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I would assume you do this outside ? My insurance provider would frown on
doing something like this within 50 feet of the house or garage. I'm almost
tempted to try it and cause a spark and see what happens :-)

A hot air gun and naphtha (lighter fluid) are my first choices.
Lighter fluid and hardware store naphtha may have contaminates so
purer options are heptane or Bestine Solvent and Thinner which is used
for rubber cement and commonly available. Plastic safe contact
cleaner for switches is another source.

I had problems with hot water causing the Tektronix paint to peel in
some cases.

Ha! Amazon's page for Bestine even says:

"EASILY REMOVE LABELS – Using this solvent, you will be able to
effortlessly remove stickers, labels and decals without leaving behind
and messy residue."



On Tue, 12 Jun 2018 00:14:35 -0400, you wrote:

Naptha, or lighter fluid does a good job, and is
mild on paints and plastics.

Hot air will often allow you to peel off a sticker
more or less intact, but will usually leave the
stickum behind... which you will still have to
remove with something like lighter fluid.

-Chuck Harris

Dennis Tillman W7PF wrote:

A far too common problem I have no solution for yet:

What will remove sticker residue on Tek blue paint without harming the

paint

finish?

...

Would boiling water soften the sticker residue and leave the paint

alone or

would it siften the paint as well.

Suggestions are welcome.

Naptha, or lighter fluid does a good job, and is
mild on paints and plastics.

Hot air will often allow you to peel off a sticker
more or less intact, but will usually leave the
stickum behind... which you will still have to
remove with something like lighter fluid.

-Chuck Harris

Dennis Tillman W7PF wrote:

A far too common problem I have no solution for yet:

What will remove sticker residue on Tek blue paint without harming the paint
finish?

...

Would boiling water soften the sticker residue and leave the paint alone or
would it siften the paint as well.

Suggestions are welcome.

Hello Ian, in response to your message further down...

I've got busy in the past couple of days which prevented me from answering
you.

First of all, please don't expect too much... because I think that, in the
end, it had a 50% of plain luck...

