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 -
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.
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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
I've already got an isolation transformer and GFCI. What are ELCB and RCCD?
Dave
Sorry, two seconds on my part answered my own question. Hate it when people post lazy questions to newsgroups.
20MHz is more than enough.
NT
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.
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.
On Fri, 04 May 2007 14:56:15 GMT, "Dave" 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.
- Franc Zabkar
-- Please remove one 'i' from my address when replying by email.
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 ---^----^---------------------------------------------------------------
Yeah, another one of those unfortunate examples of the old axiom "there ain't no such thing as a free lunch".
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.
"Dave" wrote in news:Jwo0i.39373$KN6.7185@edtnps89:
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
The trace sweeps from left to right and should be blanked on the return stroke.
If the trace only goes half way across the screen try centering it with the horizontal shift control.
The centering is set to the left.
Set all knobs to mid position and try again. Set Sync to Auto.
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