Test Equipment Anonymous (TEA) group therapy thread

[bd139]

Really liking this 2225, more than the Rigol, even though the bandwidth is half as much and it's analogue. x50 zoom is pretty cool. It is quite a good equivalent for delay sweep, at least for repetitive signals/glitch capture.

Feels like a more expensive scope!

Ah, another convert to the light side

(Grins, ducks, and runs)

Got to be honest, I probably don’t *need* the Rigol. It was just an easy purchase. Some of the tricks it does are very useful but a lot of them are shit. It’s a bit of a minefield really.

Got my beady eye on another slightly better analogue scope at the moment

There’s also a 54600b on eBay which is of interest. I used one of these for a bit when they came out, diving into the university lab first so I got the good scope.  Despite limitations, they’re a nice compromise between analogue and digital scopes. Not too much of the bad bits of either.

[HighVoltage]

Maybe googling for "femto capacitance meter" will give you some ideas

I did that already a while back and found one: Keysight E4980A
It measures from 1.000000 aF (atto E-18) to 999.9999 EF (EXA E+18)

Hmm, they are just not available used, yet!
May be one day

[SeanB]

Do you think some of the ABS cement shit would fix this up? I do not have the missing bits, it was like this before I purchased the beast?

20171117_171832 by Graham Butcher, on Flickr

You would need the talcum filler added, to build up the volume. Then you can just use a few top coats of unfilled epoxy to match the base grey. Will work but the layers have to be applied in thin coats, otherwise you get cracking as the solvent evaporates.

[HighVoltage]

I had a broken Keithley 614 in the plastic front end and fixed it up with epoxy.
Here are a few pictures of how I did it:

[Mr. Scram]

Yeah, the C versions are better, but for the price I couldn't hold out.

I just realized the B version doesn't do ESR.

[bd139]

My 2225 is not a happy bunny inside. Looks like I need to shotgun most of the PSU caps. Lots of noise, ripple and the inverter is unstable. At least they’re cheap radials in this one!

[Specmaster]

Oh dear, you seem to pick them with bad caps don't you? So far I've been lucky with my scopes, only had issues with caps generally in a large way with the Hameg 408 which needed a complete set on the PSU, not that they did any good because the damn thing is still not firing up despite having a totally rebuilt PSU fitted so it also went sick elsewhere at the same time. I hope to get this back on the bench real soon. I had to change the odd cap here or there on others mind you but nothing too bad.

[Specmaster]

Only place I find microvolts is op amp offset trimming and that’s just professional pride as I’m not doing any precision work.  And you don’t need a calibrated meter for that as it’s a differential measurement. As long as your meter zeroes when shorted.

Going to be honest here and I’m usually good with a 5% reading and won’t be buying anything better than a 4.5 digit meter. Not because I don’t want one but I can’t calibrate one that accurate so it’d sit in my mind and annoy me.

Well, I'm designing my own 6.5/7.5 digit multimeter at the moment, so that might explain why. I'm pretty much in need of an electrometer at this point since the charge injection is pretty annoying to estimate, so might just measure it directly instead    I feel an excuse coming up!

Have you seen this at all?

[bd139]

Oh dear, you seem to pick them with bad caps don't you? So far I've been lucky with my scopes, only had issues with caps generally in a large way with the Hameg 408 which needed a complete set on the PSU, not that they did any good because the damn thing is still not firing up despite having a totally rebuilt PSU fitted so it also went sick elsewhere at the same time. I hope to get this back on the bench real soon. I had to change the odd cap here or there on others mind you but nothing too bad.

Indeed. Just found the culprit here I think. There are two 470uF 50v units one of which has leaked a bit at the base. . I’ve replaced them with a couple of Panasonic low ESR units I had lying around (100v but same size). This has quietened the power supply.  Looks like the 1000uF 16v ones on the rails need doing as well. Alas I don’t have any of them so will grab some from RS for installation on Tuesday evening. The main filter cap is a monster 2200uF 80v one so I will grab a nice sexy EPCOS one and do that as well.

[Specmaster]

Nice, what type of psu is in the 2225?

[bd139]

Both types. It's got a linear front end and then a switcher after that. Fortunately it's bog standard parts. No fancy Tek parts. The front end is a big toroidal transformer and the rest is a couple of TL594 PWM controllers and a ferrite transformer to derive final voltages from. It's all carefully pre-regulated as well. Also has links you can snip to isolate bits to trace faults. Very nice design really.

That is if I can get the bastard thing stable. ATM the PWM is dropping into audible range and the rails dropping out occasionally. Ripple is terrible on -8.6v rail so I reckon this is an electrolytic dragging the rail down occasionally. Has improved slightly with replacement of the filter caps so far. Have just ordered some more and will replace and see how that goes. It's quite common that these have stalling power supplies and problems on the rails and stuff.

