Test Equipment Anonymous (TEA) group therapy thread

[psykok]

Wow looks likze I finally found my bench DMM !

https://www.leboncoin.fr/equipements_industriels/2104828351.htm

A 34401A DMM for half price ?!  250 Euros ! Guy pretends it works... looks like new, it's a modern Agilent branded one, VFD looks even an bright... what's the catch ? These HP DMM/counter/DDS usually sell for twice that, 500 Euros..; or have prices plummeted recently and nobody told me ?

Maybe it's fucked .. but then same goes for all the other ones sold at 500 so...

Of course seller will say he can't test anything, no test leads etc...so won't even bother asking... but maybe if there is a self test this thing perform on its own ? A magic key combination to trigger it ? Or some menu somewhere ? I guess if tell the guy/gal what button to press, in what sequence... he could reasonably be expected to do it... maybe.

Worse case if it really is fucked and not repairable. I can just flog it on ebay and probably get my money back and some more !

Or do you sense something obviously wrong  / fishy here, am I being naïve... and I should just keep my money and add some more for more modern unit with graphical LCD that can do stats and all, like Cerebus has ??

ALSO from this seller... another item I am interested in : an electronic load. 400 Euros so quite expensive but... it's a nice TTi unit and is beefy at 400 Watts !!! 

https://www.leboncoin.fr/equipements_industriels/2102353188.htm

I vaguely researched DC loads a while back and it seems that they cost about that much money, but for Chinese stuff, and that do only 150W.
No ? So this TTi looks great value for money what do you think ? Or am I again missing something obvious here... maybe voltage range is too limited compared to modern units ? It does 80 Volts.
TTi stuff is hard to come by over here, so it's not like I can count on seeing another one of these.
Looking at the rear panel though, it's got zero options... not GPIB... no RS232, no USB no LAN no nothing... and I now realize, looking at the pic of the back of the unit, it looks like the cooling fan is missing ?!
Hmmm... this unit was messed with maybe... which means the Agilent DMM probably was too, hence why it's cheap, he is trying to flog it... am suspicious now !
Might be why it has zero I/O at the back as well... can't believe TTi would sell a fancy unit like this without ANY knd of I/O.... I bet the guy didn't just pull the cooling fan, he pulled the I/O board as well ! 
And I don't need 400 watts.... pfff.... OK, it's more reasonable to spend the money on a brand new unit, that's under warranty, more compact, "only" 150+ Watts, good enough for me, and GPIB and other I/O.... yeah.  But it sucks, because I love this generation of TTi gear, love this industrial design !

Maybe I should keep my money that I don't even have... instead of making my financial situation even much worse than it already is 


BUT IT'S TEMPTING !!!   

i contacted the seller but after a small chat it looked like a scam to me ... be careful

More and more scam on this website regarding Lab Equipment.

[Cubdriver]

Vince the range change control knob is quite stiff on mine too. It works just fine so reckon it’s just normal.

Yeah, my 8654A has a rather stiff range selector switch, too.  I’m always afraid I’m going to snap the fin off the knob.

While heavy the range switch should be smooth between detents Pat.

The output level switch doesn’t feel right on the one I have - barely perceptible detents and no stops.  That said, it does seem to adjust the output range, so maybe I should leave well enough alone.

 
The output level control in mine has quite defined detents so something's let go in yours.

Wee look at mine here:
https://www.eevblog.com/forum/testgear/hp-8654b-10-520-mhz-sig-gen-light-teardown/

Perhaps 'stiff' was the wrong term for the feel of the frequency range selector - it is buttery smooth between detents, just feels like it’s mired in thick grease as it’s turned, and takes some effort to overcome the detent and get it moving - almost like trying to start a big heavy flywheel with sleeve bearings packed with heavy grease - big effort to initially get it to go, then smooth sailing once it’s going.  Thanks for the link to the pics - they are nice instruments.  At some point I’ll need to open it and try to figure out what ails the output range switch.

-Pat

[tautech]

Vince the range change control knob is quite stiff on mine too. It works just fine so reckon it’s just normal.

Yeah, my 8654A has a rather stiff range selector switch, too.  I’m always afraid I’m going to snap the fin off the knob.

While heavy the range switch should be smooth between detents Pat.

The output level switch doesn’t feel right on the one I have - barely perceptible detents and no stops.  That said, it does seem to adjust the output range, so maybe I should leave well enough alone.

