Craigslist Oscilloscopes & More - Tektronix 535A + Distortion Analyzers

[bowanderror]

Hey Dudeskis,

I've been not-very-seriously looking to buy an oscilloscope for a while now and stumbled upon a local Craigslist ad that looks really interesting:

tektronix ocilloscope and old test equipment - $200
"2 scopes, HP distortion testers, HP square wave generator, have a classic test bench. tek. scope has camera and cart. total of 5 pieces."
https://cleveland.craigslist.org/tls/d/euclid-tektronix-ocilloscope-and-old/6903912004.html

The seller doesn't give much info & the photos are grainy as all hell, but I think I've identified some likely candidates:

   
• Tektronix 535A Oscilloscope
• Hickok Electrical Model 770 Laboratory Oscillograph
• HP Distortion Analyzer Model 330B
• Unknown Distortion Tester
• HP 211A Square Wave Generator
  

I mainly would be using this for hobby guitar effect & 500-series development, but it would be nice to get into some digital stuff down the road. The 535A looks like a good option, but it's all-tube and I'm imagining it will need some TLC and maybe a trip to the shop. I sent the seller an email inquiring about the working state of the instruments, but I wanted to see if you guys could help me figure out if any of these are actually worth buy, and what to look for or test if I go check them out?


Also, if y'all are interested, I'd be willing to ship one or have you come pick them up if one really catches your eye (I live in Cleveland). I'm not sure what I would do with 1, never mind 2 distortion analyzers in my life!
Craigs
Feel free to talk me off the ledge on these, I've got enough half-working electronics as-is and I'd rather not buy something I won't use.


Thanks,
mike

[vigilante397]

So if I were looking to shoot a sci-fi movie based in the 60s or 70s I would scoop these up no questions asked.

As for use in pedal development, not sure they would be worth the trouble. I feel like there are enough cheaper scope options out there that you shouldn't have to use something this old.

Just my opinion though

[GibsonGM]

What Nathan said.   Now, how 'far' you want to go is up to you, Bow.   I found a Tektronix 2213 60MHz scope from 1982 on Ebay for $99.   I found one channel had something wrong and compared voltage readings from the working channel - it turned out to be a popped diode...10 cent repair.   This scope has now served me well for years.    It was over $2,000 when it was new!!!! 

I do think the one you found may be 'too old, too pricey', but I'm no big expert.     Maybe something like THIS? :   https://www.ebay.com/itm/Tektronix-2246-100MHz-4-Channel-Oscilloscope/233272259727?hash=item36501c348f:g:0SoAAOSwHv5dFTQd

Welcome to the forum!

[bowanderror]

Appreciate the feedback boys. I think I'm going to pass on this one. It turns out the seller is a little bit crusty, so there would be no help on that end. And I quote:

"for this price they should all have been tested and working fine? I don't think so, as is., thanks, george."

That's some best friend material right there.

Agreed vigilante, I almost want to pick them up just for the knobs and enclosures. Nothing helps your stage presence like 200lbs of military grade hardware!

Thanks for the reco, Gibson, having a few more channels might come in handy. How often do you find yourself utilizing more than one channel? To be honest, I'm rightfully terrified of high voltage AC, and given my record thus far in life, should probably not be poking around inside 60 year old test equipment!

I'll keep an eye on eBay for similar items, any requirements in terms of frequency range or other specs?

[GibsonGM]

Thanks for the reco, Gibson, having a few more channels might come in handy. How often do you find yourself utilizing more than one channel? To be honest, I'm rightfully terrified of high voltage AC, and given my record thus far in life, should probably not be poking around inside 60 year old test equipment!

I'll keep an eye on eBay for similar items, any requirements in terms of frequency range or other specs?

I've never needed more than 2 channels, honestly...the input signal vs. what I am doing to it.  I suppose 2 more might be 'fun' for some things, but - would likely be unused, in this hobby.     

I use my scope to see various things, such as (first and foremost)  "Is this part of the circuit working?".... and for things like: what does the distortion look like?  ( 'bat ears' signifying octaving?  Hard cutoff, or smooth? and so on).  You could use it for a live look at 'what does changing this part do?', for some things.   You can use it to determine the value of an unknown frequency, or to check that something you are trying to get to operate on a certain frequency (like an oscillator) is actually outputting that frequency...and adjust it to actually be ON frequency.   

They are not crucial to this hobby, but they're fun, educational, interesting....another tool that you could use for many things, or very few (or none).  I wouldn't invest more than $100 to $200 on one, but that's me, and what fits my uses for it. Others may want a $1,000 DSO and actually would use it...maybe...   

I suggest you read up on them on the net, peruse Ebay, get a feel...some are VERY high end, way overpriced, but the older CRO's like mine can be had cheap, are very useful still, and really are probably all you need!    If you can, try to find one from a university/school....they seem to be less used, and better cared for!   And, if they come with a manual - BONUS.   You may need to calibrate it one day. 

I'd say if the scope says "10MHz" or "20MHz" or better, you are fine expecting to use it on audio devices (our upper limit is 20KHz).  Someone more knowledgeable than I could tell you how that relates to resolution of lower frequencies.  Apparently the MHz ratings have more to do with logic circuits (computers).   If I knew a scope was made in 1978, and another in 1985, I might try to get the newer one (electrolytic capacitor aging...).     Anyway, for small money I bet you will find a useful tool, and if it peters out - buy another in 5 years!   

