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Old 21st May 2020, 11:59 pm   #1
hillmanie
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Default Oscilloscope question - not vintage

Need some advice re purchase of an oscilloscope,
1 New or secondhand
2 Re new, are USB oscilloscopes from Far East (not Dagenham) any good or a waste of money?
Many thanks
Tony T
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Old 22nd May 2020, 12:39 am   #2
Radio Wrangler
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Default Re: Oscilloscope question - not vintage

what do you want to do with it?

David
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Old 22nd May 2020, 5:47 am   #3
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Default Re: Oscilloscope question - not vintage

Never had a new scope but the problem with second hand one's is even if they work when you get them they eventually develop faults, fixing em is a pain, that and parts can be hard to source. It'd be nice to have a scope with a warranty.

If I had the money I'd buy a cheap scope like a Sigilent but then you have the issue of digital scopes are harder to drive. Tricky, lots of ins and outs as The Dude said.

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Old 22nd May 2020, 7:53 am   #4
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Default Re: Oscilloscope question - not vintage

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Originally Posted by Diabolical Artificer View Post
Never had a new scope but the problem with second hand one's is even if they work when you get them they eventually develop faults, fixing em is a pain, that and parts can be hard to source.
Andy.
I agree, my main scope is a 4 channel Tektronix but it has already cost me 100 in unobtanium custom chips, I managed to get used ones from Italy and Israel.
I keep a 50MHz dual channel Philips scope as spare for when it fails next time.

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Old 22nd May 2020, 8:27 am   #5
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Default Re: Oscilloscope question - not vintage

I should have added that when your scope does need repair you need a scope to fix it....................


Peter
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Old 22nd May 2020, 9:08 am   #6
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Default Re: Oscilloscope question - not vintage

You know where that leads. It leads down a very slippery slope indeed...
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Old 22nd May 2020, 10:51 am   #7
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Default Re: Oscilloscope question - not vintage

I went through all sorts of scopes and now use a Tek 7603/7623.

Why? Fast enough for what I want but have the sampling plug ins if needed. Yes, stuffed full of transistors and passives, but a replacement timebase or amplifier costs nothing if you need a spare. You can actually fix them, manuals available, no digital electronics, no software. I can read the dials on the switches, never need to transfer to a computer.

Did use the Tek 24x5 series for years but all failed, and they are pigs to fix, so traded backwards.

I also got caught by the input signal voltage limitations at high frequency, the capacitance across the attenuator makes it more easy to destroy the input digitiser than you would expect. With the 7603 it is just transistors, cheap and seems to be more robust.
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Old 22nd May 2020, 11:30 am   #8
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Default Re: Oscilloscope question - not vintage

Personally, I wouldn't go down the USB route. Possibly, if you dedicate a machine to the purpose of driving the USB scope, but even then the user interface for driving a scope is, frankly, rubbish unless it is touch screen.

Then you are left with old world analogue or modern digital.

If you go digital go for something new or very recent. The deep memory of modern digital scopes is a must have. Don't bother getting something with a few K's of memory - its too painful to use and is restrictive.

I tend to reach for an analogue scope first because I can make it do what I want it do do in a few seconds. Then I reach for the second one when something goes wrong

dc
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Old 22nd May 2020, 12:59 pm   #9
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Default Re: Oscilloscope question - not vintage

Most of the USB scopes i've seen are lacking in input attenuation and control. Triggering bandwidth is limited. There are a couple of exceptions, a colleague uses a floating differential one, but most are at the toy piano level when you probably could get best use out of a good old upright, but not need a Steinway.

Modern scopes are pretty much unfixable, certainly there is no support out of warranty and I think warranty means they give you a new one. Circuit diagrams are not allowed outside the manufacturers. They think they contain crown jewels secrets.

High performance analogue scopes are infested with custom ICs

There is a sort of golden age and golden performance area where fixability is best.

David
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Old 22nd May 2020, 1:25 pm   #10
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Default Re: Oscilloscope question - not vintage

Looking at his previous posts hillmanie does a lot of work with reel to reel tape recorders. So this might narrow things down a bit. Sadly I have no experience of working inside reel to reel recorders even though I do own an old/classic Elizabethan model. I assume there will be motors inside which might produce voltage transients that could harm a cheapo USB scope if used with a basic x1 probe. There could also be mains voltage and other high voltages inside the recorder.

With this in mind it might be worth buying a scope with a decent voltage rating. Some fairly modern (digital) lab scopes from HP/Agilent or other big brands are only rated to CAT 1 so there is a lot to be said for a traditional (used) analogue/CRT scope from the likes of Hameg/Philips/Iwatsu/Tektronix.

