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back to article El Reg's contraptions confessional no.4: Yamaha retro synth, valve oscilloscope and more

For the The Register features on MIDI's 30th birthday, Bob Dormon fired up his trusty Atari ST 1040FM and an Apple PowerBook Duo 270c, but there's a good deal more than old computers in his haul hall of vintage tech. Still a novice in the art of chucking things out, here he tunes up, warms up and winds up a few old favourites. …

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1963 oscilloscope??

If you had posted this a couple of years ago I could have trumped you with a 1938 Cossor (spl??) I had stored in its original teak box, out in the garage (FAR too heavy to lift into the loft!!).

The Cossor originally came from RRE in Malvern, where it probably helped to develop RADAR during WW2; I got it from my employers training centre where they had decided to dispose of it - just after I had given it a thorough service and spruce-up.

The bandwidth went all the way out to 20Khz!!!!

I also had a couple of similar era signal generators from the same source.

Sadly they all "disappeared" while I was out of the country.

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Pint

Re: 1963 oscilloscope??

@Ian "20Khz"

It's kHz. Not named after Dr. Kilo.

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So what's old there (except for the gramophone)

Test equipment in home laboratories often is fairly old since old stuff is cheap. For example I have a Tektronix 549 oscilloscope, and companies like Analog Devices still use lots of only a bit newer equipment.

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Quite.

Old analogue scopes - I use a Philips - are not only a fraction of the price of the current DSOs but in many cases they're superior - the ability to turn the brightness up and see a glitch that the sampling missed is one, and the lack of aliasing artefacts is another.

I was playing with a £5,000 DSO the other day - I won't embarrass Tektronix by saying who made it - and to be honest, a scope that requires a power-cycle restart every twenty minutes because its computer has crashed is not of great use...

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Stop

Re: Quite.

Kind of depends if you've learned how to use them (OK, and the model in question doesn't have crap firmware). Being able to do things like setting the correct timebase, trigger and gain by pressing one button is vastly superior in a DSO, as is being able to capture and record several thousand screens full of data at a time. Spotting glitches? Put the DSO into persistent display mode and you'll get an effect like the decaying phosphor image of an analog scope. Things like pass/fail comparisons against recorded waveforms are also out on the analog scape.

Analog scopes can still do useful work, but DSOs are displacing them for good reasons.

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Re: Quite.

Couldn't agree more. I've been using scopes for 35 years so I think I know my way around them and I've solved problems in hours that I couldn't have solved in days otherwise, using the aforementioned Tek. The ability to grab a couple of minutes of signal at ten nanosecond sampling and to be able to scroll quickly through it to see the bit I need is priceless - most of the cheaper DSOs just sample at some low multiple of the screen vertical rate (and don't tell you what it is!) and store only a few thousand samples... trying to explain to a junior engineer that he's not actually seeing a 3kHz signal when he thinks he is (because there's one clearly displayed on the screen) is tricky.

But the prices charged for modules to decode the common serial protocols are ludicrous - and when the scope as a whole doesn't work properly it's not exactly inspiring.

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Re: Quite.

$15K Tek scope I have is great but having to update a Oscope firmware because it has bugs in the is distressing. When set to trigger from the logic analyzer it would fail to sample the analog every other trigger. The prices for the serial decode is ridiculous but It has saved me many many debug hours and it wasn't me paying for it so..

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Re: Quite.

With any instrument you need to understand its limits and peculiarities. You can get surprisingly good results even from low budget DSOs (for example see http://www.cube.co.za/~tva/workbench/atten-ads1102cml/atten-ads-1102cml-review.xhtml ), but you normally get what you pay for. The problem with the higher end scopes is that they are low volume items, and add-on modules are even lower volume, so of course they are going to be expensive. Remember, in real terms, what those old analog scopes used to cost new and you'll see that the DSO is a real bargain.

If you want to analyse comms protocols on a budget then you can do interesting things with cheap FPGA dev boards (ALTERA FPGAs let you capture and analyse signals on every pin so they become pretty competent logic analysers).

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Re: Quite.

That's an interesting approach that hadn't occurred to me - I don't play with FPGAs on a regular basis. I was considering using a microcontroller with a built-in interface (at the moment I care only about SPI) but the FPGA should work better.

Thanks,

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Re: Quite.

You might want to take a look at the Terasic DE0-Nano board (about £60+VAT). Powered by a Cyclone IV with 22K LEs, 32MB SDRAM, 72 IO pins and a built in USB JTAG programmer.

Otherwise, have fun and you're welcome.

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Re: Quite.

I bought this via the Dangerous Prototypes guys

Although because it has an FPGA on it they wouldn't ship out of the US until I signed my life away & promise that I'm not a "Bad guy (tm)"

Had similar problems when I scored a Papillo FPGA kit .... Hmmm really need to dig that out &have another play :)

http://www.seeedstudio.com/depot/preorder-open-workbench-logic-sniffer-p-612.html?cPath=75

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Re: Quite.

