?

Hello Fabio,

The gold contacts in your pictures look like they are in good shape. Are these pictures before or after your cleaning operation? Do you have access to "WD-40"? I've been using it as a solvent to clean things in some stubborn cases lately. I'm not familiar with your unit but it's likely that there are "plastic" parts near those switches so I would not use the TCE or acetone that you mentioned. Maybe the ethyl alcohol is mild enough to not attack the plastics.

I had an HF amateur radio transceiver some years back. It had poor receiver performance after transmitting, until I "whacked" the radio. There was a relay in the receive path. I took the relay apart and it had a small amount of grease around the relay contacts. To my eye it appeared that the grease had hardened due to aging (out-gassing? if that's the right word). I cleaned off the old, hardened grease and that fixed the problem. I think I used generic contact cleaner and ran a small strip of paper between the contacts to clean off any residue.

Good luck, Jerry, WA0ACF

--- In TekScopes@..., Fabio Eboli wrote:
>
> Hello, recently I bought a 7B85.
> It has most functions working but two problems:
> bad timebase selector and unstable delta time.
> This post is about the first problem:
> the readout was giving wrong ranges in some
> selector ranges, and the timebase was wrong in
> some ranges. Turns out that S800 switches 33
> and 34 were closing mechanically, but no
> electrical contact was estabilished.
> Once removed the selector, the contacts needed
> to be pressed by too much force to make contact,
> but they seemed clean.
> After a little more inspection I found the cause:
>
> more:
>
>
> It can be barely seen that there is some grease where
> the contacts touch. To clean the two "broken" contacts
> I had to desolder them and clean.
> What would be the best way to clean all the contacts
> without desoldering, and possibly without removing
> the board from the frame?
> Unfortunately I dont have access to isopropyl alcohol,
> but I have TCE, acetone and ethyl alcohol.
>
> Thanks,
> Fabio.
>

?

I could use some... how do I get in touch with Mr. McClain?



Thanks

dan

Well not a stellar start. Try this link instead...




%20Brief.pdf



From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of Rob
Sent: Monday, January 07, 2013 8:45 PM
To: TekScopes@...
Subject: [TekScopes] Feedback solicited on repair write-up (Off topic for
Classic scopes forum?) 7844





I decided to go ahead and try my hand at documenting a repair. The document
is contained in a 1Meg PDF at the following link. The subject is a repair of
the A6/7 board/cards in a 7844. The A6/7 boards are associated with the
vertical card slots. If you click the link it will download the PDF to your
machine automatically. (I think/hope)




r%20Brief.pdf_



The repair doesn't apply to all 7000 series card slots as there seem to be a
few different designs along the way depending on mainframe type and serial
number. If any of you have expertise/knowledge/clarity/history as to what
serial numbers have the various kinds of card slots I would gladly include
it in the repair introduction. Other comments are also solicited especially
any that I can add some historical content with, etc.



It is not my intent to take a lot of board bandwidth for the feedback and/or
with this subject. So please feel free to respond off list unless it is
something that would add clarity for the group at large, etc..



Hopefully helpful. If feedback indicates value in stuff like this I have a
couple of other repairs I could write up similarly. Most notably the
decoupling cap replacements on the A-5 board and recapping the power
supplies including unsoldering the transformer and complete tear down.




Finally, I do realize that the 7000 series are not considered true classics
and are therefore off topic by definition. If feedback is that I should not
post this kind of stuff here as a result. Please take my apology on this one
learning experience. It will not be repeated if feedback indicates such.



As always, thanks for the bandwidth.

I hope this finds you well

Rob

P.S. Does anyone know what type of connector (its name.like BNC or ???) the
internal connectors for 7000 series are called. The kind that terminate with
just the wire lead plugging into the little hole in the PCB with the little
side flanges? I heard someone call it a Padilla or something close years ago
but cannot find a reference of anything close so I may have miss
heard/remembered.

The dark speckles from the readout multiplexing are definitely visible
when the oscilloscope is operating correctly. If there was a problem
with the z-axis transient response, then I would expect it to affect
the analog chop mode display also.

There could be something wrong with the readout multiplexing that
makes the speckles worse but I am pretty sure that is controlled by
the processor which makes failure unlikely without other symptoms. The
theory section of the service manual is not specific. I know the
processor controls the readout but not what controls the timing.

On Mon, 7 Jan 2013 15:10:57 -0600, "Chuck Lewis"
wrote:

Your note about the 7000 series multiplexing speckles pretty well settles it
for me. That just makes too much sense not to be a simple "normal" design
artifact. As far as chopped mode, the speckles are still there, marching
along together, but no other z-axis anomalies.

Chuck

From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of David
Sent: Monday, January 07, 2013 2:44 PM
To: TekScopes@...
Subject: Re: [TekScopes] 2232 readout/z-axis coupling (was "finally got my
2232, works, some issues")

That full CCW rotation readout intensity trick works in storage mode
as well to disable the text readout while leaving the storage mode
traces displayed. The Tektronix 7000 series and others also allow
disabling the readout to get rid of the beam multiplexing speckles.

As far as a z-axis intensity problem, does analog chop mode show any
problems?

