OSCILLOSCOPE - Page 1
Forum section: electronics / beginners

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: November 26, 2012, 02:17:51 am
content: Is it worth picking up a used 20 mhz dual channel OSCILLOSCOPE anymoreThanksJay

author: IanB
author_rank: Super Contributor
timestamp: November 26, 2012, 02:32:20 am
content: Up to now, how many circuits have you built or tested that run at a frequency higher than 20 MHz?

author: Lightages
author_rank: Unknown
timestamp: November 26, 2012, 03:32:38 am
content: Analog scopes also tend to have less noise in the end display when it comes to lower end DSOs.

author: IanB
author_rank: Super Contributor
timestamp: November 26, 2012, 03:35:58 am
content: Quote from: Lightages on November 26, 2012, 03:32:38 amTrue dat. Instrument noise on the signal display is really annoying in digital scopes.

author: Tube_Dude
author_rank: Regular Contributor
timestamp: November 26, 2012, 04:01:32 am
content: Quote from: Lightages on November 26, 2012, 03:32:38 amYes! For Audio work analog scopes are simply the best.

author: Lightages
author_rank: Unknown
timestamp: November 26, 2012, 04:20:02 am
content: I wouldn't say they are the best at everything in audio. It is really nice to do a sweep with a DSO when analyzing filter responses and even speakers if you want. It is a little easier to see when you have display that stays still, cursors, etc. A simple DSO like the Rigol 1052 with its limited FFT can give you some idea what is going on too. So they compliment each other.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: November 26, 2012, 11:32:06 am
content: Quote from: IanB on November 26, 2012, 02:32:20 amWell that would be the question... The answer unfortunately would a whole lot of Zero circuits... I just had my eye on aB+K PRECISION 20 MHZ MODEL 2120 DUAL CHANNEL OSCILLOSCOPE and it has a focusing problem but I figured I would take a whack at fixing it .... I picked it up for $10 bucks with $17 bucks shipping and what wanted to know what you guys thought about it???http://www.ebay.com/itm/200846843254?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

author: Psi
author_rank: Super Contributor
timestamp: November 26, 2012, 11:57:20 am
content: Maybe an issue around the HV section, there's normally a focus pot which may have fried.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: November 26, 2012, 11:59:55 am
content: Quote from: Psi on November 26, 2012, 11:57:20 amDo you think it's worth fixing?

author: Psi
author_rank: Super Contributor
timestamp: November 26, 2012, 12:06:01 pm
content: Dunno, you might be able to just tweak the internal focus pot to get it back into range. But that's not fixing the problem.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: November 26, 2012, 01:26:50 pm
content: Well I keep reading around that a resistor is usual is the problem when this happens and the repair is pretty basic so I will have to see what happens ...

author: robrenz
author_rank: Super Contributor
timestamp: November 26, 2012, 01:42:02 pm
content: Be carefull inside the scope and especially that HV section. If you are not aware of all the precautions you should take, don't take the cover off until you have educated yourself and understand completely.Please take no offense if this does not apply to you.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: November 26, 2012, 02:37:01 pm
content: I recently picked up the same scope from an estate of ham gear .And it had the same problem , the large trace , used some deoxit on most of the pots & switches with no change .Emailed BK for a schematic and have not had the time to get back to that project .For as cheap as the price you paid you could get a 2-3 fold value , learn to fix , then use .If you have the space , you can not have enough test gear , always a good reason to get a bigger place

author: SeanB
author_rank: Super Contributor
timestamp: November 26, 2012, 04:04:10 pm
content: Most of the time that is caused by resistors/pots going high value to open circuit, or the ceramic cap going dead short. Less common is a PCB track going leaky, or the actual socket leaking.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: November 26, 2012, 04:08:04 pm
content: Quote from: KD0CAC John on November 26, 2012, 02:37:01 pmIs there any I could get the schematic from you?

author: robrenz
author_rank: Super Contributor
timestamp: November 26, 2012, 04:14:11 pm
content: google is a wonderfull thing.service manual with schematicsEdit: Operating manual is available on the same site.

author: Lightages
author_rank: Unknown
timestamp: November 26, 2012, 09:18:19 pm
content: Quote from: robrenz on November 26, 2012, 01:42:02 pmLet me second this. And also let me add KEEP ONE HAND BEHIND YOUR BACK when poking around inside the scope. A shock to the hand is much less dangerous then one across the chest (from one hand to the other).

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: November 27, 2012, 11:29:31 pm
content: I got my scope today and it's beautiful .... I turned it on and got a unfocus screen ,so I search through the schematic and did a little bit of testing and found out that's there a resistor measuring 15m Ohm'S when it should be 2m2 Ohm's...Quote from: robrenz on November 26, 2012, 04:14:11 pmOh I wanted to thank you very much for the download it help out alot .....By the way where can I get some good probes because the one I do have is shot to hell and needs to be replaced ...

author: T4P
author_rank: Super Contributor
timestamp: November 28, 2012, 05:48:36 am
content: What's your requirements? I thinkhttp://dx.com/p/utp04-100mhz-oscilloscope-scope-clip-probe-cables-120cm-pair-black-141266is a decent one for the priceorhttp://dx.com/p/p6100-x1-x10-100mhz-oscilloscope-probes-pair-120cm-length-114330if you really want to cheap out

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: November 29, 2012, 01:08:54 am
content: Quote from: T4P on November 28, 2012, 05:48:36 amI don't know ..... The last time I used a oscilloscope was when I was in school in 2000 and I totally forgot everything I ever learned...So now I watching alot of videos in order to learn how to use one once again... But I can't really find any info on picking probes , so all I am looking for would be probes that will work with my new oscilloscope .... I was checking out 100mhz ebay probes but not sure on the quality of them ..What would you guys use with my setup ??What about something like this?http://www.ebay.com/itm/190748117925?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

author: grenert
author_rank: Frequent Contributor
timestamp: November 29, 2012, 01:53:21 am
content: For 20 MHz use, almost anything will be fine. Those ones you've linked to on eBay should be OK. I've used the ubiquitous grey-colored ones from eBay, and they were fine for my undemanding use:http://www.ebay.com/itm/New-2-X-100-MHz-Oscilloscope-Scope-Clip-Probes-Probe-Kit-Fast-USA-Ship-/280776029358?pt=LH_DefaultDomain_0&hash=item415f8e34ae

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: December 02, 2012, 12:36:13 am
content: The other day I notice the trace rotation pot is broken and I got the info off the spec sheet and it calls for 5K ohm trimmer but I am not sure what I picked is right for this application and the numbers on the original pot looks like J0502.y or 70502.y which has giving me no info ...So what do you guys think???Replacement partManufacturer Part #:409VA502MManufacturer:TE ConnectivityDescription: Trimmer Resistors - Through Hole 5KOhm 1/2W Cermethttp://www.mouser.com/Search/ProductDetail.aspx?R=409VA502Mvirtualkey20420000virtualkey279-409VA502MAlso there are some polyester caps below with a cracked outer shell ,do you think these need to be replacedThere is a resistor that was getting hot on the board but I can't show you because I can't find my camera but anyways the area around it is alot darker color but resistor is within spec but should I replace it anyways???ThanksJAy