll not be able to dig any deeper.

Richard

An update, the 160V DC measuring points are unbalanced - 160V on one side and about 90V on the other - that's probably where I'll start on this one, but I'm currently resolving the issues with my other 2465 power supply, the regulator board has troubles!