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The intensity control makes no change. Traced the 3 wires and found 1 that has no connection. The other 2 are hooked to the beam finder and the hort. plug-in. Also the p/s volts are off and adjustments have no effect. Thanks for any help.

From: "John Rehwinkel" <spam@...>
Reply-To: TekScopes@...
To: TekScopes@...
Subject: Re: [TekScopes] Coax BNC Cable Termination
Date: Thu, 5 Jul 2001 17:39:29 -0400

(snip)

1MHz signals

should tolerate a 30 meter long mismatch, and so on.

My humble twopence: Crappy rule of thumb! Few years ago while integrating an ATE we had a 1MHz square signal we thought it wouldn't need matching pretty much for the same reasons. Oh we were so bloody wrong and it took a while to figure it out. We did have to match that particular stretch of cable - 3 or 4 "lousy" meters of coax - down to 50 ohms (TDS420 alterative Zin) and through line drivers, keeping the signal below the scope's max input power rating. That's how we got it sorted.

Fernando
Portsmouth, UK




_________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at .

A quick way
is to use a BNC tee and a ThinNet terminator -- I have these
in my junk box, other folks might too. Works just fine for
most situations.

Be careful using "network-grade" coax terminators for high-frequency RF.
The ones I've seen become reactive as heck above 50 - 100 MHz or so.

Unless you have a way to check their return loss at the frequencies you're
concerned with, I would steer far, far away from 10Base2/ThinNet
terminators in RF lab work.

-- jm

Jim asks:

"You don?t HAVE to use a termination on coax if it?s a
low-frequency signal. For high-frequency or fast-pulses, yes, you
must terminate".

Can someone comment on how low is low frequency? What happens if you
try to use no termination at too high a fequency?

Basically, the phenomenon you're trying to avoid here is signal
reflection. What coax does is provide a path with a known
impedance to carry the signal from point to point without
changing it (essentially). In order to do this, the coax
(which has its own characteristic impedance, such as 50 ohms)
wants to look into the same impedance, both for maximum
signal transfer, and more importantly, to avoid reflections.
A signal bounces off of a sudden change in impedance, so if
you have a piece of 50 ohm coax connected to a 1 megohm 'scope
input, you'll get a reflection. These reflections change the
shape of the waveform and smear it out.

A generally accepted rule of thumb is that if a section of
mismatched impedance is less than a tenth of a wavelength
long (at the highest frequency of interest), the reflections
will be minor enough not to matter much.

A 100MHz signal has a wavelength of about 3 meters, so if
you run it through an unterminated piece of coax that is
less than 0.3 meters long, the signal shouldn't be affected
much. Note that if you're viewing a 100MHz square wave, it
has components that are much higher than 100MHz, so figure
accordingly.

Similarly, a 10MHz signal should be okay through three meters
of mismatched coax (long enough for most use). 1MHz signals
should tolerate a 30 meter long mismatch, and so on. Naturally,
if you really need accurate waveform measurements, you should
avoid mismatched feedlines entirely. But for most use, under
10MHz or so, any lashup will basically work.

Note also that terminating a signal is pretty easy, a 51 ohm
resistor to ground will do a passible job (or pick up one of
those fancy 50 ohm feedthru BNC terminators and put it on your
'scope input). Two 100 ohm noninductive resistors in parallel
and opposite each other will work even better. A quick way
is to use a BNC tee and a ThinNet terminator -- I have these
in my junk box, other folks might too. Works just fine for
most situations.

-- John Rehwinkel KG4L
spam@...

A few months ago, Dean Huster had included the following in a post:

"You don?t HAVE to use a termination on coax if it?s a low-frequency
signal. For high-frequency or fast-pulses, yes, you must terminate".

Can someone comment on how low is low frequency? What happens if you
try to use no termination at too high a fequency?

-Jim

Hi Stephan,

Try asking to "Deane Kidd" <dektyr@...>

He has lots of Tek spares. I have bought from him several times.

