Test Equipment Anonymous (TEA) group therapy thread

[Neomys Sapiens]

.
.
.


.
.

You certainly have a unique taste regarding your DMMs! 

[mnementh]

Thanks for that Mnem, it's helped a lot. 

I've had a read through relevant sections of the manual for the later version with no nuvistors, as mine is an older one with the three nuvistors, the quoted figures will be slightly lower.

Power consumption on DC is 26W max, current = 26 divided by the input voltage (11.5V to 35V) = 2.26A to 0.74A. 1.09A at 24V, will be higher with older version.
It takes 16 hours to charge the 20 series D NiCds, 5 hours operating time, 30 mins less with scale illumination fully on.
Charge rate is 400mA on mains charging only, 30mA when operating at the same time, no charging on external DC, the thermal cut-out also cuts charge rate to 30mA.
The low voltage indicator circuit flashes the power light when battery voltage is below 22V.

I've done some tests on mine earlier today, it appears the charging circuit is a current limiter only, open circuit voltage goes up to 62.5V, I also managed to smoke the 180Ω resistor for the 30mA trickle charge during testing, more on that below. 

First I wanted to test the charger was functioning correctly at the two charge rates, a 24V 12W lamp was used as a load, the fast charge rate was 400mA and crept up & stabilised at approx 413mA once run for a while, voltage across the load was approx 18V. The slow rate (30mA) was then selected, current was a bit higher than the book stated at 48mA after running for a while...

   

David

Glad I could help. Yes, you'll need to devise a voltage regulator circuit. The BMS will have specifications for a (usually pretty narrow) charge voltage range; should be somewhere around 27-32V for a 8S LiFEPo4 BMS. That 400mA rate is actually pretty slow; the slow charge rate is essentially irrelevant, as you charge Lixx CV with CL, not fast then trickle. We don't keep a float voltage with Lixx as we do with Nixx. So you'll need to find the correct voltage for your BMS, build a simple CV regulator using LM317 or your favorite adjustable regulator, and either build a passive/active CL circuit or, since you have so much space in that huge box, it might be easier to just mod a 29.4V eBike charger (for common 7S Li-Ion pack) in there; they're all over Amazon for ~$15-25.

https://www.amazon.com/s?k=29.4v+ebike+charger&crid=3CCUU0G1UEOGB&sprefix=29.4v+ebike+charger

22V for the low-voltage light should give a nice little buffer vs the BMS LVC. 

Cheers!

mnem
 

[Brumby]

So...  WNR (WNR) = Chicken Dinner...?   

mnem

Should I be worried that something similar crossed my mind also?

[mnementh]

I dunno... have you started to notice the smell of gemstones and precious metals? Started hanging out on FurAffinity, looking for new dragon pics? Do you feel a need to growl just because it pleases you, or to preen your scales? Have you started sleeping on your belly so your wings can breathe...? 

mnem

[AVGresponding]

Ian devices use a LM399 voltage reference. You can't really compare them to a AD584 or Mastech MS7221.

I had mostly bad luck with cheap AD584 references. Ordered 3 and were all off from each other. Like I said previously they are probably ok to check 4.5 digits meters.

You get what you pay for, usually. I'm not aware of the price Ian charges for his reference, but I'd guess it's quite a bit more than £10 shipped.

[Specmaster]

Ian devices use a LM399 voltage reference. You can't really compare them to a AD584 or Mastech MS7221.

I had mostly bad luck with cheap AD584 references. Ordered 3 and were all off from each other. Like I said previously they are probably ok to check 4.5 digits meters.

You get what you pay for, usually. I'm not aware of the price Ian charges for his reference, but I'd guess it's quite a bit more than £10 shipped.

Yep, I think I saw £285 mentioned on his site, so a similar price to the MS7221 really.

[tggzzz]

Ian devices use a LM399 voltage reference. You can't really compare them to a AD584 or Mastech MS7221.

I had mostly bad luck with cheap AD584 references. Ordered 3 and were all off from each other. Like I said previously they are probably ok to check 4.5 digits meters.

You get what you pay for, usually. I'm not aware of the price Ian charges for his reference, but I'd guess it's quite a bit more than £10 shipped.

Yep, I think I saw £285 mentioned on his site, so a similar price to the MS7221 really.