[EBK]

A good test signal generator can be more valuable in the long run than a good scope.

One example:

[toneman]

get a newer scope...the one in the pic is ancient!!!   

u can find 465, 465b, 475 all the time on ebay, sometimes craigslist.

they usually go for around $200 plus shipping.

u will never regret buying a tek 465b!!!!

[andy-h-h]

I was pretty keen on buying an old scope, felt like I had to have one for some reason.  But then I couldn't find anything that was better for my purposes than using old laptop running Visual Analyser (which is free and the laptop was one that was being thrown out as well).   I do have a set of probes from an old scope, which are great. 

I do use an old signal generator that I picked up for $20 though.  Could use the laptop, but I just find this easier.   

Visual Analyser gives you a scope view, along with a spectrum analyser sitting directly under it.  So you can see the wave, and look at where distortion is and how much is there. 

It's basic, but it does the job pretty well. 

[GibsonGM]

I've used Visual Analyser - neat software.  What I ran into was not having a circuit to separate into 2 channels (which you can make...when I was using this, I had no idea how to do so at the time!  That was like 15 yrs ago).   So I only used one.   Sample speed was an issue; might be better now w/faster computers....     

With an actual scope, I can use both channels, and since I do a fair amount of tube work, my input signals can be pretty high....way way more than enough to pop a sound card.   If you want some safety and are using a laptop, you might consider building in something to clip signals threatening to hit the limit!      The reason the scope I got on Ebay had a bad diode in one channel was probably someone far exceeding the range it was set to, in fact.

I just like using a dedicated scope, I dunno...maybe it satisfies the 'mad scientist in the lab' image, ha ha!   That said, I don't use mine that often - 10x to 20x per year, I'd bet.  But when I NEED it, I feel like I really do need it.   I'm going to download Analyser again, however 

[andy-h-h]

With an actual scope, I can use both channels, and since I do a fair amount of tube work, my input signals can be pretty high....way way more than enough to pop a sound card.

Fair point - not recommended for higher voltages....       I don't work with any high voltages, so works just fine for my purposes.  At one point I was using a simple Guitar Rig adaptor into an iPad running Faber SignalScope.  That worked pretty well too (for me), but I prefer the laptop set-up. 

[GibsonGM]

My thinking is that whatever gets you what you want in an easy way for you to realize, will mean you'll spend more time building, learning and so on.   For some, that is to seek out 'old school' tech equipment - it actually helps, ha ha!   And for others, it could be PC based, or iPhone apps.  Whatever.   

Hey, if there is an app that gives an accurate, non-stuttering voltage reading of an input signal, lets me compare it to a 2nd signal, and is NOT wicked sensitive to over-voltage - I'm all ears!     

By 'higher voltages', with a sound card - we COULD be talking about anything over 5V, right?   If you think about what they are designed for...a guitar, mic, other BS devices.....5V is WAY higher than those!  Great 'headroom' for those devices!  But many of the things we could innocently try to measure could pop that SOB in 1/2 second.  That is why my $99 Tektronix.  I can read from 1/2 volt to 600V (or more, if I want to set up correctly), and don't have to worry about "the sound card".    What owning a real scope DOES do is to force you to think about what you're doing.  It is a One Function Device...it isn't going to get your email and play jingles...and I think that helps focus people to set input voltage range and time base.    I think we need fewer distractions today, rather than more....Just my 2 cents!!   If what you have works, gives you REAL results, and is not limiting you, get to it! 

[DIY Bass]

I have seen a few circuits for amp/attenuator front end that can be used with sound cards.  I think that I would use some kind of usb sound card (replaceable) rather than a mother board sound card simply so that you don't risk as much if you do blow it.  Back in the days of PCI sound cards I blew and replaced a few.

[amptramp]

A good standalone scope is worthwhile.  It pays to be able to see the switch settings and not have to read them off the same display you are using for the waveform.  Ideally it would be triggered sweep, two channel so you can set up the conditions where you capture the signal and you can compare signals from input to output or signal edges if you ever get into digital stuff including bucket brigade or digital delays.  I would suggest a minimum of 10 MHz response since you may want to see digital edges at some point but even with analog, you may need to see if any stage is oscillating and the oscillations often are in the MHz.

[mwelch55]

I bought a cheap scope on ebay and it is great for general guitar amp and pedal building.  Only $25.

https://www.ebay.com/itm/DSO-Shell-DSO150-Oscilloscope-full-assembled-with-P6020-BNC-standard-probe/273200597585?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

[mozz]

Yes ,535 is a old tank, but so are the 465 and such. I would try for newer if possible. I've got 6 scopes here, trying to unload a few. As for the distortion analyzer, they are nice but again, would go for a newer model, 334- 339 are nice. 8903 if you have the bucks.
The nice thing about the distortion analyzers is they have a output which removes the fundimental, so on your scope you can see what the distortion actually is , 2nd harmonic. 3rd, 4th. The HP 339 has a signal gen built in, lower models don't.

I have a few 334's for sale also, trying to reclaim workbench space.

Edit, secret trick. One particular model of square wave generator has 4 pieces of 7189A's inside. I've stripped them for tubes when I find them cheap.