Oscilloscope Inquiry for Stompbox Meddling - Elenco S-1325

[StoneTones]

Hi all, brand new to the forum and yes, after registering I searched the forums first for specifics to this unit and also more broadly for oscilloscope posts. I found a great post - the Oscilloscope FAQ that had a 64 page pdf from valuetronics and a few video tutorials that folks raved about but the post was from 2010 and sadly the links are broken: https://www.diystompboxes.com/smfforum/index.php?topic=82173.0

So my question is - I'm brand new to pedal modification but purchased a Boss CE-3 Chorus that I'm planning to modify to sound closer to a CE-2. A youtuber I saw showed the desired outcome on an oscilloscope and I figured the visual display was invaluable for learning. To make a long story short, I live in Wyoming so getting my hands on a decent analog oscilloscope is limiting unless purchasing sight unseen. Since I'm not sure exactly what I need in terms of functionality (I'm looking to build and modify guitar pedals at the moment) I'm turning to you electronic/audiophiles and your infinite wisdom for a little guidance.

I found this unit, about an hour's drive from me that I can pick it up for $85, probably less. Here is a photo of the catalog sheet and the actual unit for sale it is the S-1325 model NOT the S-1330. The unit for sale and the catalog image look to identical aside from cosmetic/coloration. Assuming it works properly, will this meet my needs for monitoring, testing, troubleshooting, debugging/building pedals? Thank you for your thoughts!

[mozz]

I'd pay about 25 but that's me. Chances are even if it works perfect now, it will need to be recapped. 1 hour and $85 is too much. Deals are out there, sometimes a wanted to buy ad will bring stuff closer to home for a great price.

[PRR]

Welcome.

I've never owned or needed that much 'scope.

Can you find a service manual? It is sure old enough to be wanting service soon.

My last CRT 'scope was 0.5MHz single-trace. For decades I worked on a Leader 20MHz 2-trace but it got ill. I have Velleman's digital hand-'scope, an early one of modest bandwidth and resolution. It has an RS-232(!) port which I never bothered to hook-up.

You can get very good LCD 'scope "kits" for well under $50 on the Asian sales-sites. There is a standard chip and open-source code which everybody uses. Me, I like KNOBS but you are inexperienced and may be OK with pushbuttons and menus.
https://www.amazon.com/JYETech-Digital-LCD-oscilloscope/dp/B0041BCAUM
https://www.amazon.com/dp/B00C5TNXBW
https://www.amazon.com/dp/B088FWHKZG
https://www.amazon.com/dp/B08ML83RK2
https://www.amazon.com/dp/B088FWHKZG
https://www.amazon.com/dp/B08MKL3Z68

While many of these things run on "9VDC" the plug *polarity* may be different from guitar-pedal power supplies. (Rather: the pedal-world custom is reversed from the rest of the world.)

[StoneTones]

Thanks for the feedback Mozz! 2 hours actually given the return trip. Lots of folks mention the Tektronix units but they're fetching 2-4x the price, which is not what I'm looking to sepnd for some seriously amateur dabbling. The 'want to buy' idea is a good one. I found the place I'm currently renting (going on 4 years now) by creating a 'housing wanted' ad.

Also, thanks for chiming in PRR. I dig the analog display/function. For my brain it helps me connect the dots a little easier. I'm not opposed to a LCD/digital unit just so long as I avoid going down the rabbit hole of getting things I don't need or something I can't use. I suppose I should have titled this post: A Good Option For First Oscilloscope? Live and learn!

Again, much appreciated!
Corey

[Rob Strand]

A Good Option For First Oscilloscope? Live and learn!

IMHO, a 20MHz to 30MHz analog is great for first oscilloscope, especially for general work.    Personally I like 10MHz+ for audio since you can measure oscillation problems.   You can also debug non-audio signals like clocks and stuff if you need it.    My first CRO was about 10MHz.  It was OK but 20MHz would have been better but with limited budgets you can't be too picky.  I guess PRR and I differ a bit in our opinions here.

