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I'm looking for a UK source of 1/8" (0.125" or 3.2mm) diameter fibreglass
rods (or other hard plastic) such as is used in many 7000 series plugins.

For the specific application (the rod down the middle of plastic expansion
rivet) a 3mm rod won't do.

I only want a small quantity, so any suppliers with large minimum orders
would be a problem.

Thanks
David

From: n4buq <n4buq@...>

No, I'm not overly concerned about the pulse width. I was just wondering why there is a difference between the measured width (on the scope) vs the frequency I'd expected with 1/RC. According to Bruce, there's more to it than that and the hysteresis of the Schmitt trigger has to be taken into consideration.

Thanks,
Barry - N4BUQ

From: "Michael A. Terrell" <mike.terrell@...>
To: [email protected]
Sent: Saturday, July 7, 2018 9:14:23 AM
Subject: Re: [TekScopes] Kludging together a TDR or similar?

Both parts are 5% but that isn't important.

The time required for a pulse to travel to the discontinuity isn't affected
by the error in the pulse width. If it bothers you, use a crystal time base
instead of a simple one gate oscillator.

I have another schematic with multiple pulse widths that you can select from,
but like this design, it is built with 5% parts. That one also allows you to
select 50, 75 or 100 ohm output impedance by adding a 22 ohm, or a 50 ohm
resistor in the output path.

Even temperature has some effect on the frequency, along with the propagation
delay on the gate.


Michael A. Terrell


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

From: n4buq <n4buq@...>
Sent: Jul 7, 2018 9:03 AM
To: [email protected]
Subject: Re: [TekScopes] Kludging together a TDR or similar?

Looking at that schematic, it appears the frequency is determined by C3 and
R1. If I'm not mistaken, the exact values of those components would result
in a frequency of 3.129 kHz; however, the oscilloscope images appear to
show 4.81 kHz. Is that difference due to component tolerances or is
something else at work here?

Thanks,
Barry - N4BUQ

I'm looking for a UK source of 1/8" (0.125" or 3.2mm) diameter fibreglass
rods (or other hard plastic) such as is used in many 7000 series plugins.

For the specific application (the rod down the middle of plastic expansion
rivet) a 3mm rod won't do.

I only want a small quantity, so any suppliers with large minimum orders
would be a problem.

Thanks
David

I want to say at the scan on Bama is from Artek. I used to provide them
with very rare tektronix manuals to be scanned.

They spend many many hours cleaning up Originals making sure things are
aligned excetera excetera

They asked very little for a copy to see it on Bama makes me want to throw
up.

And makes me want to decide the other 40 or 50 tektronix manuals that exist
nowhere else will be thrown out instead.

On Sat, Jul 7, 2018, 8:10 AM 搁别苍é别 <k6fsb.1@...> wrote:

that works.....Thank you...now I can follow along
搁别苍é别

On 2018-07-07 02:45 AM, Michael A. Terrell wrote:

That link should redirect to:




Michael A. Terrell


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

From: 搁别苍é别 <k6fsb.1@...>

service manual is 404 for me as well..broken.
The user reference is fine...link works
搁别苍é别

On 2018-07-06 11:04 PM, tmillermdems wrote:

The link works fine.

The .pdf manual is here.

Thanks, Tom, for this reply, the only one I received.

I did loosen the knob set screw and remove the red VAR knob. My replacement skirted knob does have a long shaft that goes through some kind of (cam") switch near the front panel but it seems to have no means obvious to secure it inside the scope.

I did not even think of removing the small diameter plastic shaft to which the red VAR knob is attached. I just now loosened the set screw in the aluminum collar on the pot to which the plastic rod is attached and easily removed the red VAR knob and its shaft. I tugged as much as I thought wise and the skirted knob still did not come out.

The shaft on the replacement knob is long enough to enter the gray plastic collar that protrudes forward from the cam switch. Rotating the skirted knob, I see no screw to secure that knob shaft. I'm still puzzled.

I note the replacement knob has a shallow "V" groove that ends up somewhere inside the other (cam?) switch close to the front panel. Maybe there is some kind of detent spring inside that switch; I can't take that switch apart because I'd need to remove the bottom panel or side beam and I surely don't want to do that.

The red VAR knob and its shaft would hold the skirted knob in well enough but it might rub on the front panel without something to position it. The tolerances make the "V" groove seem unlikely to be what positions the knob. I don't see the thin washer you describe. Tell me again where that is located, please.

What do you mean by "...pried and pulled" to get the knob back out after first putting it back in? Pry? On what?

This seems like a high-risk task! But, that one knob has damaged nomenclature on the skirt and I was able to buy the exact replacement knob on eBay.

The interior of the end of the skirted knob shaft has some details that engage the shaft inside that switch thing near the front panel. That detail will keep the knob clocked but can't hold it in. It may be that shallow "V" groove that holds the knob in.

I surely don't want to damage something inside the cam switch or that other switch near the front panel. And, I really don't want to dribble anything down the skirted knob shaft in hopes of getting to that "V" groove.

