Test Equipment Anonymous (TEA) group therapy thread

[WastelandTek]

Hey guys, I'm hoping for some advise.

My lab is pretty modest.  I am nearing completion on the restoration of a Tek 2445 which, when calibrated, will be the nicest scope in the house.  I don't really have the equipment to verify the calibration however.  My "signal generator" is an old Lyons interlab SQ10 that I just don't trust.  There is an HP 200CD here waiting for caps that, if calibrated might suffice but there again, certainly not the thing on which to base my whole labs accuracy in its current state.

It is the age old problem, the root of all TEA really, without access to an external calibration lab where do you start?

So, I need a signal generator trustworthy enough to provide timing and amplitude to calibrate my other equipment.  Given that everything here is at least 30 years old I don't think it has to be too fancy, and I am, of course, on a budget, but something I can trust to get me pretty close.

What would you guys suggest I get in this situation?

[bitseeker]

Well, it depends on how far down the rabbit hole you want to go.

How about a GPSDO as your frequency reference? Then, put that output into a frequency counter's clock input and measure the output of the sig gen that you want to calibrate. Alternatively, you could feed the GPSDO and sig gen outputs into a sufficiently fast scope to see when they sync up.

There's also the beat-frequency method using a radio receiver and a source such WWV or an equivalent in your area.

Depending on the sig gen frequency range and method, you may have to scale down some of these reference signals.

[bd139]

Or you could write "for indication only" on a sticker, stick that on the top and pretend it's fine. That has a LOT of mileage believe it or not.

Definitely not joining the podcast today. Sitting in McDonalds at the moment half way home 

[beanflying]

I made it out of bed and the first preparation C is going in at T minus 10.

The 5am Possums of three hours ago need to be Exported to New Zealand for 'treatment' ......

[mansaxel]

What would you guys suggest I get in this situation?

The GPSDO+counter suggestion  is probably your best bet for frequency. It is impressive what even modest devices can achieve when given a reference.

For amplitude, with the 2445 in mind, you're probably looking at a ballpark of say 1% observable accuracy on voltage, and most modern DMMen keep within that pretty easily. If you've not yet gotten a respectable DMM, that is what I'd get first, and only then I'd get something to calibrate it with. DC and AC reference (as well as current and resistance) are probably best served  by a DMMCheck Plus or similar. 

There are two stands to take here -- do you need your devices to agree and be reasonably right in the absolute sense, or do you absolutely, verifiably need to know how off you are from NIST / RiSE / NPL ?  The former is probably the most useful while the latter is the mark of a true volt-nut. Or the burden of someone who gets paid to prove they're within spec.

Finally, one can argue that this is not a post that follows the TEA party line. If a true believer did this, s/he would get a calibrator of the highest quality (and weight, with Nixies and so forth). And then something to calibrate the calibrator. Et cetera ad infinitem. But we're all small first. The growth is in itself a part of the TEA coming-of-age.

[beanflying]

We are temporarily elsewhere https://discordapp.com/channels/658020677533827101/658020677533827104

[WastelandTek]

I totally get it that there is no bottom to the rabbit hole.

I did fail to mention the HP 8640B here, again in an unknown state of cal.  Perhaps for now I will compare that with the 2445 and if they reasonably agree put the "for indication only" sticker on 

[Specmaster]

Well guys, feeling pretty miffed TBH at the moment, been after another Thurlby Bench PL320 or a PL310 single supply to sit alongside my other one. Been a few on eBay and some in a Ramco auction that I was looking at. The Ramco ones really went for silly money IMO, as you know, they never show them powered, and they had the appearance of having sat around for years with a wonderful dust coat on them all. One of them (PL320) went for £74 with another £20 carriage, so I'm guessing that it was someone who was inexperienced and just got caught up in the excitement of the moment and was determined to win at all costs 

There was a faulty PL310 on the bay that I thought I had a good chance of getting and I think I would have done had I been braver with my maximum bid, I put £24 max on it in last few seconds it went up to £25 as I was typing in my revised bid and it flashed up to say that I needed to go £27 and then it closed, so I might have won it had I put that in at the start. I'm reluctant to go crazy money on these as I know that they can come up for reasonable money, I got one at Christmas for £35 working well and its a PL320 (2A).

