The saga of my first oscilloscope - Page 1
Forum section: electronics / testgear

author: elex_enthusiast
author_rank: Regular Contributor
timestamp: August 21, 2015, 05:21:07 pm
content: Hi there,Just want to share the joy of having my first oscilloscope. It's been quite long since I became a member here but this is the first time I started my own thread. I am an electronics hobbyist/repairer of consumer electronics for more than a year since I graduated. I am not a full time repairman (as I only do repairs to earn extra income, and I work as a social worker) and don't have much experience on repairing electronics. So to speak, I was learning things the hard way with only a few multimeters to depend on. Being poor and "equipment starved", I was having a hard time saving a few penny to buy an oscilloscope (without any idea where to outsource for a good one, and ebay is not an option since I am incapable of paying stuff online), I made a friend unexpectedly with a guy here a.k.a Terrahertz and offered his oscilloscope for free as he wants to get rid of stuff laying around his workshop. I didn't expect it, and never asked for it. But heh I couldn't resist his offer as much as I badly need it (it's a 20MHz BK precision 2120, and good enough for a giveaway scope). It's dead but he managed to fix it and send it to me with some other stuff. Here's how its story begun:http://everist.org/NobLog/20150731_simple_scope_funny_fault.htmAfter a few days of waiting with excitement, it finally arrived from Oz.Everything was doing fine until I noticed that the channel one (above ) overshoots and the channel two (below) undershoots a bit. And it made me think that maybe the internal adjustments was changed due to handling while on its way to Philippines, but he actually didn't noticed it before sendingI was worried and confused how to make it right myself without any available gears to use for calibration. Fortunately he also provided the instruction and service manual for it. So I scanned it hoping that I might find relevant information on how to correct the thing, then I figured out that the input attenuation needs to be adjusted using a function gen (to generate a 1KHz 20v p-p squarewave) but I have none. So i decided to do it and try my luck as I was only depending on the scope's calibrator for a reference (the out ouput frequency is close to 1KHZ only at 200mv). Luckily I was able to correct it by adjusting the trimpot VR307 and VR308 for both channels.So far everything's fine now and I enjoy playing with it. Love to see actual waveforms than just numbers. And I would like to thanks "Terrahertz" for that.So what was the story of your "first oscilloscope"? Please let us know.Best regards,elex-enthusiastAhhh!! bad english..

author: eas
author_rank: Frequent Contributor
timestamp: August 21, 2015, 06:02:00 pm
content: Sweet, you got a new tool, and the satisfaction of fixing it!And good on Terrahertz!

author: Len
author_rank: Frequent Contributor
timestamp: August 21, 2015, 06:08:42 pm
content: Quote from: eas on August 21, 2015, 06:02:00 pmAnd a child thrown in for no extra cost. What a deal!

author: xrunner
author_rank: Super Contributor
timestamp: August 21, 2015, 06:31:05 pm
content: Good deal enjoy!

author: elex_enthusiast
author_rank: Regular Contributor
timestamp: August 22, 2015, 02:35:35 pm
content: Quote from: Len on August 21, 2015, 06:08:42 pmOh! That was my son. Just got lucky to know someone with good heart to donate his scope instead of dumping it like anyone else did for such an old scope.. Old but still useful for someone like me who can hardly (and hopeless) afford to buy fancy ones.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: August 22, 2015, 04:35:31 pm
content: Don't worry about the age of that scope. When you have exhausted it's capabilities you will know a tremendous amount about electronics. With patience an a small amount of auxiliary equipment (Like the sound card in a computer), you can do quite sophisticated things like transfer functions and impulse responses.

author: jimon
author_rank: Regular Contributor
timestamp: August 22, 2015, 08:27:08 pm
content: Quote from: elex_enthusiast on August 21, 2015, 05:21:07 pmTo me it looks like slightly off compensation on probes themselves and not oscilloscope settings, but could be wrong on this one

author: JoeB83
author_rank: Regular Contributor
timestamp: August 22, 2015, 08:56:22 pm
content: Quote from: jimon on August 22, 2015, 08:27:08 pmI agree. Check the probe compensation.

author: elex_enthusiast
author_rank: Regular Contributor
timestamp: August 22, 2015, 10:55:02 pm
content: Quote from: JoeB83 on August 22, 2015, 08:56:22 pmI already adjusted the probes' compensation but it has nothing to do with the overshooting of each channels. Still a lot to learn with the scope.