Tektronix 561B scope restoration - Page 1
Forum section: electronics / repair

author: TerraHertz
author_rank: Super Contributor
timestamp: February 14, 2020, 04:34:04 am
content: I've started restoration of an old Tek 561B scope.The project writeup is here:http://everist.org/NobLog/20200208_neglected_561.htmOne immediate problem is what to do for a replacement carry handle?The existing handle is irreparably stuffed.Any ideas?The end mountings are OK, even those rusty rectangular links can be cleaned up and re-chromed if necessary.Just need a new handle, that looks relatively Tek-ish. As opposed to off an old suitcase or something.

author: tautech
author_rank: Super Contributor
timestamp: February 14, 2020, 04:39:50 am
content: Quote from: TerraHertz on February 14, 2020, 04:34:04 amA short length of nylon webbing from a small ratchet tie down or some woven strapping from a Milsurp packQuoteWhy here and not the Repair thread ?

author: TerraHertz
author_rank: Super Contributor
timestamp: February 14, 2020, 04:52:00 am
content: Doh. I briefly looked for a Repair category, didn't see it. There it is *right* underneath Projects.Can someone move this thread there please?Another question: What is a source of a solder compatible with the ceramic tag strips in these things?I've read that using ordinary leaded solder makes the solder separate from the ceramic. Which I'd like to avoid.But what is the correct solder called, and where to get it?

author: tautech
author_rank: Super Contributor
timestamp: February 14, 2020, 07:41:45 am
content: Quote from: TerraHertz on February 14, 2020, 04:52:00 amYou can Move Topic yourself, look bottom left of your page to find the button to do it.QuoteSnPbAg 62/36/2 2% silver bearing solder is the correct stuff AFAIK.RS or E14 should have some.

author: madao
author_rank: Frequent Contributor
timestamp: February 14, 2020, 02:23:01 pm
content: Solder for ceramic strips: minimum 2-3% silver. I use PB-free solder with 2.4% silver, it works.NEVER use solder with copper, it kills fast.carry handle. carefull strip down and make copy with fresh leather. I have rebuild one..

author: TerraHertz
author_rank: Super Contributor
timestamp: February 14, 2020, 11:34:36 pm
content: Quote from: madao on February 14, 2020, 02:23:01 pmYes, I am coming to this conclusion too. Maybe if I can find a hobby leatherworker nearby I could pay for it.Otherwise, do it myself. I do have a leather sewing awl. An heirloom, was my grandfathers. Would be nice to use it.There's no need to strip down the old one, there is nothing recoverable in it. Even the metal reinforcing strap is rusted through. The internal structure of the handle is just cardboard, disintegrating. The covering is thin blue PVC, also beyond reuse.One thing about leather is there are many color stains, because lady's shoes. I might find a close color match to that blue.Thanks for the tip re solder with copper content. Better to be told, than to learn by wrecking a tag strip.

author: jdragoset
author_rank: Frequent Contributor
timestamp: February 15, 2020, 05:01:41 am
content: Many Thanks to all of you who take the time to refresh the knowledge that will otherwise be lost forever!

author: David Hess
author_rank: Super Contributor
timestamp: February 16, 2020, 11:00:15 am
content: Quote from: madao on February 14, 2020, 02:23:01 pmIf your lead free solder has a higher fraction of tin, then that makes the situation worse since it is the tin which dissolves the silver. In practice even normal solder is not a problem unless repeated repairs are made to the same joints.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 16, 2020, 02:00:13 pm
content: Quote from: David Hess on February 16, 2020, 11:00:15 amWait, do you actually understand the process by which metals are adhered to ceramics?Could you explain please?I've always wondered how that is done. Things like ceramic vacuum tube bodies, large triacs and diodes, etc, where metal parts are joined to the ceramic.I can understand how glass to metal seals work, like with valve leads. The hot molten glass 'wets' the metal and sticks. But ceramics?And is that process the same as Tektronix used to put a metal coating in those ceramic tag strips slots, that solder wets?So it's a silver plating on ceraic, and if the silver is dissolved into the solder, the metal-ceramic bond fails?

author: David Hess
author_rank: Super Contributor
timestamp: February 16, 2020, 04:12:21 pm
content: Quote from: TerraHertz on February 16, 2020, 02:00:13 pmYou pretty much covered it. Tektronix had a ceramics shop and the silver was fired unto the ceramic in a kiln.I suspect they used silver solder for the extra mechanical strength but it does also lower the rate at which the tin dissolves the silver substrate which could matter if repairs were made. If the silver is dissolved, then the solder will not adhere to the ceramic.https://vintagetek.org/ceramic-strips/The above link also confirms that they used solder with 3% silver.

author: vidarr
author_rank: Frequent Contributor
timestamp: February 16, 2020, 05:44:04 pm
content: Quote from: madao on February 14, 2020, 02:23:01 pmI was going to say the same. You should definitely do it this way. If you can't yourself, it will be cheap to have made.Best would be to reuse the original material you have as a finish, over another, new, strong, strap material. Center the original fabric over the new strap and stitch it down. That would be ideal.