Topics

Push-push switch repair (need some theory of operation)

Ke-Fong Lin
 

Hi everyone,

I'm fixing a 5CT1N curve tracer plug-in.
One of the push-push switch (BJT/FET selector) is malfunctioning. It doesn't latch to FET.
The x1000 pull switch doesn't work either.
The BJT/FET switch is a 6PDT (6 poles dual throw), part number is 260-1536-00.

Do you guys have any pointer to a website or better a youtube video explaining the mechanical theory of operation?
I don't think it's a big deal, I'll just have to disassemble the switch and put it back.
But I would prefer some explanation before.

Thank you.

Best regards,

Kurt Rosenfeld
 

Mlynch001
 

Ke-Fong Lin

Those BJT/FET switches are the same type in almost all TEKTRONIX equipment of the era. They are very prone to get dirty or gum up inside. What I do with mine is give it a shot of contact cleaner, work the switch several times let it dry and then follow with a shot of DEOXIT Spray, and finally work it several times. After about 10 -15 cycles they will free up and begin to latch. You can repeat as needed until the switch works. A very common problem as I just fixed a 465 that had a beam finder that was stuck half way between the "normal" and "find" positions. The 576 curve tracer has many of these switches, the problem with them is they are very difficult to access on the 576. But this technique works on 99% of this type of switch. I am not familiar with the +1000 switch, but is may respond to the same treatment.

Good Luck!

--
Michael Lynch
Dardanelle, AR

Ke-Fong Lin
 

Hi everyone,

Thanks for your tips.
The repair document is exactly what I'm looking for.
I'll keep you posted.
Again thank you.

Best regards,

bobkrassa
 

This swithc looks similar to the one in the Sencore PR57 AC Powerite. The basic operation is that pushing the button has to cause the latch bar to move sideways. In these switcches that as done by pushing on a fairly steep, small ramp. Looks like the ramp is on the little star wheel. Using small steep ramps to get lateral motion requires a bit of lubrication to keep the ramp smooth and working. In the Powerite, the ramps are on tiny plastic pieces.

I suggest taking the board out but before you unsolder the switch from the board, try flooding the switch with your favorite plastic-safe combination cleaner-lubricant and gently moving the parts back and forth. As a preventive measure, when these switches start to become difficult, do not use force, instead take them out and clean and lube. Do not use WD40.

73 Bob Krassa ACØJL

Mlynch001
 

Definitely use a "plastic safe" lubricant. Also one that has proven non-corrosive characteristics. The vast majority of these switches are simply dried out, gentle cleaning and lubrication will restore most to service.

--
Michael Lynch
Dardanelle, AR

Greg Muir
 

Bob Krassa is very correct in regards to not using WD40 for switch (and potentiometer) cleaning/lube. When used the light volatile carrier eventually evaporates leaving a heavy sticky Cosmoline type grease film that loves to collect crud. As a demonstration spray some WD40 on a tool, don’t wipe it off and leave it for a few weeks and see what happens.

One first has to flush the switch with a compatible solvent (I see that Tek recommends IPA in their switch repair document) followed by a suitable lubricant and/or deoxidant. Many lean towards the Caig DeoxIT products as have I in the past but eventually came upon a product made by MG Chemicals called “Super Contact Cleaner” that has mysteriously similar characteristics as compared to the Caig products but at a considerably lower cost for larger quantities (I am not affiliated with either manufacturer or product offering). I have never had a problem using it on any switch or pot.

In all, it is not recommended to “goop up” switches and controls with those household products that don’t list use on delicate electronic devices. I always cringe when I open a piece of previously doctored equipment where the “doctor” used a non-recommended cleaner & lube and end up either cleaning all of the controls or having to replace them.

Greg

greenboxmaven
 

WD-40 can be a superior solvent to loosen up hardened grease and petroleum based crud. However, it can only be used as a first part of the cleaning process, and then must be promptly flushed out once it has done it's work. It does indeed leave a residue that is difficult to remove. DeOxit or comparable products use oxalic acid as one of their main ingredients. It is quite effective in removing oxides and tarnish from contacts.

Bruce Gentry, KA2IVY

On 1/2/20 12:31 PM, Greg Muir via Groups.Io wrote:
Bob Krassa is very correct in regards to not using WD40 for switch (and potentiometer) cleaning/lube. When used the light volatile carrier eventually evaporates leaving a heavy sticky Cosmoline type grease film that loves to collect crud. As a demonstration spray some WD40 on a tool, don’t wipe it off and leave it for a few weeks and see what happens.


Greg


ROLYNN PRECHTL K7DFW
 

very correct in regards to not using WD40 for switch (and potentiometer) cleaning/lube.

=========================================================================================

From this I gather that you think that the Tektronix engineers were daft when they wrote the contents of the attached.


Rolynn
Tek Bvtn and Sunset 1966-1971

ROLYNN PRECHTL K7DFW
 

What was stripped from the email was a pdf of the instructions for the Tektronix Lube Kit.


TEKTRONIX LUBE KIT INSTR 070-0496-01.pdf (3902Kbytes)

Maybe you can find it on the www.


Rolynn
Tek Bvtn and Sunset 1966-1971

Siggi
 

This <http://w140.com/tekwiki/images/8/87/070-0496-01.pdf> one?

On Thu, Jan 2, 2020 at 1:21 PM ROLYNN PRECHTL K7DFW <k7dfw@...>
wrote:




What was stripped from the email was a pdf of the instructions for the
Tektronix Lube Kit.


TEKTRONIX LUBE KIT INSTR 070-0496-01.pdf (3902Kbytes)

Maybe you can find it on the www.


