Used Oscilloscope for under 250$ - Page 1
Forum section: electronics / beginners

author: Shawnk
author_rank: Newbie
timestamp: December 11, 2017, 07:33:37 pm
content: Is there a good used model of Oscilloscope 2 to 4 channel that i could buy on ebay or something like that for under 250$. Im going to use it for home and car audio amplifier repair. I would prefer a benchtop model but I’m open to other suggestions.

author: Shawnk
author_rank: Newbie
timestamp: December 11, 2017, 11:47:41 pm
content: Thank you for the video. I have watched it. I have a snap-on 4 channel scop that i use at work but is not fast enough for my needs for amplifier repair. I am new to electronics repair (only the last 2 years). I would like to start getting more advanced and take it more seriously but i need a good Benchtop oscilloscope that will fill my needs. Like how many MHZ and the bit rate. Can i get a ok Digital one for that price or only analog. Is there any brands or models the work well and are user friendly. For the kinda of signals you see in a amplifier what should i get?

author: boffin
author_rank: Unknown
timestamp: December 11, 2017, 11:51:09 pm
content: Quote from: Shawnk on December 11, 2017, 11:47:41 pmIf you're doing audio amplifier repair, pretty much ANY scope will be sufficient, you only need perhaps 0.1MHz of bandwidth for audio

author: Shawnk
author_rank: Newbie
timestamp: December 12, 2017, 12:26:42 am
content: Ok thank you for the info. On my scope i was trying to watch the Tl494 driver for the switching power supply and i could only see a straight line because 1ms time is my fastest resolution.

author: rstofer
author_rank: Super Contributor
timestamp: December 12, 2017, 02:02:08 am
content: Quote from: Shawnk on December 12, 2017, 12:26:42 amThat's a different story! It's not audio at all and the frequency may be much higher - the datasheet recommends 300 kHz. To see that adequately, you probably need 10 MHz of scope bandwidth. That's not much at all! Almost anything you find will be 50 MHz and up.I would think you would be looking for something, analog or digital, with about 100 MHz of bandwidth. This is a hedge in case you get interested in microprocessor projects.

author: David Hess
author_rank: Super Contributor
timestamp: December 12, 2017, 03:04:30 am
content: Quote from: boffin on December 11, 2017, 11:51:09 pmHigher bandwidth is valuable for detecting higher frequency spurious oscillations in audio circuits.

author: rstofer
author_rank: Super Contributor
timestamp: December 12, 2017, 03:41:19 am
content: That Tek 2467 in the video still sells at a premium on eBay (like $700). I have the Tek 485 (also 350 MHz) that I bought for about $200 about 12 years ago. Today there is one for $325https://www.ebay.com/itm/Tektronix-485-350-Mhz-scope-I-use-it-to-500-Mhz-all-the-time/253118975022?hash=item3aef110c2e:g:GyQAAOSwxbtZo1MEAt that price, it would be a toss-up whether to buy the used Tek or a new Rigol DS1054Z. I have both and I'm not going to get rid of the 485 any time soon. The Rigol can be unlocked (easily) to provide 100 MHz of bandwidth and 4 channels plus protocol decoding, etc. Search the site...There is no comparison between an analog scope and a digital. The single shot capture alone gives the DSO the advantage. And for all of that, w2aew's videos (that I have seen) are done with analog scopes. There's not a darn thing wrong with using analog scopes. Just watch the videos!I'm not going to recommend buying a used scope - analog or digital. If it doesn't work, you might be stuck. Some scopes use custom components that are no longer available. I would just as soon have a warranty. That said, I did buy my 485 used and it has been outstanding. Caveat emptor...

author: David Hess
author_rank: Super Contributor
timestamp: December 12, 2017, 06:45:34 am
content: I only linked the video as an example of why an oscilloscope with greater than the minimum bandwidth for audio is desirable. The 2467 is special for reasons other than its bandwidth and not the oscilloscope I would recommend.There are lots of used analog oscilloscopes to be had for $250 or less and most suitable ones will be available for a lot less. The 50 MHz Tektronix 2225 shown in Dave's video is one of the better examples because of its low cost, 500uV/div sensitivity, and lower age but I would consider any similar oscilloscope. I've picked up Tektronix 2230s, 2232s, and 2236s for less than $150. The various 465 family oscilloscopes can also be had for that price or less but are more likely to have age related problems.The largest problem however with used analog oscilloscopes is finding one in good shape. Novice users have difficulty evaluating them and repairing or maintaining them.

author: Shawnk
author_rank: Newbie
timestamp: December 12, 2017, 07:12:12 pm
content: Thank you guys for your time. I think i have enough info to proceed. I would say im really in to car audio amplifiers and need something your looking atpower supply's. I think im going to buy a cheap 50$ Analog unit and save up for a few more months and try to get a decent new digtal one. I have one more question i hope someone could send be in the right direction or know somebody that can help me. I have a snubber Circuit on a car audio amplifier that keeps overheating the resistor that is placed in line between the two transformer secondary windings. It only heats up when the amplifier is under some load 20 amps or more. why does this typically happen. Why is the resistor being loaded. Is there a good source for understanding how the circuit works? And the resister is in spec and it gets up to 400f befor i shut it down.

