oscilloscope question

[Dave]

I'd like to know what the minimum useful bandwidth is for an oscilloscope to
be used for general TV and audio equipment troubleshooting and repair. I've
stumbled across a 20MHz dual-trace scope at a second-hand store, it appears
to work and they only want $50 for it. The brand is "Leader" which I'm not
familiar with. Comments?

 

[Tim]

In article <jQH_h.10486$KN6.6932@edtnps89>, dspear99ca@yahoo.delete.com
says...

I'd like to know what the minimum useful bandwidth is for an oscilloscope to
be used for general TV and audio equipment troubleshooting and repair. I've
stumbled across a 20MHz dual-trace scope at a second-hand store, it appears
to work and they only want $50 for it. The brand is "Leader" which I'm not
familiar with. Comments?



Hmmm, I recall that Leader had a fairly good name in the past. And the

company I worked for bought me a 20Mhz dual trace model to do service
work on video equipment. Of course this particular unit maybe modified
or damaged in some way, but I would likely buy it if I knew it hadn't
been abused.

- Tim -

 

[ian field]

"Dave" <dspear99ca@yahoo.delete.com> wrote in message
news:jQH_h.10486$KN6.6932@edtnps89...

I'd like to know what the minimum useful bandwidth is for an oscilloscope
to be used for general TV and audio equipment troubleshooting and repair.
I've stumbled across a 20MHz dual-trace scope at a second-hand store, it
appears to work and they only want $50 for it. The brand is "Leader"
which I'm not familiar with. Comments?

About 10 to 20Mhz is adequate for most CRT TV diagnosis, in my experience -
the more experience I gained at servicing, the less I needed a scope to
diagnose most day to day faults. IMO it might be better to get by as cheap
as possible until you assess the requirements for servicing flat panel TVs,
there might be other instruments that prove more useful than a CRO.

 

[N Cook]

Dave <dspear99ca@yahoo.delete.com> wrote in message
news:jQH_h.10486$KN6.6932@edtnps89...

I'd like to know what the minimum useful bandwidth is for an oscilloscope
to
be used for general TV and audio equipment troubleshooting and repair.
I've
stumbled across a 20MHz dual-trace scope at a second-hand store, it
appears
to work and they only want $50 for it. The brand is "Leader" which I'm
not
familiar with. Comments?

An isolation transformer may well cost the same again.
For TV work and isolation transformer is first priority and then a 'scope.
Somewhere in the list comes an ELCB/RCCD/GFCI
Then a variac for diagnosing crowbar problems etc


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[Dave]

"N Cook" <diverse8@gazeta.pl> wrote in message
news:f1fn2n$343$1@inews.gazeta.pl...

An isolation transformer may well cost the same again.
For TV work and isolation transformer is first priority and then a 'scope.
Somewhere in the list comes an ELCB/RCCD/GFCI
Then a variac for diagnosing crowbar problems etc

I've already got an isolation transformer and GFCI. What are ELCB and RCCD?

Dave

 

[Dave]

"Dave" <dspear99ca@yahoo.delete.com> wrote in message
news:2fJ_h.10773$KN6.6271@edtnps89...

I've already got an isolation transformer and GFCI. What are ELCB and
RCCD?

Sorry, two seconds on my part answered my own question. Hate it when people

post lazy questions to newsgroups.

 

On 4 May, 15:56, "Dave" <dspear9...@yahoo.delete.com> wrote:

I'd like to know what the minimum useful bandwidth is for an oscilloscope to
be used for general TV and audio equipment troubleshooting and repair. I've
stumbled across a 20MHz dual-trace scope at a second-hand store, it appears
to work and they only want $50 for it. The brand is "Leader" which I'm not
familiar with. Comments?

20MHz is more than enough.


NT

 

[Charles]

"Dave" <dspear99ca@yahoo.delete.com> wrote in message
news:jQH_h.10486$KN6.6932@edtnps89...

I'd like to know what the minimum useful bandwidth is for an oscilloscope
to be used for general TV and audio equipment troubleshooting and repair.
I've stumbled across a 20MHz dual-trace scope at a second-hand store, it
appears to work and they only want $50 for it. The brand is "Leader"
which I'm not familiar with. Comments?

Offer them $35. Leader scopes are decent and the BW is fine for your use.

 

[Heinz Schmitz]

Charles wrote:

Offer them $35. Leader scopes are decent and the BW is fine for your use.

And have them add the schematics so you can repair it yourself.
Check wether Leader used any proprietary semiconductors and
wether the CRT has burnt in trace.
You may well want to check eBay for comparable offers, too.

Regards
H.

 

[James Sweet]

"Heinz Schmitz" <HeinzSchmitz@gmx.net> wrote in message
news:nbko33lmkfm27f4hr5bl7k6vuubrj8u15c@4ax.com...

Charles wrote:

Offer them $35. Leader scopes are decent and the BW is fine for your use.

And have them add the schematics so you can repair it yourself.
Check wether Leader used any proprietary semiconductors and
wether the CRT has burnt in trace.
You may well want to check eBay for comparable offers, too.

More important than burn is to make sure the CRT can still produce a sharp
trace. It should only take a few minutes to plug it in and verify basic
functionality though. For 50 bucks it's hard to go wrong on a working 20 MHz
scope, that's more than enough scope for the average hobbyist.

