Author Topic: Rohde & Schwarz RTO Encoders  (Read 1245 times)

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Offline jjoonathan

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Rohde & Schwarz RTO Encoders
« on: July 02, 2019, 01:14:14 am »
The encoders for vertical and horizontal scale on my Rohde & Schwarz scope have begun to skip. It's not the worst of problems, about half of the detent clicks still result in a signal, as determined by KeyTestTool.exe, but obviously I would still like to repair the problem. I opened it up:;attach=775461;image

I think I see a pattern. November 2009 must not be a good vintage for encoders :) The numbers didn't lead to any direct hits, but by googling parts of the numbers I found some likely descendants, the E33 line of encoders from ELMA. Here's an overview sheet:

Fortunately, the descendants seem to keep the serial number conventions, because I was able to rationalize all of the numbers based on their decoding diagram. For instance,

* S - SMT vertical
* N - Non-threaded 7x6mm shaft
* 0 - No push button
* 2 - 16 detent, 8PPR, 1.5Ncm
* 0 - IP60 rating
* -
* N - No included shaft
* 00 - (included shaft code would have gone here)
* R Tape & reel with vacuum plug
* -
* MMYY date codes land within the ~ 2 years prior to the scope manufacture date

Unfortunately, distributor availability is, uhh, limited:  Within the octopart-o-sphere, the only parts of this line that I can find available for shipping to the US are E33-SN610 from Chip1Stop. Most of the specifics are different but they would at least fit the physical profile and preserve the detent:pulse ratio. Two questions:

1. Does anyone know how to mount / unmount the shafts? There are a couple of diagrams, but it's not obvious to me, an encoder newbie, what to make of them.

2. Does anyone happen to know any ELMA distributors that might not show up on octopart? I gather that they're a Swiss company, but I'm not familiar with the European distributor scene.
« Last Edit: July 02, 2019, 02:56:18 am by jjoonathan »

Online coromonadalix

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Re: Rohde & Schwarz RTO Encoders
« Reply #1 on: July 02, 2019, 03:34:15 am »
I would protect the leds from moving and try to remove the pots with hot air and flux,  using copper wick will have limitted effect, you may over heat the pots side tabs before it move a little ?

Not sure from the photos if the side tabs casing is simply holding the pot on the pcb, maybe with a gentle pull while desoldering one side, you could check if it move upward, while to pot stay on the pcb ??
« Last Edit: July 02, 2019, 03:36:54 am by coromonadalix »

Offline TRN

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Re: Rohde & Schwarz RTO Encoders
« Reply #2 on: July 03, 2019, 05:10:56 pm »
Hi jjoonathan,

You can order them from this German supplier, but they are made to order with a delivery time of 20 - 30 workdays.

Price is O.K 9,66 € incl VAT

Here is the link.

Elma E33-SN020-N00R

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Offline jjoonathan

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Re: Rohde & Schwarz RTO Encoders
« Reply #3 on: July 05, 2019, 05:07:48 pm »
Keen eyes! I could have sworn I looked at don-audio but didn't find SN020. Maybe I was filtering by in-stock or something.

I've already placed an order with Chip1Stop but it was for a heavy compromise: wrong detents, push-button, and seal. If it doesn't fit the keypad rubber or feels too wrong I'll put in an order with don-audio.


Offline jjoonathan

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Re: Rohde & Schwarz RTO Encoders
« Reply #4 on: July 11, 2019, 02:42:14 am »
Success! I have replaced both faulty encoders.

I used E33-SN610-M03T from in place of the original E33-SN020-N00R. There were a few cosmetic differences (heavier click, finer detents, pushable instead of not), but I didn't really expect them to matter a whole lot and they didn't. I was worried about the shaft, but fortunately it turned out not to matter either. The replacements came with a 6mm D shaft while the originals had 6mm cylindrical shafts, but it turns out the button tops fit on both equally well without slipping or rocking. That was fortunate, because the shafts are not swappable. I took the old encoders to bits and I went from 20% confident of this to 80% confident. I clamped one firmly in a vice and pulled hard -- as expected, the bottom of the shaft sheared off instead of popping out. So don't rely on being able to swap shafts on one of these that isn't designed for shaft swapping.

Desoldering them was tricky. The R&S boards do not have very firmly adhered pads, or at least the adhesive isn't very resistant to heat, because I lifted a couple of pads despite carefully desoldering and raising the corresponding encoder legs beforehand. The hot air and/or the tiniest bit of bumping must have been enough to peel them up. The tricolor LEDs singe easily, I toasted one pretty well even though it was behind kapton. A kapton/tinfoil/kapton sandwich shield may have saved it. Also, the through-hole registration prongs probably connect to a ground layer in the middle of the board, because the solder did *not* want to wick out of them or even blow out with a bit of air. Back-heating was probably the right way to handle it, but I didn't have a hotplate, so I viced the board on its edge and applied soldering irons from both sides (a pointy one in the back of the via and a hoof-tip on the front) in the presence of a taped-on section of wick. The two irons were enough to convince the stubborn solder in the middle to flow up into the wick.

If anyone else has a similar issue hopefully this helps :)

Offline dmendesf

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Re: Rohde & Schwarz RTO Encoders
« Reply #5 on: July 23, 2019, 01:49:29 am »
 I have an RTO1024 with a crashed hd. Anyone has a backup to share?  :palm:

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