Test Equipment Anonymous (TEA) group therapy thread

[med6753]

To all of our colleagues down under in Oz, how are you coping with the plaque of mice you guys are alleged to be having over there?

https://www.bbc.co.uk/news/av/world-australia-57225103

No major mice issue in central South Australia to date, we occasionally get an issue mainly in the wheat / cereal crop growing areas in spring, where the little buggers are eating the remains of the crops. I drive to those areas roughly once a fortnight and roughly a decade ago the mice were so bad that as you drove along a highway, you were running over swarms of them.
For the locals, mice in those numbers can be a real issue as they have a reputation for eating anything - electrical insulation/critical bits of cars/tractors adds some real challenges.

If you brought the Cane Toads from the other areas of the Country there would be no more mice. 

[beanflying]

To all of our colleagues down under in Oz, how are you coping with the plaque of mice you guys are alleged to be having over there?

https://www.bbc.co.uk/news/av/world-australia-57225103

No major mice issue in central South Australia to date, we occasionally get an issue mainly in the wheat / cereal crop growing areas in spring, where the little buggers are eating the remains of the crops. I drive to those areas roughly once a fortnight and roughly a decade ago the mice were so bad that as you drove along a highway, you were running over swarms of them.
For the locals, mice in those numbers can be a real issue as they have a reputation for eating anything - electrical insulation/critical bits of cars/tractors adds some real challenges.

If you brought the Cane Toads from the other areas of the Country there would be no more mice. 

That's been tried before and partly why we are in this mess. Introduced pests including us Humans and our crops along with non native species A-Z ....

While farming is a tough gig lack of taking seriously what was coming after a dry period into a better one just happens. The time for trapping and baiting is gone/missed and all they can do is chase and try and reduce the load until it gets colder.

Some of the media video grabs too are worst possible cases. Pile of unsecured grain under a tarp peel it back and look at the ratings 

[Cerebus]

There's your problem lady. Bottom wire from the delay line to the vertical output board is broken. I have to loosen that stud mount and slide the delay line slightly to the right to give enough slack to tack the wire down. More later.

What's the serial number of this scope? The way that delay line termination is handled looks totally different than the 454 I'm working on (aka Ol Sparkey).

How is that handled on yours? Is yours later than Med's? The reason I ask is that when I saw Med's I thought to myself "I'm not surprised that has broken off, a relatively long wire for its width stuck unsupported into a patch of solder. That's bound to cause trouble; I'm wouldn't be surprised if that was fixed in later scopes by an ECO". I'd be interested to see if I was right.

[Robert763]

Update on the Farnell AP60-50 1kW PSU repair.
Had to do a road trip last night  so no work on it but thought about the problem.
Interesting that the meters were at half scale and would adjust above 1/2. This immediatly made me think of negative supply failure on the analog control. Circuit shows a -15V generated by a 7815 (yes the positive version, not a typo). Got the covers off  and GPIB board removed  for access and there is a bank of TO120 devices. Quick voltage check, +12V on C30,  0V on C31 (the two yellow axial caps in the photo). Power off and a resistance check shows 0 omhs across C31. Whip the board out, Lift one end of C31 and it's a dead short. 100uF 40V aluminium electrolytic. The manual, which is branded Wayne Kerr, shows 100uF 16V. I put a 100uF 25V in. I also replaced C30, the only other cap of that type, which is across the +12V regulator.
Plugged it ain and it works 

Now to take it to work and find out what they are up to.

[med6753]

Update on the Farnell AP60-50 1kW PSU repair.
Had to do a road trip last night  so no work on it but thought about the problem.
Interesting that the meters were at half scale and would adjust above 1/2. This immediatly made me think of negative supply failure on the analog control. Circuit shows a -15V generated by a 7815 (yes the positive version, not a typo). Got the covers off  and GPIB board removed  for access and there is a bank of TO120 devices. Quick voltage check, +12V on C30,  0V on C31 (the two yellow axial caps in the photo). Power off and a resistance check shows 0 omhs across C31. Whip the board out, Lift one end of C31 and it's a dead short. 100uF 40V aluminium electrolytic. The manual, which is branded Wayne Kerr, shows 100uF 16V. I put a 100uF 25V in. I also replaced C30, the only other cap of that type, which is across the +12V regulator.
Plugged it ain and it works 

Now to take it to work and find out what they are up to.