Try http://uk.mouser.com instead. EU shipping and no need to sign anything.

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Re: Quite.

Except consumer 200MHz Digital Scope is poorer than most 10MHz Analogue ones. You need a £5,000+ 2GHz sampling scope to compete with decent S/H analogue 100MHz £50 scope.

Cheap digital scopes often only 8bit (which means less than 7 bits really), limited input ranges (not as sensitive nor high voltages) and totally rubbish triggering. Also useless for X -Y mode. Actually some quite expensive digital scopes are poor at X -Y.

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Stop

Re: Quite.

AND repeat. Do try to read the thread before chipping in. There are many things that even a consumer grade DSO can do that your old analog scope can't. 8 bit DACs are plenty good enough for a lot of uses and you are comparing new vs used equipment (what did the analog scope cost new, and what will a fault cost to repair?)

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Anonymous Coward

That oscilloscope is the coolest bit of kit I've seen for years.

I've just managed to get an immaculate casio ax-210 watch with box and instructions; definitely the greatest Casio retro digital watch ever made. It does everything!

As an off-topic aside, I saw Anchorman 2 on Thursday, and I thought it was the absolute worst film I've seen since The Intern. A real disappointment, especially how great the original was. What do you citizens of the internet think?

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Anonymous Coward

"That oscilloscope is the coolest bit of kit I've seen for years."

how cool would you say?

I have a 1014 in the loft, working when last used, several years ago. Got a manual for it somewhere too. Snags: on mine, the chassis has a tendency to float high when the link between chassis earth and mains earth (bottom right in the picture) is disconnected, and one or two rotary switches no longer index very positively.

It's a true dual beam scope (two knobs for focus, two knobs for brightness), none of this new-fangled "alternate"/"chop" dual-trace trickery.

The one pictured in the article here still has the original knobs, the one pictured at Jonz Valve Page has several generic replacements.

I paid a few quid for mine when the physics department were getting rid of them in 197x.

Is it worth owt? ((c) Mark+Lard, 199x?)

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Anonymous Coward

My dad got me an ex-MOD scope. It worked but was huge and not as nice as those I was using at college.

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78's

Play once and record and see what you can do digitally to clean them up - also as they are often out of copyright share with the world if they are please please.

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Windows

Old kit....

Small tip - I had some old valve radios that hadn't seen power for awhile. Problem sometimes was the PSU smoothing capacitors needed reforming. A couple of times they'd go spectacularly bang on first switch-on - once smashing the adjacent rectifier bottle.

Wise elderly bloke at the radio club suggested I put a low-wattage light bulb* in series with the mains when powering up after a long 'Rip-van-Winkle'. Once it's had a few minutes, short out the lamp. Didn't have that problem again.

* For the younger readers, they're the ones that haven't been banned yet.

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Re: Old kit....

I have seen a procedure for reforming old electrolytics, and it uses a high-wattage resistor and a tin box. You're supposed to remove the electrolytic from its resting place, put it in the tin box in series with the resistor and put a DC voltage across it. The box is an attempt to protect life and property should it decide to expire anyway. If you try this, don't forget to subsequently discharge the capacitor, preferably via the resistor. I was eleven when I learned that a charged capacitor can bite (valve radio with no bleed resistor across the capacitor).

Also worth noting that some old electrolytics seem to have been designed with a deliberate leakage current at high applied voltages so they would act as a crude voltage stabiliser.

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Spare needles for 78s

Find a hawthorn hedge and cut off the thorns using secateurs. They only stay sharp for a few playings, but are 'kinder' to the old shellac 78s.

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Happy

Did one have haircuts to match the synths?

And a Korg?

Ahhh Vienna ?

On the other hand I did get an R19 (I think it was) ex-military mobile comms radio from some surplus kit place - it was solid metal and weighed quite a bit.

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Black Helicopters

wow

that scope looks just like the one I used to use while being naughty for HM government all those years ago

ahh the happy memories of time gone past where we go do what we liked with little fear of it being leaked, and just remember to look under your car for surprise packages from Belfast

They were great days.. working 47 hrs a day and we had 'ole in ground to live in... gotta go on a waiting list to get 'ole in t'ground now

Boris.... lost in the misty memories of the time before he was 'Boris'

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102 valves!

I had one of these many years ago - http://www.thevalvepage.com/testeq/tek/545a/545a.htm - I think (it looked like this). It was a dual trace "storage" scope using some sort of switch to make the phosphor decay insanely long.

Given it was a reject from a school, it is probably no surprise that it didn't ever work correctly (jittery timebase). The internal construction was amazing, and I was really impressed by the little reel of silver solder inside so you don't repair it with that generic stuff!

