TDS3000B TDS3054B strange type rotary encoder repair/replacement

[analogRF]

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 are 

i 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 together

also 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 board
and 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

[james_s]

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.

[analogRF]

I thought about contact cleaner and IPO spary both from around the shaft on the top and from the bottom
and hope for the best...but two of them are so bad (universal knob on the top and the vertical position knob) that
leave 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...

[pbarton]

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.

[TheSeven]

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.

[analogRF]

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

[analogRF]

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.

yes, 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

[analogRF]

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 PCB
mounted underneath them (the whole casing and legs and shaft are identical to the TEK board) I am guessing if that little pcb is removed
it 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

[pbarton]

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.

[analogRF]

i think i found the datasheet for these things...they are indeed customized...

[analogRF]

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.

but any debris falling into the encoder is not gonna come out...for potentiometers it might be tolerable...anyways, if I wanna make a hole
into 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...

[analogRF]

guys I think i found a picture of the board when all encoders were removed 

[pbarton]

My rotary encoder parts mule.
Looks like Ch4 BNC caught fire!
I have used one rotary encoder, others available.

[james_s]

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.

[analogRF]

My rotary encoder parts mule.
Looks like Ch4 BNC caught fire!
I have used one rotary encoder, others available.

is 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?

[pbarton]

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.

[Ordinaryman1971]

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.

[analogRF]

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.

yeah, it's $299 and two people have actually bought that for $299 

[james_s]

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.

[pbarton]

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.

Send 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;

[Ordinaryman1971]

PM send, let me take the scope apart and see which one are the ones that are broken...

[analogRF]

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 Voila 
All encoders work flawlessly at least for now... I hope it lasts for a while...Next time I will have to open the encoders 

that cleaner was the only thing I had available but I have had good results with it in other occasions too.

Thank you guys 

EDIT: now I need to replace the time keeping NVRAM. Scope is made in 2003 and the battery has died 

[james_s]

EDIT: now I need to replace the time keeping NVRAM. Scope is made in 2003 and the battery has died 

You 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

[james_s]

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.

[analogRF]

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?