I've looked at some of those cheaper digital ones and it's very hit an miss with bandwidth and features.    Sensitivity can be an issue at times.   Being software based there's plenty of scope for weird unfixable behaviour.    Sound-card based scope would be a perfect example of this - works for simple test waveforms but nothing else.   By the same token, using modern signal processing smarts there's plenty of scope to be great.    You just don't know what you are getting.

A big pluses for digital are:
- you can freeze the display (called a storage oscilloscope in the old days).   That means you can grab transients and analyse them.
- on screen measurements
- ability to do screen captures and download waveforms so you and analyse them or even take the data and post process it.

With old stuff, sometimes the switches aren't great and they can develop faults.    If you get a fault it's probably not worth sending it out for repair since the repair cost is worth more than the unit.   Fixing something like an oscilloscope requires a lot of patience and a good deal of electronics knowledge.    When the new stuff fails you will probably have to bin it anyway since they are even harder to debug and hard to physically repair without SMD rework tools.

[imJonWain]

You can get a DSO Nano or similar digital "pocket scope" under $100 now.  I personally think that's the way to go.  Even if you end up wanting "more scope" at some point modern pocket scopes are still really handy for quick n dirty stuff.  If you have a decent PC and are planning to do more with electronics the Digilent OpenScope is a good start at about $85 too.  Nevermind that got discontinued.

[anotherjim]

Whatever scope you get -  it will be crippled for work on guitar circuits if you don't use x10 probes. The standard scope channel input impedance of 1M ohm can affect the circuit under test too much making for low readings and altered filter frequencies. A x10 probe will raise the impedance to 10M ohm which won't affect the accuracy too much.
Unfortunately, most 'scopes only come with x1 probes which leave the impedance at 1M ohm.

[StoneTones]

A Good Option For First Oscilloscope? Live and learn!

IMHO, a 20MHz to 30MHz analog is great for first oscilloscope, especially for general work.    Personally I like 10MHz+ for audio since you can measure oscillation problems.   You can also debug non-audio signals like clocks and stuff if you need it.

Thanks! That's the goal, I am expecting to have to adjust the bias on a Boss CE-3 and so the visual plus voltage readings are essential. I' made a 'wanted' ad to no avail yet, but have also asked around the local high school and community college. There is a DIY builders club the next town over, I know they have one the question would be if I can borrow the unit or if I'd have to join as a member to use it. Cheaper digital options could be sufficient. I'll know once I get into the unit and figure out the step where I need to visualize the waveform!

Whatever scope you get -  it will be crippled for work on guitar circuits if you don't use x10 probes. The standard scope channel input impedance of 1M ohm can affect the circuit under test too much making for low readings and altered filter frequencies. A x10 probe will raise the impedance to 10M ohm which won't affect the accuracy too much.
Unfortunately, most 'scopes only come with x1 probes which leave the impedance at 1M ohm.

Noted! Can most any scope take x10 probes or does the unit have to be engineered as such? E.g., just as it is a bad idea to plug 12V or 18V into a 9V only pedal is there a similar relationship for probes? Thank you!

[Rob Strand]

Noted! Can most any scope take x10 probes or does the unit have to be engineered as such? E.g., just as it is a bad idea to plug 12V or 18V into a 9V only pedal is there a similar relationship for probes? Thank you!

No damage the probe is only passive.

The basic idea is it is a resistive divider which forms a 1/10 divider.   They increase the impedance at the expense of losing the signal.    I'd say most professional people use x10 probes and only switch to x1 when they need to look at very small signals.

The circuit is something like the one shown below.     Take note of what parts lie in the oscilloscope and what parts are in the probe.   Instead of Cp adjustable you will get a fixed Cp and a second variable cap in parallel with cs *inside* the probe connector.     


The purpose of the capacitors is to form a 1/10 divider for high frequency to counteract the probe cable capacitance Cc, which you cannot remove.   Without the addition of the capacitors the probe would roll-off in the 1kHz to 10kHz.   A good probe could do 100MHz. 

