Date   

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


Re: Cleaning TM500 module pushbutton switches

Roy Thistle
 

On Thu, Jul 9, 2020 at 08:06 PM, walter shawlee wrote:


de-oxit is really the magic answer
Hi Walter:
I'm not a fan of that libation... as my wankometer goes full double tilt at the mention... but, seeing as you've recommended it (and I know you've worked on a ton of TM500 stuff) my mind is somewhat changed.
And yes, I have noticed the stuff has magical properties too... at least when it comes to anti-gravity: my wallet always feels so much lighter after I buy it. Inexplicable really.
Best regards and wishes.
Roy


Re: Cleaning TM500 module pushbutton switches

Chuck Harris
 

Naphtha is a very ambiguous term.

I don't know exactly what the "naphtha" in Ronsonol is, but it is
definitely not the same "naphtha" from which is derived white gas.

I think the important feature needed to be called naphtha today is
for the liquid to have 5 to 7 carbons arranged in straight or
cyclic groupings... That covers everything from Ronsonol to Coleman
fuel to benzene... And they are not even close to all being equivalent.

The structure makes all the difference in the world as to how the
substance called naptha behaves.

I switched from Ronsonol to VM&P Naphtha, available in pints and
gallons in hardware stores, as Varnish Makers and Painters Naphtha.

It smells the same, and works the same as Ronsonol... even in a
Zippo lighter. Coleman fuel works in Zippo lighters too, but gets
pretty exciting with its bright billowing flame. Gasoline also
works in Zippo lighters, but I wouldn't do it.

Rononol is the standard fair for "fire-eaters". If they were to do
their tricks with Coleman Fuel, they would end up in the burn ward.

As to Tam's suggestion on cleaning TM500 module pushbutton switches,
VM&P Naphtha, or Ronsonol would work very well.

But, you would need some lubrication, as they both would wash all the
light oils away.

-Chuck Harris

n4buq wrote:

Does lighter fluid such as Ronsonal, etc., fall into that same category?

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Chuck Harris" <cfharris@...>
To: TekScopes@groups.io
Sent: Friday, July 10, 2020 1:18:44 PM
Subject: Re: [TekScopes] Cleaning TM500 module pushbutton switches

Petroleum benzine is a redundant redundancy for white gasoline.

White gasoline is an additive free (typically) mixture of heptane
and hexane and their isomers. It is also called stove gas. And
a more pure form also exists as a rubber cement solvent.

-Chuck Harris

Colin Herbert via groups.io wrote:
Nenad,
You mention something you call "petroleum benzine". Though I am a retired
research chemist living in Britain, I have no idea of what this is and
others may not also. It _could_ be "petroleum ether", which I am familiar
with, but that comes in various boiling-point ranges and you wouldn't want
to use a high-boiling fraction; 60-40 is the most likely (boiling-range
between 60 and 40 degrees Centigrade/Celsius). Be cautious, this solvent
is very inflammable and not a little smelly. If you are actually thinking
of "benzene" (note the "e", not "i"), then I doubt that anyone in an EU
country would be able to buy that, as it is carcinogenic (causes cancer)
and is therefore controlled. Perhaps you could clarify?
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Nenad
Filipovic
Sent: 10 July 2020 15:42
To: TekScopes@groups.io
Subject: Re: [TekScopes] Cleaning TM500 module pushbutton switches

On Fri, Jul 10, 2020 at 3:05 AM W1PJE <@W1PJE> wrote:

I have multiple TM500 modules that have developed sticky / intermittent
pushbutton switches (the square small ones). Is there a recommended
cleaning procedure? I was going to do the standard use of Caig's DeOxit in
a sparing manner, but perhaps there is a better way.
In some cases hard patina forms on contact surfaces and DeOxit can be
ineffective or just a short term solution. Additionally, DeOxit cannot
restore the original grease which is likely fully decomposed and dry due to
age. In that case I use the following procedure to restore these without
any desoldering:

