Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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  #1   Report Post  
Jeff
 
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Default Scope advice needed

I am a hobbiest and have wanted a scope to for a long time. I ran across a
used Tektronix 2236 with probes today locally for $200.00 so I picked it
up. I have 7 days to take it back if I need to.

I have done the initial setup and probe calibration and so far it seems to
be working as the manual says it should. The CRT looks good, it's crisp
and bright.

I don't know how to use a scope yet and I can tell it will take some time
to learn. I mainly dabble with older vcr's and some other consumer A/V
equipment.

Did I do alright with this one? Are there any checks I can make to ensure
it's alright while I have time to return it if I need to? From what I read
on the internet this model could be 20 years old, how concerned should I be
about that? I really haven't wanted to buy one from eBay and I don't see
used ones come up locally very often especially at that price.

Thanks in advance for any advice,
Jeff

  #2   Report Post  
Jim Yanik
 
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Default Scope advice needed

Jeff wrote in
:

I am a hobbiest and have wanted a scope to for a long time. I ran
across a used Tektronix 2236 with probes today locally for $200.00 so
I picked it up. I have 7 days to take it back if I need to.

I have done the initial setup and probe calibration and so far it
seems to be working as the manual says it should. The CRT looks good,
it's crisp and bright.

I don't know how to use a scope yet and I can tell it will take some
time to learn. I mainly dabble with older vcr's and some other
consumer A/V equipment.

Did I do alright with this one? Are there any checks I can make to
ensure it's alright while I have time to return it if I need to? From
what I read on the internet this model could be 20 years old, how
concerned should I be about that? I really haven't wanted to buy one
from eBay and I don't see used ones come up locally very often
especially at that price.

Thanks in advance for any advice,
Jeff



IMO,2236 is a good scope.
I worked for TEK for 21.5 years as a repair/cal tech in the Indy and
Orlando Service centers.

You can get an approximate age of the scope if you look inside at the date
codes on the CRT and inverter transformer,and other parts,format is
yr/wk,8344 would be 1984,week 44.

--
Jim Yanik,NRA member
jyanik-at-kua.net
  #3   Report Post  
Sofie
 
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Default Scope advice needed

Jeff:
It sounds like that you have the original Tektronix manual for your
scope..... if so, at the front of the manual is an operation section that
takes you step by step through all the functions and features of the
scope..... and you will operate just about every switch and knob using the
scope's calibrator signal and your probes. It is a good learning tool for
you to get to know how to use an oscilloscope, especially the one you have.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
---------------------------------

"Jeff" wrote in message
...
I am a hobbiest and have wanted a scope to for a long time. I ran across

a
used Tektronix 2236 with probes today locally for $200.00 so I picked it
up. I have 7 days to take it back if I need to.

I have done the initial setup and probe calibration and so far it seems to
be working as the manual says it should. The CRT looks good, it's crisp
and bright.

I don't know how to use a scope yet and I can tell it will take some time
to learn. I mainly dabble with older vcr's and some other consumer A/V
equipment.

Did I do alright with this one? Are there any checks I can make to ensure
it's alright while I have time to return it if I need to? From what I

read
on the internet this model could be 20 years old, how concerned should I

be
about that? I really haven't wanted to buy one from eBay and I don't see
used ones come up locally very often especially at that price.

Thanks in advance for any advice,
Jeff



  #4   Report Post  
Dana
 
Posts: n/a
Default Scope advice needed

"Jeff" wrote in message
...
I am a hobbiest and have wanted a scope to for a long time. I ran across

a
used Tektronix 2236 with probes today locally for $200.00 so I picked it
up. I have 7 days to take it back if I need to.

I have done the initial setup and probe calibration and so far it seems to
be working as the manual says it should. The CRT looks good, it's crisp
and bright.

I don't know how to use a scope yet and I can tell it will take some time
to learn. I mainly dabble with older vcr's and some other consumer A/V
equipment.

Did I do alright with this one?


For $200 you sure did. Good scope
Will be helpful when making timing measurements

Are there any checks I can make to ensure
it's alright while I have time to return it if I need to? From what I

read
on the internet this model could be 20 years old, how concerned should I

be
about that? I really haven't wanted to buy one from eBay and I don't see
used ones come up locally very often especially at that price.