Ian Johnson's specs are better; Masstech is 200ppm.

It looks like Masstech's specs are defined to meet a market requirement, and are hence kept simple to interpret by non-specialists. OTOH, Johnson's look like they are derived from the components' specs, and are more complex to interpret. Horses for courses.

[THDplusN_bad]

Good Day,

Ok, so I decided to replace the relais in the defect GRUNDIG PN300 power supply that has provided an extra +20V - say +25V DC instead of +5V DC - in its evil...
I had checked the analogue board for bad supply caps earlier (some other owners had reported related problems), same for the transistor in the relais driver circuit. But all that was tested good.
I have an inexpensive "Toolcraft" ZD-8925 desoldering station that works very well for through-hole components (this desoldering station is sold under various brand names and all variants seem to come from the same manufacturer http://www.china-zhongdi.com/product/30.html).

But the "20V extra" condition happened again after the two relais were replaced. 
I have then found that a crimped connector X230 was partially loose. For some weird reason, GRUNDIG had decided to solder the crimped connector directly to the PCB. Not sure what they were thinking. So, another job for the mentioned desoldering station - and finally, the error was gone. I have replaced the connector with a standard 0.1" / 2.54 mm connector that I had pushed in a little and with little solder on the connector's side, so it provided a good contact. Turned out that the space was not as limited as I had thought, so I could have used the standard connector with the plastics on the connector's side. 

I have setup a simple test with my KEITHLEY 2015 DMM and a Python script. The script sets the GRUNDIG PN300's output voltages of both channels A and B to 5V, 15V and 25V and reads back the voltage at every step. After some fiddling with the DMM's readings, 10 cycles with 3 voltage settings for each channel, say 60 voltage settings overall read back ok - and so the repaired unit had passed all tests.


Cheers,

THDplusN_bad

[Peter_O]

Boat anchors are not that often offered at reasonable prices.

This guy was advertised 500 Euros with little reliable information about it's condition.
No risk, no fun. I pulled the trigger. 

Today arrived a substantial, but weak package, that managed to stay kind of in in shape during shipment.
I hoped for the best and schlepped it up to the 3rd floor.


Luckily there was no mechanical damange at all. The guy is in pretty good shape and very clean. It has the orgininal feets installed. It came with some SW disks.



It's an HP 35665A DSO from 1995.

And here comes the fun:
It has the swept sine option installed by licence, so I do not need to burn an eprom from the beginning to have some fun.
It passes all self tests.
The THD of the internal generator for 10.24 kHz is 0.037% which meets the magnitude of spec.



Winter has come back these days over here. Couldn't care less. Weekend is save. Nerd-save.   

My April 1st packet continues to be no prank.

It came with the sine swept option only,



but as there are some tutorials on the web how to add some opitons I spent some 40ct for an ST 24C01 eprom and some more cent for an programmer, did my first eprom programming ever, loosened some 20 screws, changed the socketed eprom and ...



... have some options more available.



Here' an octave measurement of the devices internal A filter:



And some recorded BASIC code:



the old battery from 2013 was not breathing any more but sended some last odors of decay at an voltage of some 200mV. As I had that card out anyway, I spent a new one.




With the new one the clock runs during power off and the non volatile inernal RAM disk keeps the makros.



The programmer aside, I spent some 10 Euros to get an 7500$ Upgrade in terms of the 1993 catalog. 

If anybody thinks it might be interesting I may start a seperate thread to report in more detail.

[mnementh]

   

Yeah, that's how I felt when I received my 54645A... I got waaaay more than I paid for. This was prior to The BumbleButt Incident, I believe... 



mnem
Man, I do miss that toolbox and that desk...

[tggzzz]

I have setup a simple test with my KEITHLEY 2015 DMM and a Python script. The script sets the GRUNDIG PN300's output voltages of both channels A and B to 5V, 15V and 25V and reads back the voltage at every step. After some fiddling with the DMM's readings, 10 cycles with 3 voltage settings for each channel, say 60 voltage settings overall read back ok - and so the repaired unit had passed all tests.

Good stuff, but where mechanics are concerned, don't forget the virtues of drop/kick tests. In this case, set the multimeter to its fastest sampling to catch transients.

