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Re: New member with a currently-dead 2465

 

Just replace U2556. It is a cheap part. Cut the leads close to the chip package, remove the package, then unsolder and remove each pin one at a time. Clear the holes and put in a new 74LS04. I wager a cheeseburger that is the problem.

Regards

On 7/10/2020 7:32 PM, Vincent Mallet wrote:
Tested +5V and GND pins of U2556 and they are as expected.
I tested the 3-4 inverter by bringing pin 3 to +5V or GND (like you
mentioned, although using a 22R shunt briefly instead as this is what I had
laying around) and hmm I didn't see much reaction on its output 4.
For kicks I tested the 9-8 inverter (not used according to the schematics)
and this one responded as expected.

Surprising things happened next when I tested the 1-2 inverter. I started
by putting my scope probe on pin 1 to make sure my 22R shunt was having the
desired effect on the input. The input was sitting at about 1.05V. I
briefly applied +5V to pin 1 (via 22R) and bam! I started seeing a sine on
pin 1. The sine had a 840mV pk-pk amplitude sitting right above a 1V
offset, 10Mhz. I touched pin 1 again and a 2.24V pk-pk sine appeared (again
sitting right above 1V), and I saw something appear on the 2465 display!
The scope had booted up! Things vanished shortly after.

I redid the experiment after putting another probe on TP505 U2092-37 and I
saw different results. Once I got a nice 2.24V pk-pk sine on pin 1 which
gave me a 1.25Mhz (almost) square on TP505 which is matching the expected
value from the service manual. It lasted 5s, then the pin1 sine shrunk to
~840mV pk-pk again. Touched it again and I got a 400mV pk-pk (offset 1V)
but this one was ~30Mhz! The resulting TP505 more-or-less square wave was
at 3.75Mhz, three times the expected frequency. Touched it again and pin 1
sine became a not-so-sine wave, 10Mhz, 560mV pk-pk.

I pulled the legs of C2565, C2566, C2572 to measure them with an LCR
meter.
C2565: 84.5pF (specs: 82pF, 5%)
C2566: 33.3pF (specs: 33pF 5%)
C2572: 100.1nF (specs: 100nF 20%)

I do not know how to measure leakage current yet.

I should have access to a better desoldering tool soon and I'll pull the
resistors and U2556 so I can measure / test them out of circuit.

Thanks,

Vince.





On Fri, Jul 10, 2020 at 12:29 PM Siggi <siggi@...> wrote:

On Fri, Jul 10, 2020 at 12:31 PM Vincent Mallet <vmallet@...> wrote:

Thanks Siggi. The scope is a 2465 300Mhz, S/N B027189. I don't see any
smd
components on the A5 board.
Yeah, only (some of) the -B version has SMD on the A5 board, as I
understand.


I don't think the scope has any options but I'm
not too sure how to tell yet.

I looked at the joints of the oscillating circuit components under a
microscope and they looked fine (to my untrained eyes); I tested
conductivity between leads around this area and it matched expectations.
I
wiggled things a bit and flexed the board very gently and powered things
back on, still a flat line there.
Well then, I guess you need to dig in, see what's up. In your shoes I'd
start by verifying that U2556 is getting 5V and ground.
You should then be able to check whether the U2556A inverter is driving
its output by measuring the voltages on pin 1 & 2. It should be safe to
test the inverter by shunting its input to +5V and GND through - say - a
100Ohm resistor to see whether it can drive both up and down.
Maybe you want to test R2571 & R2573 as well as C2572. There have been
cases where these 0.1uF capacitors have gone leaky, and that might be
enough to bring down this oscillator.

Good luck,
Siggi



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Re: Tek 465 Turns on, No Dot, No Trace

Stephen
 

On Fri, Jul 10, 2020 at 12:10 PM, Tom Miller wrote:


Can you go back and measure all the other low voltages in the HV
circuit? The base being positive so much says the HV oscillator is not
running.

Measure all the points shown on the schematic for the primary of T1420.
Let's see what is going on there.

A common problem is a shorted HV multiplier (U1432) that stops the
oscillator from running.  Lifting the ground lead of the multiplier lets
the oscillator run and the -2450 supply comes up allowing HV regulation.
If that turns out to be the issue, there are several options you can take.
All I could find to measure is at the fuse, and I found 23.43V. Another TP I found was TP1594, and I have 9.72V.
TP1486 reads from 14.59V to 31.98V depending on the Intensity pot level.
I didn’t find any other points to measure.
As for lifting the ground leg of the HV multiplier, I don’t have access to it. It’s buried and enclosed on the other side of the board.


