Test Equipment Anonymous (TEA) group therapy thread

[Wolfgang]

I am looking at hellishly complex solution for this at the moment but it should work. Going to look at a resistor-diode "sine shaper" network to generate a sine curve from a DC voltage. I can then drive this from an R2R DAC on a counter (0-60 / 0-12) chopped per hour/minute hand. That will give me one phase and two hands. Do this twice and it'll give me an objective position on a circle for two hands, then multiply these each by a simple 0-1 or 0-0.5 (depending on hours/minutes hand chopped in) ramp oscillator to draw the hand. Getting it working in all four quadrants should be fun. Haven't sussed that yet. I fully intend to do this with only opamps, diodes, resistors, capacitors and some counting logic (4000 series only).

I wrote a little python program to draw this out to see how good a sine you need to draw a clock face and it's not that scary. Only need about 7 points in the curve for people not to realise it isn’t a very good circle.

Might be worth investigating and understanding this technique https://www.electrooptical.net/News/sine-wave-generation-with-tanh-wave-shaper/ particularly if you aren't worried too much about fidelity.

The author, Phil Hobbs, is mentioned in AoE III.

IIRC, this was the technique (using transistors instead of diodes) implemented in the ICL8038 and XR2206.
It works quite well, down to half a percent of distortion, but DDS killed it all in the meantime.

[med6753]

Old school vs new school. Nice to see that everyone plays nice and gets along. 



Welcome to my Winter Wonderland. Much too early for this shit. And it started snowing again. 

[GreyWoolfe]

That irritates me actually about HP kit. It’s always ridiculously disproportionately long. 33120A only just fits on my shelf.

Fluke bench meters are no better in that regard either, no real reason for them being so long. I'm guessing they order up their enclosures in bulk and so when a model is released it has to go into their existing stock of enclosures in order to keep costs down?

My HP 3312A function generator is the same.  At least there is space at the back of the shelf that it can hang over a bit and there is no issue with the power cord. My GW Instek 8251A is almost as long as the HP 3478A.  I guess it's not just Fluke.

[xrunner]

One nice thing is that there are what appear to be decent scans of the operating and service manuals on the Keysight site; I just downloaded them a few minutes ago.  Now that I have these, perhaps I'll play with it some.

If you do, let me know what you think. I'm still mulling it over.

Oh, and despite its small front panel, this thing is loooooooooong - like over 20" long! 

-Pat

and ...

That irritates me actually about HP kit. It’s always ridiculously disproportionately long. 33120A only just fits on my shelf.

Yep, that's one thing I see that I don't like. I have only one other hp kit that is that long - hp 5316B freq. counter. I've been inside and don't completely see why they made it that loooooooong, seems like they could have made a two-tier PCB setup and it would have been a lot shorter. It doesn't fit on most shelves very well.

Old school vs new school. Nice to see that everyone plays nice and gets along. 

Looks like the old Fluke is just as accurate so why did you need the new one LOL. 

Just kidding it's a nice display. 

[med6753]

Old school vs new school. Nice to see that everyone plays nice and gets along. 

Looks like the old Fluke is just as accurate so why did you need the new one LOL. 

Just kidding it's a nice display. 

More digits to feed my volt-nuttery.   

[bd139]

My HP 3312A function generator is the same.

I had one of them a few years ago. I just opened it and looked at it and nodded to myself happily with a crazy grin. If you haven't cracked one of them open, do it. It'll make you do the same

Anyway it's successor, my 33120A is now cleaned up of sticker residue and bumper skank and the fan is replaced. Good as new! Initial calibration checks suggest it is pretty much spot on frequency and voltage-wise. At 2Vrms out it matches my 87V perfectly.

[Specmaster]

That irritates me actually about HP kit. It’s always ridiculously disproportionately long. 33120A only just fits on my shelf.

Fluke bench meters are no better in that regard either, no real reason for them being so long. I'm guessing they order up their enclosures in bulk and so when a model is released it has to go into their existing stock of enclosures in order to keep costs down?

