Tek Glass Tracing


Craig Cramb
 

Photo Album
949D5068-213D-42B6-BA83-64C59169606B.jpeg

Dealing with a touch pad that has what think is glass tracing that has developed a crack thru multiple tracks. Anyone had any experience In repair of this type of situation?
This is on a Tek Ths700 séries scope


Craig Cramb
 

Added the photo album picture number but that doesn’t link To picture.
Picture album name is Tek Glass Tracing


satbeginner
 


Dave Wright
 

No direct experience, but looks like a conductive ink was used.

Perhaps this, or something similar would work:
https://www.tierney.com/products/circuit-scribe-conductive-pen/


_Dave KC6UPS


Oz-in-DFW
 

The main feature of the photograph you provide looks more like some sort of residue to me than a crack (if I'm looking at the correct feature in the photo.). It's also not clear why a crack would develop there as it does not appear to be a flexure or stress line. The photo you provide has neither the magnification to see cracking, nor an indication of where you think the cracking has occurred.

While you may already understand that all you state is a hypothesis that needs to be proven and have made measurements to verify it, your post does not indicate you do or have. Cracking can be tricky in printed traces.
You should be able to prove your hypothesis by probing the trace. You'll want to use a rounded probe tip, or a small piece of metals as a pad so as not to damage the trace. Fix one end and drag the probe along the trace. resistance should increase steadily for a healthy trace and increase abruptly at a crack.

Most of the time when I see cracking in these kinds of older flex circuits it's at the connector pins. More often than not it's invisible without considerable magnification and careful lighting.

I've repaired these kinds of traces with conductive epoxy. If the crack is at a mechanical stress location you'll want to use a small jumper that terminates outside the stress zone and is formed to survive the stress source (like a bend or repeated motion.) I have some 17 strand silver plated 30 AWG teflon wire that I use for this kind of thing.

--
Oz (in DFW) N1OZ


Craig Cramb
 

On Fri, Nov 27, 2020 at 07:25 AM, Oz-in-DFW wrote:


If the crack is at a mechanical stress location you'll want to use a small
jumper that terminates outside the stress zone and is formed to survive the
stress source (like a bend or repeated motion.) I have some 17 strand silver
plated 30 AWG teflon wire that I use for this kind of thing.
Thank you all for your interest and replies.

https://groups.io/g/TekScopes/album?id=257176
I added some more pictures and there are duplicates that show the crack across some of the traces. Duplicate pictures I tried to remove but unable to figure out how so I will leave them up for now. (Maybe Dennis could help me with this correction)

Yes this is at a stress location but I think the bend location can be changed. I scraped away at the protective covering carefully at two spots on a trace to see what was used as the conductor. It does look like a glass which is impossible to scrap at it without getting rid of the conductor also. The conductive epoxy looks like a good solution. But I was also thinking if I could locate a terminal that has the sharp pins that could penetrate thru the trace as was original used to attach the metal terminal to the trace then I could use that as a bridge.


Ed Breya
 

Since you can see right through everything, it should be easy to check for sure which lines are actually broken open - then you don't have to guess from appearance and do unnecessary repairs. Ohm out each line end to end, while flexing (not excessively) all the stress zones, and mark the ones that are bad. It looks like the traces are metal strips, made the same way as those that would be etched on a circuit board, so yes, quite thin. If you can peel back the top plastic layer without wrecking the lines, then you can dab some silver goop to bridge the breaks, then check continuity after it sets up (it won't be conductive until dried/cured). You can get silver board repair inks and goops from many places - it's for this kind of purpose, on metal or carbon runs. It won't be as durable as the original, so be careful to not flex it too much on re-installation.

Ed