- Gain access, carefully uncouple and remove the pushbutton shaft.
- Remove the clamp next to the spring, carefully remove the tiny parts
(spring, tiny rocker bolt and its elastic support).
- Carefully pull out the switch shaft at the back of the switch body - care
must be taken to go slow and grip the two metal contacts (use tweezers)
before they fully come out (otherwise they may fly off and get lost). Note
(or take photo of) the orientation of contacts with respect to their slot
in the shaft (the bend in the middle should be oriented away from the
switch body).
- If the switch is radio button type it will contain a "clutch" sliding
plate that needs to be pushed to one side so the shaft could be released
and removed.
- Sometimes a PCB component may get in the way of shaft removal, I almost
always find it easier to remove the offending component rather than the
switch body.
- If switch parts are clogged by ancient dried up grease, clean/wash
everything (both plastic and metal parts) with a paintbrush in petroleum
benzine (pharmaceutical grade, in Europe we get it in regular pharmacies;
however most non-polar solvents which are not aggressive to plastic would
do). Do not let the plastic parts sit in benzine for too long, all this can
and should be done in just a few minutes. Let the clean parts dry.
- Using a soft brass brush (I get these at dentist supply shops) gently
scrub the patina off the active side of the metal contacts. Soft brass
brush should not damage the contact plating that needs to be preserved.
- Use cotton ear buds soaked first in petroleum benzine, then IPA to clean
the internals of the switch body. I spend at least two sticks per switch.
- Grease all sliding surfaces of parts sparingly (innards of the switch
body, shaft, contacts, rocker bolt pathway in the shaft) with plastic safe
light grease. The goal of contact greasing is protection from moisture and
oxygen that may re-deposit the patina again in time. Light grease won't
interfere with low current low voltage electrical contact properties.
- Re-assemble and exercise the switch.

HTH,
Best regards,
Nenad












Re: Cleaning TM500 module pushbutton switches

Roy Thistle
 

On Fri, Jul 10, 2020 at 09:03 AM, Nenad Filipovic wrote:


"petroleum benzine" might cause confusion
Petroleum benzine is "benzene" in the same way as Silk Almondmilk is milk (unless ur silky cow happens to be named Almond... and then, technically it's Almond's milk... and it is milk.)
The very same thing, petroleum benzine... and labeled as such, under BP, or USP... used to be sold, at drugstores, here in the colonies... in little bottles, among the witch hazel, flowers of sulphur, and saltpetre... and no... I never found any witches, flowers, or salted peters, in the lot.
I always thought petroleum benzene was highly refined (desulfanated, and hydrogenated) hexanes. But, I suppose it could have octanes et.al in it too.
As to what's in your particular petroleum benzene... mileage may very... see your local chromatograph.
As for what's not in it (or not very much at all)... that would be benzene.
By the way... in the BP... there are a number of petroleum medicinals, such as "light"... and "jellied"... and so your pharmacist comes by the name petroleum benzine legitimately.
There are a number of names for similar petroleum based non-polar (or mostly so) solvents... naptha, white gasoline, varsol, mineral spirits, petroleum spirits, lighter fluid, paint thinner (no not water)... and so on.
Call it what you will... you should know what it is still... if you want to use it safely.


Re: FG 504 function generator odd behaviour

Chuck Harris
 

Traditionally, the "function generator" had a voltage source
that fed into a polarity switcher that fed into an integrator.

The output of the integrator was a linear ramp that changed
direction whenever the polarity switcher changed polarity.

To make the function generator oscillate, the output of the
integrator was fed into a Schmidt trigger that in turn fed the
polarity switcher, and made it switch whenever the ramp got
above or below the Schmidt trigger's threshold voltages.

Draw yourself a picture using blocks.

The output of the integrator is a triangle wave, and the output
of the Schmidt trigger is a square wave.

The sine wave was made by feeding the triangle wave into a soft
clipper that clipped off the triangle wave's pointy peaks giving
an approximation to a sine wave. A good bit of art went into
that soft clipper.

The manual will describe the FG504's specific implementation, but
I would concentrate on the soft clipper stage. It typically
has a lot of trimmers, and diodes.

-Chuck Harris


Colin Herbert via groups.io wrote:

I have an FG 504 which is showing some odd behaviour. The triangle-wave shows asymmetry in that the negative peaks of the wave are rounded-off at any frequency and the positive ones have a similar but lesser problem at higher frequencies. This also seems to manifest itself as what looks like cut-off on the negative peaks of the sine-wave and lesser cut-off on positive peaks. While the triangle-waves are more-or-less symmetrical, the sine-waves are definitely not so, showing a nearly three-to-one voltage ratio in favour of positive peaks. There is also noticeably overshoot on the square-waves at anything above 1kHz and only a DC offset at frequencies below 80Hz.
I am totally ignorant of how this function generator produces triangle-waves, but I do understand that the square-waves and sine-waves are derived from the triangle-wave. Does anyone have any help that they can offer? I would be grateful to get this useful function-generator working properly.
Colin.




Re: Cleaning TM500 module pushbutton switches

n4buq
 

Does lighter fluid such as Ronsonal, etc., fall into that same category?