 
The output level control in mine has quite defined detents so something's let go in yours.

Wee look at mine here:
https://www.eevblog.com/forum/testgear/hp-8654b-10-520-mhz-sig-gen-light-teardown/

Perhaps 'stiff' was the wrong term for the feel of the frequency range selector - it is buttery smooth between detents, just feels like it’s mired in thick grease as it’s turned, and takes some effort to overcome the detent and get it moving - almost like trying to start a big heavy flywheel with sleeve bearings packed with heavy grease - big effort to initially get it to go, then smooth sailing once it’s going.  Thanks for the link to the pics - they are nice instruments.  At some point I’ll need to open it and try to figure out what ails the output range switch.

-Pat

The rather large cavity oscillator is stepped with the range selector so it's moving a big chunk of iron however with the age of these units there's a fine chance any lube on the linkage is long gone so maybe a drop of WD40 or similar might free yours up.
Feel free to add your repair to the teardown thread.

[TERRA Operative]

- I just got a cool HP 3200B 500MHz oscillator that's got a defective attenuator.
- A TDS 544A scope that can't trigger (or other problem ?) above 400MHz... reducing the usefulness of the scope somewhat...
- A TDS 694C that needs a keypad fixing...
- A 2467B that escaped the magic smoke.

I can tell you a little hack to increase the bandwidth of the TDS scopes, even upgrade them to higher models...
Maybe leaving them at the current model numbers but removing the bandwidth limiting capacitors on the acquisition boards would help a bit...

Did you recently run SPC too?

Also, one favour to ask, can you tell me what firmware you have on your units? I might task you to extract it for my firmware collection if they are versions I don't have..... It's easy with a GPIB interface and a command line app.

[TERRA Operative]

2467B update : just gave it a chance... I plugged it back and tried to power it up.... it still works just fine !!!

So the RIFA smoke and fireworks didn't kill it, still works !!!   This scope is a warrior !! 

I guess the RIFA went open circuit rather than shorting, when they released the magic smoke.

Anyway will take it apart soon to fix the PSU. This wonder of a scope deserves a good cleaning and whatever servicing it needs. This thing is not a trouble maker no.. it's an asset in the lab 

Well, the Rifa did go short circuit, albeit temporarily....  

[tautech]

The fan's probably at the other end of the heatsink tunnel like with the Siglent SDL1000X series. They don't even spin up unless you have some reasonable load on the unit.

Did not bother to open it up but it is insanely quiet, so you are right.
Welcome to TTi, the Lamborghini of PSU and DC loads.

Looks just like a Fiat to me. 

I suppose the demonstrated ability to assess quality explains a lot.

So after 6 months absence you feel you need butt in and make comment when a couple of members have a bit of fun/joust/rib with one another ?   

Please crawl back into the abyss you surfaced from.

[Atomillo]

Hi:

I'm here once again to ask probably stupid questions!

The Keithley 181 nanovoltmeter arrived today. After opening it to change the mains voltage to 230V as well as to inspect everything is ok, I power it up. I measure some normal voltages and everything is fine. Here comes the weird thing. I try to zero the meter by connecting the input cable and shorting it. When I made this measurement, the unit had been powered on for 40 minutes with the cable connected in order to let everything stabilize. And yet, look at that result! VERY far from zero. Is that normal?

I also tried a small piece of copper shorting the inputs. Letting it stabilize for 10 minutes gave me a similar result.

I'm unfamiliar with low level voltage measurements. I've watched Marco Reps video and he's able to get very close to zero. I've taken the same precautions and yet it doesn't seem to matter.

I would greatly appreaciate any advice

Might come from your test lead. Doesn't look original. The connector should be silver and cable black and relatively thin. Keithley was using a low noise triax cable.

Like so


When I had a Keithley 181, I was able to get +-60nV with my home made test lead.
https://www.eevblog.com/forum/metrology/possible-low-thermal-emf-connectors/msg1936489/#msg1936489

It might very well be... It doesn't look at all like what you show. I thought it was original because the alligator clips seem "coppery".
However the input connector just looks white, no sign of copper. Might be the alligator clips are original but the connector itself is not.

I've just turned the unit on with a short using a very short piece of copper wire. Reading the manual, it recommends a warm up of at least 1 hour for stated accuracy and, more interestingly, "To guarantee low drift, allow at least four hours".