A 16V capacitor on a 15V rail?  That's just asking for trouble and apparently did fail once before since you pulled out a 40V cap.

[Cerebus]

So, made some more changes to the GPSDO code, and also swapped out the OCXO for one of the others (just to make sure that I'm not pandering to the peculiarities of one particular OCXO).

Left it to run for a day and a bit and here's how it's looking:



Mean frequency error 0.0000159 Hz or 1 part in 1.59 x 10^-12 (\$\tau\$ = 97,200 aka 27 hours), standard deviation 0.345 Hz (There a few large outliers included in that standard deviation as you can see from the graphs). Peak-to-peak almost everything is inside a ±0.002 Hz band (or 1 part in 2 x 10^-10). So there's room for some improvement to hit the state of the art for an OCXO - not quite timenut, but certainly time-eccentric. 

However, something accurate to 2 parts in 10 billion cobbled together in a hot mess on a plugin breadboard ought to make the voltnuts weep by comparison to what's achievable in the volts/current field. 

Mean phase error -17.0 ns versus UTC, with standard deviation of 490 ns (again, includes outliers). It's pretty clear that there's a bias in the phase correction and I suspect it's a downward bias due to rounding because I have a deliberate deadband built into the code that doesn't steer it if the error is less than 2 times my measurement uncertainly, which uncertainty happens to be 17.2 nanoseconds. Obviously that's up for some careful analysis, but it's possible I might have to build in a bit of deliberate dither to avoid that bias.

A few more code tweaks and some tidying required, but it looks like the hardware side is basically sound. I have connected up the scope to the 10MHz and (locally generated) 1 PPS outputs and they look horrible, stable but horrible - but that looks down to lack of decoupling and the general kind of signal integrity issues that I'd expect from a mass of wires versus SMD decoupling caps and  nice fat ground and power planes. Then it's time to get an SPI LCD connected and check that that part of the hardware design is working, and then I think I can risk finalising the PCB design and sending it off for the Chinese elves to make.

The current mess that is the prototype:

[mnementh]

   

Sometimes you have to wonder aboot our connected world... Yesterday I went shopping for a 15mm cone wrench (an extra slim wrench that will fit the slots on the inner bearing race or "cone" of a bicycle wheel axle) and this was what came up at the top of Amazon's list for cone wrench. This is a tool which was developed primarily for plumbing work; yet it comes up as a hit for "pedal wrench" and "cone wrench" presumably from the reviews of the tool...?

What doesn't make sense here is not that they got the data from the reviews... but how did they sift that data from those reviews? This is not something easily divined from context by an algorithm. In fact, those terms would make no sense outside of the specific context of a) someone who needs a cone wrench and b) who knows what they're looking for. 

Maybe this is something that got added manually by the wetware... one at least hopes they have meat-sacks whose job it is to curate those lists to some extent; perhaps this is one of them. 

Under any circumstances, I have one on its way now... as it is the only option that will get to me in less than 2 weeks, and it is like $8 more expensive than the cheapest actual 15mm cone wrench they have.

mnem
...The consciousness of [the Cosmic] AC encompassed all of what had once been a Universe and brooded over what was now Chaos. Step by step, it must be done.  And AC said, "LET THERE BE LIGHT!"  And there was light --

[mnementh]

9:00 PM local time on May 25 and nothing's shown up.  Worse, eBay's timed out on leaving negative feedback or opening up the complaint process from what I can see.  Is there any way to get that re-opened?

Not that I am aware of.