When a big capacitor blew up, I looked around to see if anybody who knew valve tech better was interested in taking it on, but no luck. It ended its life being dumped, though I did open it up first and take some parts out. I have the CRT assembly here and it is a beautiful work of art.

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Re: 102 valves!

Ohhhh...

So sad it was dumped. As you say, a work of art. Bet there were only a couple of hundred made, too.

I'd give my eye teeth to have it!

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Unhappy

I discovered that sampling can get tricky.

You might have slow repeat frequencies (so you think you've got a low bandwidth) but the pulses may be very short, so the trace is very faint.

Bottom line. Once you go with a DSO all systems you look at become sampled data systems and if you want to look at something producing anything close to a square wave you'll need something like 3x the bandwidth of the pulse width climb.

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Sampling revisted

Hey, we had sampling scopes back in the '60's, they were wonderful! You could twiddle the knobs and make the display look like anything you wanted LOL

http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1966-10.pdf

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Re: Sampling revisted

Storage type CRT tubes date back a long way. See http://en.wikipedia.org/wiki/Direct-View_Bistable_Storage_Tubes_(Tektronix)

As an aside, my uncle used an early CAD system that worked using storage tubes. They managed to run 8 CAD workstations off a single UNIVAC mini with only 64K of storage. The down side was that the tubes were the biggest that Tektronix had ever made, they weren't very reliable and cost £20K to replace.

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Boffin

Re: Sampling revisted

"Hey, we had sampling scopes back in the '60's, they were wonderful! You could twiddle the knobs and make the display look like anything you wanted LOL"

Old school "sampling" 'scopes are a different beast.

What you're looking at is a sort of electronic "strobe" system. A timebase generates sampling pulses that drive a "sampling gate" (basically a ring of high speed diodes, possible because diode tech advances faster than transistor tech).

The system builds up a waveform 1 sample at a time, per frame.

The down side is it only works for repetitive signals which can be be accurately synchronized to.

The upside was the huge bandwidth they offered. EG 1 GHz in the 1950's. Today I think they are at 30GHz+

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Remember those 'scopes from days of yore when we used to play tricks on each other.

There are two plugs on the back that link the timebase to the X-plates so that you can drive it as an X-Y display. If you swap them from horizontal to vertical, the timebase runs backwards.

As long as the timebase is running reasonably fast, your 'victim' becomes totally confused by waveforms ringing on the trailing edge etc. Ah, nostalgia is not what it was!

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Way to go...

Great collection of tasty gear.

I have a Tek 465 Scope on my home workbench, still gets used regularly.

Very envious of your 78 player (in a very positive manner of course). Looks a treat.

Best seasonal wishes.

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Never Throw Anything [Beautiful] Away

I agree with AC: that Solartron is very cool - pretty even - and far nicer than the TelequipmenT D61a I have in the garage (which gets regular use … at least once a year). The J E Dallas 78 player is also rather fetching with its red features, although probably not as loud as my HMV portable. These things impress youngsters, which is quite satisfying. I wasn't aware of the connection with Jedson guitars - my 2nd ever guitar was a blonde Jedson Tele copy (or sorts). Nice article Bob!

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Re: Never Throw Anything [Beautiful] Away

Entirely mechanical cameras from WWII or older are also good for this, beautiful and functional. It's almost as much fun to twiddle the mechanical dials as it is to see what you get back from a day's photography (a month later of course, once it's been developed!).

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Windows

Re: Never Throw Anything [Beautiful] Away

Showing my age ...

I used to repair Nicolet 1090 'scopes. World's first DSO. Sheesh, the fast plugin used ECL quad AND-gates in the (successive approximation) A/D converter.

They ran HOT!! Still have the burn-mark from touching one.

'Processor' was 4x 74LS181 ALU's.

Sad they're probably all landfill now...

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You need to order needles

Each steel needle is only good for ONE side!

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Bah!

MIDI? Pfft!

Get yourself a real monophonic synth - a Roland SH101 - and learn the joys of CV + Gate extensibility.

Then: Get off my lawn!

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That gramophone belongs in a museum

No, I mean really.

How many of those devices are still in any recognizable shape, let alone working? I bet you'd have an easier time finding a Balmer quote that's not embarrassing.

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Re: That gramophone belongs in a museum

You can find them on eBay for ~£50.

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Anonymous Coward

Re. valve radios

Thanks for that tip.

I have an ancient 'scope here, based on transistors (Remember those?) but still works fine.

Dual trace, 18Mhz, and tube still seems to work fine although the timebase is glitchy.

Re. "dead" valves, a lot of the time if you can't get a replacement 24 hrs at 240 degrees (ie domestic oven) followed by a gentle cool down sometimes brings them back.

If the valve isn't up to air this usually helps as long as the thorium doped heater isn't fried, sometimes this can be fixed with a valve tester and some careful treatment.

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