Good luck!


JOSE
----------------------------------------------------------------------
73 EB5AGV / EC5AAU - JOSE V. GAVILA
La Canyada - Valencia (SPAIN)

EB5AGV Vintage Radio Site:

European Boatanchors List:

Hallo!

I`m sorry for my bad english, but i do my best...

In the 7B538 (Trigger-Modul) is an ic broken. It is an ECL Dual 275 Mhz
Latch, named MC1669L.
Do you knew a cross-reference ic?
Ore do you knew an adress to order such a part?

I thank you verry much,
Stephan Cordes
from Germany

Thanks for the replies. Nice to know I was on the right track. One
quick follow-up question, though. Would I place the ground of the
trigger to one end of the "pick-up" loop on the plug wire, or to
the auto's ground?

If you connect the ground lead to the auto's ground, you have
a capacitive pickup from the ignition wire. This will give you
plenty of voltage, but also plenty of noise from nearby wires.
If you connect the ground lead to the other end of the wire you
have wrapped around a plug lead, you'll get a (sort of)
inductive pickup; essentially a transformer with the plug lead
making a 1-turn primary, and your wire the secondary. This
will tend to give you much less interference from other
nearby signals, and you'll get a lower-voltage, lower-impedance
signal (which is probably what you want).

If you're curious, the timing lights with inductive pickups
use a split ferrite toroid on the clip-on lead. When the
clip is closed, the toroid is assembled as a ring around
the plug lead, and the plug lead again forms a one-turn
primary of a transformer. A winding around the non-moving
part of the toroid is the secondary, and provides the
trigger signal. You can build something like this if you
wish, using the kind of split ferrites that are sold as
clip-on noise suppressors, but I doubt it's worth your
trouble.

-- John Rehwinkel KG4L
spam@...

Thanks for the replies. Nice to know I was on the right track. One
quick follow-up question, though. Would I place the ground of the
trigger to one end of the "pick-up" loop on the plug wire, or to the
auto's ground? I'm guessing to the auto's ground.
I will place diodes across the trigger, as was suggested.

Thanks again,

-Jim

Hello james89es,

Tuesday, July 03, 2001, 10:06:14 AM, you wrote:

jyc> I know this is a little off-subject, but it does relate to using an
jyc> oscilloscope. Without going into to details about why I want to do
jyc> this, I'll pose the following scenario:

jyc> Suppose I want to view the voltage on the primary side of an
jyc> automotive coil (12v) and use the #1 cylinder spark plug wire (10-
jyc> 20kv) as a source of the trigger. I am thinking of taking a length
jyc> of wire (18-22gauge) and wrap a few loops around the outside of the
jyc> plug wire. I am wondering what kind of signal that would produce.
jyc> Would this be some kind of inductance pick-up? Processional
jyc> automotive timing lights have a little pick-up that losely clamps
jyc> around the plug wire - that's what gave me the idea.

jyc> Any insight, short of discouragement, would be appreciated.

jyc> Jim

jyc> PS: I WON"T be using my vintage Tek scope for this!! I have a very
jyc> cheap analog scope that I intend to use instead.


jyc> To unsubscribe from this group, send an email to:
jyc> TekScopes-unsubscribe@...



jyc> Your use of Yahoo! Groups is subject to
Hi James,
Your idea should work OK but place a pair of silicon
diodes each way across the external trigger input of your
scope. They will limit the pulse that you pick up to about
a volt or so and protect the CRO from spikes. If there
isn't enough trigger voltage, replace the diodes with a
zener diode of a few volts to get a bigger signal.
Don Black.






mailto:jeans@...

Jim

This will work, you may want to check the voltage spike with your scope before you apply it to your trigger input. I did this quite a few years ago and I found that 3 turns around the spark plug wire produced a 3 to 4 hundred volt spike and with today's electronic ignition systems I would think you would get an even higher voltage.