[mnementh]

...I have setup a simple test with my KEITHLEY 2015 DMM and a Python script. The script sets the GRUNDIG PN300's output voltages of both channels A and B to 5V, 15V and 25V and reads back the voltage at every step. After some fiddling with the DMM's readings, 10 cycles with 3 voltage settings for each channel, say 60 voltage settings overall read back ok - and so the repaired unit had passed all tests.


Cheers,

THDplusN_bad

Good sleuthing THD! 

After decades of dealing with them on PC HDDs, those effing connectors are always high on my list of suspects. Good to see you caught another one and put it out of your misery.

I'll be honest tho... I wouldn't call it "good" with less than 100 iterations on that test setup. 10 iterations... that feels like just enough to taunt Murphy... 

Dumb question... since it appears you aren't going to mod the thing so the default failure mode is LOW VOLTAGE RANGE instead of high... maybe a good idea would be some simple crowbar circuit PCB you could plug into the outputs when you need to operate in LV mode...? Just a bit of added protection for the DUT?

mnem

[mnementh]

Totally agree, those Chinese AD584-M really are great little units and excellent value for money, if only they also did current and AC units like them, or could even build a unit with all three tests for a bit extra cash, it would be a great device to add into the toolkit.

Agree, as long as it is the one's with a legitimate label on the back indicating it's actual measured voltage. Both mine are. The one's with no label or "cookie cutter" label should be considered suspect.

I'm not sure how trustworthy the chinese devices are w.r.t. drift over time.

I'd look at Ian Johnson's devices https://www.ianjohnston.com/index.php/onlineshop He's on this forum He's evaluating whether his stock will allow him to offer more

We had some considerable conversation on this subject in here a year or three ago... I thought the consensus was that as long as the Vref was one of those obviously made using a reclaimed AD584x, they should be considered to be pretty well-aged and therefore pretty stable...?

mnem
 

Yes, we did indeed, and considering the huge price gulf between the Chinese AD584-M devices and those that Ian produces, I'd challenge anybody to get a better bang per buck performance ratio. Ian also has a Mastech MS7221 voltage and current calibrator in his arsenal which I also have, and he likes those as well. He paid £45 on eBay as a faulty unit and mended it, I also got mine on eBay but as a working unit and IIRC for a bit less as the seller had never used it and it was indeed like brand new in its case.

Ian devices use a LM399 voltage reference. You can't really compare them to a AD584 or Mastech MS7221.

I had mostly bad luck with cheap AD584 references. Ordered 3 and were all off from each other. Like I said previously they are probably ok to check 4.5 digits meters.

In all the discussions over these, I don't think anybody ever suggested they were suitable for anything more than 3.5-4.5 digits; I always considered them just a good reality check or value as a transfer standard, as long as you gave everything plenty of time to temp-stabilize and do your cal/adj all on the same bench at the same time, with immediate post-adjustment cal confirmation.

   https://www.tindie.com/products/circuitvalley/lm399-10v-precision-voltage-reference-calibrated/

Was it you that got one of the circuitvalley LM399 references? I can't remember if it was a bought thing or built from the GitHub project when we discussed it...

mnem
Oh dear... chiddlers are awake.

[Vince]

Nice... 80 bucks, 70 Euros maybe, made in Germany so cheap shipping for me I guess.

A potential next step ./ upgrade from my cheap Chinese AD584...

[Vince]

Guy on Ebay just did as promised a new ad to sell all of his DJET 10mm in a lot, so I can get all his stuff with a single shipping fee :

https://www.ebay.fr/itm/125253262712

19 Euros on offer, I sent an offer for 15, he counter with 17, deal done. Add 6 Euros shipping, for 23 Euros shipped, I get no less than 9 of these ultra expensive switches.

- The SPDT toggle switch and push button I needed
- PLUS no less than 6 DPDT toggle switches, hence very versatile / useful ,  AND.... a QUAD pole double-throw monster !!!! 

Can't wait to receive all that...

[mnementh]

Nice... 80 bucks, 70 Euros maybe, made in Germany so cheap shipping for me I guess.

A potential next step ./ upgrade from my cheap Chinese AD584...

The github is here if you feel like building your own: https://github.com/circuitvalley/LM399_Voltage_reference

For most of us, I still believe the DMMCheck/DMMCheck+ is the best bang/buck, as it comes with a variety of standards to check pretty much all the modes of a common DMM.