Re: Tek 465 Turns on, No Dot, No Trace

 

I should say the circuitry Driving the primary of T1420, Including Q1418.

Regards

On 7/10/2020 7:09 PM, Tom Miller wrote:
Can you go back and measure all the other low voltages in the HV circuit? The base being positive so much says the HV oscillator is not running.

Measure all the points shown on the schematic for the primary of T1420. Let's see what is going on there.

A common problem is a shorted HV multiplier (U1432) that stops the oscillator from running.  Lifting the ground lead of the multiplier lets the oscillator run and the -2450 supply comes up allowing HV regulation. If that turns out to be the issue, there are several options you can take.



On 7/10/2020 6:40 PM, Stephen wrote:
I successfully changed the 2 bad caps. The good news is no more ripple whatsoever, and all voltages are absolutely right on the money.  However, bad news is nothing as changed; still no trace, dot, or beam finder...
And to top it all off the “ON” indicator light doesn’t light up anymore.  And I’m pretty sure it did before.  All others do (X10, Uncal, Volt/Div, trigger...), and graticule illumination is also working.  I took the little bulb out, and it works fine with a 3V battery.  I measured the voltages for that bulb and it reads 4.85V.  Could it be an indication for another issue?  This is madness.  It lights up with a 3V battery, but doesn’t in circuit with 4.85V.
Also, voltages across Q1404 haven’t changed much.  A few millivolts, I think.

This scope is officially driving me nuts.  I don’t know what else to do...


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Re: New member with a currently-dead 2465

Vincent Mallet
 

Tested +5V and GND pins of U2556 and they are as expected.
I tested the 3-4 inverter by bringing pin 3 to +5V or GND (like you
mentioned, although using a 22R shunt briefly instead as this is what I had
laying around) and hmm I didn't see much reaction on its output 4.
For kicks I tested the 9-8 inverter (not used according to the schematics)
and this one responded as expected.

Surprising things happened next when I tested the 1-2 inverter. I started
by putting my scope probe on pin 1 to make sure my 22R shunt was having the
desired effect on the input. The input was sitting at about 1.05V. I
briefly applied +5V to pin 1 (via 22R) and bam! I started seeing a sine on
pin 1. The sine had a 840mV pk-pk amplitude sitting right above a 1V
offset, 10Mhz. I touched pin 1 again and a 2.24V pk-pk sine appeared (again
sitting right above 1V), and I saw something appear on the 2465 display!
The scope had booted up! Things vanished shortly after.

I redid the experiment after putting another probe on TP505 U2092-37 and I
saw different results. Once I got a nice 2.24V pk-pk sine on pin 1 which
gave me a 1.25Mhz (almost) square on TP505 which is matching the expected
value from the service manual. It lasted 5s, then the pin1 sine shrunk to
~840mV pk-pk again. Touched it again and I got a 400mV pk-pk (offset 1V)
but this one was ~30Mhz! The resulting TP505 more-or-less square wave was
at 3.75Mhz, three times the expected frequency. Touched it again and pin 1
sine became a not-so-sine wave, 10Mhz, 560mV pk-pk.

I pulled the legs of C2565, C2566, C2572 to measure them with an LCR
meter.
C2565: 84.5pF (specs: 82pF, 5%)
C2566: 33.3pF (specs: 33pF 5%)
C2572: 100.1nF (specs: 100nF 20%)

I do not know how to measure leakage current yet.

I should have access to a better desoldering tool soon and I'll pull the
resistors and U2556 so I can measure / test them out of circuit.

Thanks,

Vince.

On Fri, Jul 10, 2020 at 12:29 PM Siggi <siggi@...> wrote:

On Fri, Jul 10, 2020 at 12:31 PM Vincent Mallet <vmallet@...> wrote:

Thanks Siggi. The scope is a 2465 300Mhz, S/N B027189. I don't see any
smd
components on the A5 board.

Yeah, only (some of) the -B version has SMD on the A5 board, as I
understand.


I don't think the scope has any options but I'm
not too sure how to tell yet.