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Chuck Harris" <cfharris@...>
To: TekScopes@groups.io
Sent: Friday, July 10, 2020 1:18:44 PM
Subject: Re: [TekScopes] Cleaning TM500 module pushbutton switches

Petroleum benzine is a redundant redundancy for white gasoline.

White gasoline is an additive free (typically) mixture of heptane
and hexane and their isomers. It is also called stove gas. And
a more pure form also exists as a rubber cement solvent.

-Chuck Harris

Colin Herbert via groups.io wrote:
Nenad,
You mention something you call "petroleum benzine". Though I am a retired
research chemist living in Britain, I have no idea of what this is and
others may not also. It _could_ be "petroleum ether", which I am familiar
with, but that comes in various boiling-point ranges and you wouldn't want
to use a high-boiling fraction; 60-40 is the most likely (boiling-range
between 60 and 40 degrees Centigrade/Celsius). Be cautious, this solvent
is very inflammable and not a little smelly. If you are actually thinking
of "benzene" (note the "e", not "i"), then I doubt that anyone in an EU
country would be able to buy that, as it is carcinogenic (causes cancer)
and is therefore controlled. Perhaps you could clarify?
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Nenad
Filipovic
Sent: 10 July 2020 15:42
To: TekScopes@groups.io
Subject: Re: [TekScopes] Cleaning TM500 module pushbutton switches

On Fri, Jul 10, 2020 at 3:05 AM W1PJE <@W1PJE> wrote:

I have multiple TM500 modules that have developed sticky / intermittent
pushbutton switches (the square small ones). Is there a recommended
cleaning procedure? I was going to do the standard use of Caig's DeOxit in
a sparing manner, but perhaps there is a better way.
In some cases hard patina forms on contact surfaces and DeOxit can be
ineffective or just a short term solution. Additionally, DeOxit cannot
restore the original grease which is likely fully decomposed and dry due to
age. In that case I use the following procedure to restore these without
any desoldering:

- Gain access, carefully uncouple and remove the pushbutton shaft.
- Remove the clamp next to the spring, carefully remove the tiny parts
(spring, tiny rocker bolt and its elastic support).
- Carefully pull out the switch shaft at the back of the switch body - care
must be taken to go slow and grip the two metal contacts (use tweezers)
before they fully come out (otherwise they may fly off and get lost). Note
(or take photo of) the orientation of contacts with respect to their slot
in the shaft (the bend in the middle should be oriented away from the
switch body).
- If the switch is radio button type it will contain a "clutch" sliding
plate that needs to be pushed to one side so the shaft could be released
and removed.
- Sometimes a PCB component may get in the way of shaft removal, I almost
always find it easier to remove the offending component rather than the
switch body.
- If switch parts are clogged by ancient dried up grease, clean/wash
everything (both plastic and metal parts) with a paintbrush in petroleum
benzine (pharmaceutical grade, in Europe we get it in regular pharmacies;
however most non-polar solvents which are not aggressive to plastic would
do). Do not let the plastic parts sit in benzine for too long, all this can
and should be done in just a few minutes. Let the clean parts dry.
- Using a soft brass brush (I get these at dentist supply shops) gently
scrub the patina off the active side of the metal contacts. Soft brass
brush should not damage the contact plating that needs to be preserved.
- Use cotton ear buds soaked first in petroleum benzine, then IPA to clean
the internals of the switch body. I spend at least two sticks per switch.
- Grease all sliding surfaces of parts sparingly (innards of the switch
body, shaft, contacts, rocker bolt pathway in the shaft) with plastic safe
light grease. The goal of contact greasing is protection from moisture and
oxygen that may re-deposit the patina again in time. Light grease won't
interfere with low current low voltage electrical contact properties.
- Re-assemble and exercise the switch.

HTH,
Best regards,
Nenad










Re: Cleaning TM500 module pushbutton switches

Chuck Harris
 

Petroleum benzine is a redundant redundancy for white gasoline.

White gasoline is an additive free (typically) mixture of heptane
and hexane and their isomers. It is also called stove gas. And
a more pure form also exists as a rubber cement solvent.

