TDS3000B TDS3054B strange type rotary encoder repair/replacement  - Page 1
Forum section: electronics / repair

author: analogRF
author_rank: Super Contributor
timestamp: December 08, 2019, 05:20:47 pm
content: Three rotary encoders on my recently acquired TDS3054B (dead display and dead PSU fixed) are bad , very very bad and totally unusable.I got the front panel board out hoping to repair the encoders or even replace them but look what they arei have not seen anything like this and I dont know how and if they can be opened without destroying them and if they can be put back togetheralso I cannot find a model part number or replacement, hope someone can help!they dont seem to be soldered to the board, so perhaps they have pins that just contact the boardand then they are mounted by melting the plastic legs on the back side I think?EDIT: It seems they have also been used on TDS220 scopes

author: james_s
author_rank: Super Contributor
timestamp: December 08, 2019, 06:44:18 pm
content: They're a known weak point on these scopes. I've had good luck with contact cleaner but it's a bit tricky to get it in there, with care you can get it to wick in around the shaft. It would probably work to drill a tiny hole in the casing somewhere but I would not do that without seeing inside a broken one.

author: analogRF
author_rank: Super Contributor
timestamp: December 08, 2019, 07:05:45 pm
content: I thought about contact cleaner and IPO spary both from around the shaft on the top and from the bottomand hope for the best...but two of them are so bad (universal knob on the top and the vertical position knob) thatleave the whole scope really unusable. I feel no amount of cleaner from the outside would help...pity that the scope now works excellent in any other way but with those controls absolutely unusable the scope is very hard to use ...can tektronix support help? If I knew what model encoder they are, i could perhaps replace them...

author: pbarton
author_rank: Frequent Contributor
timestamp: December 08, 2019, 07:15:51 pm
content: Tektronix had these developed by Bourns specifically for Tek scopes.So, they were a joint development and consequently they are proprietary parts, not generally available.They are held on the PCB by ‘heat staking’ the black plastic square, in the four corners.I bought a 3014B with a broken shaft. The only way to repair it was to source another PCB with the encoders on.You can take the heads off the four corner rivets to remove the rotary encoder, then clean and replace with a small dab of epoxy in the four corners.If you ruin something, I can send a spare rotary encoder, removed from my parts board.

author: TheSeven
author_rank: Newbie
timestamp: December 08, 2019, 07:17:22 pm
content: My guess would be that they are working similar to these, just "inlined" into the PCB instead of being a module:http://redhunter.com/blog/2017/11/25/inside-the-bourns-ace-128-absolute-encoder/So spraying some cleaner into the gap between the PCB and plastic part and twisting it might help. If you look very closely, you can see a tiny bit of soldermask pullback from the outer ring protruding beyond the plastic.

author: analogRF
author_rank: Super Contributor
timestamp: December 08, 2019, 07:19:55 pm
content: it seems the whole board is actually manufactured by Bourns custom made for tektronix (look at the shots from service manual) so the encoders are probably custom made and never available in market

author: analogRF
author_rank: Super Contributor
timestamp: December 08, 2019, 07:23:48 pm
content: Quote from: TheSeven on December 08, 2019, 07:17:22 pmyes, I think you are spot on. spraying with cleaner and hoping for the best seems the only way ... unless the whole board can be found very cheaply with all encoders working which is very unlikely

author: analogRF
author_rank: Super Contributor
timestamp: December 08, 2019, 07:33:12 pm
content: now based on what TheSeven suggested, I can see there are quite a few Bourns encoders on digikey that can be bought but they all have a little PCBmounted underneath them (the whole casing and legs and shaft are identical to the TEK board) I am guessing if that little pcb is removedit can be mounted on the TEK pcb board and then the legs are hot glued or something...i am tempted but I am afraid I might end up destroying the board ... I wish i had a bad front panel board to test this. TDS220/210 front panel is very similar with the same encoders....EDIT: no, I checked more closely again, what is found on digikey cannot fit. the shafts are totally different and all are longer than this...these are most probably custom made for TEK

author: pbarton
author_rank: Frequent Contributor
timestamp: December 08, 2019, 07:44:54 pm
content: To get spray cleaner into the encoder, you could always drill a 1mm hole into the black plastic square.I would suggest into a corner, where you are likely to do the least amount of damage.Then blast the spray cleaner in, using the supplied aerosol tube.This technique is often used to fix ‘noisy’ potentiometers, it should work with rotary encoder too.