On this 7623A, .as I got rid of the gross issues that it had, and could focus
on doing a careful HF step response, I noticed that no matter what I would do,
be it on the Vert. Output Amplifier, or on the Vertical Plugin, I couldn't get
a clean step response in the whereabouts of 3.5ns.
If I would push too much on the HF compensation adjustments, I would
eventually get 4.5ns at best, but with a lot of ringing on the step corner.
If I would adjust it to tame the ringing, the step response would worsen even
more to - say - 5.5 to 6ns (this is a 60MHz scope, not a 100).
But what was puzzling me was that the step was not really like a slow
transition, but it was really fast up to about 2/3rds of the amplitude, and
then it would turn into a really rounded shoulder... So, I thought there were
2 superimposed time constants at play and that maybe, only maybe, I would be
able to spot which stage was not keeping up, by probing the vert amplifier at
different nodes.
It crossed my mind, for instance, that local power supply decoupling could be
lacking at some spot and that the slower last third could be due to a
decoupling having depleted its stored charge during the first part of a hi
speed transition and then, the stage would be running on "lean" mixture and
dragging.
So I started looking at places where there should be a more or less steady
voltage value, either the power to each stage, or the biasing networks.
So I went on to probe the +15V (dcpl) that feeds the Q2405 and Q2505 (this is
the NPN pair that precedes the PNP 151-0271-00 tranny I found guilty) and also
the bias to the bases of the very stage where the 151-0271 trannies were. This
is a common base stage, that has about +8V bias, coming from the Thermal
balance adjustment voltage divider, and decoupled by a 1nF capacitor.
While probing the bases of the transistors looking for the base pin (I didn't
know it by heart), I eventually probed both emitters (of the two PNP
transistors) and noticed they were markedly different... much different than I
would expect from two complementary sides that were being driven with a nearly
symmetrical square wave, swinging in AC around the center point...
The signal at the base of one of the transistors had something like x mVpp,
while at the other emitter, if was like 4x.
Well, the bases are not tied together, but from the bias voltage, through 100R
resistors into each base, so I thought that the markedly different signals
would also be different from one base to another... but not... The bases had
pretty much the same signal (almost no signal in fact, since it's a decoupled
bias)... only the emitters were remarkably different.
So, I thought... well, either this is caused by the transistor themselves, or
it's the signal coming into them...
So I swapped the transistors, and the signal at the emitters swapped along...
So I knew the transistors were the cause for the difference... leaving only to
discover if they were just too different (un-matched) or if one of them was
faulty.
So I ran them through my AVR transistor tester, which is far from being a
curve tracer, but would be able to tell me of any gross differences they might
have...
While one of the transistors tested like a normal PNP transistor, with about
40 of gain (hfe), the other, despite showing an increased hfe of about 70
(almost double), tested like if it had an anti-parallel diode connected across
the emitter-collector, and this anti-parallel diode with a Vf of 3.5V... the
whole thing being completely unusual for a regular silicon transistor (not
being a mosfet, a darlington, or a power device).
Testing them with my DMM in diode test mode showed no differences between
them.
So, despite they test equal on the DMM, I concluded that transistor could only
be faulty.
To confirm my theory, I needed a pair of small signal transistors that were -
at least - reasonably fast and I was lucky enough to find a couple of BFQ241
in my parts bin, which are high voltage, 1GHz TO-92 transistors used as video
amplifiers of CRT computer monitors.
In the moment that I shuffled them in, not only the signals at the emitters
became similar (as they should), but I immediately got a strong overshoot on
the square wave...denoting that the HF response of that stage started
contributing a great deal to the overall response.
After readjusting the HF compensation trimmers, I managed to get a risetime
about 2ns faster than it was, with a nice top almost free of ringing or
aberrations.
At this point, it's almost at the performance we would expect from a 100MHz
amplifier but, I decided to bring the subject to the group, and see what could
come out.
A fellow member of the group contacted me off-list to tell he has one original
151-0271-00 in spare and was so kind of offering it to me... so I`m now
awaiting for it to arrive, which will still take a while, as I`m in Brazil.

Hope this illustrates well how I got there...

Rgrds,

Fabio

Greetings to all.
I have recently purchased a non-working Tektronix 2465 (not A or B). Having carefully recapped the power supply which was blowing fuses due to leaky mains input filter capacitors I am left with an unusual fault.

The scope displays a good sine wave on all inputs. But superimposed on the perfect sine wave is a rippling wave that travels from right to left in quick succession. Perhaps 6 waves per second. It does not distort the sine wave in any way but travels along the wave on both the top and bottom edge of the trace. The wave is much lower in intensity than the sine wave displayed but is very noticeable.
Perhaps a common issue so please excuse me as I am new to this group.

Many thanks and best wishes to all.

John

On Jun 12, 2018, at 9:58 AM, Chuck Harris <cfharris@...> wrote:

Over the years, I have had a wide variety of
equipment with vinyl coated aluminum panels.

I used to cuss quite a bit when I got something
that was gorgeously pretty, but was sticky like
you were touching the sticky side of a piece of
tape. Virtually nothing would clean off the
sticky, and if you did, it would come back in a
little while... I wondered what had happened to
the vinyl.

Then I found it happening to equipment that I had
brought in my lab that was good, but dirty, then
cleaned with formula 409... my go to cleaner.

I read the ingredient list and saw the butyl
cellosolve... and stuck it away in my memory
somewhere.

Years passed, and more and more of my equipment
was getting sticky, when I bought a new truck.

The owner's manual had a warning about using window
cleaners containing butyl cellosolve, on the
instrument panel's windows. They said that it
would soften the plastic over time and make it fog.