A good solid choice for this type of work would be something like a 20MHz Hameg analogue scope assuming you can find one that isn't very old.
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Old 22nd May 2020, 2:34 pm   #11
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Default Re: Oscilloscope question - not vintage

Thanks for input. In my case doing a lot means much fumbling and finding out, sometimes the hard way! I didn't realise the import of those voltages you cite which certainly hang around. I'm cagy about buying good quality brands secondhand as if anything went wrong with it I might as well bin it
Rgds
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Old 22nd May 2020, 2:51 pm   #12
hillmanie
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Default Re: Oscilloscope question - not vintage

Quote:
Originally Posted by Radio Wrangler View Post
what do you want to do with it?

David
Hi
Insofar as I can think ahead I only need it to measure and examine the waveform of AF voltages in intervalve amplifier circuits looking for distortion that finds its way to the loudspeaker, or for testing absence of tape head erasing voltages
You must know that I'm a first time user and must first find that 'Oscilloscopes for Dummies' book or its companion volume 'Idiots' Guide to Oscilloscopes'
TT
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Old 22nd May 2020, 5:37 pm   #13
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Default Re: Oscilloscope question - not vintage

HI!

If you reasonably sure you only need audio bandwidth, plus a bit extra to cope with tape recorder h.f. bias oscillators, then I can recommend you go for one of the Unilab student ones – these are made entirely of discrete components and standard wafer/rotary switches you can buy new or surplus, and I've a Unilab 032.602 you can have for the cost of postage!

I haven't any instructions or manual for it unfortunately as the schools keep all those (it's part of Teacher's Curriculum documents), however, I do have one other 031.602 that I wish to keep for the purpose of writing up a basic manual for it at a later date!

Chris Williams
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Old 22nd May 2020, 9:13 pm   #14
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Default Re: Oscilloscope question - not vintage

Oscilloscope question.
I would endorse the comments by David "RadioWrangler" ad Jeremy "G0HZU".
The scopes produced at the end of the analogue era can be excellent and reliable. Those aimed at the radio, TV and computer servicing market did not need design techniques which stretched components to the edge of what they were capable of, and so tended to be much more reliable and lasting.
End of valve era, 6-10Mhz, the Solartron CD1400 series, CD1014 and the MoD specified CT436 (fabulously reliable, and a very good manual). Telequipment D31-D43-D53 tended to give uncertain trigger unless the power rails are carefully set up.
Then transistors completely changed the market. 20Mhz to 50Mhz straightforward to provide, without using any integrated circuts, so even now easy to repair and components available. The Telequipment D75 -D83, DM63, Hameg 203 etc, Cossor CDU150, SE Labs SM111 or SM113, Advance OS200/300/1000 series. Various Japanese and Far East models, all surprisingly reliable.
Philips suitcase style PM3217, 3240 etc are magnificent, well made, but I seem to be fated to have ones with troublesome power supplies, all switched mode and very nasty to service unless you have a second scope and an isolation transformer.
My favourite is the SELabs SM111/CT570 (or TF2204), very good manual. Mine is amazingly reliable and I supplement it with the HP1707 which is 75Mhz with no special IC, no tunnel diodes and nice and small.
Other scopes of that era use tunnel diodes for the trigger, so avoid e.g. Tek453, Solartron CD1642, CD1740, Dynamco 71 series. These all give lovely performance, but you need to be prepared to buy Russian tunnel diodes as the only source of spares.
Once over 50Mhz bandwidth, then specialist ICs appear- Philips PM3261/2, Tek 456, 2200 series, and all the digital scopes.
Some of the HP180 series, with a marvellous fine trace tube use tunnel diodes in the TB plug-in (HP1820 and 1821) though later ones (HP1825, 1824) use standard ECL and perform well. But they were made in late 1960s', so reliability is a factor.
Later scopes for the lower end of the market use may use standard commodity integrated circuits, so easily replaceable. Such as Telequipment/Tektronix D1010 series, D61 series and D65/66/67 which are all 1970-1980.
Another problem is that due to world wide shortage of transistors at that time, manufacturers often used in-house codes for all semiconductors, and then fitted whatever they could buy that was suitable.
I have built up a list of alternatives by looking at manuals and scrutinising inside the actual unit. But it is usually easy to estimate a suitable alternative from the circuit and operating voltages. The Y Amplifier bandwidth is the challenge, but even with the specified parts, with age the bandwidth falls off quite surprisingly.
You really need a second simple scope to keep the main one going, as Electronpusher says.
Those aimed for the eduational market, such as Advance 300, Telequipment S51 (valve), Hameg 203 or the Unilab mentioned by Chris 55000. These may well be best for your audio checking work anyway.
But you must have the service manual and circuit. I have them for all the scopes mentioned above, data on tunnel diodes and the CRT specifications (as many of them are interchangeable), if you are stuck.
wme_bill M0wpn

Last edited by WME_bill; 22nd May 2020 at 9:21 pm.
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Old 22nd May 2020, 9:50 pm   #15
hillmanie
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Default Re: Oscilloscope question - not vintage

Quote:
Originally Posted by Chris55000 View Post
HI!

