Trouble making my low end TDR work, Help.

[Tom Gardner]

On 02/05/20 20:35, Joerg wrote:

It's been too long ago and I can't find the Greek guy anymore who sold us the
2465 knob set.

Perhaps https://www.qservice.tv/

They also sell on fleabay

 

[Clifford Heath]

On 3/5/20 9:49 am, Carl wrote:

"Joerg"  wrote in message news:hh60cfF3ebU1@mid.individual.net...

On 2020-04-30 17:00, Clifford Heath wrote:
On 1/5/20 8:29 am, Joerg wrote:
On 2020-04-30 15:15, Phil Hobbs wrote:
On 2020-04-30 13:29, Joerg wrote:
Good! I once became very frustrated because a delayed-trigger setup
just didn't show what I was expecting. Until I found out that the
little plastic (!) delayed-trigger clutch inside the otherwise very
expensive Tektronix scope had quietly broken off.
A 485, right?


No, AFAIR it was a Tektronix 2465. To my surprise there was a guy in
Greece who made new knobs and other mechanical parts for these.
Shipping to the US was pricey but afterwards the scope felt great.
That was before 3D printing, he had made molds for all that.

Speaking of broken knobs, I have a Tek 7904 with a 7a26 (400 MHz dual
vertical) and the volts/div knob is broken - 3/4 of the knob is missing.
Still usable, but I'd like to fix it.

I've searched, but not found any print files to 3D print a new knob. Any
hints on where to look?

It will need disassembly, as the calibration knob is also gone and the
end of that shaft is broken off.


Maybe ask guys that sell knob sets for other Tektronix series? They
might know the market.

https://www.ebay.com/itm/Lot-of-20-Tektronix-Oscilloscope-Knobs-Type-500-Series/324148242863


It's been too long ago and I can't find the Greek guy anymore who sold
us the 2465 knob set.

If you have a matching knob or the pieces to glue the busted knob back
together you can make a polyurethane rubber mold from that, and then
cast as many polyurethane plastic copies as you want.  My favorite
source is www.smooth-on.com.  I've used their Reoflex stuff to make a
few small molds, and cast rigid parts from their Smooth0Cast resin.  I'd
suggest a 30A or 40A rubber for the mold and a 70D hardness resin for
the knob.  They have color pigments for the resin so you can make a nice
red knob , and lots of great tutorial videos on their site.  Email or
call them for advice.  They have always been very helpful and
knowledgeable when I've needed it.  Not counting time spent down the
rabbit hole of watching their videos , it should take you maybe an
hour to make and pour your first mold and after an overnight cure and a
few minutes for demolding and cleaning you should be able to get your
first knob cast in less than 30 minutes.  Biggest downside is that their
small test kits are about $30 each, so $60ish plus mold release for one
knob but you will have plenty of material left over.

I played with resin and elastomer casting a few years back, built a
vacuum rig and everything, but had limited success due mainly to not
having the right resins available. I had already learned to trust
Smooth-on, so I should get some and resurrect the skills.

Thanks for the reminder.


CH