Rolynn
Tek Bvtn and Sunset 1966-1971



ROLYNN PRECHTL K7DFW
 

"Siggi" <siggi@...> wrote:
This <http://w140.com/tekwiki/images/8/87/070-0496-01.pdf> one?
====================================================================


Affirmative.


Rolynn

Mlynch001
 

A vast majority of these switches which I have encountered seem to stop working because they get dried out (no lube) or full of congealed lubricants or just plain old crud. The 2213 and 2215 come to mind as I have bought several as "non-working". All they needed was the power switch cleaned and proper lubrication to restore them to function. On occasion, one sees corrosion damage due to some well meaning individual using a cleaner which leaves a reactive film or residue. This is the exception to the rule, at least in my experience. I have repaired many an instrument that simply needed a switch or two properly cleaned to restore primary functions.
--
Michael Lynch
Dardanelle, AR

Greg Muir
 

Reference Tek Lubrication Kit Instructions 070-0496-01

Wow. Tek actually recommended WD40 even to use on pot resistive surfaces.

Granted the penetrant in WD40 does permeate between tiny interfaces and the lubricant will serve its function but I’m really leery about it otherwise unless I can remove it promptly after applying. And i doubt if anyone has done any research into the long term effects of it on resistive elements or other sensitive materials.

I’m wondering if the specifying engineer had any regrets afterwards making this decision. On the other hand any problems resulting from the use of WD40 apparently has not been significant enough as to cause poor operation of the equipment. And the continual upgrade (purchase) to new equipment by the first users left us on this site dealing with the long lost after effects if any are lingering.

As it has been said in the past “You pays your money and takes your chances” sort of akin to driving at high rates of speed on icy roads. Most of the time it will be successful.

Greg

KB6NAX
 

A vast majority of these switches which I have encountered seem to stop
working because they get dried out (no lube) or full of congealed
lubricants or just plain old crud. The 2213 and 2215 come to mind as I
have bought several as "non-working". All they needed was the power
switch cleaned and proper lubrication to restore them to function. On
occasion, one sees corrosion damage due to some well meaning individual
using a cleaner which leaves a reactive film or residue. This is the
exception to the rule, at least in my experience. I have repaired many an
instrument that simply needed a switch or two properly cleaned to restore
primary functions. <
The switch bugaboo that is the most trouble is using a non lubricating
contact cleaner. Lubricants, unless they are dried to hardness, "wash" the
accumulated dust and dirt allowing metal to metal contact. If the contacts
are dry the dirt gets ground into the metal and with the ever present
moisture corrosion takes over. By applying a lubricating cleaner, like Caig
D5 or MG Chemical Super Contact Cleaner for examples, the old lube gets
dissolved and lubricating is restored. The lubricant holds off the
moisture. The exception to the corrosion dilemma is gold plated contacts
but lubrication is still required or else the gold gets ground down to the
base metal which is usually copper or brass and that's the recipe for
corrosion problems.

Arden

KB6NAX
 

Wow. Tek actually recommended WD40 even to use on pot resistive surfaces. <
WD-40 has wooed a lot of folks into believing their stuff was heaven sent. Nope, I learned the hard way WD-40 is not good for pots or switches. It eventually dries to the point that contacts ride over it instead of it assuring metal to metal contact.

Never put WD-40 next to a roll of duct tape. The two are mutual enemies and will annihilate each other. That has been proven by scientific experiment. Duct tape sticks things. WD-40 unsticks things. It's a fight to the death....

Arden

 

Hi Ke-Fong,

YIKES! That is not a very common switch! I searched everything I have and didn't find one on any parts board I have.

You will be delighted to hear there is an alternative however: C&K makes a 6 pole double-throw switch for less than $4.00 in single quantities. The part number is F6UEETB. It is sold by many distributors. I got mine from Mouser. The pinouts are an exact replacement for the one in the 5CT1N and 7CT1N. I just checked. I also believe the same extender rods will connect correctly to the push button shaft on the front of it.

That leaves the really big problem of getting the old switch out. That will not be easy. Since there is a little space under the switch I would recommend you cut the switch off its pins and leave the pins in place until the switch is out of the way. At that point you can remove each pin one at a time and clean out that hole before going on to the next pin. You might even be able to do this without removing the board from the plugin if you are really clever and careful.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Ke-Fong Lin
Sent: Thursday, January 02, 2020 1:05 AM
Subject: Re: [TekScopes] Push-push switch repair (need some theory of operation)

Hi everyone,

Thanks for your tips.
The repair document is exactly what I'm looking for.
I'll keep you posted.
Again thank you.

Best regards,




--
Dennis Tillman W7PF
TekScopes Moderator

Ke-Fong Lin
 

Hi everyone,

Thanks for your comments and advices. I'll work on the switch this week-end.
My intention was to open it and "twick" it back to work. But I got convinced to use some cleaner/lubricant on it.
I've settled on MG chemical's super contact cleaner. I'll order that monday.
So basically, I'll open it this week-end and hopefully re-assemble and hopefully make it work by the end of next week.

Best regards,

EJP
 

http://w140.com/tekwiki/images/2/24/Repairing_tek-made_board-mounted_push-button_switches.pdf
For the record, that document does not describe these switches.

EJP

 

Hi EJP,
I Believe the reason the document does not describe them is because they can't be repaired. The only option was to replace them.

Perhaps it's time to order the drop-in replacement switches I told you about in my Thursday, January 02, 2020 8:06 PM post. The price makes them a no-brainer.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of EJP
Sent: Tuesday, January 07, 2020 7:47 PM
Subject: Re: [TekScopes] Push-push switch repair (need some theory of operation)

http://w140.com/tekwiki/images/2/24/Repairing_tek-made_board-mounted_push-button_switches.pdf
For the record, that document does not describe these switches.

EJP




--
Dennis Tillman W7PF
TekScopes Moderator