Date   

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?



Typical 1502B faults?

Reginald Beardsley
 

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


Re: SMA caps for sampling heads

Harvey White
 

On Fri, 19 Apr 2019 19:30:06 +0000 (UTC), you wrote:

My SD-26 heads came with shorting caps. And I need caps for my SD-22 heads. I'm wondering though if non-shorting caps would be more appropriate. The male pin rotating in the female sleeve seems as if it presents a wear issue. And a non-shorting cap should protect the input diodes from ESD just as well.

The label on the head says to use a 015-1020-00 for shipping which according to Test Equipment Depot and TekWiki is an SMA male shorting plug.

Non-shorting Amphenol caps are $1.85 each from Digikey and shorting are $3.46 each in quantity of 25.

Comments?
No reason you couldn't use a termination for the same thing, unless
you think that a static discharge across a 50 ohm termination might be
a problem.

Harvey



Thanks,
Reg



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

Nenad Filipovic
 

Hi Albert,

W.r.t. sensitivity for DC input (did you try?) I forgot that the setting
of S901 "Correction Memory Switch", see page 2-5, is important. For now the
best way is to set the switch in the rear (OFF) position (as long as you
don't have a pulse generator head).
Explanation of S901 purpose is quite vague in 7S12 manual, I did try all 3
positions and there is no change. Btw I also fed the head with very low
freq sine wave thus simulating DC input, and still no go.

With a DMM attached to the front panel Vertical Out connector you can see
that Memory is slowly drifting.... the DMM reading will immediately jump
back to the normal value. The trace should reappear immediately at the
previous vertical position.
Yes, the drift is very very slow. I'd say it would tale a whole minute for
it to cross 1 div, with the settings I used. When I switch free running
back on, it immediately jumps back to its old position.

The heads have different connectors, SMA and BNC, and your signal
generator perhaps one of these. You need a power divider or a splitter or a
T and at least an adapter to from one type connector to another. All these
things could introduce faults. Are you 100% sure that the sine wave signal
arrives "inside" the S-4?
Yes, I'm using BNC-SMA adapters and BNC T adapters. I can definitely
measure 50Ohm (52 to be exact) at the point where I'm inserting the signal,
so I guess that's the best I can tell that I'm feeding the signal to S-4.

Even though this feedback-offset loop seems to be working, I decided to
check the head internally, namely the gate bias. It is possible to adjust
R32 according to manual, and its position falls around midpoint. However I
found the gate bias to be somewhat asymmetric, it's all part of a feedback
loop so it's hard to tell what causes it. The voltages on the S-4 internal
preamp board points are:
- C (feedback): -337mV (500mV/div), -146mV (200mV/div), -79mV
(100mV/div)...and reducing geometrically while increasing mV/div
- M=1.93V, H=-2.29V, V (at 100mV/div - I kept this setting because of the
relatively small feedback voltage on C, also applies to measurements below)
- Voltage across D20=405mV, D23=412mV, D25=424mV, D28=422mV
- on Q36 Vg= approx. -1.80V, Vs=-1.76V, so Vgs seems to be slightly
positive (can't measure directly between gate and ground as this point is
very sensitive)

I can't say if this slight asymmetry can be a problem. Preamp output (point
E) shows sampling pulses, but zero reaction to my low freq sine wave input
signal. I still cannot say whether the snap-diode circuit works, is there
any test I could do to verify if it's working? (E.g. are the sampling
spikes observed on point E due to snap-off working, or are these coming
through the feedback line?)

Best Regards, Nenad


Re: 7L5 knob removal

Cliff Carrie
 

On the right side: loosen two setscrews in the top and bottom rails just behind the front panel.
One the left side: loosen a small setscrew on the top of the lower rail. It holds the left module pivot in place. Remove two Philips flathead screws on top of the upper rail. These are the same ones you take out to pivot the left module out. Do not remove the left module screws at the rear of the plug-in.
Unplug the calibrator output cable from behind the front panel connector. Work the front panel connectors off of the internal circuit boards. That should be all it takes. The 3 pins that were held by the setscrews should slide out easily. They are the only mechanical connection to the rest of the unit. The pots at the lower right of the front panel are on a separate internal bracket and the knobs pass through the front panel without being removed.

Reassembly: Do not tighten the lower left setscrew to the point that it interferes with pivoting the left module out. It's not necessary. Be gentle with the two right side pins. They are plastic and can be broken. They can even be cut in two by overtightening the setscrews. If you end up with one of these pins to spare and in good condition, I need one for my 7L5.

Regards, Cliff Carrie
________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Ed Breya via Groups.Io <edbreya=yahoo.com@groups.io>
Sent: Friday, April 19, 2019 2:38 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7L5 knob removal

OK. I found screws from the inside, but they are inaccessible without pulling the right side RF casting assembly. It also appears the front of the casting is held with setscrews on some kind of pins in the front panel, rather that the usual screws hidden under the faceplate, that I expected. This must be how they managed to assemble everything from behind. It's gonna be a lot of stuff to pull apart.

Ed


SMA caps for sampling heads

Reginald Beardsley
 

My SD-26 heads came with shorting caps. And I need caps for my SD-22 heads. I'm wondering though if non-shorting caps would be more appropriate. The male pin rotating in the female sleeve seems as if it presents a wear issue. And a non-shorting cap should protect the input diodes from ESD just as well.