Hopefully it's not the HT arcing. It doesn't seem to be that though as that usually causes the entire thing to stall rather than drop out a bit. I've just about had it with HT transformers and arcing!

[Specmaster]

Hopefully its just a Tant playing up again, seems a common mode of failures with Tek scopes 

[Specmaster]

Heres a heads up for the UK members especially if you're looking for a inexpensive function generator, then these might fit the bill, there's about 5 of these on offer at the moment from a company in Essex.

[Mr. Scram]

Heres a heads up for the UK members especially if you're looking for a inexpensive function generator, then these might fit the bill, there's about 5 of these on offer at the moment from a company in Essex.

How much are those?

[HalFET]

Only place I find microvolts is op amp offset trimming and that’s just professional pride as I’m not doing any precision work.  And you don’t need a calibrated meter for that as it’s a differential measurement. As long as your meter zeroes when shorted.

Going to be honest here and I’m usually good with a 5% reading and won’t be buying anything better than a 4.5 digit meter. Not because I don’t want one but I can’t calibrate one that accurate so it’d sit in my mind and annoy me.

Well, I'm designing my own 6.5/7.5 digit multimeter at the moment, so that might explain why. I'm pretty much in need of an electrometer at this point since the charge injection is pretty annoying to estimate, so might just measure it directly instead    I feel an excuse coming up!

Have you seen this at all?

All nice and well, but won't reach the actual performance. If it were that easy everyone would be doing it. This is good for 4.5 digit, you might be able to push it to 5.5 if you're lucky with the parts. You could calibrate this away, but the moment you have any temperature variation you're done for with this circuit. To quickly go over it, 6.5 digit would mean you have to achieve stable operation down in the microvolt territory, and get at least 22 bit out of your ADC (digits , but unless you're happy with one reading per second you're never getting there (http://cds.linear.com/docs/en/datasheet/2400fa.pdf page . Additionally the reference is not shielded from the supply, nor is the ADC supply voltage. And that's not mentioning the >100 µV magnitude offset and non-linearity errors you're going to get on that opamp and ADC. He's not even shifting signals away from the supply voltages, where most ADCs and opamps start behaving "funky" to use a less formal tone. My conclusion: nice idea, naive implementation.

[Specmaster]

Heres a heads up for the UK members especially if you're looking for a inexpensive function generator, then these might fit the bill, there's about 5 of these on offer at the moment from a company in Essex.

How much are those?

They are on Ebay (oops I forgot to mention that) and they are currently around the £30 mark and the same company has these Black Star TTI 3225 meters at around £20 currently, may be worth a look, I'm going after them so knock yourselves out, the meter by the way is battery powered so is a floater but bench based.

[Specmaster]

Only place I find microvolts is op amp offset trimming and that’s just professional pride as I’m not doing any precision work.  And you don’t need a calibrated meter for that as it’s a differential measurement. As long as your meter zeroes when shorted.

Going to be honest here and I’m usually good with a 5% reading and won’t be buying anything better than a 4.5 digit meter. Not because I don’t want one but I can’t calibrate one that accurate so it’d sit in my mind and annoy me.

I think you're right, I noticed in his list of vids, that he does a MK2 version later on 

Well, I'm designing my own 6.5/7.5 digit multimeter at the moment, so that might explain why. I'm pretty much in need of an electrometer at this point since the charge injection is pretty annoying to estimate, so might just measure it directly instead    I feel an excuse coming up!

Have you seen this at all?

All nice and well, but won't reach the actual performance. If it were that easy everyone would be doing it. This is good for 4.5 digit, you might be able to push it to 5.5 if you're lucky with the parts. You could calibrate this away, but the moment you have any temperature variation you're done for with this circuit. To quickly go over it, 6.5 digit would mean you have to achieve stable operation down in the microvolt territory, and get at least 22 bit out of your ADC (digits , but unless you're happy with one reading per second you're never getting there (http://cds.linear.com/docs/en/datasheet/2400fa.pdf page . Additionally the reference is not shielded from the supply, nor is the ADC supply voltage. And that's not mentioning the >100 µV magnitude offset and non-linearity errors you're going to get on that opamp and ADC. He's not even shifting signals away from the supply voltages, where most ADCs and opamps start behaving "funky" to use a less formal tone. My conclusion: nice idea, naive implementation.

Yes you're right, I noticed that he does a MK2 version later in his vids.

[Mr. Scram]

They are on Ebay (oops I forgot to mention that) and they are currently around the £30 mark and the same company has these Black Star TTI 3225 meters at around £20 currently, may be worth a look, I'm going after them so knock yourselves out, the meter by the way is battery powered so is a floater but bench based.

I think the TEAities are protecting me. Despite fuzzing all sort of terms I'm not finding anything. Probably for the better!