Will post results in a couple of hours!

[Saskia]

felt quite rotten over the week end. Headache, joint aches, slight fever, coughing, nose clogged.
C rapid test negative, boss told me to get a PCR test.
Doctor said: no positive rapid antigene test, no PCR test.

D'oh.

In other news negotiating for a PAT (made by Megger).
Is Megger a reputable company ?

[BU508A]

Hi:

I'm here once again to ask probably stupid questions!

The Keithley 181 nanovoltmeter arrived today. After opening it to change the mains voltage to 230V as well as to inspect everything is ok, I power it up. I measure some normal voltages and everything is fine. Here comes the weird thing. I try to zero the meter by connecting the input cable and shorting it. When I made this measurement, the unit had been powered on for 40 minutes with the cable connected in order to let everything stabilize. And yet, look at that result! VERY far from zero. Is that normal?

I also tried a small piece of copper shorting the inputs. Letting it stabilize for 10 minutes gave me a similar result.

I'm unfamiliar with low level voltage measurements. I've watched Marco Reps video and he's able to get very close to zero. I've taken the same precautions and yet it doesn't seem to matter.

I would greatly appreaciate any advice

Might come from your test lead. Doesn't look original. The connector should be silver and cable black and relatively thin. Keithley was using a low noise triax cable.

Like so


When I had a Keithley 181, I was able to get +-60nV with my home made test lead.
https://www.eevblog.com/forum/metrology/possible-low-thermal-emf-connectors/msg1936489/#msg1936489

It might very well be... It doesn't look at all like what you show. I thought it was original because the alligator clips seem "coppery".
However the input connector just looks white, no sign of copper. Might be the alligator clips are original but the connector itself is not.

I've just turned the unit on with a short using a very short piece of copper wire. Reading the manual, it recommends a warm up of at least 1 hour for stated accuracy and, more interestingly, "To guarantee low drift, allow at least four hours".

Will post results in a couple of hours!

Perhaps you might find this interesting.
https://www.eevblog.com/forum/repair/keithley-181-nanovoltmeter/msg2802190/#msg2802190

[Saskia]

@mnem get well soon !

[Atomillo]

Hi:

I'm here once again to ask probably stupid questions!

The Keithley 181 nanovoltmeter arrived today. After opening it to change the mains voltage to 230V as well as to inspect everything is ok, I power it up. I measure some normal voltages and everything is fine. Here comes the weird thing. I try to zero the meter by connecting the input cable and shorting it. When I made this measurement, the unit had been powered on for 40 minutes with the cable connected in order to let everything stabilize. And yet, look at that result! VERY far from zero. Is that normal?

I also tried a small piece of copper shorting the inputs. Letting it stabilize for 10 minutes gave me a similar result.

I'm unfamiliar with low level voltage measurements. I've watched Marco Reps video and he's able to get very close to zero. I've taken the same precautions and yet it doesn't seem to matter.

I would greatly appreaciate any advice

Might come from your test lead. Doesn't look original. The connector should be silver and cable black and relatively thin. Keithley was using a low noise triax cable.

Like so


When I had a Keithley 181, I was able to get +-60nV with my home made test lead.
https://www.eevblog.com/forum/metrology/possible-low-thermal-emf-connectors/msg1936489/#msg1936489

It might very well be... It doesn't look at all like what you show. I thought it was original because the alligator clips seem "coppery".
However the input connector just looks white, no sign of copper. Might be the alligator clips are original but the connector itself is not.

I've just turned the unit on with a short using a very short piece of copper wire. Reading the manual, it recommends a warm up of at least 1 hour for stated accuracy and, more interestingly, "To guarantee low drift, allow at least four hours".

Will post results in a couple of hours!

Perhaps you might find this interesting.
https://www.eevblog.com/forum/repair/keithley-181-nanovoltmeter/msg2802190/#msg2802190

Yes! In the manual, one can find out that Keithley sold special shorting plugs for the meter, which are very similar to the one machined in the thread. It definetely seems that thermal insulation is needed though.
Also, I will try what branadic did, to short the input directly in the input screw terminals. For now I'm gonna let it sit a couple of hours.

Thanks again for all the help!

