Digest for sci.electronics.repair@googlegroups.com - 7 updates in 3 topics

9:41 AM Penedão 0 comments
guijarrosoy <algenta@gmail.com>: Aug 30 09:47AM -0700

Hello colleagues. I am in neeed of schematic and service manuals for TAMPA model M-AUDIO mixer.
 
Unit is noisy. Tradicional techniques did not work. (I.E. Contact cleaner on potentiometers, etc)
 
Any help is appreciated.
 
Al.
bitrex <user@example.net>: Aug 31 12:27AM -0400

On 8/30/2021 12:47 PM, guijarrosoy wrote:
 
> Unit is noisy. Tradicional techniques did not work. (I.E. Contact cleaner on potentiometers, etc)
 
> Any help is appreciated.
 
> Al.
 
Tampa's a mic pre-amp. Do you have the mic/line switch and impedance
selection knob configured correctly for whatever is plugged into it? You
have a mic actually connected when you're listening for noise on the
"mic" setting, yeah?
three_jeeps <jjhudak@gmail.com>: Aug 30 05:46PM -0700


> Their job is to facilitate cable *identification* where multiples exist.
 
> OTOH a buried mains cable reveals it *location * by the magnetic field created by all the damn AC current flowing in it !!
 
> ..... Phil
 
Thanks for pointing out the inaccuracy of my post. My task is one of identification.
I just bought an inexpensive one from one of the references. I'll use my flashlight arrangement as a backup.
I did learn something from Jeff about cable locators - TY. Will file that away as I may be doing some of that in the future.
 
J
legg <legg@nospam.magma.ca>: Aug 30 03:36PM -0400

On Mon, 30 Aug 2021 08:01:01 -0400, Bob Engelhardt
>and hours to fix a $100 scope". I do have the service manual & another
>scope.
 
>Thanks, Bob
 
It's a relatively simple part of the scope, if it's
an accurate diagnosis.
 
Helps if you have a working scope to repair this one.
 
https://groups.io/g/TekScopes/messages
 
RL
Phil Allison <pallison49@gmail.com>: Aug 30 02:45PM -0700

bobenge...@gmail.com wrote:
=========================
> case: "It could be any number of things and you'll likely spend hours
> and hours to fix a $100 scope". I do have the service manual & another
> scope.
 
** You are asking a " Schrodinger's Cat " type question.
 
The cat can be thought dead or alive - until you open the box.
 
 
...... Phil
Trevor Wilson <trevor@rageaudio.com.au>: Aug 31 10:03AM +1000

On 30/08/2021 10:01 pm, Bob Engelhardt wrote:
> and hours to fix a $100 scope".  I do have the service manual & another
> scope.
 
> Thanks, Bob
 
**Who knows? Download a service manual and get to work. The 465/b is an
excellent 'scope and built to last a VERY long time.
three_jeeps <jjhudak@gmail.com>: Aug 30 05:39PM -0700

On Monday, August 30, 2021 at 3:34:42 PM UTC-4, legg wrote:
 
> Helps if you have a working scope to repair this one.
 
> https://groups.io/g/TekScopes/messages
 
> RL
 
I second the motion to join & post on the TekScopes message board. A lot of *very* knowledgeable ppl hang out there. IMHO, I'd spend 15 mins with it plugged in to understand more clearly the characteristics of the malfunction. If you put that info in your post, you might get a bit more of an answer along the lines you are looking for.
A 465 is a very well-known and popular scope. It was standard gear for DEC and IBM field circus back in the day, and a typical scope in a lot of college EE labs.
good luck
J
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Digest for sci.electronics.repair@googlegroups.com - 6 updates in 3 topics

9:40 AM Penedão 0 comments
Bob Engelhardt <BobEngelhardt@comcast.net>: Aug 30 08:01AM -0400

I found a 465 at the dump with a sticker on it saying "Horizontal
deflection bad". Before I even power it up I thought that I'd get
opinions on how bad the problem likely is. Best case: "That happens all
the time & it's a bad Qxxx transistor in the framazazzle". LOL Worst
case: "It could be any number of things and you'll likely spend hours
and hours to fix a $100 scope". I do have the service manual & another
scope.
 
Thanks, Bob
Rob <nomail@example.com>: Aug 30 03:39PM +0200

> and hours to fix a $100 scope". I do have the service manual & another
> scope.
 
> Thanks, Bob
 
https://w140.com/tekwiki/wiki/465
Mike Coon <gravity@mjcoon.plus.com>: Aug 30 03:19PM +0100

In article <sgih9s02vqh@news1.newsguy.com>, BobEngelhardt@comcast.net
says...
> and hours to fix a $100 scope". I do have the service manual & another
> scope.
 