You should be able to find it back and open a case over here: https://resolutioncentre.ebay.ca/

Even if your time has run out?

If you can get a dispute open or leave feedback, I would like to know!


Of course, if your payment came via a credit card, you could seek redress via the card issuer.  You won't be able to leave feedback or have it noted in your eBay profile, but you will probably get your money back.  I don't know what happens behind the scenes with a seller who causes this, but I would expect they will not get away untarnished.


My approach on the time limits involved is very firm.  I work out when the last day is supposed to be and then subtract two days from that.  On that day, if there are any outstanding issues, a dispute is raised REGARDLESS OF WHAT THE SELLER SAYS.  If you don't, you're stuffed ... and there are sellers out there that will deliberately play this game to keep your money.

Should the item turn up later, you can always contact the seller and sort out a means to make good - but you are in the drivers seat.  In all the years on eBay, I've had several no-shows and three occasions where I've had very late delivery (ie after dispute and refund) and I've contacted the seller to sort out payment.

This is also how I've played the eBay game for 3 decades; at first it was just being extra cautious... but not anymore. if one person in 10 forgets, that's cash in their pocket for nothing more than a few clicks on a computer.

eBay really is just a flea market... but devoid of the one benefit thereof: being able to hold and inspect the goods firsthand. You have to gird your loins and expect the worst every. fucking. time.

mnem
 

[0culus]

There's your problem lady. Bottom wire from the delay line to the vertical output board is broken. I have to loosen that stud mount and slide the delay line slightly to the right to give enough slack to tack the wire down. More later.

What's the serial number of this scope? The way that delay line termination is handled looks totally different than the 454 I'm working on (aka Ol Sparkey).

How is that handled on yours? Is yours later than Med's? The reason I ask is that when I saw Med's I thought to myself "I'm not surprised that has broken off, a relatively long wire for its width stuck unsupported into a patch of solder. That's bound to cause trouble; I'm wouldn't be surprised if that was fixed in later scopes by an ECO". I'd be interested to see if I was right.

See quote below, and photo.

What's the serial number of this scope? The way that delay line termination is handled looks totally different than the 454 I'm working on (aka Ol Sparkey).

This scope: B132966. It's brother: B298577.

B266304 here. I'm definitely fighting a temperature-dependent gain issue on this one. The horizontal gain is fine when the scope is cold, but after a few minutes, it becomes low.

[mnementh]

Hmmm... I'm not sure I believe that's a better solution.  That means any thin-wire break from thermal expansion/contraction is going to be inside the epoxy-potted end of that delay line itself where it cannot be repaired; at least here said break is an easy fix.

Furthermore... I'm not entirely sure that was the actual cause of the break; I'm seeing scars in the chassis right by that PCB screw makes me think a penis fingers might have been in there right close to that hair-thin wire with a screwdriver.

mnem
 

[Robert763]

Update on the Farnell AP60-50 1kW PSU repair.
Had to do a road trip last night  so no work on it but thought about the problem.
Interesting that the meters were at half scale and would adjust above 1/2. This immediatly made me think of negative supply failure on the analog control. Circuit shows a -15V generated by a 7815 (yes the positive version, not a typo). Got the covers off  and GPIB board removed  for access and there is a bank of TO120 devices. Quick voltage check, +12V on C30,  0V on C31 (the two yellow axial caps in the photo). Power off and a resistance check shows 0 omhs across C31. Whip the board out, Lift one end of C31 and it's a dead short. 100uF 40V aluminium electrolytic. The manual, which is branded Wayne Kerr, shows 100uF 16V. I put a 100uF 25V in. I also replaced C30, the only other cap of that type, which is across the +12V regulator.
Plugged it ain and it works 

Now to take it to work and find out what they are up to.

A 16V capacitor on a 15V rail?  That's just asking for trouble and apparently did fail once before since you pulled out a 40V cap.