I looked at the joints of the oscillating circuit components under a
microscope and they looked fine (to my untrained eyes); I tested
conductivity between leads around this area and it matched expectations.
I
wiggled things a bit and flexed the board very gently and powered things
back on, still a flat line there.
Well then, I guess you need to dig in, see what's up. In your shoes I'd
start by verifying that U2556 is getting 5V and ground.
You should then be able to check whether the U2556A inverter is driving
its output by measuring the voltages on pin 1 & 2. It should be safe to
test the inverter by shunting its input to +5V and GND through - say - a
100Ohm resistor to see whether it can drive both up and down.
Maybe you want to test R2571 & R2573 as well as C2572. There have been
cases where these 0.1uF capacitors have gone leaky, and that might be
enough to bring down this oscillator.

Good luck,
Siggi




Re: Tek 465 Turns on, No Dot, No Trace

 

Can you go back and measure all the other low voltages in the HV circuit? The base being positive so much says the HV oscillator is not running.

Measure all the points shown on the schematic for the primary of T1420. Let's see what is going on there.

A common problem is a shorted HV multiplier (U1432) that stops the oscillator from running.  Lifting the ground lead of the multiplier lets the oscillator run and the -2450 supply comes up allowing HV regulation. If that turns out to be the issue, there are several options you can take.

On 7/10/2020 6:40 PM, Stephen wrote:
I successfully changed the 2 bad caps. The good news is no more ripple whatsoever, and all voltages are absolutely right on the money. However, bad news is nothing as changed; still no trace, dot, or beam finder...
And to top it all off the “ON” indicator light doesn’t light up anymore. And I’m pretty sure it did before. All others do (X10, Uncal, Volt/Div, trigger...), and graticule illumination is also working. I took the little bulb out, and it works fine with a 3V battery. I measured the voltages for that bulb and it reads 4.85V. Could it be an indication for another issue? This is madness. It lights up with a 3V battery, but doesn’t in circuit with 4.85V.
Also, voltages across Q1404 haven’t changed much. A few millivolts, I think.

This scope is officially driving me nuts. I don’t know what else to do...

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Re: Cleaning TM500 module pushbutton switches

Renée
 

Somehow this has moved in the wrong direction...however, Greg is correct!.
WD40 is only good for the shafts ( Think rotary switch shaft, stuck and the proper stuff for electrical equipment is not working btw Kroil etc...falls in the same category of bad for electrical items) in loosening/softening the hardened grease/rust etc....god forbid one gets it on electrical switch contacts or especially the insulating material.  It is not a lube in any way shape or form. Once the original shaft is loose and the assembly moves, I am able to completely disassemble the mechanical portion and I mean FULLY disassemble. Then fully clean removing the WD40 and the old grease lube, rust, debris etc . then if necessary lightly polish the shaft put in the proper lube and reassemble.
I work on some pretty rough poorly stored stuff...like stored in a barn for years with "stuff" sprayed on it by animals etc....

Every product has a proper usage. BTW I have been using Craig and MG chem stuff for years...they work great.

I am sorry I mentioned WD40 earlier. Never again will I mention it or like material.
Renée

On 7/10/20 2:37 PM, Greg Muir via groups.io wrote:
I keep constantly preaching to people that WD40 is not intended for application to electrical items such as switches. It is basically a heavy oil that is thinned by a lighter more solvent-style carrier. Over time the lighter carrier will evaporate leaving behind the heavier, sticky oil that then starts to gum things up and collects dirt and dust.

in addition, WD40 has no properties to clean switch contacts short of initially carrying away any loose dirt that may be present on them. Use of electronic grade contact lubricants/cleaners is the recommended practice.

The Caig Laboratories line of contact cleaners and lubricants has gained wide acceptance as a reliable product for switches. But I have also found that MG Chemicals produces a very similar product under the name “Super Contact Cleaner” which is much cheaper in larger quantities. I have had no reliability issues using it cleaning & lubricating switches of all types, some found in very dirty and corroded conditions. And use of either product does not leave behind any sticky liquids that can attract dirt in the future.

I do understand that Caig has developed a high reputation and their prices show it. I try to save money if I can locate a similar product that functions the same way. (And I am not affiliated with either manufacturer).

Greg


Re: FG-504 not-so odd behavior

keantoken
 

For the unit with frequency pegged high, I would look for an open x40 cal trimmer or dial min cal trimmer. Anything pulling the U30A/B inputs low will peg the frequency high.


