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Tek p5205 HV differential probe teardown. BTW, what are the red and brown wires?

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romantao:
@Fluxed Matter, I think i was overbid by you :P damn!

I'll keep waiting for my right to buy one myself!

Fluxed Matter:
@romantao, I was out bid on 3 others before winning this one! ;D

romantao:
Hi!

Anyone knows a reference for the probe switches ( teh ones for attenuation/ overrange and bandwidth)
They have this inscription on the side 0113 201, but from it found nothing relevant...

Two of mine are kind of funky...

regards

128er:

--- Quote from: romantao on February 09, 2015, 10:03:43 am ---Hi!

Anyone knows a reference for the probe switches ( teh ones for attenuation/ overrange and bandwidth)
They have this inscription on the side 0113 201, but from it found nothing relevant...

Two of mine are kind of funky...

regards

--- End quote ---

I had the same problem. Couldn't find any switches like them. But I repaired all switches at my four probes.

Remove the grey cap from the switch by pulling it off. Then carefully remove the top half from the switch by bending the plastic latches on both sides. Remove the white top half slowly to avoid a mess inside the switch (spring and steel wire for the latching function). Be carefull in the end, that you put all back together as it was. You can put the red piece backwards in the white top cover. And you'll not be able to close the casing of the switch.

Now the important part. You have two springy metal pieces inside. They get actuated by the red piece and shorting the contacts together. They wear out over time, because their shape gets flatter. The result is bad contact and all sorts of weird signals comming out of the probe.

I have tried to illustrate that in the last picture, where you can see the cross section of the contact pieces. The one that is worn out, is less in width. The challenge is, to bring the contact piece in it's old shape. I have done that with my fingers. I repaired twelve switches. Several switches I had to open twice. Because it's a bit tricky to bend the pieces in the right way, so that it makes good contact.

Man, I hope that is understandable. Very difficult to describe such a fiddly thing in a foreign language  ::)

P.S.:
Good luck!  :-+

romantao:
Eheh! I know what you mean when you lack some technical terms in a foreign language!

I manage to fix them :)

I left the probe on during all day after compensating its gain and offset (internal trims).

The differential gain is accurate now.

However ... (there's always something wrong...) i'm noticing that under 500x the offset keeps running up once i close the case. That's not happening with the 50x. Even if i under-compensate while i have open case... as soon as i close it the offset keeps rising till 400mv approx.

Is this a normal behaviour and i Just need to trim it using the compensation box? This way, depending on which attenuation range i'm working, i'll have to do different offset of the 50x and 500x range.

Noticed that the lm317 and 337 get a little warm but they are putting around + - 5.1V respectively

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