It's worse than that. The PSU is old, Farnell branded and the 40V capacitors were clearly original. The manual is for a later version by Wayne Kerr (who bought out Advance who were spun out of Farnell or some such combination) which specifies a 16V capacitor on a 15V rail. Not good design.

[mnementh]

To all of our colleagues down under in Oz, how are you coping with the plaque of mice you guys are alleged to be having over there?

https://www.bbc.co.uk/news/av/world-australia-57225103

No major mice issue in central South Australia to date, we occasionally get an issue mainly in the wheat / cereal crop growing areas in spring, where the little buggers are eating the remains of the crops. I drive to those areas roughly once a fortnight and roughly a decade ago the mice were so bad that as you drove along a highway, you were running over swarms of them.
For the locals, mice in those numbers can be a real issue as they have a reputation for eating anything - electrical insulation/critical bits of cars/tractors adds some real challenges.

If you brought the Cane Toads from the other areas of the Country there would be no more mice. 

That's been tried before and partly why we are in this mess. Introduced pests including us Humans and our crops along with non native species A-Z ....

While farming is a tough gig lack of taking seriously what was coming after a dry period into a better one just happens. The time for trapping and baiting is gone/missed and all they can do is chase and try and reduce the load until it gets colder.

Some of the media video grabs too are worst possible cases. Pile of unsecured grain under a tarp peel it back and look at the ratings 

The kind of mouse that wears gloves like this...? That would be a plague...   

mnem
off. slightly.

[mnementh]

med... which do you like better; the gloss black or satin black filament? Finished product is pretty close to the correct dimensions now; just trying to get the surface looking presentable.

mnem
 

[med6753]

med... which do you like better; the gloss black or satin black filament? Finished product is pretty close to the correct dimensions now; just trying to get the surface looking presentable.

mnem
 

Actually it doesn't matter because it's in the back of scope and out of sight. What ever is easier for you.

[mnementh]

Neither one will be easier... it's just a matter of whether you like the gloss or satin finish better.  Of course nobody else will know what evils lurk back there... but you will.

mnem

[cyclin_al]

   

Sometimes you have to wonder aboot our connected world... Yesterday I went shopping for a 15mm cone wrench (an extra slim wrench that will fit the slots on the inner bearing race or "cone" of a bicycle wheel axle) and this was what came up at the top of Amazon's list for cone wrench. This is a tool which was developed primarily for plumbing work; yet it comes up as a hit for "pedal wrench" and "cone wrench" presumably from the reviews of the tool...?

What doesn't make sense here is not that they got the data from the reviews... but how did they sift that data from those reviews? This is not something easily divined from context by an algorithm. In fact, those terms would make no sense outside of the specific context of a) someone who needs a cone wrench and b) who knows what they're looking for. 

Maybe this is something that got added manually by the wetware... one at least hopes they have meat-sacks whose job it is to curate those lists to some extent; perhaps this is one of them. 

Under any circumstances, I have one on its way now... as it is the only option that will get to me in less than 2 weeks, and it is like $8 more expensive than the cheapest actual 15mm cone wrench they have.

mnem
...The consciousness of [the Cosmic] AC encompassed all of what had once been a Universe and brooded over what was now Chaos. Step by step, it must be done.  And AC said, "LET THERE BE LIGHT!"  And there was light --

Huh?

Here you go:
https://www.mec.ca/en/product/5048-516/DCW-Double-Ended-Cone-Wrench
Price is only $8.15 CAD
It is out of stock at your local store, but they have it downtown so you could pick it up today.

[mnementh]

So, made some more changes to the GPSDO code, and also swapped out the OCXO for one of the others (just to make sure that I'm not pandering to the peculiarities of one particular OCXO).

Left it to run for a day and a bit and here's how it's looking:      The current mess that is the prototype:   

Mean frequency error 0.0000159 Hz or 1 part in 1.59 x 10^-12 (\$\tau\$ = 97,200 aka 27 hours), standard deviation 0.345 Hz (There a few large outliers included in that standard deviation as you can see from the graphs). Peak-to-peak almost everything is inside a ±0.002 Hz band (or 1 part in 2 x 10^-10). So there's room for some improvement to hit the state of the art for an OCXO - not quite timenut, but certainly time-eccentric. 

