On Apr 14, 2016, at 7:43 PM, 'Dennis Tillman' dennis@ridesoft.com [TekScopes] <TekScopes@yahoogroups.com> wrote:

Hi Christoph,
It is not unusual for Tek to design the power supplies where they use one as
a "reference" and use that voltage as the reference for the others. In these
cases you have to first get the "reference" supply to work. Sometimes if
other supplies are shorting out they can drag down this "reference" supply
and make it very hard to troubleshoot the entire power supply section. In
that case the only way to proceed is to remove the load from the other
supplies one at a time until the "reference" pops up to correct voltage.
Then you can narrow down the source of the short or excessive load.

ALWAYS, I can't stress this enough, ALWAYS be suspicious of the tantalum
capacitors. They have a notorious failure rate as everyone on the forum will
tell you. Tek (and everyone else in the industry) used them extensively
before their critical weaknesses were understood. They are used extensively
in the power supply section of every Tek product. Check every one of them
with an ohmmeter. Some people replace them all as a precaution even if they
don't appear to be bad.

-----Original Message-----
Sent: Thursday, April 14, 2016 1:17 AM
Subject: [TekScopes] PG-502 blowing fuses - PS repair

On a PG-502 I had here laying around and had partially repaired such that at
least the pulse train and the levels were workiing - only pulse width was
still defunct - suddenly it blew the 1A fuses F600 and F670.

I measured all transistors, found a few burnt ones, replaces the "normal"
ones with BC546/BC556 and the metal case with BC 161. Still it looks like
the Thyristor 2N4441 plays its role as a crowbar and closes on power up.

I will do another round and check *all* transistors, diodes, zeners etc.

I also tested the thyristor outside the board in a little testcircuit. It
fired on demand and opened as well.

This power supply seems to be a bit tricky because all voltages seems to
depend on other voltages somehow.

Any expert on this modules out there?
Christoph
------------------------------------
Posted by: christophkukulies@me.com
------------------------------------

It is quite possible to install the screw-together type really well, but
it
takes some skill and patience. It's not fast but you don't need much in
the way
of special tools.

Buy connectors new, with all the bits and pieces. Get high quality ones; I
like
Kings among others. Make sure the connector is specifically designed for
the
cable you are using. Fudging it doesn't usually work out very well. You
may
need to grind down the thickness of an open end wrench to work with the
flats on
the body.

The cable prep and installation directions are easily found with Google.
Learn
to follow the directions precisely, including tightening torque. It took
me a
while but the ones I do now have the pin in correctly and there is no play
in
the cable, it's gripped nice and solidly. Impedance is as good as it gets
with BNC.

I'd love to have a high quality crimper setup but just can't justify the
cost
for the limited use I'd get from it. Yes, with the prep tool and crimper
you're
done in no time with great results, it's just very costly per connector if
you're doing under 5 connectors a year.


On 4/14/2016 9:51 PM, Bob Albert bob91343@yahoo.com [TekScopes] wrote:

BNC connectors seem to be ubiquitous and so it behooves us to find a

suitable

way of installing those connectors on cables.
I have seen some crimpers but none are cheap. I have also seen some

variety

in connectors that lead me to believe that one crimper won't work for

everything.

I don't mind soldering the center conductor but the issue arises as to

whether

to tin it first and how to get all the strands into the pin. I have

trimmed

off many strands in an effort to insert the center conductor.
Most of my work on the test bench is with RG-58A/U or its equivalents.

If you

know of an inexpensive way of installing inexpensive connectors with
acceptable reliability, please share it. I am one person with a small
laboratory and need to put a BNC on a cable perhaps a few times a year.

If I

have to spend a trifle more it won't matter much but some of the

solutions

appear to be more than a trifle higher in cost.
I also want to know a good procedure for installing all parts of the
connector, the center conductor, the shield, the pin, the funny little

washers

and insulators and all the other stuff that comes in the bag.
Bob


On Thursday, April 14, 2016 2:25 PM, "big_sky_explorer@yahoo.com

[TekScopes]"

<TekScopes@yahoogroups.com> wrote:


I think that we have to separate out the pros and cons of

crimping/soldering

to a finer degree. Not that I disagree with the crimping approach as

Walter

has commented on but there is a certain degree of poor reliability that

I have

witnessed with this approach when employed by the (shall we say) the

“commonly

found” user in the field.

I say “commonly found” because these are the people who are somewhat
unknowledgable about connectors and crimping processes in general since

they

are trained either by OJT or by another who has learned by intuition to
assemble connectors but not investigated the nitty-gritty technical

aspects of

them. Usually these people and/or their employers have had little

exposure to

the subtleties of connector reliability and associated tooling as

affected by

sourcing, manufacturing quality and such.

First, we look at sourcing. Obviously a smaller installing or repair

agency

will consider cost as a fairly important issue. This means that they

will

probably purchase their connectors from a source that offers fairly
inexpensive (<$2) connectors that are a given to be made in China.

Next, given the propensity for tooling to either become lost, damaged or

worn

out, these people will most likely look for the first supplier who

offers

inexpensive crimp tooling. Again the Chinese come to bat with their

offerings.

When we add minimal experience and knowledge to low quality connectors

and

tooling, we can have the setting for a connector installation that could
possibly be unreliable.