-Chuck Harris

Colin Herbert via groups.io wrote:

Nenad,
You mention something you call "petroleum benzine". Though I am a retired research chemist living in Britain, I have no idea of what this is and others may not also. It _could_ be "petroleum ether", which I am familiar with, but that comes in various boiling-point ranges and you wouldn't want to use a high-boiling fraction; 60-40 is the most likely (boiling-range between 60 and 40 degrees Centigrade/Celsius). Be cautious, this solvent is very inflammable and not a little smelly. If you are actually thinking of "benzene" (note the "e", not "i"), then I doubt that anyone in an EU country would be able to buy that, as it is carcinogenic (causes cancer) and is therefore controlled. Perhaps you could clarify?
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Nenad Filipovic
Sent: 10 July 2020 15:42
To: TekScopes@groups.io
Subject: Re: [TekScopes] Cleaning TM500 module pushbutton switches

On Fri, Jul 10, 2020 at 3:05 AM W1PJE <@W1PJE> wrote:

I have multiple TM500 modules that have developed sticky / intermittent
pushbutton switches (the square small ones). Is there a recommended
cleaning procedure? I was going to do the standard use of Caig's DeOxit in
a sparing manner, but perhaps there is a better way.
In some cases hard patina forms on contact surfaces and DeOxit can be
ineffective or just a short term solution. Additionally, DeOxit cannot
restore the original grease which is likely fully decomposed and dry due to
age. In that case I use the following procedure to restore these without
any desoldering:

- Gain access, carefully uncouple and remove the pushbutton shaft.
- Remove the clamp next to the spring, carefully remove the tiny parts
(spring, tiny rocker bolt and its elastic support).
- Carefully pull out the switch shaft at the back of the switch body - care
must be taken to go slow and grip the two metal contacts (use tweezers)
before they fully come out (otherwise they may fly off and get lost). Note
(or take photo of) the orientation of contacts with respect to their slot
in the shaft (the bend in the middle should be oriented away from the
switch body).
- If the switch is radio button type it will contain a "clutch" sliding
plate that needs to be pushed to one side so the shaft could be released
and removed.
- Sometimes a PCB component may get in the way of shaft removal, I almost
always find it easier to remove the offending component rather than the
switch body.
- If switch parts are clogged by ancient dried up grease, clean/wash
everything (both plastic and metal parts) with a paintbrush in petroleum
benzine (pharmaceutical grade, in Europe we get it in regular pharmacies;
however most non-polar solvents which are not aggressive to plastic would
do). Do not let the plastic parts sit in benzine for too long, all this can
and should be done in just a few minutes. Let the clean parts dry.
- Using a soft brass brush (I get these at dentist supply shops) gently
scrub the patina off the active side of the metal contacts. Soft brass
brush should not damage the contact plating that needs to be preserved.
- Use cotton ear buds soaked first in petroleum benzine, then IPA to clean
the internals of the switch body. I spend at least two sticks per switch.
- Grease all sliding surfaces of parts sparingly (innards of the switch
body, shaft, contacts, rocker bolt pathway in the shaft) with plastic safe
light grease. The goal of contact greasing is protection from moisture and
oxygen that may re-deposit the patina again in time. Light grease won't
interfere with low current low voltage electrical contact properties.
- Re-assemble and exercise the switch.

HTH,
Best regards,
Nenad








Re: FG 504 function generator odd behaviour

Colin Herbert
 

Yes, Dave. I did indeed check and slightly adjust the +15 V and -15 V rails
some time ago. I also checked the +25 , -25 and +5 V supplies and had a go
at checking ripple using the differential method in the Service Manual, but
I didn't really comprehend the ripple results at the time. I should say that
this didn't cause the odd behaviour, it was already there and I was
attempting to solve it. I suppose I should have another go at looking at the
supplies, power rails and ripple again...
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave
Daniel
Sent: 10 July 2020 18:13
To: TekScopes@groups.io
Subject: Re: [TekScopes] FG 504 function generator odd behaviour

The first thing to do is measure the power rails to make sure that the
voltages are in spec and clean.

DaveD

On Jul 10, 2020, at 13:04, Colin Herbert via groups.io
<colingherbert=blueyonder.co.uk@groups.io> wrote:

I have an FG 504 which is showing some odd behaviour. The triangle-wave
shows asymmetry in that the negative peaks of the wave are rounded-off at
any frequency and the positive ones have a similar but lesser problem at
higher frequencies. This also seems to manifest itself as what looks like
cut-off on the negative peaks of the sine-wave and lesser cut-off on
positive peaks. While the triangle-waves are more-or-less symmetrical, the
sine-waves are definitely not so, showing a nearly three-to-one voltage
ratio in favour of positive peaks. There is also noticeably overshoot on the
square-waves at anything above 1kHz and only a DC offset at frequencies
below 80Hz.
I am totally ignorant of how this function generator produces
triangle-waves, but I do understand that the square-waves and sine-waves are
derived from the triangle-wave. Does anyone have any help that they can
offer? I would be grateful to get this useful function-generator working
properly.
Colin.



