Products > Test Equipment
Need help! Test bench equipment recommendations. $2k+ budget
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kcbrown:

--- Quote from: geneonline on April 01, 2022, 05:41:35 am ---This is a thorough implementation of patience tracking the information and specification. Taking the oscilloscope apart only later to discover that putting back together was all it needed :-/O.

--- End quote ---

It may be that there was a cracked solder joint.  It certainly seems there was at least an intermittent contact somewhere, and I think most of the problem was limited to the timebase control.

It's possible that the encoder wasn't mounted quite flush with the board, such that pressing on it put stress on one of the solder joints, and that cracked it.   Stranger things have happened.  That said, the legs to the side of the encoders should have provided more than enough stability.  Hard to say what really happened.



--- Quote ---If swapping the encoders back, then changing the remaining refines use, that feeling of adjustments should be oddly satisfying with lingering love/hate. :-BROKE. 

--- End quote ---

In thinking about it, chances are I'll leave the remaining two encoders (that control vertical and horizontal position) alone.  Those, more than any other, are likely to get substantial fast movements on them while not needing the kind of precision you would want elsewhere, and putting detented encoders there would eliminate the ability to move them in that fast manner.



--- Quote ---When and if you do this procedure, I would love to see your findings from the end result! I would be tempted to make the same modifications with the encoders you linked if they perform great in the respective adjustment purposes.

--- End quote ---

Well, so far I very much like having a detented encoder on the trigger, and consider having a detented encoder on the multifunction knob a near-necessity.  I honestly can't fathom why a smooth encoder is used on the multifunction knob.



--- Quote ---While you have the oscilloscope apart, is there a safe way to test the encoders on the board before fully assembling again?

--- End quote ---

Not really.  You have to apply power to something in order to get anything out of the encoders when they're mounted.  I built a simple breadboard setup for testing the desoldered encoders.  It's how I was able to hook them up to my scope in the first place.  The best I could do with them soldered onto the encoder board is to buzz out the connections.



--- Quote ---If it's a reverse signal between pins A/B in regard to Bourns, would the timing be sufficient if you crossed the lines? ie.  bend pins away from board to solder a wire to the correct path?

--- End quote ---

If the original encoders weren't working then this is exactly what I would do.  Swapping A with B is sufficient to yield the desired result.  But it appears that won't be necessary.

The large legs on either side of the encoder are soldered into large holes in the encoder board, and they provide (or should provide) a lot of stability.



--- Quote ---Which probes did you use for checking the logic of the encoders?

--- End quote ---

Just the standard probes that came with the scope.  I used my 2104X+ to test the encoders (which felt a bit ironic, honestly, seeing how the encoders came out of that very scope :) ).

You can do a lot with the standard probes that come with the scope.
geneonline:
It is a little funny about hearing about your running the scope on the very same parts that were removed from it! I'll not jump the gun and see how things go. I'm sure it will be manageable.


--- Quote ---Just the standard probes that came with the scope.  I used my 2104X+ to test the encoders (which felt a bit ironic, honestly, seeing how the encoders came out of that very scope :) ).

You can do a lot with the standard probes that come with the scope.

--- End quote ---

That's great to hear! I was reading posts of people recommending leads running from 5-150! I'll stick with what's in the box. I won't be  doing any thing that would require that level of precision.

quick question, for the best safe practices of ESD and grounding, is it usually better to run a decent gauged wire tied to a metal rod into earth, ground onto the bench PSU, or just a simple grounding through a wall outlet ok? I have a few different silcone mats with grounding clips and wrist straps, but that doesnt do anything till its ran to a acutal ground. Just getting a better sense how to not kill myself when probing. I fail to see many to use safe practices in tear down videos, but I'm guessing many do the tear downs before they ever power it up.
kcbrown:

--- Quote from: geneonline on April 01, 2022, 08:46:23 am ---
--- Quote ---You can do a lot with the standard probes that come with the scope.

--- End quote ---

That's great to hear! I was reading posts of people recommending leads running from 5-150! I'll stick with what's in the box. I won't be  doing any thing that would require that level of precision.

--- End quote ---

It's not so much a question of precision as it is things like bandwidth and safety.  For safety, see below.

For bandwidth, the thing to remember is that once you get into the many tens of megahertz range and above, you're in territory where probing technique becomes critical.  In particular, you have to minimize your ground path because at those frequencies, everything is an antenna.  That little ground pin that you attach to the probe lead becomes crucial.  And that's at frequencies well below the bandwidth of the passive probes that will come with your scope.

When you're at the point where you need probes that can exceed a couple of hundred megahertz, you'll know it.  Not only will you know it, it may be that your scope requirements at that point will be much greater than what your scope (even when fully hacked) is capable of. 

So yeah, stick with the probes that come with the scope. 



--- Quote ---quick question, for the best safe practices of ESD and grounding, is it usually better to run a decent gauged wire tied to a metal rod into earth, ground onto the bench PSU, or just a simple grounding through a wall outlet ok? I have a few different silcone mats with grounding clips and wrist straps, but that doesnt do anything till its ran to a acutal ground. Just getting a better sense how to not kill myself when probing. I fail to see many to use safe practices in tear down videos, but I'm guessing many do the tear downs before they ever power it up.

--- End quote ---

Everything depends on the quality of the ground at the outlet.  Most reasonably modern homes are constructed such that the ground at the outlet is completely adequate.  Anything that it's not sufficient for is likely to be of such high energy that you don't want it anywhere near your house anyway.

By far the best thing you can do is to get a conductive silicone mat and attach that to ground, and use a ground strap around your wrist.

That leaves probing technique.  The issue with probing isn't really ESD (obviously that's something to be careful about, but you're more likely to damage the DUT by handling it than by probing it), it's with ground loops.  You need to always ensure that the ground attach point of your lead is not connected to a point on the DUT that is at a driven potential relative to earth ground, because your probe's ground attach point is itself already connected to earth ground.  If the test point's local ground reference point is at a driven potential relative to earth ground, then you've got three options:


* attach the grounds of your leads to a ground on the DUT (Device Under Test) that matches earth ground and then use two probes to probe the circuit, one for the signal and one for the local ground, and then use the scope to show the difference
* use a proper isolated differential probe
* (not recommended!!) power the scope through an isolation transformer with a floating ground on the power output side
A proper isolated differential probe will set you back a minimum of a couple of hundred dollars.  And if you need high bandwidth and isolation, it'll cost you quite a lot more than that, particularly if you need to see relatively small signals.

Anyway, if differential probing were as commonly needed as you might think, then differential probes would probably cost a lot less than they do.  Most people are obviously able to do without.
nctnico:
Nowadays you can buy decent differential HV probes for less than $200 (the ones from Micsig for example) and sometimes good deals come along as well.
kcbrown:

--- Quote from: nctnico on April 01, 2022, 08:36:13 pm ---Nowadays you can buy decent differential HV probes for less than $200 (the ones from Micsig for example) and sometimes good deals come along as well.

--- End quote ---

This is true, but all of the inexpensive ones compromise on something.  For instance, the Micsig has a bandwidth of 100 MHz, which is pretty decent, but has a minimum of 50X signal reduction, so it's not going to be the greatest thing for looking at small signals.

Getting good bandwidth and 10X signal reduction is going to cost you, near as I can tell.  Examples to the contrary would be welcome.
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