A lightbulb went on, and I did some research on
butyl cellosolve, and found it was a super solvent
capable of soaking into almost all grease, dirt,
pitch, tar, and plastics. It cleaned by getting
inside of the dirt, expanding, and breaking it
apart so that it could be removed with a little
scrubbing... With plastics, it was to displace the
incredibly sticky stuff called plasticizer that is
used to make ridged PVC into flexible PVC... which
is what the stuff on the panels was.

A lot of pressure sensitive adhesives are very
similar chemically to plasticizer. And a lot of
the permanently affixed ID tags use a killer solvent
to bond them to plastic, vinyl, and painted panels.

-Chuck Harris

Kevin Oconnor wrote:

from Chuck:
"Goo gone is not aqueous. It is more like terpene,
made from the citrus, with mineral oil added to
prevent re-adhesion of the stickum."

Yes, oils seem to passivate the glue surface adhesion bond mechanism. Same as pouring Canola oil on a snake stuck in a glue trap. Slowly the glue is rendered ineffective and the snake squirms away none the worse for the experience! Not sure the atomic mechanism going on though.

I have seen some stickers on vinyl covered aluminum that seem to have modified the underlying vinyl by flattening out the orange peal surface. You can remove all trace of the adhesive, but you can do little regarding the latent outline of the sticker. The adhesive, when first applied, must react with the vinyl in some way. Any one else encounter this?

This butyl cellosolve sounds like it can wreck more stuff than it fixes. I wanted proof that my beloved 409 should now be considered a member of the problem set and went searching. I found this NIH site that lists stuff with particular ingredients,



And it looks like it was “old” 409 that had it. But of note is that there are other things suggested in this thread that do still contain it that might be a risk. Simple Green (of several flavors) as one example.

Be careful out there...

Chris
--
Chris Elmquist N0JCF

On Jun 12, 2018, at 9:58 AM, Chuck Harris <cfharris@...> wrote:

Over the years, I have had a wide variety of
equipment with vinyl coated aluminum panels.

I used to cuss quite a bit when I got something
that was gorgeously pretty, but was sticky like
you were touching the sticky side of a piece of
tape. Virtually nothing would clean off the
sticky, and if you did, it would come back in a
little while... I wondered what had happened to
the vinyl.

Then I found it happening to equipment that I had
brought in my lab that was good, but dirty, then
cleaned with formula 409... my go to cleaner.

I read the ingredient list and saw the butyl
cellosolve... and stuck it away in my memory
somewhere.

Years passed, and more and more of my equipment
was getting sticky, when I bought a new truck.

The owner's manual had a warning about using window
cleaners containing butyl cellosolve, on the
instrument panel's windows. They said that it
would soften the plastic over time and make it fog.

A lightbulb went on, and I did some research on
butyl cellosolve, and found it was a super solvent
capable of soaking into almost all grease, dirt,
pitch, tar, and plastics. It cleaned by getting
inside of the dirt, expanding, and breaking it
apart so that it could be removed with a little
scrubbing... With plastics, it was to displace the
incredibly sticky stuff called plasticizer that is
used to make ridged PVC into flexible PVC... which
is what the stuff on the panels was.

A lot of pressure sensitive adhesives are very
similar chemically to plasticizer. And a lot of
the permanently affixed ID tags use a killer solvent
to bond them to plastic, vinyl, and painted panels.

-Chuck Harris

Kevin Oconnor wrote:

from Chuck:
"Goo gone is not aqueous. It is more like terpene,
made from the citrus, with mineral oil added to
prevent re-adhesion of the stickum."

Yes, oils seem to passivate the glue surface adhesion bond mechanism. Same as pouring Canola oil on a snake stuck in a glue trap. Slowly the glue is rendered ineffective and the snake squirms away none the worse for the experience! Not sure the atomic mechanism going on though.

I have seen some stickers on vinyl covered aluminum that seem to have modified the underlying vinyl by flattening out the orange peal surface. You can remove all trace of the adhesive, but you can do little regarding the latent outline of the sticker. The adhesive, when first applied, must react with the vinyl in some way. Any one else encounter this?