Thanks in advance for any advice,
Jeff



  #5   Report Post  
Mark
 
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Default Scope advice needed

Jeff:

I think you will be happy with this scope. They seem to be going for around
$300 or more on eBay, so you also got a good deal.

This series of scopes is among the last "repairable" analog scope models
made by Tektronix. Later models used more custom ICs and microprocessors,
and are more difficult to repair by the average (non-Tektronix) technician.

In case you ever do need to work on your scope, this site
http://www.reprise.com/host/tektronix/home/default.asp is a good source of
information.

Mark

"Jeff" wrote in message
...
I am a hobbiest and have wanted a scope to for a long time. I ran across

a
used Tektronix 2236 with probes today locally for $200.00 so I picked it
up. I have 7 days to take it back if I need to.

I have done the initial setup and probe calibration and so far it seems to
be working as the manual says it should. The CRT looks good, it's crisp
and bright.

I don't know how to use a scope yet and I can tell it will take some time
to learn. I mainly dabble with older vcr's and some other consumer A/V
equipment.

Did I do alright with this one? Are there any checks I can make to ensure
it's alright while I have time to return it if I need to? From what I

read
on the internet this model could be 20 years old, how concerned should I

be
about that? I really haven't wanted to buy one from eBay and I don't see
used ones come up locally very often especially at that price.

Thanks in advance for any advice,
Jeff





  #6   Report Post  
Jeff
 
Posts: n/a
Default Scope advice needed

Thank you so much for the feedback. So far it's been lots of fun and I've only
had it for a day. I have been able to duplicate all the patterns and tests in
the manual so far, but I am moving slowly. I was afraid that it would be so
complicated I wouldn't even be able to test it within a week.

After years of playing around with electronics and only my Fluke 87 the best
analogy I can think of is "I was blind and soon I will be able to see" :-).
Seriously though I can see several months or more of working with it before I
am comfortable.

Thanks again you are a great group.

Jeff




I think you will be happy with this scope. They seem to be going for around
$300 or more on eBay, so you also got a good deal.



  #7   Report Post  
Thomas P. Gootee
 
Posts: n/a
Default Scope advice needed

Jeff wrote in message ...
I am a hobbiest and have wanted a scope to for a long time. I ran across a
used Tektronix 2236 with probes today locally for $200.00 so I picked it
up. I have 7 days to take it back if I need to.

I have done the initial setup and probe calibration and so far it seems to
be working as the manual says it should. The CRT looks good, it's crisp
and bright.

I don't know how to use a scope yet and I can tell it will take some time
to learn. I mainly dabble with older vcr's and some other consumer A/V
equipment.

Did I do alright with this one? Are there any checks I can make to ensure
it's alright while I have time to return it if I need to? From what I read
on the internet this model could be 20 years old, how concerned should I be
about that? I really haven't wanted to buy one from eBay and I don't see
used ones come up locally very often especially at that price.

Thanks in advance for any advice,
Jeff


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

Jeff,

You did GREAT. Congratulations! You are now the proud owner of a
Tektronix oscilloscope.

The 2236 is a very nice portable 100 MHz scope, with a well-made and
rugged feel to it. It's a joy to use and I think you'll love owning
it.

I sold one a few years back that got snapped up pretty quickly for
$399, without a manual or probes. They're less than that, now. But you
still got a good deal.

About the only common failure-point that I can recall hearing about in
the 2236 is the cable that connects the LCD, in the hinged cover, to
the scope. So you might want to be a little careful with that. I don't
know how difficult it would be to try to replace or repair it. But, as
Jim Yanik said, that scope *IS* user-repairable. So if anything ever
goes wrong with it, just open it up and take a look. And you'd
probably be able to get lots of help, in this newsgroup and in the
TekScopes group at http://www.yahoogroups.com .

There's also a pretty good tutorial for general scope usage, called
"The XYZs of Oscilloscopes", on the Tektronix website, at

http://www.tek.com

Or, you might be able to find it more easily from my links page, at

http://www.fullnet.com/u/tomg/links.htm ,

which also has lots of other interesting Tektronix-related links.