S-6 troubleshooting conditions

unclebanjoman
 

Hi,
After successful repair of the S-52 pulse head, now I'm going to repair one S-6 that has a very distorted output waveform (I've another one, fully functional).
Before to dismantle the broken one I've read the manual and schematics.
Somewhat surprisingly, I found no troubleshooting conditions apart few lines indicating where to find a suitable the trigger signal for the test oscilloscope (from a 7S12).
Should I use a 7S12? Or the 7S11/7T11 pair? Which settings? With which input signal into the S-6 (if any)?

Max


Re: Tek 465 Turns on, No Dot, No Trace

Stephen
 

I successfully changed the 2 bad caps. The good news is no more ripple whatsoever, and all voltages are absolutely right on the money. However, bad news is nothing as changed; still no trace, dot, or beam finder...
And to top it all off the “ON” indicator light doesn’t light up anymore. And I’m pretty sure it did before. All others do (X10, Uncal, Volt/Div, trigger...), and graticule illumination is also working. I took the little bulb out, and it works fine with a 3V battery. I measured the voltages for that bulb and it reads 4.85V. Could it be an indication for another issue? This is madness. It lights up with a 3V battery, but doesn’t in circuit with 4.85V.
Also, voltages across Q1404 haven’t changed much. A few millivolts, I think.

This scope is officially driving me nuts. I don’t know what else to do...


Re: Tektronix 465 No Trace, No Dot

Stephen
 

On Fri, Jul 10, 2020 at 09:15 AM, Brenda wrote:


Hi Steven, I would highly recommend that you change out all electrolytics. My
rule of thumb is if one is bad, it will only be a matter of time before more
will go bad. I learned that the hard way with my Tektronix 535A.

Brenda
Will do, thank you. It’s also what i usually do. But for now I’m just trying to get it to work since the other caps show no sign of problems yet...
I posted a new thread on this. Please do go there to see more updates.


Re: FG-504 not-so odd behavior

keantoken
 

Start by checking the PSU voltages.
See where the oscillation stops, starting at the oscillator board on the left side of the plugin. J300 is the output connector for the oscillator. If the oscillator is dead, check the open case trimmers for open wipers as this will stop oscillation or peg the output frequency (check any voltages marked on the schematic for hints). Replace with sealed Bourns trimmers as necessary, working them back and forth may sort of bring them back to life but they will drift or die again. The frequency vernier var pot may be open if it is broken, or you may just have a broken coupler allowing the knob to spin freely.

This is on the triangle wave generator schematic in the service manual (page 138 in the PDF I have). Check any voltages marked on the schematic. The start, stop and var pots may stop oscillation if they go open.

On my FG504, the open case trimmers are all losing wiper continuity due to age.

I also had the regulator trimmers go open so check your voltages. On either side of the power output transistors on the right side of the FG504 I had the large MLCC capacitors short out, they crumbled when I replaced them. Oddly enough I have had no problems with the tantalums so far, but check them and see if any are getting hot.


Re: Cleaning TM500 module pushbutton switches

Greg Muir
 

I keep constantly preaching to people that WD40 is not intended for application to electrical items such as switches. It is basically a heavy oil that is thinned by a lighter more solvent-style carrier. Over time the lighter carrier will evaporate leaving behind the heavier, sticky oil that then starts to gum things up and collects dirt and dust.

in addition, WD40 has no properties to clean switch contacts short of initially carrying away any loose dirt that may be present on them. Use of electronic grade contact lubricants/cleaners is the recommended practice.

The Caig Laboratories line of contact cleaners and lubricants has gained wide acceptance as a reliable product for switches. But I have also found that MG Chemicals produces a very similar product under the name “Super Contact Cleaner” which is much cheaper in larger quantities. I have had no reliability issues using it cleaning & lubricating switches of all types, some found in very dirty and corroded conditions. And use of either product does not leave behind any sticky liquids that can attract dirt in the future.

I do understand that Caig has developed a high reputation and their prices show it. I try to save money if I can locate a similar product that functions the same way. (And I am not affiliated with either manufacturer).

Greg


Re: My first scope, a Tektronix 11401 with option 2D extended memory and two 11A34 plugins and an 11A33 plugin.