[Specmaster]

felt quite rotten over the week end. Headache, joint aches, slight fever, coughing, nose clogged.
C rapid test negative, boss told me to get a PCR test.
Doctor said: no positive rapid antigene test, no PCR test.

D'oh.

In other news negotiating for a PAT (made by Megger).
Is Megger a reputable company ?

Oh dear, sounds like you may have C, but how the hell are you going to know what to do if there are no tests available? I guess you'll have to assume you have it and act accordingly.

Yes Megger is an excellent company, it is the main brand of PAT gear in the UK.

[Atomillo]

Hi:

I'm here once again to ask probably stupid questions!

The Keithley 181 nanovoltmeter arrived today. After opening it to change the mains voltage to 230V as well as to inspect everything is ok, I power it up. I measure some normal voltages and everything is fine. Here comes the weird thing. I try to zero the meter by connecting the input cable and shorting it. When I made this measurement, the unit had been powered on for 40 minutes with the cable connected in order to let everything stabilize. And yet, look at that result! VERY far from zero. Is that normal?

I also tried a small piece of copper shorting the inputs. Letting it stabilize for 10 minutes gave me a similar result.

I'm unfamiliar with low level voltage measurements. I've watched Marco Reps video and he's able to get very close to zero. I've taken the same precautions and yet it doesn't seem to matter.

I would greatly appreaciate any advice

Might come from your test lead. Doesn't look original. The connector should be silver and cable black and relatively thin. Keithley was using a low noise triax cable.

Like so


When I had a Keithley 181, I was able to get +-60nV with my home made test lead.
https://www.eevblog.com/forum/metrology/possible-low-thermal-emf-connectors/msg1936489/#msg1936489

It might very well be... It doesn't look at all like what you show. I thought it was original because the alligator clips seem "coppery".
However the input connector just looks white, no sign of copper. Might be the alligator clips are original but the connector itself is not.

I've just turned the unit on with a short using a very short piece of copper wire. Reading the manual, it recommends a warm up of at least 1 hour for stated accuracy and, more interestingly, "To guarantee low drift, allow at least four hours".

Will post results in a couple of hours!

Found a teardown of the original shorting plug: https://www.eevblog.com/forum/metrology/keithley-1488-low-thermal-shorting-plug-(a-quick-teardown)/

It seems like the input connector has copper plated connection so mine is probably not an original at all.

[Specmaster]

For all of those who have been wondering where Med6753 is, I can tell you that he is lurking in the background, fit and well, hasn't had one of his boat anchor scopes fall on him etc, he has just been too busy lately and that he'll be back on the thread before too long.

[mnementh]

felt quite rotten over the week end. Headache, joint aches, slight fever, coughing, nose clogged.
C rapid test negative, boss told me to get a PCR test.
Doctor said: no positive rapid antigene test, no PCR test.

D'oh.

In other news negotiating for a PAT (made by Megger).
Is Megger a reputable company ?

Yes, quite. They've been making insulation testers forever and their product is a standard in industry.

Also, thanks for the get well soon. I'm currently in that early morning limbo fugue state... trying to decide whether to go make coffee or crawl back under my rock and die...

mnem
grr. arrg.

[Saskia]

PCR Test tomorrow. Doc said that symptoms are in line with omicron version, however they need to ration the PCR tests. They would get me one in this case.

[BU508A]

Just stumbled over this YT-channel:
https://www.youtube.com/c/MachiningandMicrowaves/videos

A cross-over of machining things and playing around with RF.

Example:

[Saskia]

felt quite rotten over the week end. Headache, joint aches, slight fever, coughing, nose clogged.
C rapid test negative, boss told me to get a PCR test.
Doctor said: no positive rapid antigene test, no PCR test.

D'oh.

In other news negotiating for a PAT (made by Megger).
Is Megger a reputable company ?

Yes, quite. They've been making insulation testers forever and their product is a standard in industry.

Also, thanks for the get well soon. I'm currently in that early morning limbo fugue state... trying to decide whether to go make coffee or crawl back under my rock and die...

mnem
grr. arrg.

coffee is always good.

my symptoms are subsiding, only very slight headache remaining. Nose clogged, coughing a bit. But apart from that nothing serious. 2 Ibuprofen 400 mg were all I needed ...
Could have been the flu or some flulike infection as well.

[mnementh]

Glad you're on the mend. 