You might also want to try doing a general search of the newsgroups
*archive*, at

http://groups.google.com ,

for something like "tek OR tektronix 2236" (without the quotes), just
to see what all has been asked about and answered, regarding your
model. You could also add " -FS -FA -sale" to that search syntax, to
filter out the "for sale" ads. (And note that the "OR", above, must be
in caps.)

Enjoy your scope!

Regards,

Tom Gootee

http://www.fullnet.com/u/tomg (Lots of good used Tek and other test
equipment)

-------------------
  #8   Report Post  
Tim Kettring
 
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Default Scope advice needed

Jeff , make sure the trigger works !!!

If it can lock in a reoccuring wave form like a square wave , or better yet
a composite video signal ( say from a VCR output ) then it is probably OK .

The trigger function is usually the first thing to fail , in my 30 years
experience .

tim


"Jeff" wrote in message
...
Thank you so much for the feedback. So far it's been lots of fun and I've

only
had it for a day. I have been able to duplicate all the patterns and tests

in
the manual so far, but I am moving slowly. I was afraid that it would be

so
complicated I wouldn't even be able to test it within a week.

After years of playing around with electronics and only my Fluke 87 the

best
analogy I can think of is "I was blind and soon I will be able to see"

:-).
Seriously though I can see several months or more of working with it

before I
am comfortable.

Thanks again you are a great group.

Jeff




I think you will be happy with this scope. They seem to be going for

around
$300 or more on eBay, so you also got a good deal.





  #9   Report Post  
 
Posts: n/a
Default Scope advice needed



I don't know how to use a scope yet and I can tell it will take some time
to learn. I mainly dabble with older vcr's and some other consumer A/V
equipment.


I was a bench tech at one time, I think sometime in the late 1800's
:-) and I used scopes a lot. Maybe some of the current techs could
fill you in better on this, but you need to be aware of the hazards
involved in using a scope in a hot chassis. In older television sets,
for example, one side of the 120 volt input went straight to the TV
chassis. There is no power transformer in this kind of equipment. If
the AC cord plug gets reversed in the receptacle, you have 120 volts
on the chassis. If you get between that chassis and ground...ZOT!!! If
your scope probe connected to that 120 volts....ZOT!!

With much of the modern test equipment, which is handheld, battery
operated, you don't have to worry about this as much. With an AC
operated scope you do.

ALWAYS use the third prong on the AC plug if your scope has one. It's
a bonding ground and connects your scope chassis to ground. And be
sure to plug it into a receptacle with a good bonding ground. Don't
use those 3 prong to 2 prong cheaters. On a single phase circuit (120
volt), one power conductor is at 120 volts and the other is at ground
potential. Most modern receptacles are keyed so you can only get the
plug in one way. This is a basic safety step to TRY to ensure the hot
goes to hot and the neutral to ground. The third prong almost
certainly ensures this. I say almost, because your receptacle may be
wired wrong. If they become reversed, you can have a hazardous
situation.

Also, as my scope manual suggests, use an isolation transformer (if
you can afford one) when working in a hot chassis situation. This
prevents current flow directly between equipment, and maybe you and
ground. The manual also suggest connecting the scope chassis directly
to the equipment under test (bonding) with a separate conductor. Most
techs probably omit this step as being overkill. But if you're working
on a piece of equipment that uses a 2 prong AC power connection, and
you connect your probe in certain ways, you can get a ground fault
current running through your probe that might damage it, the scope
input circuitry or the equipment under test. .

Most entertainment equipment, like VCR's, don't have a bonding
conductor (3 prong plug). With semiconductor circuits in most
equipment, the DC voltages are under 60 volts and not a hazard to you.
But, you can still blow things if the scope is connected wrong. In TV
sets, it's a different story, even with solid state devices. The video
output transistors can be running well above 100 volts.

I suggest you don't work on television sets with a scope till you
clearly understand the dangers. The high voltage circuits in colour
TV's are regulated to 1 amp. At those voltages, that is lethal. Also,
the horizontal output stages have transient voltages that are not
apparent. On the older tube sets, you never used a scope or a meter
directly on the plate of the horizontal output stage. If you didn't
know that, you could be in for a dull surprise.

