Test Equipment Anonymous (TEA) group therapy thread

[Robert763]

and a little mysterious TE thingie:   

It's a under-load cell tester for old-school Lead-Acid batteries with exposed bus bars between the cells. Grand-dad had one; also had such a battery in Miss Allis (old diesel tractor ~110HP or so).

mnem
 

AKA the crackle tester, so named for the noise it makes when you stab the probes onto the battery terminals. Make sure it's a 12V and not a 6V one before you test it on your car battery, as these things get HOT under nominal voltage; put a 6V one on a 12V battery and the resistive element may well melt before you can disengage it, as the probes have a tendency to weld themselves to the battery terminals.

Nooo it is not a complete battery tester but an old-fashioned cell tester, back in the day when batteries also had the cell connections visible rather than just the final + and - terminals on todays batteries. Also, I think you may want to revise your statement,  as a 6V battery only provide 50% of the heat generated as a 12V one would do to the load resistor.

Err
A 6V tester on 12V battery = 4 times the power I think the statement about putting a 6V tester on a 12V battery getting hot is valid.
Put a 2V tester on a 12V battery and it's 36 times the power 

[mansaxel]

That is an odd motor configuration. I suspect a faulty contact in the switch or other fault in the installation caused both the original failure and the post-rewind failure.

I'm suspecting a non-standard wired CEE 3-phase outlet, and the plug configuration altered to suit. The problem occurred when the unit was moved to a new site, where the outlet has been measured, by me, to be correct.

While the practice of always fitting 5-pole outlets with a neutral, even for Delta-coupled loads that do not require a neutral, is something I support and practice, it nevertheless creates a risk of confusion, like so:



Since a Delta load will only have three phase conductors plus PE, it is possible to wire neutral and L1 wrong. One's not supposed to, but...

(Why do I support this, since it has risks associated? Simply because I've been trying to borrow the kitchen heavy appliance outlets for sound and lighting gear so many times, only to find that they lacked neutral. I'm paying it forward. )

[Robert763]

The Tektronix LCD portable scope has been relisted from yesterday https://www.ebay.co.uk/itm/203545772627

It has a bid too...

[AVGresponding]

My bad, didn't look closely enough.

@Specmaster, if you put a 6V tester on a 12V battery, it will go incandescent quite quickly.

Testing a batch of a hundred or so newly delivered batteries used to be quite a warm job...



The Keithley 480 picoammeter arrived yesterday. Fortunately the connector is a quite mundane BNC, and not some exotica as I had feared.

Unfortunately, it seems there are some issues with it; the difference in readings it gives for a given current in different ranges is an order of magnitude in some cases.
I suspect the ganged range switches need a good cleaning, and the power switch too, as it's very sticky.

There's also the possibility it's missing a shield, as there's what appears to be a spring contact on the main board, but no shield in the case for it to connect to. Need to find and read a service manual it seems.
I am reluctant to get too deep into the gubbins as this thing has seriously sensitive inputs, and I don't want to risk contaminating the board or damaging some sensitive component.
It may end up waiting in the repair queue for quite a while.

[AVGresponding]

The Tektronix LCD portable scope has been relisted from yesterday https://www.ebay.co.uk/itm/203545772627

It has a bid too...

Yep that's me.   

[duckduck]

Beat me to it!

Sometimes you can get a bucket of slicia-gel packets from a footwear shop for free.  A packet in each shoe box adds up quickly...

Tip:  you can bake these packets in the oven to recharge (dry) them, to be used again or after a humid period.  Just not too hot to burn the paper packet.

I'll do you one better. Silica gel is sold as "crystal kitty litter". You can buy kilos of the stuff for around USD15 at your local supermarket. Making up little packets is easy enough with any kind of textile and a stapler. I have attached an example that I just found on a popular online shopping site.

EDIT:

It's even unscented.

[Cerebus]

...  as a 6V battery only provide 50% of the heat generated as a 12V one ...

Someone's forgetting their Ohm's Law - \$ V = IR \$, multiply both sides by \$ V \$ to get power on the right -> \$ V^2 = PR \$,  so power is proportional to voltage squared, \$ 6^2 = 36, 12^2 = 144 \$ so the ratio is \$ \frac{36}{144} = \frac{1}{4} \$ so 6V produces \$ \frac{1}{4} \$ the power that 12V does into the same resistance, not \$ \frac{1}{2} \$.