My HP 3312A function generator is the same.  At least there is space at the back of the shelf that it can hang over a bit and there is no issue with the power cord. My GW Instek 8251A is almost as long as the HP 3478A.  I guess it's not just Fluke.

No its not, I have some HP bench meters and they are as big as the Flukes 

[Specmaster]

My HP 3312A function generator is the same.

I had one of them a few years ago. I just opened it and looked at it and nodded to myself happily with a crazy grin. If you haven't cracked one of them open, do it. It'll make you do the same

Anyway it's successor, my 33120A is now cleaned up of sticker residue and bumper skank and the fan is replaced. Good as new! Initial calibration checks suggest it is pretty much spot on frequency and voltage-wise. At 2Vrms out it matches my 87V perfectly.

Pictures? Well done with that, it will serve you well. I'm still struggling to find a decent RF signal generator at a sensible price, especially as I don't use them all that often but heyho I'll keep looking, be nice to reduce the size and weight of the one I already have at some point.

[bd139]

Pictures?

Not my photo for ref:

I'm still struggling to find a decent RF signal generator at a sensible price, especially as I don't use them all that often but heyho I'll keep looking, be nice to reduce the size and weight of the one I already have at some point.

Yes I'm trying to find one that isn't crap. Slightly hoping that a CMU200 or something will turn up at a hamfest one day. Not gonna happen 

[capt bullshot]

This HP kit looks nice inside.
For comparison, my latest TEA addition: https://cb.wunderkis.de/wk/AC-Source-EAC/teardown/

Still have to figure out how to operate the thing, it doesn't have any controls, everything via RS232, no description or manual nor software available. Manufacturer has still to answer my email, wonder if they'll ever do. About the same time this thing was manufactured (1990 ... 2000), I've worked for a small company, the boss would have declined support for a long time out of production unit.

[Housedad]

Pictures?

Not my photo for ref:

I'm still struggling to find a decent RF signal generator at a sensible price, especially as I don't use them all that often but heyho I'll keep looking, be nice to reduce the size and weight of the one I already have at some point.

Yes I'm trying to find one that isn't crap. Slightly hoping that a CMU200 or something will turn up at a hamfest one day. Not gonna happen 

 Pure TEA porn.

[mnementh]

OOOOOOOOOOHHHHHMMMMMMMMMMMMM...

mnem
AliEx strikes again! 

There's something quite "Zen" about that image.

Hence the caption when I first posted it. Thank you for noticing!      The "unbagging" was quite Zen in its own right.

Everything just fell out in that general arrangement; the bits in a pile, and the cables looped around them. I merely tidied it up a bit for the pic. 

If you squint it looks like a test card.

Yeah, I can see that; even down to the grid underneath and how it intersects the spiraling cables. 



MMMMMMHHHHOOOOOOOO...!

Here's what I woke up to on the bench this morning over my first cuppa coffee... kinda the inverse function thereof. Once the deed was done, I had to be elsewhere for a while.   

Maybe a better title would be Chaos Theory? Dinner Conversation? Politics?   

mnem
Feeling totally pants this morning.

[FransW]

Where did you get them?
Could not find them myself.

Thanks,

Frans

[mnementh]

Had no idea that existed! Thanks for the tip. What an amazing little IC. Worth 20 EUR.

However I feel it may be cheating a bit

So? Get the bugs worked out of the design using the IC, then reverse-engineer and simplify. Then it's not cheating; it's empirical engineering. 

Yeah, I know, right? All this BS so they can put a little old lady whose job it is to dust a metal cube out of work... 

mnem
My tongue tastes like a skidmark.    I need more coffee.

[med6753]

More pron to make your day. The Siglent SD3055 DMM. Analog board on the right. Digital board on the left. Next pix is the linear supply. The filter caps for the power supply are some unknown Chinese brand. It looks well laid out with no bodges. And yes, there is a slight amount of the trademark Siglent rust on the edges of the metalwork.