> Thanks, Bob
 
That's what I call "right to repair". In the UK it is not permitted to
take kit away from a dump, in case you are not as competent as you think
you are...
Chris K-Man <thekmanrocks@gmail.com>: Aug 30 09:17AM -0700

On Monday, August 30, 2021 at 10:19:13 AM UTC-4, Mike Coon wrote:
> That's what I call "right to repair". In the UK it is not permitted to
> take kit away from a dump, in case you are not as competent as you think
> you are...
_________
 
Where do you think I got my stash of spare TV remotes from?
 
If a bar's got a Sony on the wall, in Vivid mode, Im can whip out
my Sony remote, and at least put it in Standard mode.
Tim R <timothy42bach@gmail.com>: Aug 29 12:49PM -0700

I had another idea but will read the links about locating cable first.
Michael Terrell <terrell.michael.a@gmail.com>: Aug 29 11:29AM -0700

I recently had to replace my Glucose meter because it could no longer hold the correct date. I ripped the old one apart, and found a nice pair of Zebra Strips in it.
It was an Abbot Labs Freestyle freedom, and the strips are about 5/32" high and 1-9/32" long
Maybe this will help someone repair an old LCD in their equipment. This is a small meter, some have a screen twice its size
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Digest for sci.electronics.repair@googlegroups.com - 10 updates in 2 topics

9:40 AM Penedão 0 comments
"Peter W." <peterwieck33@gmail.com>: Aug 28 11:29AM -0700

> Works well tracing house wiring.
> Just remember to turn off ALL circuit breakers in the mains panel.
 
No. "Designed for use with telephone lines, alarm cables, computer cables, intercom lines, speaker wires, and thermostat wiring."
 
Not line voltage. And not for underground tracing either.
 
Peter Wieck
Melrose Park, PA
Rob <nomail@example.com>: Aug 28 08:54PM +0200

>> Just remember to turn off ALL circuit breakers in the mains panel.
 
> No. "Designed for use with telephone lines, alarm cables, computer cables, intercom lines, speaker wires, and thermostat wiring."
 
> Not line voltage. And not for underground tracing either.
 
But the question was "I need to trace some cables (phone catv, ethernet)
throughout a house.".
So what is your problem?
Phil Allison <pallison49@gmail.com>: Aug 28 01:26PM -0700

Rob wrote:
========
> But the question was "I need to trace some cables (phone catv, ethernet)
> throughout a house.".
> So what is your problem?
 
** There are TWO different questions here from TWO posters.
Pay attention.
 
..... Phil
"Peter W." <peterwieck33@gmail.com>: Aug 28 03:31PM -0700

> So what is your problem?
 
Do you not read for content?
 
Peter Wieck
Melrose Park, PA
Tim R <timothy42bach@gmail.com>: Aug 28 05:47PM -0700

On Saturday, August 28, 2021 at 10:45:55 AM UTC-4, Peter W. wrote:
> That is a low-voltage device, not for power lines. Underground cable tracers are very different animals, and substantially more costly. if all you need to do is 6-8" or so, borrow a decent metal detector and trace that way. You will be within inches - dig out that area by hand. In any case, do call your local One-Call service, it is free and often you have no idea of what may be down there. And they DO have the costly devices.
> Peter Wieck
> Melrose Park, PA
 
Sorry to confuse the thread with two different applications.
 
My thought was that if a signal generator can put a tone on my line, I could shut the breaker in the house, leave the shed dead, put the signal on the shed end, and trace the wire back to the house. It seems like that should work if the wire is 6 inches down, maybe not if it's 18. Or maybe those tone generators don't work at all underground, I've never tried it. I did borrow a metal detector some years ago but got inconclusive results. Maybe i could rent a better one from a big box or electrical place. I'm sure the there is no conduit, I hit a wire some years back that looked like UFB, so I know where at least one piece of it is, and it wasn't where I expected it.
Phil Allison <pallison49@gmail.com>: Aug 28 06:03PM -0700

timoth...@gmail.com wrote:
----------------------------------------------------
 
> Sorry to confuse the thread with two different applications.
 
> My thought was that if a signal generator can put a tone on my line, I could shut the breaker in the house, leave the shed dead, put the signal on the shed end, and trace the wire back to the house.
 
** LOL - that is NOT what tone generators do !!
 
Their job is to facilitate cable *identification* where multiples exist.
 
OTOH a buried mains cable reveals it *location * by the magnetic field created by all the damn AC current flowing in it !!
 