Coffee is always good; it's that infernal bootstrapping conundrum I mentioned earlier:

How do I get enough coffee in me that I can make coffee...?

mnem
*sniffle... honnnnnnnnk... koffff*

[mnementh]

Hi:

I'm here once again to ask probably stupid questions!

The Keithley 181 nanovoltmeter arrived today. After opening it to change the mains voltage to 230V as well as to inspect everything is ok, I power it up. I measure some normal voltages and everything is fine. Here comes the weird thing. I try to zero the meter by connecting the input cable and shorting it. When I made this measurement, the unit had been powered on for 40 minutes with the cable connected in order to let everything stabilize. And yet, look at that result! VERY far from zero. Is that normal?

I also tried a small piece of copper shorting the inputs. Letting it stabilize for 10 minutes gave me a similar result.

I'm unfamiliar with low level voltage measurements. I've watched Marco Reps video and he's able to get very close to zero. I've taken the same precautions and yet it doesn't seem to matter.

I would greatly appreaciate any advice

Might come from your test lead. Doesn't look original. The connector should be silver and cable black and relatively thin. Keithley was using a low noise triax cable.

Like so


When I had a Keithley 181, I was able to get +-60nV with my home made test lead.
https://www.eevblog.com/forum/metrology/possible-low-thermal-emf-connectors/msg1936489/#msg1936489

It might very well be... It doesn't look at all like what you show. I thought it was original because the alligator clips seem "coppery".
However the input connector just looks white, no sign of copper. Might be the alligator clips are original but the connector itself is not.

I've just turned the unit on with a short using a very short piece of copper wire. Reading the manual, it recommends a warm up of at least 1 hour for stated accuracy and, more interestingly, "To guarantee low drift, allow at least four hours".

Will post results in a couple of hours!

Perhaps you might find this interesting.
https://www.eevblog.com/forum/repair/keithley-181-nanovoltmeter/msg2802190/#msg2802190

Yeah, now that's what I was talking about with my "loop antenna" comment. I was pretty sure there had to be a shielded shorting plug for the thing. Interesting that the original is crimped rather than soldered; this is also a "thing" with the volt-nuts as the dissimilar metals affects accuracy at this range. I'd try to explain better, but I'm a card-carrying volt-mutt.

mnem
[FLUKE] sez BAMMM!!!

[BU508A]

Yeah, now that's what I was talking about with my "loop antenna" comment. I was pretty sure there had to be a shielded shorting plug for the thing. Interesting that the original is crimped rather than soldered; this is also a "thing" with the volt-nuts as the dissimilar metals affects accuracy at this range. I'd try to explain better, but I'm a card-carrying volt-mutt.

mnem
[FLUKE] sez BAMMM!!!

The keywords here are:
- symmetry
- no temperature gradient (as low as possible)

Then, but only then, you are allowed to solder it. Otherwise, crimping is the better solution.
And using the same metals, of course (and clean them before crimping).

[Saskia]

received commercial invoice and tracking information for the N6700. He's sending per UPS and UPS already announced delivery for Thursday.

which brings me to the question: is 600 yankee bucks a good price for a Keysight N6700 ?

[mnementh]

Coffee is always good; it's that infernal bootstrapping conundrum I mentioned earlier:

How do I get enough coffee in me that I can make coffee...?

mnem
*sniffle... honnnnnnnnk... koffff*

Oh, praise the Goddess (my wife ); SWMBO made coffee before she left for work.

mnem

  I am unworthy.

[mnementh]

For all of those who have been wondering where Med6753 is, I can tell you that he is lurking in the background, fit and well, hasn't had one of his boat anchor scopes fall on him etc, he has just been too busy lately and that he'll be back on the thread before too long.

Thanks for checking in on him; I was starting to worry that he might have caught the same wave of C-word that I did.

I have tried not to worry too loudly, we know how the resident caveman hates all that mushy stuff. 

mnem
*toddles off to drug himself up again*

[mnementh]

received commercial invoice and tracking information for the N6700. He's sending per UPS and UPS already announced delivery for Thursday.

which brings me to the question: is 600 yankee bucks a good price for a Keysight N6700 ?

A quick Gurrgle shows the 6700C going for ~$3K; I see a refurb one for $2400. I think you got a decent deal, yeah; as long as it isn't going to sit unused. If you don't need it, obviously a good arbitrage acquisition.

mnem