I'm talking worst case and I've never had any of that happen. Then
again, I was trained by responsible techs. It's good to be aware of
it, however. If the equipment you are testing only has one power
supply ground (common), you connect your scope probe ground to it. If
there are separate power supply grounds, you have to be more careful.
Always identify the ground of the supply you are measuring relative
to. Remember that you're inserting a grounded lead into the circuit.
If your connection point is above chassis ground, and the chassis is
bonded to ground, and you ground it, you'll get an unpleasant
reaction. It's not the same with DVM's, where the ground lead is not
grounded.

There is another basic rule with oscilliscopes. NEVER leave the beam
on the screen as a dot or a small area. This would only happen when
the time base is off and there is no sweep. You need to be very aware
of it however. If the beam becomes focused in a small area...like a
dot...for any amount of time, it will burn the phosphors on the
screen. You'll end up with an area 1/4 inch in diameter, burned and
useless. If you find yourself in an X-Y input situation, immediately
reduce the brilliance of the beam so the dot is barely visible. It's a
good idea to keep the brilliance as low as practicable anyway. When
you're not using the scope for any amount of time, turn it down.

Speaking of which....it's always a good idea with any test equipment
to start on a high scale and work down. I never left my scopes on a
millivolt scale when not in use. I also left the probe on 10x.

Finally, the probe usually has a direct and a 10x setting. I always
left mine on 10X since it reduces the input signal 10 times. If I
needed direct, I'd just switch over. Some probes need to be
calibrated. There's a small capacitor built in that can be adjusted.

Tektronics has always had a good name. The price you paid seems like a
decent deal. The problem with older equipment is that the
electrolytics in the power supply tend to dry out eventually. Also,
other capacitors may become leaky.

  #10   Report Post  
James Sweet
 
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Default Scope advice needed



Also, as my scope manual suggests, use an isolation transformer (if
you can afford one) when working in a hot chassis situation. This
prevents current flow directly between equipment, and maybe you and
ground. The manual also suggest connecting the scope chassis directly
to the equipment under test (bonding) with a separate conductor.



This isn't a matter of "if you can afford one", when working on hot chassis
equipment an isolation transformer is *absolutely* nessesary, if you can't
afford to spend $50 or do some scrounging and cobble one together for free,
you shouldn't be poking around in the equipment under test in the first
place. If you try working on something without isolation you *will* fry your
scope sooner or later if not yourself in the process.




  #11   Report Post  
 
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Default Scope advice needed

I agree. Problem is, many shops wont buy you one. If you buy your own,
you can bet it will go missing. Even with an isolation transformer,
you really need one for each piece of equipment that is connected to
an AC source. It's not only the potential between pieces of equipment
that is the danger, it's the potential between equipment and ground.
The electrical codes in North America are set up to limit voltages to
ground to 150 volts or less. The 150 volts is not as likely to kill
you, although it can quite easily.

If you have a hot chassis plugged into an isolation transformer,
you've disconnected the chassis from building ground, which is earth
ground. The secondary of the transformer is it's own system, and the
120 volts across it are not related to building ground. You wont get
a shock from touching the chassis if you're standing in a puddle, or
touching a grounded piece of equipment. The 120 volts will be between
the chassis and the other end of the transformer secondary. There's no
need for current to travel from the chassis to earth ground. It has no
circuit there. Unless, of course, the isolation transformer develops a
short between primary and secondary, :-(

If you understand why a hot chassis is dangerous, you can prepare
yourself. I used to measure between each piece of equipment with a
meter to be sure I had no potential between them. I was also very
careful about where I placed my probe ground lead. Also, I tried to be
vigilant about the rule of keeping one hand in my pocket. I work as an
electrician now and I still obey that rule. If I have to get two hands
in th circuit while it's hot, I make sure one is well insulated, or
isolated with well-insulated tools.


This isn't a matter of "if you can afford one", when working on hot chassis
equipment an isolation transformer is *absolutely* nessesary, if you can't
afford to spend $50 or do some scrounging and cobble one together for free,
you shouldn't be poking around in the equipment under test in the first
place. If you try working on something without isolation you *will* fry your
scope sooner or later if not yourself in the process.


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