Keithley 220 Output Triax connector Mod

[rastro]

Is the diameter on the pomona 5219 larger than the original connector?

[Zucca]

Hey rastro, thank you to stay with me in this pure madness. Yes the Keithley connector is a D5 hole (see my previous posts) and the Pomona 5219 is a D4.

See the comparison between the suggested hole from the Pomona 5219 datasheet and the Keithley stock hole:



Moreove it is facebook official do not trust the Pomona 5219 datasheet, that hole is too big. This is the pattern I will use,



Please be aware of the declared +-0.005" tolerance on the datasheet, so please measure your  Pomona 5219 and then decide what to do.

[rastro]

zucca,

Thanks for the comparison picture and posting the template. 

I am also wondering about the solder process and best approach to avoid damage and contamination during removal of old and install of new connector. 

For removal:
-----------------------------------
1) looks like you have to cut back the outer heat shrink - can't slide it back to expose solder joints
2) Unsolder outer sleeve from old connector tab.  In my case this tab is broken (motivating reason to replace)
3) At this point I'm not sure if there is enough wiggle room to slide back the metal sleeve and outer shield in order to expose the center wire/connector solder joint.
My preferred approach is to use original connection points and avoid stripping cable for new contacts.  I'm not sure if this is realistic. 

For Install:
----------------------------------
1) looks like a tight fit for a solder iron tip to reach center connector pin and wire without touching cable insulation. 
I thought about preheating pin from other side with a different solder iron set low to ~100-degree C.  This might speed up solder flow at the rear of connector and reduce solder heat exposure time on the cable.
2) What kind of solder(flux and metal/mix) to avoid affecting impedance?
3) What is the ideal solder iron temperature for solid connection but minimum risk of damaging nearby insulation.   

Thanks for all your postings - I'm sure there is more than a few 220 owners who want to do this replacement.

Regards
rastro

[Zucca]

Hi Rastro!

For removal answers:
-----------------------------------

1) Yes, you have to do a surgery and gently cut the heat shrink with a scalpel.
2) That´s exactly what I did
3) I then desolder the black common wire at the other side of the metal pipe
4) At this point I could slide the metal pipe a little bit back and get the iron on the central conductor to disconnect the Triax connector
5) Finally desolder the metal pipe and remove the teflon pipe inside.

As a general procedure use the iron only for the shortest time, you will avoid to damage the isolation like I did.

My preferred approach is to use original connection points and avoid stripping cable for new contacts.  I'm not sure if this is realistic. 

This was my plan too, but I think it is not realistic. A small amount of well done stripping it is not a problem.
 

For Install:
----------------------------------
1) looks like a tight fit for a solder iron tip to reach center connector pin and wire without touching cable insulation. 
I thought about preheating pin from other side with a different solder iron set low to ~100-degree C.  This might speed up solder flow at the rear of connector and reduce solder heat exposure time on the cable.
2) What kind of solder(flux and metal/mix) to avoid affecting impedance?
3) What is the ideal solder iron temperature for solid connection but minimum risk of damaging nearby insulation.   

I'm a happy Metcal iron owner and I can not set the temperature. To me the key is presolder, use little flux a clean all up with an antistatic brush and IPA.
I will document my install process soon.

Tonight the Pomona 5219 was on my Keithley, I did it!

Initial setup


after 15min of filing


done:



Here in attachment the stencil I used, it was slightly small but better so than insane big like in the datasheet, with 2 more minutes of filing I reached the perfect spot.

[Zucca]

It was a long surgery but now the patient is doing very well.

First of all I wanted to make sure my salivation and my finger printer are not causing any problem on such a delicate electronic. Moreover I cleaned the Teflon and the metal pipes with IPA prior the installation.



Heat shrinks... how many times I forgot that... The big is for cover the 5219 chassis, the small for the entire central stuff



cleaning up the metal pipe from the solder blob from the past (wick and then IPA):



presolder the central concuctor on the Pomona 5219



Now the funny part, cut and strip the Triax cable to get this (use a scalpel and a lot of patience, take your time). Presolder the central conductor.



Basically you want the Silver Braided shield as long as possible (do not cut it if it is possible, keep it from what you get from before) because the Pomona 5219 has a different geometry from the original Triax connector, so the metal pipe has to go further deeper.

insert the Teflon and the metal pipe. The Silver Braided shield should stay outside, keep the Teflon pipe slightly out from the metal pipe



"Eagle is landed, over"



With a scalpel use the sharp blade to pull gently the Teflon pipe



so the central conductor is totally covered



I used a little flux to solder the metal pipe on both ends, and then clean it up with an antistatic brush and IPA. Next step solder the metal pipe to the Pomona 5219



Don´t forget the common wire for the Banana jack on the back, pass it inside the heat shrinks:



It´s time to solder that wire and the Silver Braided shield with the metal pipe



Do a quick functional check to see if everything still works, if it pass let´s manage the heat shrink, too easy now



Done




Does it still works? Yes, cheers!




If someone of you need the old Keithley 220 connector just PM me.

[Vgkid]

Good job on the repair, and good beer choice as well. Even though I drink much more wine then beer.

[robrenz]

Very nicely done 

[Zucca]

Thanks, robrenz and Vgkid,

BTW the old Triax is now on sale:

http://www.ebay.com/itm/291108474844?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1558.l2649

[Zucca]

FYI This unit is now on sale:

https://www.eevblog.com/forum/buysellwanted/zucca-sales-(d)-keithley-220/

[bozidarms]

Sorry,
have not right understand that you sell cables only with Keithley,
Thanks