[Specmaster]

They are on Ebay (oops I forgot to mention that) and they are currently around the £30 mark and the same company has these Black Star TTI 3225 meters at around £20 currently, may be worth a look, I'm going after them so knock yourselves out, the meter by the way is battery powered so is a floater but bench based.

I think the TEAities are protecting me. Despite fuzzing all sort of terms I'm not finding anything. Probably for the better!

Here you go try these

https://www.ebay.co.uk/itm/Metrix-GX320-Function-Generator-20MHz/272939635033?hash=item3f8c785159:g:ua4AAOSw-xVaDslc
https://www.ebay.co.uk/itm/Thurlby-Thandar-Instruments-TTi-TF830-1-3-GHz-Universal-Frequency-Counter-Cream/302532327376?hash=item467054f7d0:g:6LIAAOSw3fZaDrwy
https://www.ebay.co.uk/itm/Thurlby-Thandar-Instruments-TTi-TF930-3GHz-Frequency-Counter/122813360033?hash=item1c983f27a1:g:i8UAAOSwIFtaDrDp
https://www.ebay.co.uk/itm/Black-Star-3225-Multimeter/302532373429?hash=item467055abb5:g:V3MAAOSw-wJaDsZB
https://www.ebay.co.uk/itm/Black-Star-3225MP-Multimeter/302532368359?hash=item46705597e7:g:ryAAAOSwVA5aDsVV
https://www.ebay.co.uk/itm/Thurlby-Thandar-Instruments-TTi-TGP110-10MHz-Pulse-Generator-Cream/122812175805?hash=item1c982d15bd:g:jw4AAOSwVtZaDcQ0
https://www.ebay.co.uk/itm/Black-Star-Apollo-10-Universal-Counter-Timer/272935132785?hash=item3f8c339e71:g:RUMAAOSwWLBaDFlp

This is a selection of the test gear they have on offer, their main product line is old computer parts but every now and then they get some test gear in as well.

[bd139]

I’d stay away from the black star meters. Notorious for having leaked batteries in.  End game if that happens.

[HalFET]

Yes you're right, I noticed that he does a MK2 version later in his vids.

The only noticable improvement is that he called it a millivolt meter instead of a 6.5 digit meter. It still has the same basic issues.

[Specmaster]

I’d stay away from the black star meters. Notorious for having leaked batteries in.  End game if that happens.

Hmm, I'm sure the battery compartment could be rebuilt to use AA's or others if the terminals have been destroyed because if the construction inside is like their frequency counters, its all hung of the front panel and so should be well away from any battery leakage, unless I've got it all wrong?

[Mr. Scram]

Probably a naive question, but what are these universal frequency counters? I know what a frequency counter is, I know what a universal counter is, but a universal frequency counter? Does it do both absolute and relative measurements? The UI doesn't really suggest that.

[Mr. Scram]

Here you go try these

https://www.ebay.co.uk/itm/Metrix-GX320-Function-Generator-20MHz/272939635033?hash=item3f8c785159:g:ua4AAOSw-xVaDslc
https://www.ebay.co.uk/itm/Thurlby-Thandar-Instruments-TTi-TF830-1-3-GHz-Universal-Frequency-Counter-Cream/302532327376?hash=item467054f7d0:g:6LIAAOSw3fZaDrwy
https://www.ebay.co.uk/itm/Thurlby-Thandar-Instruments-TTi-TF930-3GHz-Frequency-Counter/122813360033?hash=item1c983f27a1:g:i8UAAOSwIFtaDrDp
https://www.ebay.co.uk/itm/Black-Star-3225-Multimeter/302532373429?hash=item467055abb5:g:V3MAAOSw-wJaDsZB
https://www.ebay.co.uk/itm/Black-Star-3225MP-Multimeter/302532368359?hash=item46705597e7:g:ryAAAOSwVA5aDsVV
https://www.ebay.co.uk/itm/Thurlby-Thandar-Instruments-TTi-TGP110-10MHz-Pulse-Generator-Cream/122812175805?hash=item1c982d15bd:g:jw4AAOSwVtZaDcQ0
https://www.ebay.co.uk/itm/Black-Star-Apollo-10-Universal-Counter-Timer/272935132785?hash=item3f8c339e71:g:RUMAAOSwWLBaDFlp

This is a selection of the test gear they have on offer, their main product line is old computer parts but every now and then they get some test gear in as well.

That's slightly worrying. Copy pasting key parts into the eBay search doesn't return these listings. Even literally copying "Metrix GX320 Function Generator" doesn't do it, both on the UK and regular eBay sites. I don't know what's going on there.

[Specmaster]

I'm not sure of your location in the world as you not stated that on your profile, but anyway, you do not copy and paste, they are active hyperlinks and clicking on them should take you directly to relative page on Ebay UK.

If not, then copy each complete line and then paste directly in the address bar of your browser and press enter and you will again be transported direct to the page.