author: analogRF
author_rank: Super Contributor
timestamp: December 08, 2019, 07:49:06 pm
content: i think i found the datasheet for these things...they are indeed customized...

author: analogRF
author_rank: Super Contributor
timestamp: December 08, 2019, 08:03:22 pm
content: Quote from: pbarton on December 08, 2019, 07:44:54 pmbut any debris falling into the encoder is not gonna come out...for potentiometers it might be tolerable...anyways, if I wanna make a holeinto it I might as well cut the legs from the other side and lift the whole housing and then try to glue it back...for now I will only try spraying from all angles and see what happens...

author: analogRF
author_rank: Super Contributor
timestamp: December 08, 2019, 08:16:08 pm
content: guys I think i found a picture of the board when all encoders were removed

author: pbarton
author_rank: Frequent Contributor
timestamp: December 08, 2019, 08:42:26 pm
content: My rotary encoder parts mule.Looks like Ch4 BNC caught fire!I have used one rotary encoder, others available.

author: james_s
author_rank: Super Contributor
timestamp: December 08, 2019, 09:18:35 pm
content: Yikes, I wonder what happened to that thing? Maybe someone tried to probe a really high energy circuit with a 1x passive probe?I hadn't realized the encoders were etched right into the PCB like that. I've doused them in contact cleaner before and achieved significant improvement but had not ever tried taking one apart. I wonder why they did it that way? Kind of silly since mechanical encoders are notorious for getting flaky.

author: analogRF
author_rank: Super Contributor
timestamp: December 08, 2019, 09:57:26 pm
content: Quote from: pbarton on December 08, 2019, 08:42:26 pmis there any trick if I decide to take the encoders out for repair/cleaning? also is it possible to glue them back to the board easily such that they are stable and solid?

author: pbarton
author_rank: Frequent Contributor
timestamp: December 08, 2019, 10:23:10 pm
content: Use a sharp blade around the edge the plastic rivet ‘heat staked’ head and lever the rivet edge away from the PCB.A peripheral annular plastic ring should break away from the original central shaft.You only need to remove this peripheral annular plastic ring (the central bit should remain).Indeed there should be sufficient plastic remaining on the central shaft to re-stake the encoder when you come to reassemble it.I don’t think that I even bothered to use any epoxy in my repair.There should be just about, sufficient plastic remaining, to re-stake the encoder.

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: December 08, 2019, 10:36:00 pm
content: I have TDS3012 scope with three of those broken... they work... just the shaft is sheered off.I'm using scope like this hoping to stumble upon a donor board.I've seen a replacement board on ebay for $250 if I'm correct.

author: analogRF
author_rank: Super Contributor
timestamp: December 09, 2019, 02:05:59 am
content: Quote from: Ordinaryman1971 on December 08, 2019, 10:36:00 pmyeah, it's $299 and two people have actually bought that for $299

author: james_s
author_rank: Super Contributor
timestamp: December 09, 2019, 03:06:41 am
content: I think the same parts are used in all of the TDS3000 scopes. Given the higher spec instruments can sell for around $2k and a brand new TDS3054C still retails for over $20k, $299 doesn't sound too bad if it has the parts you need.Sure would be nice if they used off the shelf encoders but Tek scopes are a bit like high end luxury cars, expensive things are made of expensive parts. A 10 year old luxury car may be worth a fraction of what it cost new but new parts are still expensive.

author: pbarton
author_rank: Frequent Contributor
timestamp: December 09, 2019, 10:18:20 am
content: Quote from: Ordinaryman1971 on December 08, 2019, 10:36:00 pmSend me a PM identifying the specific encoder type you require and your email address. You can have them for the cost of postage.You need three?‘To lose one parent, Mr Worthing, may be regarded as a misfortune; to lose both looks like carelessness.’With apologies to Lady Bracknell in Oscar Wilde's, The Importance of Being Earnest;

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: December 09, 2019, 03:33:59 pm
content: PM send, let me take the scope apart and see which one are the ones that are broken...