 
 
..... Phil
Jeff Liebermann <jeffl@cruzio.com>: Aug 28 06:46PM -0700

On Sat, 28 Aug 2021 18:03:03 -0700 (PDT), Phil Allison
 
>Their job is to facilitate cable *identification* where multiples exist.
 
>OTOH a buried mains cable reveals it *location * by the magnetic field created by all the damn AC current flowing in it !!
 
>..... Phil
 
This might help:
"Buyers Guide To Cable Locators"
<https://www.tigersupplies.com/LC/Buyers-Guide-To-Cable-Locators-.aspx>
There are some that work at 60 Hz, but most use higher frequencies.
There's just too much interference at 60 Hz. Also, the higher the
frequency, the higher the resolution, which translates in a more
accurately located cable.
"Successful Locating Depends on Knowing Which Frequency to Use"
<https://www.utilityproducts.com/tools-supplies/article/16003409/successful-locating-depends-on-knowing-which-frequency-to-use>
 
More than you probably wanted to know:
"The theory of buried cable and pipe location"
<https://www.radiodetection.com/sites/default/files/Theory-Buried-pipe-manual-V10.pdf>
 
For what it's worth, I used an RF signal generator to locate buried
cables. The trick is to build a series resonant RF transformer
(ferrite torroid) for your choice of RF frequency. I picked the 160
meter ham band (1.8 to 2.0Mhz), much to the irritation of the local
ham radio operators. The generator was set to about 70% AM modulation
at 1KHz to produce a detectable tone. The resonant transformer will
pass the RF but not the 60 Hz line frequency, thus insuring that there
is some hope that the RF generator will survive the exercise. It also
provides an ungrounded connection to the power line, which should
prevent some types accidental electrocutions.
 
The difficult part was designing and building a suitable pickup coil.
I finally resorted to a ferrite rod (loopstick) antenna similar to
what is found in many SW (short wave) receivers.
<https://www.google.com/search?q=loopstick+antenna&tbm=isch>
Such a loopstick antenna a nice deep null in the antenna pattern off
the end of the rod, which makes direction finding possible.
 
If I were to design a cable locator today, the system would be quite
different. The problem with using only one frequency is that various
types of dirt attenuate different frequencies differently. Instead of
one frequency, I would use a range of frequencies (spread spectrum),
in the hope that at least one frequency will make it through the dirt
(and interference). That's how ground penetrating radar works.
<https://ieeexplore.ieee.org/abstract/document/9381259>
 
The last time I had to locate some underground wiring, I was lazy and
used an acoustic method. I made a low frequency "buzzer" that ran
from compressed air. I shoved the air hose as far up the PVC conduit
as possible and turned on the buzzer. With a 1 HP motor, that might
produce 200 watts of audible buzz, which should be audible at ground
level. I used a stethoscope to locate the buried conduit. It wasn't
very precise at locating the conduit, but good enough to provide
clearance for a backhoe trencher.
 
Good luck.
 
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
Bob F <bobnospam@gmail.com>: Aug 28 08:15PM -0700

On 8/26/2021 11:30 AM, three_jeeps wrote:
> I did make a 'break out box' for the rj45 and rj11 sockets where needed.
> Thanks
> j
 
https://www.harborfreight.com/cable-tracker-94181.html
"Peter W." <peterwieck33@gmail.com>: Aug 29 04:31AM -0700

> https://www.harborfreight.com/cable-tracker-94181.html
 
Designed for use with telephone lines, alarm cables, computer cables, intercom lines, speaker wires, and thermostat wiring
 
Do you NOT read for content, or is it that you cannot read at all?
 
Apples: Low-voltage signal wire inside a structure - where only one end may be identified - and getting to the other is the exercise, and possibly identifying individual conductors within a cable.
Oranges: Line-voltage wiring buried underground - where both ends are identified, but the pathway is not.
 
Peter WIeck
Melrose Park, PA
"Dušan Köszeghy" <dusan.koszeghy@gmail.com>: Aug 28 05:17PM -0700

Dňa piatok 27. augusta 2021 o 18:56:25 UTC+2 používateľ Peter W. napísal:
 
> Generalized warning: OEM belts for obsolete equipment are generally a bad choice, as those parts in may cases are as old and have sat around just as long as the parts inside the unit. I have had 100% success ordering generic O-rings from McMaster-Carr to the correct size, configuration and diameter (and at a fraction of the OEM cost). I have a choice of materials, O, [], D, 0 or otherwise, even toothed, and they are fresh.
> Peter Wieck
> Melrose Park, PA
 
And? Got mine problem now, so what is the big deal?
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