IIRC, the consensus was that it is adequate reference for up to 4.5-5.5 digits, or as a transfer standard for higher...?

https://dmmcheckplus.com/technical-information#

mnem
 

[med6753]

Well call me impressed. The vintage Tek LED light went from Washington State on Friday to my local PO this morning and out for delivery. This is not typical USPS. Should I be worried? 

It should be delivered here in about 3 hours or so.

[mnementh]

   Now problem #2. I used a cheap (16$) video recorder. The video out of the thermal camera was connected to the recorder and led / button of the recorder removed and replaced by a led / button on the camera.

Wow I didn't even know such tiny cheap modules existed for such purposes, incredible !  You learn a little something new every day on TEA !

Those Chinese are so nice spitting out all sorts of cool useful cheap tiny modules and stuff, what would we do without them... long live the Chinese ! -DD

Skip ahead to 1:20 if you want to get to the meat of the scene; which is that China plays the long game. 

mnem
"Patience was born in China." ~ancient Persian proverb

[Specmaster]

Ian devices use a LM399 voltage reference. You can't really compare them to a AD584 or Mastech MS7221.

I had mostly bad luck with cheap AD584 references. Ordered 3 and were all off from each other. Like I said previously they are probably ok to check 4.5 digits meters.

You get what you pay for, usually. I'm not aware of the price Ian charges for his reference, but I'd guess it's quite a bit more than £10 shipped.

Yep, I think I saw £285 mentioned on his site, so a similar price to the MS7221 really.

Ian Johnson's specs are better; Masstech is 200ppm.

It looks like Masstech's specs are defined to meet a market requirement, and are hence kept simple to interpret by non-specialists. OTOH, Johnson's look like they are derived from the components' specs, and are more complex to interpret. Horses for courses.

Yep, all very true, but as far I'm concerned, and I suspect many more people, the cheap AD584-M and the Mastech with its far greater settings for voltage and current are more than capable for most applications that we use a DMM for. I personally use my meters to assist in the repair of low tech TE and audio gear in the main part and for the application, a 3.5 digit meter is really adequate as I have yet to see reference voltages in a service manual / schematic go beyond 2 decimal places. Yes, I have DMM's with far higher resolution, not that I need it, but to me the extra digits are useful in indicating a trend with values increasing or decreasing over a period of time, way before a lesser DMM could detect it. They might well be critical in say Avionics or some Military applications, but I suspect for most people they are merely bragging rights, trump cards, and in no way are they mission critical.

That said this is TEA and if I could secure better DMM's or calibrators, at an affordable price, you'd better believe I'd go for it, but it has to be affordable for me, and it would be because I want it rather than I need it

[med6753]

Yep, all very true, but as far I'm concerned, and I suspect many more people, the cheap AD584-M and the Mastech with its far greater settings for voltage and current are more than capable for most applications that we use a DMM for. I personally use my meters to assist in the repair of low tech TE and audio gear in the main part and for the application, a 3.5 digit meter is really adequate as I have yet to see reference voltages in a service manual / schematic go beyond 2 decimal places. Yes, I have DMM's with far higher resolution, not that I need it, but to me the extra digits are useful in indicating a trend with values increasing or decreasing over a period of time, way before a lesser DMM could detect it. They might well be critical in say Avionics or some Military applications, but I suspect for most people they are merely bragging rights, trump cards, and in no way are they mission critical.

That said this is TEA and if I could secure better DMM's or calibrators, at an affordable price, you'd better believe I'd go for it, but it has to be affordable for me, and it would be because I want it rather than I need it

Exactly. And accounts for about 90% of my pile of stuff. 

[Vince]

Nice... 80 bucks, 70 Euros maybe, made in Germany so cheap shipping for me I guess.

A potential next step ./ upgrade from my cheap Chinese AD584...

The github is here if you feel like building your own: https://github.com/circuitvalley/LM399_Voltage_reference

For most of us, I still believe the DMMCheck/DMMCheck is the best bang/buck, as it comes with a variety of standards to check pretty much all the modes of a common DMM.

IIRC, the consensus was that it is adequate reference for up to 4.5-5.5 digits, or as a transfer standard for higher...?

https://dmmcheckplus.com/technical-information#

mnem
 

Oh yeah the DMMcheck of course, how could I forget about this one !