I do understand one’s desire for a reliable connection within the

connector.

Having worked on space hardware it was a given that this had to happen.

And,

of course, we had no qualms about multi-hundred $$ tooling and expensive

MIL

qualified connectors at our disposal. But I have to ask how many members

of

this group have access to that type of quality hardware for their home
projects let alone want to spend the money for same?

My experience using inexpensive (Chinese) BNC connectors with

off-the-street

tooling is that the center pin is often made of a fairly brittle alloy

that

tends to crack if the correct crimp pressure is not applied or the crimp

die

is not of the exact dimensions. This has led me to occasionally find

field

installations where the installer had over crimped the center contact

causing

cracking but not to a point where it was obvious when the connector was
assembled. Later, through flexing and movement of the cable, the contact
between the pin and center conductor became erratic and very obvious

when used

at higher frequencies.

When using “cheap” connectors I personally solder the center conductor

into

the pin. I find it easy to do and know that the connection will last and

that

I don’t end up having to throw away a connector should the crimp cause
cracking to occur. A little heat applied from the iron and the job is

done.

And has anyone ever wondered what that tiny hole is for in the side of

the

pin? To accept solder.

I believe that an earlier comment was made where the user is tinning the
center contact when assembling a connector. That can create problems as

the

connector sees use. First, the gold strike on the pin is there for a

reason –

to afford a highly reliable, non-oxidizing contact surface. Obviously a

tin

strike contact in many other (non-RF) multi-pin connectors can exhibit

higher

contact resistance, oxidation and, hence, possible intermittents when in

use.

Second, the sliding of the pin into the mating receptacle can deposit

the tin

onto the mating contact surface. If this surface also contains a gold

strike,

the overlay of tin on that surface will reduce the contact reliability

and RF

characteristics of that connector as well.

When working in Colorado, I had the opportunity to attend a seminar at

the

(then) National Bureau of Standards on RF connector reliability. It was

quite

informative to learn about connector contact plating techniques and how

it

affects the reliability of the connector. And it was also a real

eye-opener to

find out how limited the number of mate/un-mate cycles a typical

connector can

go through before the RF characteristics begin to degrade. Of the ones

found

around the lab, N connectors were the most substantial. BNC connectors

were

significantly less.

Greg



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[Non-text portions of this message have been removed]

Hi Dave,
Right now we support the downloading of the member list and the downloading

Hope this helps.
Mark

Dwayne

Great:

Are you using and having success with the "Yahoo Message Export" Chrome
plugin?

When it shuts you down, does it cut off only the one you are
downloading, or
all the groups you are joined?

If it looks like you need some help splitting things up to make it in
time,
let me know other wise a single download would seem better

John

-----Original Message-----
From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com]
Sent: Thursday, April 14, 2016 1:29 PM
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] TekScopes Moderator

On 14/04/2016 12:12 PM, 'John Snyder' Kochcal@earthlink.net [TekScopes]
wrote:

Has anyone used any of the tools and succeeded in getting a text backup?

I am in the process. Up to 2007 now (Yahoo locks me out if I take too
much too fast)

When I have it all, I will put the archive on tecscopes.info, where any
of you can grab a copy.

------------------------------------
Posted by: Dwayne Verhey <tekscopes@verhey.org>
------------------------------------

------------------------------------

Yahoo Groups Links

Yup, tubes all gone. Thought about emailing the guy to inform him that

From: "Richard Solomon dickw1ksz@gmail.com [TekScopes]" <

To: TekScopes <TekScopes@yahoogroups.com>
Sent: Thursday, April 14, 2016 4:47 PM
Subject: Re: [TekScopes] - Plug-ins from the 1960s & 70s


From what I can see, some "tube merchant"
has already plundered them.

Pity,

73, Dick, W1KSZ

On Thu, Apr 14, 2016 at 12:53 PM, John Dickens jake_117_dickens@yahoo.com
[TekScopes] <TekScopes@yahoogroups.com> wrote:

In case anyone is interested, I just ran across the following Craigslist
add selling 23 plug-ins from the 60s and 70s: "These units are plug ins

Tektronix oscilloscopes commonly found on U.S. aircraft carriers in the
60's and 70's. Selling for 20 - 40.00 each or make offer on all 23. I

have an oscilloscope for 40.00. Sold as is untested.”

https://dubuque.craigslist.org/for/5522355104.html <
https://dubuque.craigslist.org/for/5522355104.html>

Jake

In case anyone is interested, I just ran across the following Craigslist
add selling 23 plug-ins from the 60s and 70s: "These units are plug ins for
Tektronix oscilloscopes commonly found on U.S. aircraft carriers in the
60's and 70's. Selling for 20 - 40.00 each or make offer on all 23. I also
have an oscilloscope for 40.00. Sold as is untested.”

https://dubuque.craigslist.org/for/5522355104.html <
https://dubuque.craigslist.org/for/5522355104.html>

Jake

On 14/04/2016 3:29 PM, David DiGiacomo telists@davmar.org [TekScopes]
wrote:

OK, but this doesn't explain why CATV has switched over to compression
connectors. Does anyone know?

_

If you are referring to F type 75 ohm co-ax connectors, they don't use a
centre pin. The solid centre conductor acts as the pin. The compression
only has to deal with the outer shield.

Portola Valley, CA