10 Mhz Scope enough ??

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10 Mhz Scope enought ??

Evening all,

I have been offered a 2nd hand scope (Advance OS250) rated at 10 Mhz, which is kinda slow compared to today’s standards, but.....

Is there any reason why one would want a higher frequency scope for audio work (amplifiers etc.)??

Should be able to trigger even on the 44 KHz of CD - or am I missing something here.....??

Any specific comments on the Advance OS250 scope (pros/cons, what to look for etc.)

I'm awaiting education from you all.

Thanks in advance

Regards
Henrik Juhl
 
Not bad but not spectacular. Normally you should be able to pick something up on Ebay for less money with better specs. Good thing is that you can check that it works OK before buying. If both units are working OK I would feel OK to pick it up even if I would feel that a bit lower would be reasonable.
 
At that price level you can purchase a good, 50 or 100 MHz B&K or Hitachi scope on EBay and have it shipped to Copenhagen.

Bandwidth is nice to have, but you really have to decide what end you want to pursue. There's no need for most DIYr;s to purchase 400 MHz.scopes -- one of the most useful scopes I have is an old Tektronix 5113 with a 5A22n differential amplifier plug-in -- even after 30 years in service you can measure the noise of many power supplies at levels which many modern scopes can't attain unassisted.

Buy at least one good set of probes for your scope -- they don't have to be very expensive, but of a reliable manufacturer. Bad probing leads to bad analysis.
 
The os250 is a VERY old scope (approx mid 60's to mid 70's, sorry I can't remeber more precise).

Gould scopes of this vintage are failure prone: switches go bad, spare parts hard to get. Trigger is a little bit nasty to get stable.

If you a paying a 110 euro, I would not do so. You get a 30 MHz 2 ch analog vintage 1998 for 260, which serves you better and wil be more "up to date" (see posting here about the digital or the one from Steve Eddy).

You definetely do not need to go for a > 300Mhz scope for the beginning, this will be more in the 600 - 700 euro range. Or if you have an unlimeted budget :)

But for settign up you basic workbench, I would not recommend to go for very aged equipment: If your os250 gets fried, you will be in a helpless situation (if you don't have quite expierenced people around who can repair the old scopes from Gould).

So (my personal view):
1. Look for a scope not too old.
2. Check if manual is included.
3. check if probe is included or at least: can be used with "every probe".
4. check if there is some kind of "scope works indication": A valid calibration shows that the previous owner has taken care that the scopes readings are reliable. Or ask for other warranties.
5. check if there is some kind of Service, help in case of accidental scope failure, etc. -- so you won't be lost.
6. Be careful with so looking bargains (e.g. ebay): Everything in the market has it's price. If a deal sounds too good to be true, than it is usually not good enough.

Ok, if you are stil on the search, send me a personal mail (I think it might get too off-topic here, so the exception for PM) - I see you are too located in europe, so I might be able to help.


hth,
 
For audio you don't need a lot of bandwidth unless you are working on non-audio stuff like digital sections. If you work with tubes, the input voltage rating can make a difference. Many more modern scopes only go up to 5v/div, while older scopes go up to 10v/div. WIth a x10 probe, I can see the whole range of a 500VDC B+ on the screen with a 10v/div scope, but unless the screen is huge, you will not on a 5v/div scope. Just a thought.
 
The Eagle has landed........

Hi all,

Thank you for all your kind advise which is sincerely appreciated.

Last week the scope hunt ended when I came across a Plilips PM6260E. Still old (early eighties I guess) but with a extremely clear and contrast full tube, and with 2 channels at 120 Mhz plenty more than what I personally need. Got the scope inclusive an Exact 7030 function generator for 120 €, so in this light the old Gould was overprized....... I shyed away for remote buys (E-bay) and recommend that you physically examine the scope hands-on.

Just to add a few answers to my initial own questions, as well as some useful information that I picked up along the way (Might come in handy for future users of the 'search' button)

1) For analogue audio work 30 Mhz will work OK - and as shown by this thread many get along just fine with less.

2) Frequency ratings refer to pure sine waves. I reality it's all about rise times. Hence as square waveforms (digital equipment) has steeper slopes; you need a higher rating to follow the signal. Rule of thumb is 10 times the frequency (120 Mhz scope will show 12 Mhz square etc.)

3) Unless the majority of your measurement are well below 1 V get yourself a x10 prode and shy away from those cheaper switchable probes - the switch itself may cause problems or degrade the performance of the probe.

