I have a 2432A scope which works fine but has a slightly noise trace (the readout text is fine), see photo. Any hint where I have to start lokking to repair this?

 

I have a 2432A scope which works fine but has a slightly noise trace (the readout text is fine), see photo. Any hint where I have to start lokking to repair this?

I just changed all the caps on the power supply and main board to yield some nice crisp lines on a Tek 2430A. Usually all it takes. Make sure the cap voltages and capacitances are correct.

 

I have a 2432A scope which works fine but has a slightly noise trace (the readout text is fine), see photo. Any hint where I have to start lokking to repair this?

What do the traces look like if you short the vertical input connectors?

 

What does the traces look like with the inputs shorted to ground?

 

What do the traces look like if you short the vertical input connectors?

Look the same.

 

What does the traces look like with the inputs shorted to ground?

Look the same.

 

I have a 2432A scope which works fine but has a slightly noise trace (the readout text is fine), see photo. Any hint where I have to start lokking to repair this?

My old 2432 (now dead with a PS problem) was always noisy.
https://forum.allaboutcircuits.com/threads/tek-2432-nvram-replacement.165205/#post-1454665


Service manual.
https://w140.com/tekwiki/images/e/e4/070-6285-00.pdf

 

What do the traces look like if you short the vertical input connectors?

It's the same.

 

My old 2432 (now dead with a PS problem) was always noisy.
https://forum.allaboutcircuits.com/threads/tek-2432-nvram-replacement.165205/#post-1454665

View attachment 287760
Service manual.
https://w140.com/tekwiki/images/e/e4/070-6285-00.pdf

Looks quite similar, but the traces should be a lot more crisp I think.

 

What do the traces look like if you short the vertical input connectors?

Looks the same.

 

Looks quite similar, but the traces should be a lot more crisp I think.

Sure, but it's an old scope, they get wrinkles too. The old CCD (Fast In, Slow Out) devices that act as a analog signal sampling buffer in the ADC stage are aging.
https://www.tek.com/en/blog/sample-processing-digital-oscilloscope

See section 3-48, page 82 in the Service Manual PDF.

 

What do the traces look like if you short the vertical input connectors?

Look the same.

 

What does the traces look like with the inputs shorted to ground?

Look the same.

 

If the pre-amp processing noise is at the same level as my old scope it's just an artifact of old TEK equipment. There really is no practical fix.

 

If I remember right, these scopes show the number of hours used in their lifetime. Check yours. It may be tens-of-thousands if in a lab and it was turned on every morning to warm up in case it was needed. Mine had very few hours and spent its life with the dust cover on it on a shelf. Total hours is under 1000. It's either my 2440 or my 2465 that shows hours (or both?).

 

Diag test 5 doesn't show run time on my 2465A DM.

 

If I remember right, these scopes show the number of hours used in their lifetime. Check yours. It may be tens-of-thousands if in a lab and it was turned on every morning to warm up in case it was needed. Mine had very few hours and spent its life with the dust cover on it on a shelf. Total hours is under 1000. It's either my 2440 or my 2465 that shows hours (or both?).

My scope has 4400 hours running time, that's not much I suppose.

 

My scope has 4400 hours running time, that's not much I suppose.

I think it is pretty low. Your caps may be old or that scope may just be a little noisy.

 

Consider quantization noise:

https://www.sciencedirect.com/topics/engineering/quantization-noise#:~:text=Quantization noise results when a,occurs in the acquisition process.