What I don't like. There's apparently no way that I see for the user to calibrate this instrument himself. And the user manual is totally mute on the subject. I assume it's calibration procedure would be to connect to that white header near the fan and then invoke some hidden routine to put it into calibration mode and then load specific constants into memory. But without a service manual I'm purely guessing. From what I can find so far a service manual is not available to the unwashed masses like me. Only Siglent can do the cal. Tautech, can you shed some light on this? Am I right concerning this or is the calibration procedure available?

[mnementh]

One of my fixes for knobs with cracked hubs like you're describing is to glue as you've done, then 2-4 lines of CA on the outside along the long axis of the hub, then slip a length of heat-shrink over it all and hit it with the heat gun. The CA on the outside dries almost instantly, but watch out for CA creeping inside the hub. When it's all dry ( you can test with a Q-Tip swab to be sure ), trim the excess HS tubing off the end and good for another couple decades unless some college kid gets a-hold of it. 

I was thinking heat shrink tubing, too. Good idea, the CA reinforcement. I shall keep that in mind.

Yup, gluing the hub to the heat-shrink really improves the rigidity of the repair; helps the knob not feel wobbly underhand. 

    TinkerDwagon Minute: Patching Cables

I've used a similar process to repair cables on lawnmowers that have been damaged by careless folding and cracked out to uselessness; often these are unobtanium or if they are available they cost more than the mower is worth, so it's either fix the one you have or cobble a generic one in to sortof work. Okay, okay... I'll admit I've done the same thing on bicycle cables too,    just because I couldn't be arsed to go out to three different stores to find the right one. 

Trim off the excess peeled up plastic sheathing, then hand-straighten the damaged area so the cable moves properly if you hold it straight. Clean with alcohol, then coat the entire outside of the cable with hot glue approx 2-3mm thick, covering any bare metal spiral and 50mm-ish down over good sheathing either side of the damaged area. Just make sure you get good coverage and as even layering as possible without going crazy; it doesn't have to be pretty. 

Next, cut yourself a piece of heat-shrink with the right ID that that it will easily go over the entire mass but still will shrink down to the cable diameter (finding this balance is key for a good repair), and about 20-25mm longer than the hot-glued area. Uninstall one end of the cable from the mower, put the heat-shrink in place, and then reinstall the end of the cable. Now commit your heat-gun abuse; the hot-glue under the tubing will coalesce into a little bullet-shaped "lump in the cable". While it's all hardening, operate the cable and adjust alignment by hand for free movement, then hold it in place until it's done setting. 

I've used this repair on my lawnmower here in the middle of the Tejas summer and it still holds, so pretty sure it'll hold for most applications, unless the damaged portion is right against a hot area of the engine.

Happy Tinkering!

mnem
Rocket Raccoon is my spirit animal.

[bd139]

More pron to make your day. The Siglent SD3055 DMM. Analog board on the right. Digital board on the left. Next pix is the linear supply. The filter caps for the power supply are some unknown Chinese brand. It looks well laid out with no bodges. And yes, there is a slight amount of the trademark Siglent rust on the edges of the metalwork.

What I don't like. There's apparently no way that I see for the user to calibrate this instrument himself. And the user manual is totally mute on the subject. I assume it's calibration procedure would be to connect to that white header near the fan and then invoke some hidden routine to put it into calibration mode and then load specific constants into memory. But without a service manual I'm purely guessing. From what I can find so far a service manual is not available to the unwashed masses like me. Only Siglent can do the cal. Tautech, can you shed some light on this? Am I right concerning this or is the calibration procedure available?

Looks reasonable. Protection looks a bit weak and a bit crammed. Compare to GW GDM-8341 [1] [2]

Calibration you'd hope was closed box. Anything in the manual? I know on the GDM-8341 there's a cal port on the back. This scared me away from it a bit. May be done via USB / serial emulation instead using SCPI (or whatever Siglent uses)

[1]

[2]

[0culus]

Wow, that really makes one appreciate the engineering that went into the HP 3455 and similar meters. The analog parts in those are shielded inside a metal case.