In order to measure correctly, the probes require calibration.  It's  simple to do.    You only need to recalibrate when you move probes to another oscilloscope because Cs is not fixed or defined to be a specific value.
https://www.electronics-notes.com/articles/test-methods/oscilloscope/scope-probe-compensation.php

A few of things worth remembering:
- You will lose 1/10 the signal.   So when you take measurements on the screen you have to multiply the readings by 10.
   (Digital oscilloscopes with on screen measurements often have setting which multiplies the numbers for you,  some
    have special probe which detect the setting.)
- Because you lose signal your oscilloscope is less sensitive.  Usually no problem for real oscilloscopes with the exception
  of perhaps some old tube based oscilloscopes from the 50's and 60's.   Some of the cheap ebay modules have limited
  sensitivities which can be an annoyance with x10 probes.
- Real oscilloscopes have a fairly will defined input impedance in terms of resistance and capacitance (it covers a narrow range).    That means x10 probes tend to work without thinking about it.    If those really cheap ebay probes use 5% tolerance resistors that could introduce an additional 5% reading error with a x10 probe.   Most will use 1% but there's always some dodgy stuff to be aware of.

[duck_arse]

A few of things worth remembering:
- You will lose 1/10 the signal.   So when you take measurements on the screen you have to multiply the readings by 10.

you will lose 9/10 of the signal with x10 probe.

and welcome, of course.

[merlinb]

I found this unit, about an hour's drive from me that I can pick it up for $85, probably less. Here is a photo of the catalog sheet and the actual unit for sale it is the S-1325 model NOT the S-1330. The unit for sale and the catalog image look to identical aside from cosmetic/coloration. Assuming it works properly, will this meet my needs for monitoring, testing, troubleshooting, debugging/building pedals? Thank you for your thoughts!

That scope is perfect, assuming it works. Price does seem rather high though, but maybe it depends where you live.
That scope is built on the same pattern as millions of scopes produced by a few OEMs who then sell them on to other companies who slap their own brand name on them. Simple, easy to use, can't go wrong. But that's also why $85 is unusually high -those scopes are ten a penny.
EDIT: Yep, identical to this 'Rapid Electronics' and 'BK precision' model, for example. Should be easy to find the service manual for one of these -they're all the same.
The probes in the photo almost certainly have a x10 switch on them, but don't worry about that at this stage. You will hardly ever need the x10 option anway, since you'll be mostly looking at stuff in the middle of the circuit where it's not high impeance.

[PRR]

...a few OEMs who then sell them on to other companies who slap their own brand name on them.

IMHO: Elenco, BK, and Rapid didn't do their own slapping. They wrote-out a purchase contract to Wang&Wong Ltd:

Please quote:
W&W #47 oscilloscope as seen at ShangHai Fair
Deluxe bezel, add $2/unit
Custom logo, add $500 setup (art attached)
Change control area color to fushia, add $100 setup
Change control area overlay per attached, add $700 setup
Owner Manual with our logo (N/C)
Retail package with our logo
5,000 units
shipped to our warehouse ready to sell
Banking # 123-456-789

[merlinb]

IMHO: Elenco, BK, and Rapid didn't do their own slapping. They wrote-out a purchase contract to Wang&Wong Ltd:

Economically that amounts to the same thing, Dr Pedantic

[PRR]

forgot the picture

[duck_arse]

IMHO: Elenco, BK, and Rapid didn't do their own slapping. They wrote-out a purchase contract to Wang&Wong Ltd:

Economically that amounts to the same thing, Dr Pedantic

a doctorate in pedantry? or a doctorate in pedantics? is this a real degree offered by an esteemed seat of higher learning, or just bought on the interwires? sounds like something to aspire to.

[PRR]

a doctorate in pedantry? or a doctorate in pedantics? is this a real degree offered by an esteemed seat of higher learning, or just bought on the interwires? sounds like something to aspire to.

Deviant Art, where else?
https://www.deviantart.com/nuro-chan/art/Dr-Pedantic-445861306

(Note: some adjacent images may not be safe for work or home.)