So I think I'll just have to lurk and wait for another to appear and try again, I'm not desperate, I have a couple Chinese 30v 5A ones on the bench at the moment as well which have served me well and perform well.

[med6753]

RE: Our first Discord meet. Really enjoyed it. Looking forward to the next one.   But it seems our pals in OZ and NZ had the most audio issues. Is it internet, distance, equipment or perhaps of combo of all? 

[Zucca]

RE: Our first Discord meet. Really enjoyed it. Looking forward to the next one.   But it seems our pals in OZ and NZ had the most audio issues. Is it internet, distance, equipment or perhaps of combo of all? 

FUUU I missed it, I had guets at dinner and a snowboard day behind me.
Next time next time.

[beanflying]

RE: Our first Discord meet. Really enjoyed it. Looking forward to the next one.   But it seems our pals in OZ and NZ had the most audio issues. Is it internet, distance, equipment or perhaps of combo of all? 

Seems there is a quirk with the Microsoft Lifecam 3000 and discord and my cheapy Chinese bluetooth earbuds/mic has never worked on W10 as far as the Mic goes. I will have a look at some sort of dedicated usb Microphone while I am in town shopping today.

[tautech]

RE: Our first Discord meet. Really enjoyed it. Looking forward to the next one.   But it seems our pals in OZ and NZ had the most audio issues. Is it internet, distance, equipment or perhaps of combo of all? 

No issues here with the audio coming in Med only my old POS mic HW stopped me from getting in on the fun.
Gunna install Discord on a laptop for now and use its mic until I can get something working on the workstation.

Rob (in Perth IIRC) had issues with a few getting heard but Bean and I had no probs. 

[Sam Spastic]

At first I thought I could hear everyone.  Then it seemed everyone but one dropped out. That was mostly dead air. So I logged out then signed back in. When I finally got back to TEA I could hear everyone again.

Next time I'll try that if there is a problem. Also discord complained about my mic possible because it was muted?

[bd139]

Just got home. Boo hiss. Missed it all   

Well guys, feeling pretty miffed TBH at the moment, been after another Thurlby Bench PL320 or a PL310 single supply to sit alongside my other one. Been a few on eBay and some in a Ramco auction that I was looking at. The Ramco ones really went for silly money IMO, as you know, they never show them powered, and they had the appearance of having sat around for years with a wonderful dust coat on them all. One of them (PL320) went for £74 with another £20 carriage, so I'm guessing that it was someone who was inexperienced and just got caught up in the excitement of the moment and was determined to win at all costs 

There was a faulty PL310 on the bay that I thought I had a good chance of getting and I think I would have done had I been braver with my maximum bid, I put £24 max on it in last few seconds it went up to £25 as I was typing in my revised bid and it flashed up to say that I needed to go £27 and then it closed, so I might have won it had I put that in at the start. I'm reluctant to go crazy money on these as I know that they can come up for reasonable money, I got one at Christmas for £35 working well and its a PL320 (2A).

So I think I'll just have to lurk and wait for another to appear and try again, I'm not desperate, I have a couple Chinese 30v 5A ones on the bench at the moment as well which have served me well and perform well.

Honestly I think all the best deals on the PL supplies are around hamfests. They seem to come up in large quantities around 30-40 a pop and are shown working (when there's power available). There were 5-6 of them at Kempton last year for that price range. Either that or snagging them on ebay.

The first one I got years ago was a new grey PL330 which I got for £26 in a mixed lot because it was buyer collect somewhere near Carshalton. Proper win that was as the lot contained a crap load of other stuff which I didn't need but sold on ebay and made about £100 back as well 

[Neomys Sapiens]

I was actually gifted a position of nobility a while back which means I should be referred as lord bd139.

(This could be entertaining....  )

The territory is somewhat disputed and the legitimacy dubious though

That sounds about right.

I would have also suggested to select a less crappy transistor for a name before invoking such titles.

[Mortymore]

I was actually gifted a position of nobility a while back which means I should be referred as lord bd139.

A paparazzi took a picture of Lord's bd139 curves, excited to see a calculator

[Neomys Sapiens]

Martin, what is that slider under the Nixie display?