However, something accurate to 2 parts in 10 billion cobbled together in a hot mess on a plugin breadboard ought to make the voltnuts weep by comparison to what's achievable in the volts/current field. 

Mean phase error -17.0 ns versus UTC, with standard deviation of 490 ns (again, includes outliers). It's pretty clear that there's a bias in the phase correction and I suspect it's a downward bias due to rounding because I have a deliberate deadband built into the code that doesn't steer it if the error is less than 2 times my measurement uncertainly, which uncertainty happens to be 17.2 nanoseconds. Obviously that's up for some careful analysis, but it's possible I might have to build in a bit of deliberate dither to avoid that bias.

A few more code tweaks and some tidying required, but it looks like the hardware side is basically sound. I have connected up the scope to the 10MHz and (locally generated) 1 PPS outputs and they look horrible, stable but horrible - but that looks down to lack of decoupling and the general kind of signal integrity issues that I'd expect from a mass of wires versus SMD decoupling caps and  nice fat ground and power planes. Then it's time to get an SPI LCD connected and check that that part of the hardware design is working, and then I think I can risk finalizing the PCB design and sending it off for the Chinese elves to make.

So... this will make sure my quadcopters arrive at their waypoints on time...?   

Nice bit of coding & hardware tinkery, C. I wish I were nearly as proficient in either arena.

mnem

[Cerebus]

Nice bit of coding & hardware tinkery, C. I wish I were nearly as proficient in either arena.

mnem

I'm sure you could do just as good a job as me at making a tangled crochet of jump wires. 

That's the problem with what's essentially a very simple bit of hardware that basically consists of gluing the right bits together - I don't tend to plan it, I tend to just do it. If that was as many transistors, a few resistors, the odd cap and a sprinkling of diodes I'd do a much, much tidier job of it.

[med6753]

Neither one will be easier... it's just a matter of whether you like the gloss or satin finish better.  Of course nobody else will know what evils lurk back there... but you will.

mnem

OK, surprise me. 

[tautech]

med... which do you like better; the gloss black or satin black filament? Finished product is pretty close to the correct dimensions now; just trying to get the surface looking presentable.

mnem
 

They need be subjected to the Bean test first:

[mnementh]

   

Sometimes you have to wonder aboot our connected world... Yesterday I went shopping for a 15mm cone wrench...

Huh?   Here you go:   https://www.mec.ca/en/product/5048-516/DCW-Double-Ended-Cone-Wrench   Price is only $8.15 CAD
It is out of stock at your local store, but they have it downtown so you could pick it up today.

Huh... never heard of them... Mountain Equipment Co-op...?  Also did not come up in my local search for "cone wrench", either on webcrawler or Googs.    I guess the owners probably don't pay for search-engine top-ranking out of principle, given the backstory on their Aboot: page.

The closest I know of from the Corporate Hinterlands south of the border would be Academy Sports & Outdoors; aside from a few boutique outfitters who are more designer outlets than actual outdoorsman shops.

Looked into pick up at store... they show a regular Park 15mm cone wrench at my local store for only $14 which I would gladly pay, but "available for pickup in 5-10 days"... My wrench from Amazon is paid for, and will be here Saturday. I can get either wrench from the downtown MEC tomorrow afternoon... but they are literally down-downtown and I loathe driving there. ehhhhhhh....

