Probes for Nicolet 3091 scope?

Lewin, I worked for Nicolet as a final test tech about 20 years ago, and of course we just shipped the probes we were given not realizing they were anything out of the ordinary. Unfortunately, my service manual for the 3091 either doesn't seem to want to be found. They are available via the web. The only genuine Nic' scope probe I have has no adjustment apparent to me on the probe itself. (?? and !) That would seem to suggest an internal adjustment -- I recall a cylindrical pf range trimmer that needed adjustment, with a brass screw. One hint, from the 1x scope probe I have here, is that it does have a 33 Ohm resistor in series with the probe cable, located at the BNC. So perhaps they are more special than I ever realized or at least remember. The 4094 that I own works fine with plain old scope probes of "today."

Given your present slow application, you should be fine for your immediate need with nearly any probe.

Don't know if this really helps much. I'll try to rattle a few cob webs in my mind and ask a few old contacts to see what I can find yet. My 4094 needs several new Grigsby switches, but so do they all; I doubt I can find what I need myself.

Thanks, Steve

Lew> I recently acquired a Nicolet 3091 digital storage scope, vintage

Hi Steve,

anything out

Heh, heh. Well, maybe you handled this one. It was last cal'd in December 1983 and it was signed off by one Douglas M. Abner. In actual point of fact, it was probably never cal'd after manufacture, because it was used for engineering tests - at my company, equipment that isn't used for actual final Q/A or other important things (e.g. UL or FCC cert work) is tagged "CALIBRATION NOT REQUIRED".

We've got vast graveyards of equipment that are slowly being tagged for disposal. A true friend, gentleman and potential saint in the "graveyard" building occasionally drops by my cube (I work in a different building) and says "There's a [xyz] about to go in the trash..." I'm hoping for another one of these 3091s, rumored to be in the same general area of the junkpile, to use as spare parts if necessary. I was shocked to see that a unit on eBay was going with a starting bid of $200-and-something. It didn't sell, of course.

I've got the original letter-size printed service manual, as well as the half-letter-size user manual. There isn't any information in the service manual on what's inside the probes or how to calibrate them.

Hmmm.

Well yes, that's true, but I would like to get the instrument working as nominally as possible. I'm contemplating hacking up a probe myself, by modifying an existing probe. Since it appears to get a good waveform if I use a dumb wire, maybe I should take a "new" probe, pull out any smarts inside it, and add that 33R resistor. Thanks for the pointer!

Grigsby switches - what are those? I found the only thing wrong with this old beastie was (a) tube rather out of focus (I can compensate slightly with the focus adjustment, but not much - I'm guessing a cap job is called for at this point in time), and (b) all the rotary switches desperately needed cleaning.

Steve,

Did you ever work with a John Holton while you were at Nicolet?

Tom Woodrow

Steve wrote:

anything out

I don't remember him. Actually I showed up in '85 to '86.

My working 4094 I bought for $5.00. A non-working one I got for $15.00! They sold originally sold for 1000 to near 10,000 times that new if you bought a lot of bells and whistles!

I did just find a box O' junk, with a 3091 ADC board in it, and there is no such piston cap on it. There are two pairs of 3 to 10 pf trimmers. Please just forget what I said about the internal adjustment... I even wonder if this Nicolet scope probe was for a 3091. The years cloud the memory.

The rotary switches are made by Grigsby. They are the major source of demise for many a Nicolet scope. Cleaning only delays the inevitable. As I only got the two 4094's in the past year, I don't really have much experience about the "end of life" of these scopes! Very unsure about how much luck one would have ripping one apart to clean it, or if possible at all. At the factory we would have never done anything but put a new one in for the occasional infant failure during final test.

Good luck, and I'll try to see if I can come up with anymore help. May take weeks.

Thanks, Steve

Sorry, he looks to be before my time there, from what I could Google about him, if this is him:

Looks like he may have been in the Bio-medical division. Of course I was in the O-scope division. There were hundreds working there, in 1/2 dozen buildings. Not anything close to what's left, from what I've heard.

Don't think that this was the same guy although the time frame is about right. The John Holton I knew was a vietnam vet and still had long hair and beard so I can't tell from the picture.

On another note, when I was at Aydin we had a 4094. Was a great DSO and was the world's best glitch catcher. We did high voltage stuff and just the ground faults would kill a Tec scope. We never did fry a 4094. I coud still use one once in a while, but the last one we bought (another company) disappeared after a move to a new building.

Tom Woodrow

Steve wrote:

I'm thinking of offering that eBay seller $50 + shipping for his 3091 (he claims it has bubble, but it doesn't have that option fitted) as a parts unit. It really is very (surprisingly) useful to have a DSO that can go down to such slow sample rates.

Mine work, but when you change the settings you need to massage a little to make sure the setting isn't twitchy. I want to try blind-squirting contact cleaner into them and working them vigorously, then blowing compressed air through to get rid of any loosened debris. But I want to be sure I have a donor unit for spares first ;)

Hey, thanks. Would you mind emailing me if you do find something? If it's just a random message drifting by in this NG I may well not see it.

The scope will have an input resistance and capacitance. On Tek scopes this is marked on the front panel. What does the NIC scope say?

You need to use a probe which has a compensation range that includes the input capacitance of your scope.

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Hi,

It's not characterized on the front panel. I think it's probably in the range ~150pF, at a guess, and my probes are designed for ~13-15pF input capacitance. I'll look closer at the instructions (they are filed now.. didn't think I would be needing them immediately).

At the moment the scope is running a ten-day data acquisition operation, I'll play when that's over (it has an ultra-low sample rate, down to 1 sample per 200 seconds, and a 4096-point memory).

The probe you use does not satisfy the scope'S input capacitance with it's (the probes trimmer) compensation range.

That is NOT unusual: The 3091 has a quite high (compared to nowadays) scopes capcitance (AFAIK 1Mohm par. 47 or 60pF). Only a few probes you can buy nowadays can satisfy that input. check the probes data, or go for an older probe (e.g. Tektronix has some probes for the "legacy" scopes from the 70's to satify the range). I don'T know the product number by heart, but you can look it up in the Tektronix catalogue together with the probe data.

hth, Andreas

I doubt if it's as high as 150 pF. I believe the highest input C that Tek ever used was 40 or 45 pF.

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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I say this number because googling around I've found a couple of people using it with probes that are speced at "147pF". Oh well. In a few days I'll be able to play again...