I'm feeling kinda stymied...

By the way, I'm a mechanical engineer with a lifetime of small, precision instrumentation design. I'm not intimidated by this problem, just really cautious!

I'm in Anaheim, California, near Disneyland. Good Grief! It was 115.1°F here this afternoon!

Larry




On 7/6/2018 4:18 PM, tom jobe wrote:

Hi Larry,
Your question got me wondering about this, so I took the side cover off of an SC504 to have a look.
The service manual mechanical parts diagram shows the knob has a longer part that goes back into the Channel switch so I looked to see if there was a screw or other fastening device back inside of the scope. I removed the plastic rod that goes through the knob assembly by disconnecting it at the aluminum collar on the VAR switch, and then the knob just fell out for some reason. I put the knob back in and then it would not come out again. So I nervously pried and pulled and got it back out again without damaging it.
A study of the knob shaft showed no locking mechanisms of any kind, so I rubbed a very thin smear of Johnson's paste wax on the knob shaft extension and put it back in. After that the knob slid in and out nicely and the only thing holding the knob in is the 1/8" fiberglass VAR shaft and small VAR knob in the center of the knob in question.
I guess the knob was just stuck from being in there for 30 or 40 years plastic on plastic?
Do be careful about a very thin aluminum washer that is on the knob's rear shaft extension, as it would be very easy to drop that washer into the scope. My guess is that this washer is part of the spacing arrangement that keeps the lettering on the back side of the knob skirt from hitting the front panel and getting damaged, and it also might keep the two plastic parts from rubbing on each other at the knob extension / attenuator surfaces?
tom jobe...
PS I wonder if one drop of water could be put in from the side where the knob shaft extension goes into the attenuator assembly to break it free as you wiggled the knob to spread it around? You would want to be very careful about anything you put in there, as the short and long term effects on the plastic parts could be devastating.





On 7/6/2018 11:30 AM, Larry McDavid wrote:

I have a SC504 scope module with a damaged Channel 1 knob skirt and I have a Tek replacement skirted knob. I can remove the small red central knob by loosening a set screw.

How is the skirted knob removed? I've tried gently pulling on it without success. The knob has a long plastic shaft with some internal ribs to fit over another shaft but I don't know how the knob is attached.

Anyone done this?

From: cheater cheater <cheater00@...>
Sent: Jul 7, 2018 10:48 AM
To: [email protected]
Subject: Re: [TekScopes] Kludging together a TDR or similar?

interesting design for a cheap tdr. thanks!

On Sat, 7 Jul 2018, 16:16 Michael A. Terrell, <mike.terrell@...>
wrote:

Both parts are 5% but that isn't important.

The time required for a pulse to travel to the discontinuity isn't
affected by the error in the pulse width. If it bothers you, use a crystal
time base instead of a simple one gate oscillator.

I have another schematic with multiple pulse widths that you can select
from, but like this design, it is built with 5% parts. That one also allows
you to select 50, 75 or 100 ohm output impedance by adding a 22 ohm, or a
50 ohm resistor in the output path.

Even temperature has some effect on the frequency, along with the
propagation delay on the gate.

From: Pete Lancashire <xyzzypdx@...>
Sent: Jul 7, 2018 11:12 AM
To: [email protected]
Subject: Re: [TekScopes] 114xx bezzel buttons

I want to say at the scan on Bama is from Artek. I used to provide them
with very rare tektronix manuals to be scanned.

They spend many many hours cleaning up Originals making sure things are
aligned excetera excetera

They asked very little for a copy to see it on Bama makes me want to throw
up.

And makes me want to decide the other 40 or 50 tektronix manuals that exist
nowhere else will be thrown out instead.

that works.....Thank you...now I can follow along
搁别苍é别

On 2018-07-07 02:45 AM, Michael A. Terrell wrote:

That link should redirect to:




Michael A. Terrell


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

From: 搁别苍é别 <k6fsb.1@...>

service manual is 404 for me as well..broken.
The user reference is fine...link works
搁别苍é别

On 2018-07-06 11:04 PM, tmillermdems wrote:

The link works fine.

The .pdf manual is here.

That link should redirect to:




Michael A. Terrell


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

From: 搁别苍é别 <k6fsb.1@...>

service manual is 404 for me as well..broken.
The user reference is fine...link works
搁别苍é别

On 2018-07-06 11:04 PM, tmillermdems wrote:

The link works fine.

The .pdf manual is here.

From: n4buq <n4buq@...>
Sent: Jul 7, 2018 9:03 AM
To: [email protected]
Subject: Re: [TekScopes] Kludging together a TDR or similar?

Looking at that schematic, it appears the frequency is determined by C3 and R1. If I'm not mistaken, the exact values of those components would result in a frequency of 3.129 kHz; however, the oscilloscope images appear to show 4.81 kHz. Is that difference due to component tolerances or is something else at work here?

Thanks,
Barry - N4BUQ