Again
Thanks to all of you
Henrik Juhl

PS: Anyone who knows about the Exact Model 7030 Function Generator (age?). User manual and schematic would be very nice. Its working and can produce a fairly good base form, but some of the 'advanced' features like symmetry and DC offset adjustments seems to ruin the signal completely.........
 

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2 Geek: Yes, 10 MHz already help a lot. But don't forget:

1. times have changed. Today, I won't do less than 30 MHz. Even in TV. I did and do many TV repairs.
2. The buyer might be interested to do the invest once, so why pay 50 euros for a 10 MHz (just example price; but not uncommon - e.g. ebay)

2 Henrik: Perfect buy! The 3260 (i think there was never a 6260 scope made by Phil) is a classic. Switches might be a little bit failure prone, but the trace is the BEST SHARP I have ever seen in scopes.

All the best for DIY!
 
Try to get an used but not so old oscilloscope. This oscilloscope may not be so healthy, I'm thinking of all switches etc. If you get it for free, that's OK but 110 EUR seems a bit much.

10MHz is a bit low these days. It was low even 20 years ago! It gives you not much overhead to pick oscillations and micro details.

If you were in Göteborg I could probably dig up a working oscilloscope for free and give it to you.

EDIT: You have got a 120 MHz scope :up: that's better :nod:
 
I just bourght a scope too! :)

It's a Philips PM3218 35MHz. I think 35MHz is a 'good' minimum for my hobby which is audio repair and building. I bourght it from Helmut Singer. They have a awfull lot of used instruments. They also have a few other interesting things. If you need the taperecorder from a patriot misile, Helmut Singer is your man!

I have used scopes before, but I never had to buy one before now, so I have just one or two questions about probes. The input impedance is 1Mohm and 20pf on the scope. Should the probes be matched in some way to this, or...? Is there any reason to buy 'faster' probes than 35MHz?
 
Fast probes ?

Hi Thomas,

The combined 'Rise time' of the measurering system (scope + probe) is the sum of the rise times of the probe and the scope itself. So it all depends on how close to those 35 Mhz you want to be operating. My Philips PM 3260 has a rise time of 3 nS and is rated at 120 MHz.

Rise time is typically defined as the time of the trace to go from
10% to 90% of the 'true' value.

Capacity wise I don't know what is wise, but I guess you balance that out when adjusting the capacity of the probe with the calibration output of your scope.

PS: Reichelt in Germany sells probes at resonable cost (17 € 150 Mhz/ 2.3 nS or 23.15€ for 250 Mhz/1.4 nS)
 
Re: Fast probes ?

Henrik Juhl said:

PS: Reichelt in Germany sells probes at resonable cost (17 € 150 Mhz/ 2.3 nS or 23.15€ for 250 Mhz/1.4 nS)


The current issue of Elektor (yes we do read it in the States !) has a great article on a FET probe which should cost less than $10 to make -- it uses a dual-gate FET, one gate of which is biased -- performance should be good above 1 gHz.

FET probes and Differential probes never come cheaply on EBay -- not an area in which to be cheap.
 
2 Thomas: Yes, Singer has a lot of stuff. He is in the business since more than 30 years.
My personal (and friends) experiences:
The prices are higher, and the quality is not better than average ebay sales.
But if you are happy with your scope: No problem, go for it!

2 Henrik:
Well, things are a little more complicated with the rise time. It would take a litte long writing to put i down here.
So, if you are willing to go deeper into this matter, I made good expereinces with these two:

www.tektronix.com
tutorials: abc of probes AND abc of scopes.

The risetime rule of thumb I can't state as valid. Usually, a probes risetime of e.g. 3.5 ns is alright for a 100Mhz scope (which is a 3.5 scope risetime, considering:

T (rise) = 0.35 / freq. (scope bandwith)

The reichelt ans RS probes are a real good "bang for the buck". I especially like the ones from RS: solid contruction, good behaviour up to 200 Mhz.

Okay, that's muc hmore than you really need for audio.
but, refering to Jim Williams artciel in edn in 1995 about taking care care of personal equipment: A good probe last's appr. a year i nthe industry, bt most times more than 20 years in your personal diy lab. So, it does not matter much to me if I bay 20 $ for a no-brand probe or a 60 $ fora well working used Tektronix P6137. That's lees difference than a billet for cinema per year -- but I am shure I am better of with the Tektronix.

So fellows - you are wiling to pay lots of money and tiem for DIYing a real good amp -- why do you scrifice on chap probes or other test equipment?

sorry, just my opinion..:)
 
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