author: analogRF
author_rank: Super Contributor
timestamp: December 11, 2019, 01:33:55 pm
content: I literally soaked the encoders by super contact cleaner with PPE (https://www.mgchemicals.com/products/cleaning-products-for-electronics/cleaners/contact-cleaners/super-contact-cleaner-with-ppe-801b) by spraying underneath them and after rotating them quite a bit and let it dry (also used compressed air to hopefully push the dirt away) I repeated the same thing again with IPA spray and put everything back together and VoilaAll encoders work flawlessly at least for now... I hope it lasts for a while...Next time I will have to open the encodersthat cleaner was the only thing I had available but I have had good results with it in other occasions too.Thank you guysEDIT: now I need to replace the time keeping NVRAM. Scope is made in 2003 and the battery has died

author: james_s
author_rank: Super Contributor
timestamp: December 12, 2019, 06:19:06 am
content: Quote from: analogRF on December 11, 2019, 01:33:55 pmYou can cut it out with a razor knife and solder a CR2032 or similar holder to it.Or you can make one of the adapters I came up with to replace the DS1742W in my TDS3000 with a DS1744WP. This is the PowerCap variety which has the battery and crystal in a replaceable snap-on cap. I laid out the board in an hour or two one afternoon so it's not the most polished I've ever done but it works perfectly.https://github.com/james10952001/DS1744WP-to-DS1742W-adapter

author: james_s
author_rank: Super Contributor
timestamp: December 12, 2019, 06:30:03 pm
content: I forgot to mention, the scope power-on hours are stored in this NVRAM, it's stored as the number of minutes in locations x7E0-x7E4. My device programmer doesn't properly handle these but I was able to program it by hand. I used an FPGA dev board that has a bunch of switches and LEDs with the FPGA being used as essentially just a patch panel. It would be trivial to write some code for an arduino or other micocontroller of choice to do the same thing.All other data can be programmed into the blank chip by the scope itself, it's just all the configuration settings and state, the error log and of course the date and time.

author: analogRF
author_rank: Super Contributor
timestamp: December 13, 2019, 02:01:53 pm
content: i dont have the means to program the chip. i just want to replace its battery. am I gonna lose anything important other than the number of power on and number of hours?is it possible to rewrite these numbers in the new chip through LAN connection for example?by the way how come I have not lost those numbers if the chip's battery cannot keep the time/date?

author: james_s
author_rank: Super Contributor
timestamp: December 13, 2019, 05:23:28 pm
content: The number of power on cycles is stored elsewhere, the hours is the only thing that I found no other way to set. There may be a way to write it via ethernet console, I don't know. Programming the part manually is pretty trivial since there are only 5 bytes that matter, it could be done in a breadboard with a bunch of jumper wires.

author: Jwalling
author_rank: Unknown
timestamp: December 13, 2019, 05:33:53 pm
content: Quote from: analogRF on December 13, 2019, 02:01:53 pmBattery has enough voltage left to power SRAM, but not enough to run the oscillator.

author: analogRF
author_rank: Super Contributor
timestamp: December 13, 2019, 06:26:46 pm
content: Quote from: Jwalling on December 13, 2019, 05:33:53 pmyes, makes perfect sense. Why didnt i think of that

author: analogRF
author_rank: Super Contributor
timestamp: December 13, 2019, 06:29:21 pm
content: if there is a way to change the model number and smapling rate through LAN and GPIB...i think there must be a way to set the hours and No of power cycles, too.Does anybody know?

author: james_s
author_rank: Super Contributor
timestamp: December 14, 2019, 04:14:09 am
content: Quote from: Jwalling on December 13, 2019, 05:33:53 pmThat was exactly what mine was doing. When I cut the battery out it measured 0.6V, pretty remarkable really that it was enough to keep the RAM going.I attached a new battery and it worked for a while and then failed. Later I discovered I had tugged a little too hard and cracked the solder joint at the PCB but I had already gone down the path of designing an adapter to install the DS1744 so I took that route in order to verify my design.If you want to try replacing the battery while preserving the RAM contents, wire up a socket to a 3.3V power supply and plug the chip into that while you carve into it and cut the battery out. With care it's not too hard, I've "fixed" a number of other Dallas chips without issue.

author: analogRF
author_rank: Super Contributor
timestamp: December 14, 2019, 06:38:17 pm
content: how do you take that battery out? to what points do you solder the new one? I mean, do I necessarily need a spot welder or something? because i dont have one.