The label on the head says to use a 015-1020-00 for shipping which according to Test Equipment Depot and TekWiki is an SMA male shorting plug.

Non-shorting Amphenol caps are $1.85 each from Digikey and shorting are $3.46 each in quantity of 25.

Comments?

Thanks,
Reg


Re: 7L5 knob removal

Ed Breya
 

Thanks Cliff. Before seeing your post, I figured out that the whole front comes off - the hard way. I started unscrewing everything front and back, and whole plug-in began to fall apart. It's pretty slick they way they did it. I have often had to take front panels apart, and always dreaded removing everything on the panel in order to pop the front plate just to access the rail screws. The 7L5 assembly is fairly complicated, but it works. I now have the front panel assembly separated, and the special switches removed.

Fortunately, these switches, the rotary encoder, and other items up front survived in good shape, especially considering what must have happened to this poor thing. It appears it was probably in a mainframe that got dropped or hit with a forklift from the back, deforming it such that the plug-in is severely distorted. The depth is off-square by almost a cm side to side. The guts seem to be intact, although all misaligned, and the front panel casting and face are bent, but otherwise not a scratch on it. The only damage up front was a broken small knob and bent shaft on the dot frequency fine tune. The back plate is mangled up, but should be fairly easy to straighten back out.

I'm hoping that I can just strip the front panel and straighten the pieces, straighten the back plate, and replace one or both busted plastic board edge connector supports to get it mechanically square again. The rest should be about realigning the guts and figuring out how to put everything back together. After all this, I can then plug it into a mainframe and see if it even works.

I have to mention again, that I like this pinned assembly method used here. It probably saved this plug-in from nearly certain destruction. If the front was held on the rails with the typical screwed-on method, the casting would have likely snapped and taken out the special switches, and more. With the pins, everything still bent, but the pins pulled loose, allowing some give on the assemblies, without fractures. Actually, there is one other broken item - one of the plastic pins from the front panel snapped, and the end is probably still in the side casting. I'll be able to rig up a simple replacement for the pin.

Ed


Re: Scope-Mobile Cart Model 3 Disassemble

Roy Thistle
 

On Thu, Apr 18, 2019 at 08:15 PM, Leon Robinson wrote:


Take a few pictures
Along with picture, I use a sharpie, and mark the parts on the inside... where it isn't visible. I use 1A, 2A... and so on, for the left... and 2A, 2B...and so on for the right. I also mark the part, and where the part was attached.


Re: Scope-Mobile Cart Model 3 Disassemble

Roy Thistle
 

On Thu, Apr 18, 2019 at 04:01 PM, John Griessen wrote:


advise on the tools
along with the tools above, I'd take an adjustable wrench, a socket set (with ratchet, and drivers)… and a set of deep sockets, for removing recessed bolts.


Re: Scope-Mobile Cart Model 3 Disassemble

Roy Thistle
 

On Thu, Apr 18, 2019 at 05:04 PM, Dennis Tillman W7PF wrote:


there are two VERY UNUSUAL screws that the top shelf pivots on.
Those have to be removed with care.
Hi All: If I remember... and it is the hex bolts/screws, in the pivot.. that are recessed... I used a ratchet and a socket, from a set of "deep sockets" to remove those. It's straight forward with that kind of socket... I found a regular socket didn't have the reach... but, you might be able to carefully extract the bolt, using a socket, from a regular socket set.

Also I posted to a couple other threads, on the topics of scope cart disassembly.

Regards all.


Re: 7L5 knob removal

Ed Breya
 

OK. I found screws from the inside, but they are inaccessible without pulling the right side RF casting assembly. It also appears the front of the casting is held with setscrews on some kind of pins in the front panel, rather that the usual screws hidden under the faceplate, that I expected. This must be how they managed to assemble everything from behind. It's gonna be a lot of stuff to pull apart.

Ed


Re: 7L5 knob removal

Cliff Carrie
 

Ed,
Be careful with those knobs. The switching (partly physical contacts and partly an optical encoder) is contained entirely inside the knobs themselves. Disassembly is not recommended unless they have a specific problem, although I did it successfully to relubricate them.
Follow the manual procedure for removing the front panel as a unit (not so obvious, but not too difficult). The knobs are attached by screws installed from the rear of the front panel. They have pins that plug into the front panel circuit board. I did this some time ago, so I would need a close look at my unit and the manual to give you more detail.
Regards, Cliff Carrie
________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Ed Breya via Groups.Io <edbreya=yahoo.com@groups.io>
Sent: Friday, April 19, 2019 2:10 PM
To: TekScopes@groups.io
Subject: [TekScopes] 7L5 knob removal

I just picked up a severely mechanically damaged 7L5, and trying to rebuild it. I started taking apart the front panel, removing the knobs as usual. The frequency span/resolution and time/div knobs have no setscrews, and appear attached somehow from inside and behind the front panel. I peeled off the black knob face covers too, hoping to find some attachment hardware, but they're blank underneath. Does anyone know the trick to removing these knobs? I R'dTFM but didn't find any explanation, and it's not clear at all from the mechanical diagrams.

Ed

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