Date   

Re: SMA caps for sampling heads

 

Hi Reginald,

How did you find out the operating hours and power up figures? I have an 11403A and there is nothing in the Utility Menus that would give me that kind of information.

Just a wild guess but given your figures the 11801 was running an average of 22 hours each time it was powered up. Could it have been in some kind of installation where they used the scope on a daily basis, but always shut it off at the end of the day?

To make another even wilder guess, if it was used all day long and into the night before being turned off each time then it would make sense to assume it was used for 22 hours per day on average for 2,000 days average. That comes out to about 500 days that it was used. That would equate to about 2 years that it was in use like this.

This is nothing more than wild speculation on my part. I must be momentarily bored. More likely I am avoiding something unpleasant I have to do.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Reginald Beardsley via Groups.Io
Sent: Saturday, April 20, 2019 5:39 AM
Subject: Re: [TekScopes] SMA caps for sampling heads

A termination would present the same issue of wear. I'm not going to
be monitoring a data link 24x7, so I'll be connecting and disconnecting
more often. My 11801 had 44,000 operating hours but was only powered
up 2000 times.



--
Dennis Tillman W7PF
TekScopes Moderator


Re: Searching for a Tek 7000 series scope

Sean Turner
 

Harvey,

Thanks for your thoughts. Right now I definitely don't have the floor space for a scope cart, but I'm planning a move in the near future and am looking at houses. One criteria is enough floor space for a couple of benches and rolling carts (already have a small rolling metal cart I got at the container store which I keep my small tools on, such as screwdrivers, pliers, flux bottle, etc on.

Sean

On Sat, Apr 20, 2019 at 02:05 PM, Harvey White wrote:


Point is, they had a lot of floor space.

Your lab may not.

Mine doesn't, so my scope cart is sitting elsewhere waiting for a
larger lab.... (one day).


Re: 7S12 with S-4 and S-53 troubleshooting

Albert Otten
 

Hi Nenad,

I agree that the avalanche pulse alone is probably so slow that the clipping lines simply act as a shortcut.
But how to explain the response to the Offset control? When you change Offset then this change is balanced by an opposite change in Memory voltage in order the maintain the same voltage at feedback pins 2 & B of the S-4 connector. When the S-4 does nothing then that feedback voltage would change freely and Memory would not change at all. What is wrong in this reasoning?

Albert

On Sat, Apr 20, 2019 at 11:12 PM, Nenad Filipovic wrote:


Hi Albert,

In my case (without the snap-off signal) the head sensitivity to input
signal was zero. The explanation is in the structure of the strip line to
which C52 and C54 are attached. This structure has (intentionally) a very
low inductance, making it a very high frequency tuned circuit with respect
to its own capacitance (these parameters guarantee the specified high rise
time of the gate strobe signal, which is the key parameter of S-4 design).
Slow dv/dt signal off Q69 could never produce a large enough voltage on it
to forward bias the gate diodes. However given the ratio of C52/C63 and
C54/C64 dividers, Q69 can reverse bias the snap-off diode D61. Reverse
recovery process of D61 yields the high dv/dt (high harmonic content)
snap-off pulse, to which the strip line resonator will now happily react.
R50 fine tunes the Q factor of this circuit (its transient response).
Therefore without the fast snap-off pulses, input gate diodes will never
conduct.

What kept being confusing during my troubleshooting was the presence of
sampling pulses in the signal path (all the way to vertical output). At
first I could not tell whether these were coming from the input gate (which
would imply a working snap-off), or somewhere else. Later I determined that
these are present in the complete memory-vertical amp-feedback loop,
leaving no guarantee that the gate is sampling at all. Being sure that gate
is functional (my previous tests) I focused on the snap-off, and that's how
I found the issue. I was very lucky, I have no extension cables for S-4,
and snap-off board is completely inaccessible when S-4 is inserted in 7S12.

Best Regards, Nenad

On Sat, Apr 20, 2019 at 10:07 PM Albert Otten <aodiversen@concepts.nl>
wrote:

Hi Nenad, I overlooked your second last message in which you answered my
question about DC response and more. I have to admit that I fail to
understand what is exactly going on when R62 is interrupted.
Is there someone else with an explanation?