author: james_s
author_rank: Super Contributor
timestamp: December 14, 2019, 08:36:21 pm
content: I stuck the chip into a cheap IC socket to protect the pins, then I used a razor knife to cut the plastic potting cup off the side with the battery (confirmed with a magnet) and then started digging into the epoxy with a screwdriver. A heat gun or hot air tool is very helpful to soften the epoxy, then I pried up the corner of the nickel strip and used pliers to peel it off the battery. After that I dug around the battery a bit more until I could pry the whole battery out enough to cut the strip welded to the other side. Then I simply soldered wires to the ends of the strips that were formerly welded to the battery and soldered those to a CR2032 holder which can be glued right on top of the chip or mounted remotely.Just be careful not to yank too hard on the strips as you're prying the battery out of there, that's how I broke the solder joint on mine. At some point I'll dig in further and repair that but my replacement adapter is working perfectly well so I plan to just leave that in the scope.

author: analogRF
author_rank: Super Contributor
timestamp: January 01, 2020, 02:18:29 am
content: My TL866 programmer can read and write DS1220 and it has exactly the same pin out as the DS1742. It seems to be the same NVRAM as ds1220 plus the clock which only reserves the top (or bottom?) 8 bytes as clock registers.so I am thinking of buying a DS1742 and then reading mine and writing it into the new chip as a DS1220. what do you think the problem would be?people have done this for DS1486 firmware IC on TDS700 series by reading/writing it as a DS1250 (offset by 8 bytes for the clock registers maybe)

author: james_s
author_rank: Super Contributor
timestamp: January 01, 2020, 08:02:10 am
content: Quote from: analogRF on January 01, 2020, 02:18:29 amBeen there, tried that, it doesn't work.I wasn't entirely sure why until I lashed up a rig to manually twiddle the address and data pins with switches and monitor the outputs and then studied the datasheet. You have to set a bit in a control register then write the desired data in the timekeeping and configuration areas and then clear the bit you set to enable writing. The pinout is the same as a plain NVRAM but it requires a more complex procedure to work with it. Once the battery has gone dead it defaults to frequency test mode where the LSB data line is pulsing at 512Hz.

author: analogRF
author_rank: Super Contributor
timestamp: January 01, 2020, 12:28:32 pm
content: my theory was also flawed because DS1742W is a 3.3V chip and DS1220 (and DS1742) are 5V chips so in any case R/W with TL866 would not have been possiblebut there is GQ-4x programmer which can be had with a pretty good price and it has listed 1742 and 1742W specifically in the list of supported chips.Does anybody have any experience with this?Also Xeltek SuperPRO 610P lists 1742/1742W as supported but that is an expensive gear not worth the money...

author: james_s
author_rank: Super Contributor
timestamp: January 01, 2020, 07:16:21 pm
content: I was able to read my DS1742W in a TL866, pretty sure it just hit it with 5V which eventually would likely harm it but in the short term it didn't seem to do anything. I found an interesting behavior though, the first time I read it I got garbage, but if I read it twice I was able to successfully dump it. Writing however did not work, at least not in the clock and config areas.I tried a borrowed GQ-4X also and that didn't work for me either but I've had some general problems with that unit and suspect it may have a fault.In the case of the DS1742 the easiest thing I found was to just twiddle it manually, I used a FPGA board but an arduino or even just a breadboard with some jumpers or dip switches would work fine. I recently picked up an Arduino mega clone with the thought of making an adapter to read and write these NVRAM/RTC chips.

author: xymox
author_rank: Contributor
timestamp: December 11, 2023, 12:27:11 am
content: This was a very useful thread.. I was able to easily use a razor blade and cut loose some encoders and clean everything which restored the knobs to perfect functionality. I used a fine tip on my weller to spread back out the plastic to hold them in place. Easy peasy..But then... I was able to run it for a bit and a new problem appeared. After warm up, the whole front panel board seems to get wacky. LEDs flicker, it fails self test. This is a seperate issue from the encoder knobs being dirty. I had not noticed it as I never had it on long. It takes like 30 mins. Then it starts failing lightly then will go into a flashing EVERY LED mode and no longer accept any knob or button.As its a thermal issue it could be a number of things. Just wondering if anyone has seen this before. I would hate for it to be the front panel IC itself.. I am thinking maybe a solder joint. I will get it back out and look it over better.YEA those Dallas semiconductor things are just terrible. I run into them on the Tek Waveform monitors and its fatal as the unit will no longer come up unless you use special software, which, you cant find anymore. Even the Tek museum does not have the software. So all the NTSC waveform monitors will all die..