author: David Hess
author_rank: Super Contributor
timestamp: December 12, 2017, 07:21:16 pm
content: Quote from: Shawnk on December 12, 2017, 07:12:12 pmHuh? Is this part of the power supply?

author: rstofer
author_rank: Super Contributor
timestamp: December 12, 2017, 07:28:55 pm
content: Quote from: David Hess on December 12, 2017, 06:45:34 amAs always, the video was excellent. I tend to see what equipment is being used in the various tutorials and then price it on eBay. No particular reason, just curiosity.QuoteThe problem is, those asking about 'first' scopes are in no position to evaluate the alternatives. I suppose it already exists but a list of desirable scopes, in some kind of ordering, would be handy. "Here's your shopping list, start at the top and work down.".When I was in college, the Tek 454 was fairly new and one of the other fellows worked for Burroughs and he had one. I decided that I wanted that form factor. It was 30+ years later before I bought the 485.QuoteAnd this is the reason I don't recommend buying used <anything> but especially complex test equipment. Yes, there are some bargains out there but there is also a lot of junk. Repairing scopes isn't something I would think a newcomer was up to although there are forums that can help.

author: james_s
author_rank: Super Contributor
timestamp: December 12, 2017, 08:02:54 pm
content: Used is always a gamble, but overall I've had excellent luck. There are plenty of less risky used options out there if one is willing to pay a premium, which should be possible within the $250 budget. There are reputable people who sell tested working/refurbished used gear, it costs more than as-is random used stuff but it's still often considerably cheaper than new.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 12, 2017, 11:50:12 pm
content: As always, I recommend having a look at Hamfests in your region.There are often ,but not always, secondhand Oscilloscopes for sale, often running on the sale table.All those I have seen at our local Hamfest have been well below the prices common on eBay.Some years back, I bought a Tek 7613 for $A135 at just such an event.Big & bulky?Yes, but extremely capable.

author: GreyWoolfe
author_rank: Unknown
timestamp: December 13, 2017, 12:16:09 am
content: Here is a GW-Instek GOS-6112 100 MHz scope for about $130 USD shipped. Don't know if this will help as you didn't set country.https://www.ebay.com/itm/GW-INSTEK-Oscilloscope-GOS-6112-2-Channel-100MHz/332433863943?epid=1901705456&hash=item4d669a3507:g:8vcAAOSwvR5Z-g~nThat will get you to your new DSO faster. If you do decide to buy, I can provide a digital copy of the manual. Actually, I should probably upload it to KO4BB.

author: Old Printer
author_rank: Frequent Contributor
timestamp: December 13, 2017, 01:12:29 am
content: After buying a noname clunker at a garage sale, I bought my Tek 2225 on eBay for $125 shipped. I picked it for a few reasons. Dave had made two indepth videos on it, so I learned a lot about it in a hurry. Both the factory operator and service manuals were easily available online, very important. Finialy, I bought it from a seller with good feedback, and though he had no particular scope experience, he did offer returns. It had a couple noisy pots on the front panel, but I got a very good replacement board for $45. It all worked out well but you do take a chance. With new Rigol 1054Zs going under $350 new, if you have a need for a working scope I think that is a very safe choice.

author: phil from seattle
author_rank: Super Contributor
timestamp: December 13, 2017, 01:32:39 am
content: If you buy used, look for a scope that has a good track record of being repairable. The Tek 2225 is a great example of that. I have had a 2225 for 15 or so years and last month it up and died. With the service manual, I was able to repair it - bad cap and 2 fried transistors. Total cost about about $8 including about 6 other caps I replaced just to be safe. In retrospect it was actually pretty easy because the service manual showed test points and expected voltages. That pointed to what I should check and quickly found the culprits. For any scope over 15 or so years old, expect the caps to start failing. So, it's really a matter of when, not if - especially in the cheaper brands that didn't use super high quality caps.

author: Shawnk
author_rank: Newbie
timestamp: December 13, 2017, 06:41:41 pm
content: Thank you for all your input. You have all been verry helpful. What do you think of these 2 options.1 Tektronix TDS420 Four Channel Digitizing Oscilloscope 150MHz for 200$ shipped2 rigol ds1052d for 200$ shipped.What do you think would be the best option and why.Obviously I completely understand that i’m taking a risk buying a used unit.