Albert


Re: Searching for a Tek 7000 series scope

 

Hi Sean,
Where are you located?
Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
sdturne@q.com
Sent: Saturday, April 20, 2019 1:12 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Searching for a Tek 7000 series scope

I wanted to thank everyone for their replies, direct emails, and
advice. After consideration of many kind offers, I ended up purchasing
a 7904A + plugins from John Griessen. It arrived yesterday! Absolutely
thrilled with it.

https://groups.io/g/TekScopes/album?id=89735

I think the next thing I need to find is a scope mobile cart for it to
free up bench space. :o)

Sean



--
Dennis Tillman W7PF
TekScopes Moderator


Re: 7S12 with S-4 and S-53 troubleshooting

Nenad Filipovic
 

Hi Albert,

In my case (without the snap-off signal) the head sensitivity to input
signal was zero. The explanation is in the structure of the strip line to
which C52 and C54 are attached. This structure has (intentionally) a very
low inductance, making it a very high frequency tuned circuit with respect
to its own capacitance (these parameters guarantee the specified high rise
time of the gate strobe signal, which is the key parameter of S-4 design).
Slow dv/dt signal off Q69 could never produce a large enough voltage on it
to forward bias the gate diodes. However given the ratio of C52/C63 and
C54/C64 dividers, Q69 can reverse bias the snap-off diode D61. Reverse
recovery process of D61 yields the high dv/dt (high harmonic content)
snap-off pulse, to which the strip line resonator will now happily react.
R50 fine tunes the Q factor of this circuit (its transient response).
Therefore without the fast snap-off pulses, input gate diodes will never
conduct.

What kept being confusing during my troubleshooting was the presence of
sampling pulses in the signal path (all the way to vertical output). At
first I could not tell whether these were coming from the input gate (which
would imply a working snap-off), or somewhere else. Later I determined that
these are present in the complete memory-vertical amp-feedback loop,
leaving no guarantee that the gate is sampling at all. Being sure that gate
is functional (my previous tests) I focused on the snap-off, and that's how
I found the issue. I was very lucky, I have no extension cables for S-4,
and snap-off board is completely inaccessible when S-4 is inserted in 7S12.

Best Regards, Nenad

On Sat, Apr 20, 2019 at 10:07 PM Albert Otten <aodiversen@concepts.nl>
wrote:

Hi Nenad, I overlooked your second last message in which you answered my
question about DC response and more. I have to admit that I fail to
understand what is exactly going on when R62 is interrupted.
Is there someone else with an explanation?

Albert


Re: Searching for a Tek 7000 series scope

Harvey White
 

On Sat, 20 Apr 2019 13:12:15 -0700, you wrote:

I wanted to thank everyone for their replies, direct emails, and advice. After consideration of many kind offers, I ended up purchasing a 7904A + plugins from John Griessen. It arrived yesterday! Absolutely thrilled with it.

https://groups.io/g/TekScopes/album?id=89735

I think the next thing I need to find is a scope mobile cart for it to free up bench space. :o)
I have a scope mobile cart that will hold a 7000 series scope (no, not
for sale).

Some observations: The scopemobile was designed to be a roll around
home for a scope in a lab/facility that had a lot of bench space. The
typical electronics bench of the time was a workbench maybe 35 to 40
inches deep, relatively high off the floor (people used stools), with
a single shelf about 2-3 feet above the workbench.

You'd put instruments, etc., on that shelf. However, given the depth
of the average 7000 series scope (and that there'd not likely be one
for each technician, either), the scope would not sit on the bench.
Hence, the scope cart with plugins, TM500/TM5000 stuff, etc.

Point is, they had a lot of floor space.

Your lab may not.

Mine doesn't, so my scope cart is sitting elsewhere waiting for a
larger lab.... (one day).

Now, as far as my arrangements go, and you may want to consider this,
I use the roll around wire shelves, 4 feet wide, 2 feet deep, 6 feet
or so high, with six shelves (not all necessarily used). You *really*
want the kind that does not have that little helpful basket shape, you
want the kind where things could roll off, with the flanges down.
(BJ's wholesale seems to sell on the turned up type, good for boxes
and bins, not so hot for test equipment.