I will keep them in mind tho... have already added them to my business contacts. Thanks for the heads-up! 

mnem
 

[tautech]

Update on the Farnell AP60-50 1kW PSU repair.
Had to do a road trip last night  so no work on it but thought about the problem.
Interesting that the meters were at half scale and would adjust above 1/2. This immediatly made me think of negative supply failure on the analog control. Circuit shows a -15V generated by a 7815 (yes the positive version, not a typo). Got the covers off  and GPIB board removed  for access and there is a bank of TO120 devices. Quick voltage check, +12V on C30,  0V on C31 (the two yellow axial caps in the photo). Power off and a resistance check shows 0 omhs across C31. Whip the board out, Lift one end of C31 and it's a dead short. 100uF 40V aluminium electrolytic. The manual, which is branded Wayne Kerr, shows 100uF 16V. I put a 100uF 25V in. I also replaced C30, the only other cap of that type, which is across the +12V regulator.
Plugged it ain and it works 

Now to take it to work and find out what they are up to.

A 16V capacitor on a 15V rail?  That's just asking for trouble and apparently did fail once before since you pulled out a 40V cap.

It's worse than that. The PSU is old, Farnell branded and the 40V capacitors were clearly original. The manual is for a later version by Wayne Kerr (who bought out Advance who were spun out of Farnell or some such combination) which specifies a 16V capacitor on a 15V rail. Not good design.

No worse than Tek Tant derating. EE's that graduated from the same institution perhaps ? 

[med6753]

The 2nd Type 454 put back together. Even cleaned up and with a freshly painted cabinet the front panel still looks dingy. This scope must have sat in some crappy (but dry) area for many years. I wanted to pull the Time/Div knob assembly so I could clean the rear of the clear plastic. But the center metal insert is tightly galled against the switch shaft and won't come off. And if you pry the plastic itself sure as hell it will crack. I put some penetrating oil in there and I'll let it sit for a few days and try again.

I'm seriously considering putting this guy out on my local CL. I'll make sure all critical calibrations are in spec but I won't perform a PSU re-cap. The other Type 454 will be a keeper.


 

[med6753]

Update on the Farnell AP60-50 1kW PSU repair.
Had to do a road trip last night  so no work on it but thought about the problem.
Interesting that the meters were at half scale and would adjust above 1/2. This immediatly made me think of negative supply failure on the analog control. Circuit shows a -15V generated by a 7815 (yes the positive version, not a typo). Got the covers off  and GPIB board removed  for access and there is a bank of TO120 devices. Quick voltage check, +12V on C30,  0V on C31 (the two yellow axial caps in the photo). Power off and a resistance check shows 0 omhs across C31. Whip the board out, Lift one end of C31 and it's a dead short. 100uF 40V aluminium electrolytic. The manual, which is branded Wayne Kerr, shows 100uF 16V. I put a 100uF 25V in. I also replaced C30, the only other cap of that type, which is across the +12V regulator.
Plugged it ain and it works 

Now to take it to work and find out what they are up to.

A 16V capacitor on a 15V rail?  That's just asking for trouble and apparently did fail once before since you pulled out a 40V cap.

It's worse than that. The PSU is old, Farnell branded and the 40V capacitors were clearly original. The manual is for a later version by Wayne Kerr (who bought out Advance who were spun out of Farnell or some such combination) which specifies a 16V capacitor on a 15V rail. Not good design.

No worse than Tek Tant derating. EE's that graduated from the same institution perhaps ? 

Not quite. At least Tek used 20V rated in 15V circuits. And I'll bet that was the recommendation from the capacitor mfg themselves. "It will work just fine" and in reality it did. No one predicted that 40 - 50 years later this stuff would still be in use.   

[mnementh]

Nice bit of coding & hardware tinkery, C. I wish I were nearly as proficient in either arena.

mnem

I'm sure you could do just as good a job as me at making a tangled crochet of jump wires. 

That's the problem with what's essentially a very simple bit of hardware that basically consists of gluing the right bits together - I don't tend to plan it, I tend to just do it. If that was as many transistors, a few resistors, the odd cap and a sprinkling of diodes I'd do a much, much tidier job of it.

Challenge accepted:


            "Electric Spaghetti with Motorballs"    by mnem    ca 2010

mnem