The 2232 does not have an adjustment for z-axis transient response but
I would measure the waveform at test point TP842 on schematic 9 to see
if that is the problem. Several examples under different operating
conditions are shown in the service manual.

On Mon, 7 Jan 2013 13:40:20 -0600, "Chuck Lewis" clewis@...

wrote:

Mike,



I have a 2232 with the same problem ("black spots in analog mode"). I
noticed that the spots' length and spacing correspond with the analog data
readouts' horizontal length and spacing. It's only noticeable at slow sweep
speeds. The spots will disappear if you turn the readout intensity control
fully CCW, then back to some positive level; the readout disappears, too!
Then repeat the full CCW rotation and both readout and z-axis crosstalk

will

re-appear. That little 'delete readout' function is really cool and is
documented in the manual somewhere. Betcha didn't know it would do that!



It looks to me that the analog readout is leaking into the z-axis circuitry
somehow. I have been meaning to write this up as a question for the group
but hadn't gotten around to it until your message this morning confirmed
that I'm not "the only one"!.



So at least two of us have the readout-coupling-into-the-z-axis in analog
mode issue. It's not been a real problem for me, but it would be nice to
know where to begin looking next time I have the scope apart.



Mike and I would love to have the benefit of the assembled knowledge and
experience in this group.anyone - anyone?





Chuck Lewis



From: TekScopes@...

[mailto:TekScopes@... ] On
Behalf

Of mikehostalek
Sent: Sunday, January 06, 2013 9:55 PM
To: TekScopes@...
Subject: [TekScopes] finally got my 2232, works, some issues





_____i just got back in town a few days ago and picked up my tek 2232 from
the post office. it works okay with a few issues,
_____the first problem i notice is that when looking at lower frequencies,
it doesnt show the whole wave at once, for example, a 60hz sine will show
one cycle fine, showing 3 cycles you can see it flicker and looking at 6
cycles it shows about half of it at a time, going left to right a few times
each second, if i try to show more cycles, the amount of the wave shown on
the screen is less and it takes longer to cross the screen.
_____The other issue i noticed is that when showing a wave, it is steady

but

you see very little black spots in it kind of riding along the wave left to
right which take a few seconds to cross the screen. this doesnt happen in
storage mode only in analog mode.
_____As far as storage mode, as faras i can tell everything seems to work

as

it should, also i was able to connect to my computer via a rs-232c cable to
a serial port using wavestar (and docuwave) software to display waves, etc.
cool bonus i didnt know about when i picked that scope out. A tip for

anyone

using wavestar for 22xx scopes, while ive seen in instructions to set the
first 4 switches to 0110 for 2400bps, it is infact 0101 that equals

2400bps.

I played with settings for a couple hours trying to get it to work before i
figured that out. it may work at much higher speeds but i know these

setting

work.

?

?

I just received a 2465 and it seems to be in cal based on some quick spot checks, but the trace is a bit fuzzy. The best focus setting for the trace and text are not the same and the difference becomes worse as the brightness is increased.

I must have something wrong because I don't see how the 485-1 can work with a high voltage sine wave coming out of the rectifiers.
I would appreciate some help interpreting this.

?

Check the adjustments section, CRT section for the proper setup. You will need a RF sig gen to get the full screen adjustments done.

?

As always, the first step is check the power supplies for level and ripple.

?

The CRT adjustments all interact to some degree and it takes some back and forth to get the optimum display.

?

?

----- Original Message -----

From: Scott Harris

To: TekScopes@...

Sent: Monday, January 07, 2013 4:38 PM

Subject: [TekScopes] Fuzzy trace 2465

?

I just received a 2465 and it seems to be in cal based on some quick spot checks, but the trace is a bit fuzzy. The best focus setting for the trace and text are not the same and the difference becomes worse as the brightness is increased.

Do those symptoms ring a bell? Ideas?

I just got the scope in the mail today. I'll dig into it soon.

Thanks,
-Scott

Hello, recently I bought a 7B85.
It has most functions working but two problems:
bad timebase selector and unstable delta time.
This post is about the first problem:
the readout was giving wrong ranges in some
selector ranges, and the timebase was wrong in
some ranges. Turns out that S800 switches 33
and 34 were closing mechanically, but no
electrical contact was estabilished.
Once removed the selector, the contacts needed
to be pressed by too much force to make contact,
but they seemed clean.
After a little more inspection I found the cause:

more:


It can be barely seen that there is some grease where
the contacts touch. To clean the two "broken" contacts
I had to desolder them and clean.
What would be the best way to clean all the contacts
without desoldering, and possibly without removing
the board from the frame?
Unfortunately I dont have access to isopropyl alcohol,
but I have TCE, acetone and ethyl alcohol.

Thanks,
Fabio.

Found my measurement problem on the three HV diodes. The probe I was using was too large in diameter to fit between the slots on the ceramic mounts. More careful probing yielded better results. The diodes look OK from a simple ohm check.

My next test will be comparing a working 485-1 to the problem 485. (just acquired the 485-1 over the holidays) From the other message, it looks like the scope version difference won't affect the HV investigation.

So far a basic Ohm comparison hasn't yielded anything obvious. Will try HV voltage and signal checks next.

Bob