EEVblog #452 - Stanford Research SR430 Teardown

Inside the Stanford Research SR430 Multi Channel Scaler Photon Counter

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[joewang]

Hi, this is Joe Wang from Stanford Research Systems. Just watched your tear-down and it's great. I haven't looked inside one of these in 20 years myself. It's a little weird hearing your observations today about design decisions made over 20 years ago. Boy am I getting old. BTW, both Andrew Mendelsohn and I are still at SRS designing new instruments (with new technology!). Almost all of this instrument will fit into a single FPGA now. Fun to watch your video here at work!

[douggale]

An LED is a photon counter. Just reverse bias it to charge it up with electrons, turn off the voltage and time how long it takes for it to the voltage to drop back down with a high impedance input. Generally 20000 microseconds in shadow, but much less time in light, and a very long time in the dark. Yellow LEDs are the quickest, blue are the slowest. Photons cause the electrons to be knocked out of the cathode.

[EEVblog]

The blue ones usually indicate metal film, with a lower temperature coefficient than carbon film types.

[billysgeo]

As Dave said, this device is just a counter.
But if you are interested in how photon detection is done, Google "Photomultiplier tubes", as well as a Wiki page there is a video here on YouTube called "Photomultiplier"

[gglovato]

it's used for wheel alignment, you make a chalk mark on the wheel, spin it very fast and strobe it at precise intervals, your eyes are going to see the wheel "freeze" on each strobe(same effects as in a night/dance club). if the mark moves/wobbles then you change weights until it stops. nowadays there are machines that do that automagically with the wheel outside the car

[FranLab]

@22:07 - Are those Signetics ROMS? Old school Rules!

[Petertronic]

The "dot shifting" part may have been to slowly oscillate the display on the CRT to reduce phosphor burn-in.

[Razor]

awww but it's fun to service power supplies while they are still charged. The electricity keeps you energized (just as good as an energy drink), which helps keep you alert and focused. :)

[eniever]

All that hardware done by only one person ? Fascinating!

[cyr]

Two possible reasons:

1) You need the battery for a real time clock
2) EEPROM (or Flash) wasn't available or proven technology when it was designed.

[Dyaxxis]

This vid had me curious as I have used several SRS products during my MSysEng studies at UQ (University of Queensland). After looking at the website, I discovered they're still in the same location with he same contact info listed on that CRT. I drove by it on the way home from work (I live in San Jose, CA) and it's still there.

Beyond all of that, a new SR430 appears to be available starting with a price of ~7950 USD.

[EEVblog]

No, just in purpose designed gear or computing devices that need a CRT display

[ThSu]

It sometimes indicates the composition of the resistor i.e. metal foil, metal oxide, carbon. Sometimes means nothing at all other than a different manufacturer.

[ThatElectronicsFool]

What happened to the teardown video that was up yesterday?

[ChipGuy]

No, but you can find them in CAD Systems from the late 80's and early 90's. There were IBM ISA bus cards for "LPKF" CAD Desing System and there was also a card for the Atari Mega ST using that chip. I quite liked them. Google for Atari and ACRTC for instance.

[chrisvighagen]

Could use a photomultiplier tube (PMT), they are used both in high end drum scanners (10k+ DPI) from Heidelberg or Scitex.

Also the Kamiokande neutron observatory uses PMTs of a sort.

[DanKalc]

How does this device count a single photon, i heard about using a avalanche diod but it require a high voltice circuit which isnt here. Are there any others method do detect a single photon?

[skonkfactory]

Interestingly, ECL doesn't really need all that much decoupling, since being current-mode logic it *doesn't* draw pulses of current when switching. They probably just did it to reduce the ground plane sag.

[iprot]

So there's no standard for that type of marking like for the resistance value? I've searched for that several times but it has proven inconclusive every time, a few mentions of possible tempco relation.

Thanks!

[FakeName]

Lithium battery backed memory is generally from before EEPROM or flash memory were commonly available.