You could also use a Prox switch to sense TDC on the crank pulley and then use the scope to measure the spark advance over you full rpm range. This would be great for dialing in the distributor for the best performance. I am assuming that the ignition is not controlled by an computer.


Jim Nunn

Suppose I want to view the voltage on the primary side of an
automotive coil (12v) and use the #1 cylinder spark plug wire (10-
20kv) as a source of the trigger. I am thinking of taking a length
of wire (18-22gauge) and wrap a few loops around the outside of the
plug wire. I am wondering what kind of signal that would produce.
Would this be some kind of inductance pick-up? Processional
automotive timing lights have a little pick-up that losely clamps
around the plug wire - that's what gave me the idea.

I know this is a little off-subject, but it does relate to using an
oscilloscope. Without going into to details about why I want to do
this, I'll pose the following scenario:

Suppose I want to view the voltage on the primary side of an
automotive coil (12v) and use the #1 cylinder spark plug wire (10-
20kv) as a source of the trigger. I am thinking of taking a length
of wire (18-22gauge) and wrap a few loops around the outside of the
plug wire. I am wondering what kind of signal that would produce.
Would this be some kind of inductance pick-up? Processional
automotive timing lights have a little pick-up that losely clamps
around the plug wire - that's what gave me the idea.

Any insight, short of discouragement, would be appreciated.

Jim

PS: I WON"T be using my vintage Tek scope for this!! I have a very
cheap analog scope that I intend to use instead.

Hello,

Stan said that they are the same. We looked for a manual for D10 but we could not find an extra one.

Thanks,
Patricia for Stan

fitelind@... wrote:

Andrew,
have you tried here?



I have a 2235 too
What happened to yours?

Adri

Hi All,

I am still looking for a Vertical Amplifier IC for a Tektronix 2235A
Oscilloscope.

Tektronix Part Number is 234-0133-20

Can anybody help?

If not, does anyone have a 2235A for sale?

Regards,

Andrew
Sydney, Australia

Greetings, Rob;

--- In TekScopes@y..., Rob F <robert177@s...> wrote:

I have two used E55L tubes in my wee collection that I pulled from

some

equipment last year. Unfortunately, the pinout won't fit my tube

tester so I

can't tell you how strong they are. However, the tubes were working

in the

piece before I dismantled it.

If you kill your present E55L tube while fixing your equipment, let

me know

and I'll mail you one or both as needed.

Thank you for the generous offer. I may need to take you up on it. It
appears I may be down one or two to fill what P-Is are in the pile.

Best Rgds; Steve

Greetings, Stan;
--- In TekScopes@y..., Stan or Patricia Griffiths <w7ni@e...> wrote:

There is a description of cathode interface and how to determine if
you have it on my web page at:

I appreciate your response. The refs were most useful and
informative. Seems this should be easy to identify using the cal
source into the P-I under test.
The latest E55L price from AES are lower than I expected for recent,
but even so still come out somewhat over $80 bux per pair shipped.
Perhaps having just a couple good working 3A1/3A6s out of the bunch
is the most economical solution with the easier-to-outfit 3A3 and
63/2A63 diff amps as the audio frequency work-horses & for X-Y.
Thankful that a rare 3M1 was also in that crate of P-Is, to
eventually standardize response of my M-Fs.

Thanx again. Best Rgds; Steve

Problem is the manual I have is for a 5103N D11/D15. I have r242 as 22k, r101 as 100, r251 as 5.6, r239 as 100, r274 as 1m, and r213 as 62k. Need to know if these are listed as the same for a D10 5103N.Thanks for any help.

Does anyone have a Tek 455 service manual for sale? Could also trade
other manuals, probes, plugins, etc. I've already tried the usual dealers.
Thanks...

Hi All,

Has anyone a spare Tektronix 2432 Rear Cover lying around?

Tek part number 200-2961-00.

Thanks.

Andrew