That is the resolution knob, all Nixies right side from the knob are always Zero.

Ooh, I like that - a proper 'intuitive' user interface.

Intuitive in quotes because when most people call a UI 'intuitive' they mean "just the the ones I've learned before" rather than "follows from innate knowledge".

Yes, R&S is very special there. Same as their notation on the power supplies for the control potentiometers range/span.

[bitseeker]

RE: Our first Discord meet. Really enjoyed it. Looking forward to the next one.   But it seems our pals in OZ and NZ had the most audio issues. Is it internet, distance, equipment or perhaps of combo of all? 

Yeah, that was a hoot. Great meeting everyone. Many had some audio issues, myself included. Disconnecting from the Discord voice channel and reconnecting seems to be a good first step at rectification of sudden audio issues.

I checked a bit of the recording and my mic sounds really quiet, although it was fine during my initial check. I recorded with 24-bit samples, so hopefully there's enough dynamic range to amplify it without too much noise.

The consensus seemed to be to have the next one in a couple of weeks.

[xrunner]

Yeah, that was a hoot. Great meeting everyone. Many had some audio issues, myself included. Disconnecting from the Discord voice channel and reconnecting seems to be a good first step at rectification of sudden audio issues.

Oh crap I missed it! Sorry Bitseeker I apologize. 

I guess I'll have to put the next one in my calendar.

[bitseeker]

No worries! It was an experiment.

[supperman]

I'm new here... but I have a problem..

Every time my handheld multimeter does the timeout beep and shuts off I'm reminded that I really really need a Bench DMM.. and then I'm reminded that it really needs to be 5.5,.. I mean 6.5 digits because that clearly is important.. and then I'm reminded that my MDO3054 with all options has a useless DMM AND then that it does not have a time-integrated Spectrum Analyzer (It just has a standalone 3Ghz SA) and that I really need an MDO4k (no haters please, Dave) even though I have not yet actually done real "work" with the SA yet..

So clearly I need to buy that Bench DMM so I'm not longer reminded of the MDO4K issue since them things are expensive?
Make sense?

[bitseeker]

Welcome!

Yes, makes sense. The first step is always the hardest. Get the bench DMM and the rest will come naturally.

Be sure to post pics of your new (to you) DMM!

[beanflying]

I'm new here... but I have a problem..

Every time my handheld multimeter does the timeout beep and shuts off I'm reminded that I really really need a Bench DMM.. and then I'm reminded that it really needs to be 5.5,.. I mean 6.5 digits because that clearly is important.. and then I'm reminded that my MDO3054 with all options has a useless DMM AND then that it does not have a time-integrated Spectrum Analyzer (It just has a standalone 3Ghz SA) and that I really need an MDO4k (no haters please, Dave) even though I have not yet actually done real "work" with the SA yet..

So clearly I need to buy that Bench DMM so I'm not longer reminded of the MDO4K issue since them things are expensive?
Make sense?

Lucky for you you are in the land of secondhand TEA a plenty unlike those of us from distant shores  The hard part will be choosing which one but we are here to help ENABLE your budding addiction 

[med6753]

I totally get it that there is no bottom to the rabbit hole.

I did fail to mention the HP 8640B here, again in an unknown state of cal.  Perhaps for now I will compare that with the 2445 and if they reasonably agree put the "for indication only" sticker on 

I wouldn't even do that. If they are reasonably close run them as is. No sticker. But you'll have to decide the definition of "reasonably close". Do you think that every Tek scope I have here is fully calibrated to factory specs? Hell no. Are they "reasonably close"? Hell yes. The 3 important parameters to me are sweep speed accuracy, vertical accuracy, and compensation accuracy. All can be easily achieved "reasonably close" with standard equipment. I don't have the thousands of dollars of equipment to do a factory spec cal and I don't care.

The only time I do sticker something is equipment I KNOW is out of spec. For example: The DMM option on the 2465 DMS. I know the ACV is out of spec. I don't have the equipment required to calibrate it so it's stickered as "not calibrated". 

[mc1822]

I keep telling my wife that it's "audio gear" and she keeps telling me I have too much! Then I ask her if I can buy a few pieces of test gear to maintain my "audio gear" and I'm good for another year before she catches on!