Hmm.. let me see the pros and cons of each product.

Circuit Valley :

- Half the price
- Open H/W.
- 10V output which is versatile, allows me to test all the digits all my DMM : 3,200 counts, 4,000 counts, and 50,000 counts.
- Super accurate.


DMMCheck :

- 5V output won't let me test properly my 3,200 and 4,000 meters, I would lose a precious digit. Even my 50,000 count meters well... the ref could still make them overflow and again lose the MSD.
- Less accurate than the other one.
- Twice the price or maybe more, their site doesn't say how much it would cost, shipped, when buying from their German stock.
- Features I don't need/want : frequency and duty cycle and AC.
- Good : does current, and offers a few precision resistors.


So if I could be arsed, the best bang for buck for me only for meeee.. would be to mix both products.
That is, make my own PCB, using the CircuitValley one and add precision resistors to the board, and add current as well. I guess I could simply connect the on-board precision resistors to the Vref and call it a day. The shunt value of the DMM ammeter would be much less than the ref Resistor on the board so it would still be plenty accurate enough for a very decent sanity check.

Oh, does that mean I have just added yet another project to my pile of projects ?! 

[TERRA Operative]

My April 1st packet continues to be no prank.

It came with the sine swept option only,

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1460659

but as there are some tutorials on the web how to add some opitons I spent some 40ct for an ST 24C01 eprom and some more cent for an programmer, did my first eprom programming ever, loosened some 20 screws, changed the socketed eprom and ...

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1460701

... have some options more available.

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1460665

Here' an octave measurement of the devices internal A filter:

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1460671

And some recorded BASIC code:

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1460677

the old battery from 2013 was not breathing any more but sended some last odors of decay at an voltage of some 200mV. As I had that card out anyway, I spent a new one.

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1460683
https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1460689

With the new one the clock runs during power off and the non volatile inernal RAM disk keeps the makros.

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1460695

The programmer aside, I spent some 10 Euros to get an 7500$ Upgrade in terms of the 1993 catalog. 

If anybody thinks it might be interesting I may start a seperate thread to report in more detail.

Even a quick writeup in its own thread with the steps involved would be awesome for future posterity and reference.

[THDplusN_bad]

[..]

I'll be honest tho... I wouldn't call it "good" with less than 100 iterations on that test setup. 10 iterations... that feels like just enough to taunt Murphy... 

[..]
mnem

Hi,

Thanks, mnem.

Oh, yes, I could not agree more. You need to make sure to be sure, right... 
I actually ran more tests today and have completed overall 3 rounds each with 50 cycles which equals 450 voltage settings and readings. A plot from one of these is attached; although there is not much to see there other than multiple straight lines overlaying. No fail. I was very happy to see that, of course. And this shows the value of scripting and automated measurements, of course.

@ Peter: I would certainly like to see more from your recent acquisition, the HP 35665A.

Cheers,

THDplusN_bad

[Vince]

There is one problem in this kind of testing / situation, though, which often haunts me... you don't know how many cycles it would take for the thing to FAIL, I mean, due its normal life expectancy.

Say it's good for a 1,000 cycles before it needs fixing/servicing... then by testing it 500 times, you are happy thinking cool, it works but... you have now just significantly reduced the life of the thing and will need to fix it again much sooner than it would otherwise have needed to ! 

[mnementh]

...I'll be honest tho... I wouldn't call it "good" with less than 100 iterations on that test setup. 10 iterations... that feels like just enough to taunt Murphy... 

Hi,

Thanks, mnem.

Oh, yes, I could not agree more. You need to make sure to be sure, right... 
I actually ran more tests today and have completed overall 3 rounds each with 50 cycles which equals 450 voltage settings and readings. A plot from one of these is attached; although there is not much to see there other than multiple straight lines overlaying. No fail. I was very happy to see that, of course. And this shows the value of scripting and automated measurements, of course.

@ Peter: I would certainly like to see more from your recent acquisition, the HP 35665A.

Cheers,

THDplusN_bad

Yeah, 450 measurements...? Guaranteed at least a few gonna be off due to human error... and then there's the lack of consistent timing on the test events.

Automated Test Process FTW. 

mnem
Now is that For The Win or Fuck The World? In this case... Ehhhh...?