I took a power strip and bolted it to the back of one of the shelves.
I took a closet flourescent lamp and bolted it to the back of the top
shelf. Saves needing a flashlight.

I then went to the local Home Despot and bought a sheet of 4x8 1/8th
inch masonite (brown particle board to others, but without the holes).
I had them cut it into sheets that exactly fit the top of the shelves,
closing off the wire holes. Now everything with feet doesn't catch on
the shelves.

One of those shelves is an inch or so off the main workbench surface,
and behind it. The 7000 series scope rests on the back of the shelf
and with the bail down, is at a slight angle when resting on the
workbench.

This works for me. Striplights on the shelves for background lighting
on the bench, outlet strips below the bench, and so on.

You may not use that scope cart as much as you might think, depending
on your lab layout.


Harvey



Sean



Re: Searching for a Tek 7000 series scope

Sean Turner
 

I wanted to thank everyone for their replies, direct emails, and advice. After consideration of many kind offers, I ended up purchasing a 7904A + plugins from John Griessen. It arrived yesterday! Absolutely thrilled with it.

https://groups.io/g/TekScopes/album?id=89735

I think the next thing I need to find is a scope mobile cart for it to free up bench space. :o)

Sean


Re: 7S12 with S-4 and S-53 troubleshooting

Albert Otten
 

Hi Nenad, I overlooked your second last message in which you answered my question about DC response and more. I have to admit that I fail to understand what is exactly going on when R62 is interrupted.
Is there someone else with an explanation?

Albert


Re: 7S12 with S-4 and S-53 troubleshooting

Albert Otten
 

On Sat, Apr 20, 2019 at 04:45 PM, Nenad Filipovic wrote:


Heh, I just fixed it, it's working now. While probing all components inside
S-4, I found that the bottom lead of R62 was cold soldered (the one
soldered to the gold plated PCB strip), it snapped off at some point and
was floating. I noticed it only after touching it with probe tip and seeing
it move, otherwise it was undetectable. After fixing this soldering
everything came to life.

Regardless of this S-4 issue, the dreaded TI IC sockets are a nightmare.
Even though all IC leads are clean and shiny in my 7S12, the sockets act
out. The previously posted "Morse code" trace was the result of that, with
proper contact the trace is pretty much continuous. Will need to replace
them all.

@Albert: Thank you for your help. Hope I get some more heads for this setup
to make it a bit more useful.

Best Regards, Nenad
Whaw Nenad, what a good luck that you discovered the fault in S-4/R62! Congratulations.
I tried to understand what happens when R62 is interrupted. The snap-off diode receives no bias current but the avalanche transistor Q69 will still function and send a kind of strobe pulse to D2F (and not to D2A, so totally unbalanced). The bridge might more or less response but with extremely bad efficiency. If so, it is similar to extremely heavy smoothing because of which your sine wave reduces to an average value. But also response to sudden Offset changes would be very slow. Do you remember if that was the case? You didn't try DC input is it?
My "theory" might be wrong in that the avalanche pulse is far too slow to proceed further then the clipping line. But then I still don't understand how Offset could function.

Albert


Re: 7L5 knob removal

Ed Breya
 

It's alive - sort of. I had to perform quite a bit of surgery on the guts. I found that the mounting posts on the big board that attaches to the right side RF module had broken loose from the board, and a board edge connector socket on it that joins the back interface cluster board, was split down the middle. The posts were easy to tap through and put screws in from underneath, then I straightened out and realigned all those %^^*% long inter-board square pins.

I didn't have the right kind of board edge connector in stock to replace the busted one, and I was concerned about removing all those socket pins from this multi-layer board, so I opted to put a steel band around the socket housing, which drew everything back in pretty well.

The front casting did have some cracks in the skimpy areas, and I couldn't flatten it out quite right without risking major fractures, so it still has a bit of concavity. The front plate did flatten out OK, so it looks good assembled, even though the casting behind it dips inward. I put it all back together sufficiently to plug into a mainframe, but it's still a little (and too much) out of square, so will need more mechanical tweaking.