 

[Franc Zabkar]

On Fri, 04 May 2007 14:56:15 GMT, "Dave" <dspear99ca@yahoo.delete.com>
put finger to keyboard and composed:

I'd like to know what the minimum useful bandwidth is for an oscilloscope to
be used for general TV and audio equipment troubleshooting and repair. I've
stumbled across a 20MHz dual-trace scope at a second-hand store, it appears
to work and they only want $50 for it. The brand is "Leader" which I'm not
familiar with. Comments?

I have a Leader LBO-514 10MHz scope. It seems to be adequate for most
jobs. I had to fix about 50 dry joints, though. If yours is anything
like mine, you will need to redo all the interconnects between the top
and bottom layers of each PCB.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[Lionel]

On Fri, 04 May 2007 16:33:02 GMT, "Dave" <dspear99ca@yahoo.delete.com>
wrote:

"N Cook" <diverse8@gazeta.pl> wrote in message
news:f1fn2n$343$1@inews.gazeta.pl...
An isolation transformer may well cost the same again.
For TV work and isolation transformer is first priority and then a 'scope.
Somewhere in the list comes an ELCB/RCCD/GFCI
Then a variac for diagnosing crowbar problems etc


I've already got an isolation transformer and GFCI. What are ELCB and RCCD?

Other names for GFCI. They're called all sorts of different names
around the world.

--
W "Some people are alive only because it is illegal to kill them."
. | ,. w ,
\|/ \|/ Perna condita delenda est
---^----^---------------------------------------------------------------

 

[Dave]

"Franc Zabkar" <fzabkar@iinternode.on.net> wrote in message
news:3sbo331omm1dinklpun6ud94j8sr9obe17@4ax.com...

On Fri, 04 May 2007 14:56:15 GMT, "Dave" <dspear99ca@yahoo.delete.com
put finger to keyboard and composed:


I have a Leader LBO-514 10MHz scope. It seems to be adequate for most
jobs. I had to fix about 50 dry joints, though. If yours is anything
like mine, you will need to redo all the interconnects between the top
and bottom layers of each PCB.

Yeah, another one of those unfortunate examples of the old axiom "there
ain't no such thing as a free lunch".

 

[Dave]

"Dave" <dspear99ca@yahoo.delete.com> wrote in message
news:jQH_h.10486$KN6.6932@edtnps89...

I'd like to know what the minimum useful bandwidth is for an oscilloscope
to be used for general TV and audio equipment troubleshooting and repair.
I've stumbled across a 20MHz dual-trace scope at a second-hand store, it
appears to work and they only want $50 for it. The brand is "Leader"
which I'm not familiar with. Comments?

When the scope is powered up, it has a white line which starts to cross the

screen from left to right. The line gets about halfway across, then
disappears and doesn't come back.

Does this mean the scope is disfunctional? I thought it should have a
steady horizontal line when it's turned on with no inputs.

 

[ian field]

"Dave" <dspear99ca@yahoo.delete.com> wrote in message
news:Jwo0i.39373$KN6.7185@edtnps89...

"Dave" <dspear99ca@yahoo.delete.com> wrote in message
news:jQH_h.10486$KN6.6932@edtnps89...
I'd like to know what the minimum useful bandwidth is for an oscilloscope
to be used for general TV and audio equipment troubleshooting and repair.
I've stumbled across a 20MHz dual-trace scope at a second-hand store, it
appears to work and they only want $50 for it. The brand is "Leader"
which I'm not familiar with. Comments?

When the scope is powered up, it has a white line which starts to cross
the screen from left to right. The line gets about halfway across, then
disappears and doesn't come back.

The trace sweeps from left to right and should be blanked on the return
stroke.

Does this mean the scope is disfunctional? I thought it should have a
steady horizontal line when it's turned on with no inputs.

If the trace only goes half way across the screen try centering it with the
horizontal shift control.

 

[bz]

"Dave" <dspear99ca@yahoo.delete.com> wrote in
news:Jwo0i.39373$KN6.7185@edtnps89:

"Dave" <dspear99ca@yahoo.delete.com> wrote in message
news:jQH_h.10486$KN6.6932@edtnps89...
I'd like to know what the minimum useful bandwidth is for an
oscilloscope to be used for general TV and audio equipment
troubleshooting and repair. I've stumbled across a 20MHz dual-trace
scope at a second-hand store, it appears to work and they only want $50
for it. The brand is "Leader" which I'm not familiar with. Comments?

When the scope is powered up, it has a white line which starts to cross
the screen from left to right. The line gets about halfway across, then
disappears and doesn't come back.

Does this mean the scope is disfunctional? I thought it should have a
steady horizontal line when it's turned on with no inputs.

That depends on how the triggering is set.

You could be set for single sweep. It almost sounds like that and a slow
sweep at that.

You could be set for triggered sweep and not have a trigger.

You need to play with a properly working scope for a while to learn how to
use it and then you can test a questionable scope.






--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap

 

[Homer J Simpson]

"Dave" <dspear99ca@yahoo.delete.com> wrote in message
news:Jwo0i.39373$KN6.7185@edtnps89...

When the scope is powered up, it has a white line which starts to cross
the screen from left to right. The line gets about halfway across, then
disappears and doesn't come back.

The centering is set to the left.

Set all knobs to mid position and try again. Set Sync to Auto.