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

Stephen
 

On Fri, Jul 10, 2020 at 06:36 AM, Colin Herbert wrote:


I don't suppose you live in London, UK and anywhere near Wimbledon, do you? I
have a P6015A probe that is good for around 20KV. Mind you, I would ask that
you don't fiddle with the compensation adjustments. Incidentally, the P6015A
probe doesn't use the nasty Freon dielectric.
Colin.
Unfortunately no. I’m not very far, but I can’t just stop by either. I’m in Paris/France.
But thanks for the offer. I appreciate it.


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

Colin Herbert
 

I don't suppose you live in London, UK and anywhere near Wimbledon, do you? I have a P6015A probe that is good for around 20KV. Mind you, I would ask that you don't fiddle with the compensation adjustments. Incidentally, the P6015A probe doesn't use the nasty Freon dielectric.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Stephen
Sent: 10 July 2020 12:12
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek 465 Turns on, No Dot, No Trace

On Thu, Jul 9, 2020 at 03:48 PM, Tom Miller wrote:

Second, get the supplies working correctly. I suspect C1552 5000uF and
C1562 3000uF as being low capacity. Confirm by looking at the ripple on
the +5 and -8 test points.
Lots of ripple indeed!! You were right!!
I’m gonna change those 2 and report back.
I never would’ve thought that would have such a drastic impact on the trace.

Is there a way to check and adjust the -2450V HV without a HV probe??

Thanks again.


Re: Cleaning TM500 module pushbutton switches

 

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

--
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on us.
We are not the only experiment. (R. Buckminster Fuller)


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

Stephen
 

On Fri, Jul 10, 2020 at 05:46 AM, Paul Amaranth wrote:


Some notes:

The caps have 4 pins: 3 ground and 1 +. When you replace the cap all 3
ground pads must be connected together.
Yes, I’ve done scopes a few weeks back. A 2215 and a 2235. Same deal, just much much easier to access.

There are little pcb adapters floating around that adapt a modern snap cap
to that footprint. You can buy them on ebay and they make a nice repair.
There are also gerbers floating around and, if you get desperate, you can
etch them yourself.
I’ll just run jumper wires. It works just fine.

Use 105C caps for replacements.
All I found were 85C caps at my local electronics store. They should be fine for now. I’ll replace the rest of them after all is working properly.

Unless you play with HV frequently, I'd go find a HV probe off of ebay.
That may or may not be lethal but you want avoid being in the circuit
path.

Paul
The only time I come across HV is this....

Will report back when it’s completed. Hopefully with a nice trace.


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

Stephen
 

On Fri, Jul 10, 2020 at 05:49 AM, Keith Erickson wrote:

Ok

The HV actual potential is not that critical for operation of the scope, my
opinion.

Keith in Wayzata, MN
On Jul 10, 2020, at 11:46 AM, Paul Amaranth <paul@...> wrote:

Some notes:

The caps have 4 pins: 3 ground and 1 +. When you replace the cap all 3
ground pads must be connected together.

There are little pcb adapters floating around that adapt a modern snap cap
to that footprint. You can buy them on ebay and they make a nice repair.
There are also gerbers floating around and, if you get desperate, you can
etch them yourself.

Use 105C caps for replacements.

Use good desoldering equipment to get the caps out. Overheating the board
will lead to trace separation. Some people cut the ground lugs on top of
the board to make it easier to desolder the pin.

If I have to replace 1 or 2, I generally do all of them. This is a common
failure.

Unless you play with HV frequently, I'd go find a HV probe off of ebay.
That may or may not be lethal but you want avoid being in the circuit
path.

Paul

On Fri, Jul 10, 2020 at 09:34:22AM -0700, Stephen wrote:
In the process of replacing those 2 caps.
They are not easy to take out.
Replacing the 3000uF 35v with a modern 3300uF 63V, and the 5000uF 25V with
a modern 4700uF 63V (or maybe a 6800uF 63V), whichever fits better...





!DSPAM:5f08989e109681011215572!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows



Re: Tektronix 465 No Trace, No Dot

Stephen
 

On Fri, Jul 10, 2020 at 06:15 AM, <toby@...> wrote:


On 2020-07-09 11:32 p.m., Stephen wrote:
Thank you very much for answering.
I didn’t know ripple could have such a drastic effect..
Will do.
I've learned this year that ripple can cause very dramatic effects in
the CRT display including doubling, squiggles, apparently unresponsive
controls... I even made a bad guess at a CRT fault.

Low voltage supply checks and recapping is often the place to start.

--Toby


PS: I ended up making a new thread though.


Yes, apparently. I’m in the process of recapping. Just the 2 faulty one to start. I’ll probably do the 3 remaining ones though.