I plugged it in and fired it up, and it immediately crashed the mainframe. I figured a bad Ta cap somewhere deep inside was the problem. However, forcing the right side of the plug-in in deeper made it come to life. So far it has most of the readouts and knob functions indicating, and a baseline, but apparently no video signal. The sweep time/div readout is stuck at "500 kHz" regardless of the knob position, although there's evidence that the actual setting is doing something inside. I'm next going to loosen up the back end rail mounting screws so there will be a little more play side to side, and hope that getting deeper engagement on the right will fix the remaining problems. If not, it could be that I missed or connected something wrongly on assembly, or knocked something loose, or it already had a fault, etc. I'm happy that at least it lights up though.

Ed


Re: 7S12 with S-4 and S-53 troubleshooting

Nenad Filipovic
 

Heh, I just fixed it, it's working now. While probing all components inside
S-4, I found that the bottom lead of R62 was cold soldered (the one
soldered to the gold plated PCB strip), it snapped off at some point and
was floating. I noticed it only after touching it with probe tip and seeing
it move, otherwise it was undetectable. After fixing this soldering
everything came to life.

Regardless of this S-4 issue, the dreaded TI IC sockets are a nightmare.
Even though all IC leads are clean and shiny in my 7S12, the sockets act
out. The previously posted "Morse code" trace was the result of that, with
proper contact the trace is pretty much continuous. Will need to replace
them all.

@Albert: Thank you for your help. Hope I get some more heads for this setup
to make it a bit more useful.

Best Regards, Nenad


Re: SMA caps for sampling heads

Reginald Beardsley
 

A termination would present the same issue of wear. I'm not going to be monitoring a data link 24x7, so I'll be connecting and disconnecting more often. My 11801 had 44,000 operating hours but was only powered up 2000 times.


Re: Typical 1502B faults?

Reginald Beardsley
 

Thanks for the responses. I think I'll skip that project. It's not something I need.

I'm getting a custom 1 MHz version of Leo Bodnar's <40 ps rise time square wave generator for TDR work with a DSO. I'll stick to that.

Have Fun!
Reg


Re: Absurdly simple way to get contact cleaner into some Tek pots

n4buq
 

If possible, position things so that the tip of the drill points up. Stray shavings will fall away from instead into the hole.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Chuck Harris" <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Friday, April 19, 2019 9:39:39 PM
Subject: Re: [TekScopes] Absurdly simple way to get contact cleaner into some Tek pots

The easiest way is not to let them get in in the first
place.

What I do, though I don't do this very often, preferring
to disassemble pots where I can, is to first slide a piece
of brass tubing over the bit, to limit how far it can reach
into the pot, and second, put a dab of grease on the point I
am going to drill. The grease holds the shavings.

Twist drill bits, by their design pull the shavings out of
the cut. Where they get into the "hole" is when the drill
bit passes through the object being drilled. The grease,
and the tubing limit, prevents most of the problem.

-Chuck Harris

Dennis Tillman W7PF wrote:
Hi Richard,

And how do you get the drill shavings out of the pot?

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Richard Solomon
Sent: Tuesday, April 16, 2019 10:52 AM
Subject: Re: [TekScopes] Absurdly simple way to get contact cleaner
into some Tek pots

My foolproof method is to drill
a small hole on the top side at
the rear. Pump in De-Oxit Fader
Lube and seal the hole with some
black tape.

73, Dick, W1KSZ



Re: Typical 1502B faults?

Harvey White
 

On Fri, 19 Apr 2019 16:48:01 -0700, you wrote:

Unknown, but I suspect (don’t really know) that the tunnel diodes are broke. Most of the earlier 1502’s that we sent to customers on rent came back with blown diodes
Do the 1502 (A/B) even have the tunnel diodes?

I know that the 1503 has an avalance transistor pulse generator, which
does not have the same sensitivity to static damage as the tunnel
diode (which is pretty much connected across the entire input channel
directly). IIRC, the 1503 is capacitively coupled, too.