 

Oh, i forgot to mention, I'm new here! Not sure if my humor really came across like joking about the dead channel causing a time fault. (it was a joke on how i am dumb)

Anyways im reading the extended service manual 1 and the timebase G2121 can either be 1, 2, or 3 of 2 things. lol. Basically either the 19MHz clock Y2040 <10> on the Acquisition Board or the MPU clock Y220 <16> on the Time Base board is out of tolerance. I am willing to bet it's the Y2040 <10> because there is only one timebase fault not two. if there were two timebase faults I'd have a G2111 fault as well since that test also uses the Y220 <16> for timing reference. The G2111 fault is when the 10MHz crystal Y100 on the acquisition board is within 0.01% and the circuits necessary to generate the time base board's system block are somewhat functional. If there were 2 time base faults, it'd hard to diagnose which chip is causing which fault, is it the MPU causing both?, or is the MPU fine and Y220 <16> and Y2040 <10> are both out ? Or are they all three out lol? Ooof, glad it's only the G2121 atm.

The Artek manuals are amazing. The 11401 extended service manuals, which are not just scanned in either, they are digitally remastered. Highly worth the $15 for all 4 major books, but mostly just for those three service manuals remastered. Please if you need these extended service manuals, don't ask me I won't give them to you, please support Artek!

I should say also some other various stuff about this machine and it's upgrades through out it's life. there are two extra extended lifetime service manuals. One is a U350 and U552 replacement guide, mostly just a ESD sensitive slam-pak install tutorial, might have more didn't fully read it yet. Two is a Reliability Improvements for 11401 on serial numbers B010100 - B019999. It talks about firmware version 3 upgrade chips and a trigger enhancement, essentially from what i read it will avoid spiking the waveform when the end of holdoff and the triggering signal coincides. I'm willing to bet most 11401's have had the trigger enhancement, because the manual is from 1988 and Tektronix, i believe from what I was told was giving out free improvements customers could pickup. Additionally after the improvements were made public and distributed, Tektronix were already supplying 11401 scopes with the improvements installed. Hence why you can find model numbers for 11401's after the service manual supports with an age older than the manual. Both were scanned by Zenith and they are here http://www.hakanh.com/dl/kits.htm right now, i don't believe i found them anywhere else. That site also has an incomplete 067-0587-10 manual supplement to 067-0587-02, you can find a more complete one on the tek wiki. which is actually the manual which shows how all 7k calibration fixture signal standardizer can be switched to a 7612D, and 11k calibration fixture signal standardizer. once the modification is installed it just depends on what way the internal S135 switch on the 067-0587-02 is set to. With S135 pushed facing forward toward front is for 11k and 7612D it's called the 067-0587-10 in this mode, and switch pushed back, facing rear is for 7k and called a 067-0587-02. You can find the original 067-0587-02 calibration fixture signal standardizer instruction service manual on tekwiki or The Boat Anchor Manual Archive. Once you have both 067-0587-02 and 067-0587-10 manuals, i'd edit 067-0587-02 by placing 067-0587-10 manual before section 1 like it says in the 067-0587-10 manual. I've seen a few 067-0587-02's with the 067-0587-10 mod already installed, so you might already have it, but i wouldnt buy a 067-0587-02 betting it had a 067-0587-10 mod... Also http://www.hakanh.com/dl/ page has several useful tools and obsolete Tek software like Docuwave 1.2. Which was hard as heck to find. I believe this is the last version working for the 11401's.

Also just picked up some probemaster 8017S's, pretty sure these are the best leads for the price, if 8017S's arent for your meter or you, checkout probemaster cross reference to find the right probes! i really wanna buy probemasters oscilloscope probes, but golly they are almost the price of my scope, one day.

That's all for today :)


Looking for

stevenhorii
 

I am looking for a rare 7000-series plug-in: A 7J11 optical spectrum analyzer with the external detector head. I know that these are uncommon as I don't think Tek made many of them (high price). If anyone knows of one for sale, let me know off-list. Thanks!


FG-504 not-so odd behavior

John Ferguson
 

I now have two FG 504's.  The first doesn't oscillate despite all manner of exercising the buttons and switches and has a defective VAR pot for the frequency vernier - knob turns through 360 degrees.

The second one seems to be functional except for square wave.  I haven't tied down the frequency but it puts out a very high frequency triangular signal.  It seems to be within the range of my 2445b scope, so tomorrow when my spouse lets me return to this I should be able to measure it.

The manual for this instrument is really good. It runs you through some exercises for first time power on (or first time use for me) and except for square wave and the functions associated with it all seems ok.