[SilverSolder]

That [the length of the enclosure] irritates me actually about HP kit. It’s always ridiculously disproportionately long. 33120A only just fits on my shelf.

I have an ancient WaveTek 175,  just to make HP equipment look more compact.   The unit is fully 24" deep...   

[med6753]

More pron to make your day. The Siglent SD3055 DMM. Analog board on the right. Digital board on the left. Next pix is the linear supply. The filter caps for the power supply are some unknown Chinese brand. It looks well laid out with no bodges. And yes, there is a slight amount of the trademark Siglent rust on the edges of the metalwork.

What I don't like. There's apparently no way that I see for the user to calibrate this instrument himself. And the user manual is totally mute on the subject. I assume it's calibration procedure would be to connect to that white header near the fan and then invoke some hidden routine to put it into calibration mode and then load specific constants into memory. But without a service manual I'm purely guessing. From what I can find so far a service manual is not available to the unwashed masses like me. Only Siglent can do the cal. Tautech, can you shed some light on this? Am I right concerning this or is the calibration procedure available?

Looks reasonable. Protection looks a bit weak and a bit crammed. Compare to GW GDM-8341 [1] [2]

Calibration you'd hope was closed box. Anything in the manual? I know on the GDM-8341 there's a cal port on the back. This scared me away from it a bit. May be done via USB / serial emulation instead using SCPI (or whatever Siglent uses)

[1]

[2]

Absolutely nothing in the user manual concerning calibration. We'll see what Tautech knows.

[tautech]

More pron to make your day. The Siglent SD3055 DMM. Analog board on the right. Digital board on the left. Next pix is the linear supply. The filter caps for the power supply are some unknown Chinese brand. It looks well laid out with no bodges. And yes, there is a slight amount of the trademark Siglent rust on the edges of the metalwork.

What I don't like. There's apparently no way that I see for the user to calibrate this instrument himself. And the user manual is totally mute on the subject. I assume it's calibration procedure would be to connect to that white header near the fan and then invoke some hidden routine to put it into calibration mode and then load specific constants into memory. But without a service manual I'm purely guessing. From what I can find so far a service manual is not available to the unwashed masses like me. Only Siglent can do the cal. Tautech, can you shed some light on this? Am I right concerning this or is the calibration procedure available?

Yeah I know Siglent changed their western websites but the full documentation is not at all hard to find.....just go to the product page, then Resources for that product, then Documentation and then list with all the manuals is available for download.
I could just leave you do find them but nah, nice guy that I am. 
https://www.siglentamerica.com/resources/documents/digital-multimeter/#sdm3055-series

[bd139]

One service manual: https://www.thelabeshop.com/files/5/3846/SDM3055_ServiceManual.pdf

No schematics (nothing has them these days) but it does show the calibration procedure and it's closed box cal via NI VISA drivers/computer/calibrator.

[mnementh]

Now that I have all this additional space I need to think about how to fill it up. 

That gave me a chuckle.   

I know, right? "Have to think about it..." ?!? 1st law, man.

The 10 Laws of TEA (and counting) :

1 )  TE will expand to fill all space available. And then some.
2 )  It's never "just a blown fuse."
3 )  That bodge will come back to bite you in the ass.
4 )  The availability of service documentation varies inversely with your current level of diagnostic frustration.
5 )  There's always more to fix than you first think.
6 )  Thou shalt use a probe prophylactic.
7 )  There is no substitute for exhaustive burn-in testing.
8 )  The TE you have on hand is never the TE you need to fix the TE you want.
9 )  Capacitors are Murphy's footsoldiers.
10) The adhesive used to apply a label is always stronger than the label itself.

mnem

*Falling in love with my MetCal all over again*

[tautech]

Gawd, that iron needs a clean mnem !

[Specmaster]

Gawd, that iron needs a clean mnem !

You beat me to it [emoji1787]