If you reasonably sure you only need audio bandwidth, plus a bit extra to cope with tape recorder h.f. bias oscillators, then I can recommend you go for one of the Unilab student ones these are made entirely of discrete components and standard wafer/rotary switches you can buy new or surplus, and I've a Unilab 032.602 you can have for the cost of postage!

Chris Williams

My goodness Chris, that's uncommonly decent of you and of course I'll be very grateful to accept. Please let me know all the information you need which is best done by PMs from here on in I guess.
Tony
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Old 22nd May 2020, 11:05 pm   #16
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Default Re: Oscilloscope question - not vintage

Quote:
Originally Posted by Electronpusher0 View Post
I should have added that when your scope does need repair you need a scope to fix it....................


Peter
Unless you get stupidly lucky and it just needs a few lockfits replaced as my Philips PM3200X... Then again, I don't know how much more basic a vintage 'scope could get. Single trace, 10MHz, only real features are TV line/frame triggering.

Sounds like the OP would be more than suited with even a 1MHz unit for the time being & also looks as if he's kindly been sorted with just the ticket as an introduction to oscilloscopes... I do warn you though, when you get familiar with using one and realise just how useful they are you'll soon find uses that push the boundaries & will eventually want to upgrade.... I thought mine above was going to see me out but now I need (well, want!) more bandwidth and channels.
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Old 22nd May 2020, 11:54 pm   #17
hillmanie
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Default Re: Oscilloscope question - not vintage

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HI!

, and I've a Unilab 032.602 you can have for the cost of postage!

Chris Williams
Need I remind you folks that Chris's offer reflects the spirit of this Group, something I've noticed from the beginning, offers of advice and of practical parts.
Long may it outlast COVED-19 and his heirs!
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Old 23rd May 2020, 12:14 pm   #18
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Default Re: Oscilloscope question - not vintage

Another suggestion based on my personal experience are the Hitachi scopes, I have a V-212. These all transistor scopes are reliable and easy to service should that be necessary. Circuits and service information is readily available, 20MHz bandwidth is a bit limited but it depends what you want to use it for. Nice and light as well!
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Old 23rd May 2020, 8:12 pm   #19
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Default Re: Oscilloscope question - not vintage

Quote:
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Insofar as I can think ahead I only need it to measure and examine the waveform of AF voltages in intervalve amplifier circuits looking for distortion that finds its way to the loudspeaker, or for testing absence of tape head erasing voltages
You must know that I'm a first time user and must first find that 'Oscilloscopes for Dummies' book or its companion volume 'Idiots' Guide to Oscilloscopes'
TT
Ah, you may be heading for a small pitfall.

You're planning your scope needs around the signals you expect to have in a working piece of gear.

You will also come across things which go unstable and oscillate. A low bandwidth scope might not show this and give you a smooth low freq trace that looks OK.

I'd suggest you should get at least a 10 or 20MHz scope to cover the sorts of misbehaviours you'll come across. Any less and you'll miss some clues that could make life a lot easier.

Two channels are handy for comparing things. You'll get along fine without needing more.

Some have dual timebases, one runs part way through the run of the main one, these allow you to zoom in on things. For basic use, you won't need it unless you go in for video. BUT don't reject a good scope at a good price simply because it looks too complicated. They aren't really, they just look fearsome. Just learn how to park the facilities you don't understand, and thy'll still be sitting there waiting for when you need them. Inside the most complicated looking scope, there is a simple one waiting to get out.

David
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Old 23rd May 2020, 8:36 pm   #20
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Default Re: Oscilloscope question - not vintage

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Originally Posted by Vintage_RC View Post
Another suggestion based on my personal experience are the Hitachi scopes, I have a V-212. These all transistor scopes are reliable and easy to service should that be necessary. Circuits and service information is readily available, 20MHz bandwidth is a bit limited but it depends what you want to use it for. Nice and light as well!
I'll second this - I've got the smaller portable version of this (V-209, 3.5 inch screen and internal battery option). More often used than my Tek 2465 which is a bit fragile and OTT most of the time. The Hitachi range is a bit overlooked, I think.
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