author: james_s
author_rank: Super Contributor
timestamp: December 13, 2017, 06:55:16 pm
content: I do like the TDS400 series scopes but it's important to remember that they're ~25 years old and are notorious for leaky SMT electrolytic capacitors all over the place so if you buy one of those make sure it has been re-capped unless you want a project.I have no direct experience with the Rigol but they are generally well liked as entry level DSOs.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 14, 2017, 01:41:24 am
content: Quote from: Shawnk on December 13, 2017, 06:41:41 pmI think you will be disappointed with the TDS 420 as a general purpose Oscilloscope, for the following reason.Early DSOs have very limited memory, so that when you use them at longish time/div settings, they have to reduce the sample rate to fit into this low memory.This is OK if you only look at sine waves, but things like looking at analog video signals at field rate are pretty much impossible.In many specialist applications this is not a big handicap, but as I said above, they are not good general purpose instruments.Modern DSOs , by & large, do not suffer from this problem.i do not have one, or, indeed, any DSO, but the DS 1052d is well regarded by many on this forum, so I would recommend it as the best choice.

author: Old Printer
author_rank: Frequent Contributor
timestamp: December 14, 2017, 02:58:53 am
content: Plus one on the 1052, but I have to think that soon they will be discontinued and discounted. Right now they are selling at the same price of a 1054z so I cannot think they are selling many. Something has to give. My 2 cents.

author: David Hess
author_rank: Super Contributor
timestamp: December 15, 2017, 02:46:04 am
content: I would rather have the TDS420 than a Rigol DS1052D but I would not recommend the TDS420 to a novice because of age related maintenance requirements. The TDS420 has peak detection and makes measurements on its acquisition record while the Rigol DS1052D lacks both of these things. The dual delayed timebase of the TDS420 largely makes up for its short record length although its record length is longer than "short".

author: jgalak
author_rank: Regular Contributor
timestamp: December 15, 2017, 02:41:25 pm
content: I was seriously considering a 2465B that I found at a good price, but after reading threads here about the need for recap, replacing the battery-protected RAM, and the other possibly overheating chip, I decided that this was too much work for a newbie like me.So I got the Rigol 1054z. For $350, it's pretty amazing, especially once it was "unlocked".

author: tszaboo
author_rank: Super Contributor
timestamp: December 15, 2017, 03:27:48 pm
content: Quote from: boffin on December 11, 2017, 11:51:09 pmClass D amplifier, I2S signals, SPDIF, IR remote, switching power supply, capacitive voltage doubler.Just to name half a dozen things that are in an audio amplifier and require a 10+ MHz scope.

author: Mr. Scram
author_rank: Super Contributor
timestamp: December 15, 2017, 03:30:38 pm
content: Quote from: jgalak on December 15, 2017, 02:41:25 pmCan't go wrong with the DS1054Z.

author: james_s
author_rank: Super Contributor
timestamp: December 15, 2017, 06:11:07 pm
content: Quote from: NANDBlog on December 15, 2017, 03:27:48 pmAside from the various little toy DSOs around you'd be hard pressed to even find a <10MHz scope made within the last 35 years so that's still not really an issue.

author: Shawnk
author_rank: Newbie
timestamp: December 16, 2017, 01:38:42 am
content: I ended up hopefully got a good geal on a tds 1002 76$ shipped. It passed the seld test but that back light is inoperative (should be a eazy fix). Should have it next friday. I only had a few minutes to bid on it so I just went for it. Hopefully I didn’t make a mistake. Has anyone ever used this model and where they happy with it.

author: Old Printer
author_rank: Frequent Contributor
timestamp: December 16, 2017, 04:14:23 am
content: Quote from: jgalak on December 15, 2017, 02:41:25 pmThe 2465B is an amazing machine, but has the potential to quickly become a money pit if you are not an experienced scope tech. I think you made a smart move.

author: Shawnk
author_rank: Newbie
timestamp: December 19, 2017, 02:04:31 am
content: The 1002 dose not come with any test leads. What set do i need to be able to test voltages up to 150v+ to 150-.Thanks shawn

author: tautech
author_rank: Super Contributor
timestamp: December 19, 2017, 02:59:50 am
content: Quote from: Shawnk on December 16, 2017, 01:38:42 amIf it's like one I was given with no backlight, very easy.The backlight HV will maybe have failed, it's derived from LV and via a free running RC push/pull bipolar pair on the primary. One I had the C measured just a few pFbut that's all it was. Dipped TH MLCC that IIRC was 470nF.Here in NZ there's dozens of them in Unitec labs.Quote from: Shawnk on December 19, 2017, 02:04:31 amGrab some new P6100 probes from eBay, easy to find them for less than $20/pair.

author: Muttley Snickers
author_rank: Unknown
timestamp: December 19, 2017, 03:02:57 am
content: It was a damn shame you had to spoil your seventeenth binary post, I saved it for posterity anyway.

author: tautech
author_rank: Super Contributor
timestamp: December 19, 2017, 03:13:59 am
content: Thanks Muttley ol' mate. I'm not sure if it's a great achievement or not.All I know is I've left one club of nutters and joined another of which it seems there's very few.Merry Christmas to you all and thanks for putting up with my ramblings.