Tektronix 2465B Vertical Adjustment Amplitude Distortion


David Baum
 

Hello,

I've recently got my hands on a Tek 2465B. The only issue I'm having is that increasing the vertical position of any waveform on channel 1 or channel 2 causes the displayed amplitude to drop. As long as the DC level is roughly below the center graticule, there is not amplitude distortion. However, if the waveform higher, the amplitude drops off to roughly half. This problem only occurs on channel 1 and 2, not channel 3 and 4.
Here is a video of the issue: https://youtu.be/RgNdBXvQveA

I've read people having similar issues due to the U400 hybrid. Is this the likely suspect? Would it be a power supply issue? Seems doubtful.

Thanks


satbeginner
 

Hi,

After a quick look on your video I don't think it's power supply related, because the readout is rock solid, and also channel 3&4 do not show the artifact, however...

Always start by checking voltages and ripple on J119.

After that, I would clean the contacts of the vertical switch U400.

If you have another 2465(*), you can temporarily swap the U400's.

Good luck,

Leo


 

Looks like a bad or wrongly biased Channel Switch (U400), as Leo suggests.

Raymond


Jean-Paul
 

Bonsoir I just Had exactly the same problem

WasU400 channel switch hybride

Verify by triangle function gen n every channel
checking waveshapes at U400 inputs and outputs
Swapping with a known good U400 solved it

Very common problem

Bon courage

Jon


David Baum
 

Thank you all for the suggestions.
The power rails all measure good (unfortunately). I've tried cleaning the U400 contacts to no avail. Looks like it's the hybrid itself, as you have all said.
Unfortunately, I've got no spare 2465x lying around. Anyone selling a U400? :)
If I purchase one from the usual location (ebay), are there any differences between U400s pulled from different versions of the 2465/2465A/2465B, for example bandwidth. Or are they all identical.

Thanks


satbeginner
 

The typical place to look for Tek parts are Qservice.eu in Greece and www.sphere.bc.ca.

Can be trusted, no affiliation, just a happy customer.

Leo


David Baum
 

Unfortunately it looks like they are both out of U400 stock. Thanks for the suggestions though, I'll check back occasionally.


Jean-Paul
 

Hello again: Contact cleaning is never a solution, see Chuck Harris tips on removal/reinstall of TEK hybrids.

Please avoid any U800 on epay, many Chinese pulls, dead, relabel. avoid the epay seller (ID is like the scope number)




Qservice is excellent and eventually will have some, also ask Walter at Sphere Res in Canada.


Bon Chance,

Jon


toby@...
 

On 2021-05-30 11:22 a.m., Jean-Paul wrote:
Hello again: Contact cleaning is never a solution, see Chuck Harris tips on removal/reinstall of TEK hybrids.

Please avoid any U800 on epay, many Chinese pulls, dead, relabel. avoid the epay seller (ID is like the scope number)




Qservice is excellent and eventually will have some, also ask Walter at Sphere Res in Canada.
"Eventually" they'll run out completely.

What are the chances of a non-integrated clone? (Noting the recent
mention of a U800(?) clone). Can we as a community fund that work?

--Toby




Bon Chance,

Jon