Harvey



Regards,

Stephen Hanselman
Datagate Systems, LLC
3107 North Deer Run Road #24
Carson City, Nevada, 89701
(775) 882-5117 office
(775) 720-6020 mobile
s.hanselman@datagatesystems.com
www.datagatesystems.com
a Service Disabled, Veteran Owned Small Business
DISCLAIMER:
This e-mail and any attachments are intended only for use by the addressee(s) named herein and may contain legally privileged and/or proprietary information. If you are not the intended recipient, any dissemination, distribution or copying of this e-mail and any attachments is strictly prohibited. If you have received this e-mail in error, please immediately notify me and permanently delete the original and all copies and printouts of this e-mail and any attachments.
On Apr 19, 2019, at 16:39, Reginald Beardsley via Groups.Io <pulaskite=yahoo.com@groups.io> wrote:

There are a slew of them on eBay for pretty nominal prices as parts units. How hard are they to repair?




Re: Absurdly simple way to get contact cleaner into some Tek pots

Chuck Harris <cfharris@...>
 

The easiest way is not to let them get in in the first
place.

What I do, though I don't do this very often, preferring
to disassemble pots where I can, is to first slide a piece
of brass tubing over the bit, to limit how far it can reach
into the pot, and second, put a dab of grease on the point I
am going to drill. The grease holds the shavings.

Twist drill bits, by their design pull the shavings out of
the cut. Where they get into the "hole" is when the drill
bit passes through the object being drilled. The grease,
and the tubing limit, prevents most of the problem.

-Chuck Harris

Dennis Tillman W7PF wrote:

Hi Richard,

And how do you get the drill shavings out of the pot?

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Richard Solomon
Sent: Tuesday, April 16, 2019 10:52 AM
Subject: Re: [TekScopes] Absurdly simple way to get contact cleaner
into some Tek pots

My foolproof method is to drill
a small hole on the top side at
the rear. Pump in De-Oxit Fader
Lube and seal the hole with some
black tape.

73, Dick, W1KSZ


Re: Absurdly simple way to get contact cleaner into some Tek pots

 

Hi Richard,

And how do you get the drill shavings out of the pot?

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Richard Solomon
Sent: Tuesday, April 16, 2019 10:52 AM
Subject: Re: [TekScopes] Absurdly simple way to get contact cleaner
into some Tek pots

My foolproof method is to drill
a small hole on the top side at
the rear. Pump in De-Oxit Fader
Lube and seal the hole with some
black tape.

73, Dick, W1KSZ

On Tue, Apr 16, 2019 at 10:45 AM Terry Gray via Groups.Io <tlgray42=
yahoo.com@groups.io> wrote:

I also have restored 100's of "sealed"? noisy controls by
pointing
the control shaft straight up vertically, wrapping something around
the bottom of the control to catch the excess contact CLEANER/LUBE,
spray around the base of the shaft where it goes into the control,
and
"pump" the shaft up and down and give it time to "pump" the contact
cleaner/lube down into the control---remember patience is a virtue.
If at first it doesn't seem to be getting the spray down the shaft,
make a dam" just below the point where the shaft enters into the
control and try spraying a little additional cleaner/lube into that
area keeping it saturated and at the same time periodically "pumping'
the shaft up and down to allow the cleaner/lube to migrate along with
capillary action down the shaft. Allow the potentiometer shaft to
remain pointed up vertically. Sometimes it can take overnight or
longer to get the cleaner/lube down into the control but I have found
over the last 50-60 years that it very, very rarely fails. Just be
patient and I think this will work for you, even for the difficult
ones. I remember setting upright on their backs some of the big
monster stereos and doing just that, especially when the
potentiometer access was not readily accessible even with the long
extended flexible tubing that sometimes came
with the contact cleaner/lube or that were also available at the
time. I
also remember running into some well sealed potentiometers and TV
tuners that we had to drill a small access hole into/through the
metal
or plastic housing to get the cleaner/lube inside to do its job. Just
be very careful to not drill into the tuner or control doing any
internal damage. I remember disassembling throw-away pots and tuners
to learn where to drill the holes to prevent any internal damage and
you could then seal the hole
up with solder or glue when you completed the cleaning/lube process.
One
additional point, DO NOT use a contact cleaner with no lubricating
agent in its ingredients. Many years ago I attended a Channel Master
seminar on their contact cleaners and tuner (and switch)
cleaner/lubes. The company representative showed us under a fairly
high-powered microscope a video of what happens when you spray a
contact cleaner (with no lube) on the old TV tuner switch contacts
You completely wash away all lubrication from the individual contact
points and he showed us under the microscope what happens when you
rotate the switch thru the washed contacts. It scrapes the plating
off
the contacts and now being unplated in that area it is oxidizes and
you end up with intermittent high resistance contacts down the
line(with time) that play havoc with your circuit. You think that you
are "fixing" the intermittent switch contact(s) (or the intermittent
internal potentiometer wiper problem) but in reality you are totally
ruining (for the future) whatever you are so-called restoring by using
a non-lubricated
spray. I wish the video that the Channel Master rep showed us was
still
available>>>>it looked like a chisel scraping the plating off the
available>>>>contact
under the high-magnification microscope when all the lubrication had
been previously "cleaned" off the contact areas. He said DO NOT EVER
use a contact cleaner that has no lubrication in it or at least
follow
up the "cleaning" process by spraying or adding some additional
lubrication to the
contact points. Hope this is helpful information to some of you, it
sure
was for me.
On Tuesday, April 16, 2019, 9:51:07 AM CDT, Bob Koller via
Groups.Io <testtech=yahoo.com@groups.io> wrote:

Try it sometime, I have literally done hundreds this way. Some last
week..



--
Dennis Tillman W7PF
TekScopes Moderator


Re: Typical 1502B faults?

Harvey White
 

On Fri, 19 Apr 2019 17:04:26 -0700, you wrote:

The LCD display on these are miserable.. An early electroluminescent backlight with a heater for cold environments, difficult to read in almost any condition. If the display is bad, ie, looks like it has a dark spot, it's gone. There were a few "improved" versions of the display assembly.
The input sampler on this model is a hybrid, not repairable, and impossible to find.
The chart recorder has a roller that turns to molasses, making a huge sticky mess.
The interesting counterpoint is that the weak point in the 1502 is the
unobtanium tunnel diode. I did have one with a bad CRT and a bad HV
power supply (and a bad horizontal amplifier). Finding one that had a
bad tunnel diode (as well as other nasty things) gave me enough spare
parts that I could construct one that worked.

Harvey



When working they are fine, save the lousy display.



Re: Typical 1502B faults?

Bob Koller <testtech@...>
 

The LCD display on these are miserable.. An early electroluminescent backlight with a heater for cold environments, difficult to read in almost any condition. If the display is bad, ie, looks like it has a dark spot, it's gone. There were a few "improved" versions of the display assembly.
The input sampler on this model is a hybrid, not repairable, and impossible to find.
The chart recorder has a roller that turns to molasses, making a huge sticky mess.

When working they are fine, save the lousy display.


Re: Typical 1502B faults?

Stephen Hanselman
 

Unknown, but I suspect (don’t really know) that the tunnel diodes are broke. Most of the earlier 1502’s that we sent to customers on rent came back with blown diodes

Regards,

Stephen Hanselman
Datagate Systems, LLC
3107 North Deer Run Road #24
Carson City, Nevada, 89701
(775) 882-5117 office
(775) 720-6020 mobile
s.hanselman@datagatesystems.com
www.datagatesystems.com
a Service Disabled, Veteran Owned Small Business
DISCLAIMER:
This e-mail and any attachments are intended only for use by the addressee(s) named herein and may contain legally privileged and/or proprietary information. If you are not the intended recipient, any dissemination, distribution or copying of this e-mail and any attachments is strictly prohibited. If you have received this e-mail in error, please immediately notify me and permanently delete the original and all copies and printouts of this e-mail and any attachments.

On Apr 19, 2019, at 16:39, Reginald Beardsley via Groups.Io <pulaskite=yahoo.com@groups.io> wrote:

There are a slew of them on eBay for pretty nominal prices as parts units. How hard are they to repair?


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