Could this be a defective Schmidt trigger (circuit)  and if so, is it possible for only the square wave functions to be affected by it?

john ferguson


Re: Tektronix 465 No Trace, No Dot

Brenda
 

Hi Steven, I would highly recommend that you change out all electrolytics. My rule of thumb is if one is bad, it will only be a matter of time before more will go bad. I learned that the hard way with my Tektronix 535A.

Brenda


Re: FG 504 function generator odd behaviour

Roger Evans
 

Colin,

If you have a problem with the triangle wave symmetry then I would begin with that before looking elsewhere. The operation is well described in the manual but I need the big screen to look at that, not the phone! If memory serves me right there are two constant current sources driving the integrating capacitor and limit comparators to define the end points. If the waveform is distorted at the integrating capacitor then you need to look at the current sources, any associated decoupling circuitry and the FET that buffers the integrator. If the triangle wave looks OK at its source then you can follow it through the switching and amplifying stages. The output stage is quite beefy to drive 50 ohm loads and I had to replace some components in mine to get it up to spec.

The push buttons on the 500 series are unreliable with age, there is a thread here about cleaning so try exercising the waveform selector buttons several times.

Regards,

Roger


Re: Cleaning TM500 module pushbutton switches

Roy Thistle
 

On Fri, Jul 10, 2020 at 12:20 PM, Chuck Harris wrote:


I don't know exactly what the "naphtha" in Ronsonol is
Hydrocarbons, aliphatic hydrocarbons, C7-C9, n-alkanes, isoalkanes, cyclics.... so ya... we don't really know... but the guys at Ronson do... but, what matters to Ronson is the refinery tank cars them the "good stuff"... that is the stuff that meets Ronson's physio-chemical properties. I'm sure Ronson tests for that data, and they may use chromatography, et. al. to see what's really in the latest conforming batch too.


Re: New member with a currently-dead 2465

Siggi
 

On Fri, Jul 10, 2020 at 12:31 PM Vincent Mallet <vmallet@...> wrote:

Thanks Siggi. The scope is a 2465 300Mhz, S/N B027189. I don't see any smd
components on the A5 board.

Yeah, only (some of) the -B version has SMD on the A5 board, as I
understand.


I don't think the scope has any options but I'm
not too sure how to tell yet.

I looked at the joints of the oscillating circuit components under a
microscope and they looked fine (to my untrained eyes); I tested
conductivity between leads around this area and it matched expectations. I
wiggled things a bit and flexed the board very gently and powered things
back on, still a flat line there.
Well then, I guess you need to dig in, see what's up. In your shoes I'd
start by verifying that U2556 is getting 5V and ground.
You should then be able to check whether the U2556A inverter is driving
its output by measuring the voltages on pin 1 & 2. It should be safe to
test the inverter by shunting its input to +5V and GND through - say - a
100Ohm resistor to see whether it can drive both up and down.
Maybe you want to test R2571 & R2573 as well as C2572. There have been
cases where these 0.1uF capacitors have gone leaky, and that might be
enough to bring down this oscillator.

Good luck,
Siggi


Re: Cleaning TM500 module pushbutton switches

Bill Perkins
 

Walter:
Looking eBay:

https://tinyurl.com/y9s93ean

I see about 27 different offerings, what's your recommendation ?

Thx,
Bill

I do not recommend using WD40 anywhere near the TM500 switches.
as I explained earlier, using de-oxit (which is slightly lubricating),
and letting it fall right
to the front plastic shaft solves ALL seizing problems in the switch
assembly, as well as fixing the contacts.
let it drain down to the shaft from the open back, work the mechanism
rapidly at least a dozen times, and
you should have good results. I have also had good success with nu-trol,
used in the same way from the
 open back of the switch.
I have done hundreds of these switches both in the TM500 and 7K /5K
series. I am 100% confident
that the process I described will work IF ANYTHING CAN WORK (in other
words if there's any good
contact surface left in the switch). I strongly advise against anything
like solvents, WD40, oils or
other highly active chemicals, and I have NOT found that disassembly and
manual cleaning works
any better than the process I described, although disassembly can be
useful when the sliding
contact has to be replaced. to be candid, if it's at that point, the
switch itself has to go.
we used a variant of this same switch (the origin of which goes WAY back
to itt-schadow in europe) for many
years in avionics systems as well, but paid to have the contacts gold
plated from E-switch, and had almost no failures over decades of use.
just my $0.02 worth on this topic.
all the best,
walter