Edit: Beaten to it, but mine does show my workings and is prettier so, nyah!

[Robert763]

That is an odd motor configuration. I suspect a faulty contact in the switch or other fault in the installation caused both the original failure and the post-rewind failure.

I'm suspecting a non-standard wired CEE 3-phase outlet, and the plug configuration altered to suit. The problem occurred when the unit was moved to a new site, where the outlet has been measured, by me, to be correct.

While the practice of always fitting 5-pole outlets with a neutral, even for Delta-coupled loads that do not require a neutral, is something I support and practice, it nevertheless creates a risk of confusion, like so:



Since a Delta load will only have three phase conductors plus PE, it is possible to wire neutral and L1 wrong. One's not supposed to, but...

(Why do I support this, since it has risks associated? Simply because I've been trying to borrow the kitchen heavy appliance outlets for sound and lighting gear so many times, only to find that they lacked neutral. I'm paying it forward. )

Ahh that bit of history is useful. You are probably correct, wrong wiring, but its' also possible something got broken during the move.
Yesterday I was checking a box with 1 CEE inlet and two outlets. Found nothing connected to the earth terminals
But that's why we check...

[Specmaster]

and a little mysterious TE thingie:   

It's a under-load cell tester for old-school Lead-Acid batteries with exposed bus bars between the cells. Grand-dad had one; also had such a battery in Miss Allis (old diesel tractor ~110HP or so).

mnem
 

AKA the crackle tester, so named for the noise it makes when you stab the probes onto the battery terminals. Make sure it's a 12V and not a 6V one before you test it on your car battery, as these things get HOT under nominal voltage; put a 6V one on a 12V battery and the resistive element may well melt before you can disengage it, as the probes have a tendency to weld themselves to the battery terminals.

Nooo it is not a complete battery tester but an old-fashioned cell tester, back in the day when batteries also had the cell connections visible rather than just the final + and - terminals on todays batteries. Also, I think you may want to revise your statement,  as a 6V battery only provide 50% of the heat generated as a 12V one would do to the load resistor.

Err
A 6V tester on 12V battery = 4 times the power I think the statement about putting a 6V tester on a 12V battery getting hot is valid.
Put a 2V tester on a 12V battery and it's 36 times the power 

Yeah I misread it. I thought it was the battery being referred to and not the tester, but the tester is in fact as Mnem and I called it, a cell tester to be used on the old vintage batteries that had all the cell connections exposed and as such the battery voltage does not matter, 6V or 12V, the cell voltage is always going around 2.5V on a fully charged battery.

Take another look at the actual meter on that tester and you will see that reads -2.5V 0V +2.5V so its not a requirement to observe the polarity when testing a cell on old vintage batteries like these.

I just wish I had £1 for each time I have used these testers on bus batteries while doing my apprenticeship.

[bd139]

Looks like it’s for torturing interns with.

[Specmaster]

My bad, didn't look closely enough.

@Specmaster, if you put a 6V tester on a 12V battery, it will go incandescent quite quickly.

Testing a batch of a hundred or so newly delivered batteries used to be quite a warm job...

Not with the type of tester shown, read the meter scale for starters, the 2nd clue is that the actual prods of the tester are just to close to span across either 6V or 12V batteries. It is, as I mentioned, just an old style cell tester, these I don't think are in use today as most modern batteries are sealed for life, so you are not able to top up the acid levels or access the individual cell terminals, only the final terminals of the assembled battery.

EDIT.
Infact a whole battery should not be tested under load in this fashion because of the increased chances of an explosion happening. Whole battery testers are operated remotely where the meter and the load resistor is away from the battery and only heavy duty croc clips are connected to the battery, wired back to the tester and then the tester is operated usually via a push button to switch in the load to keep any potential ignition sources away from hydrogen gases that LA batteries give off.

[med6753]

Well I was able to test the replacement vertical output transistors (both good) and that's as far as I got. Family matters and other stuff intervened. Maybe tonight or tomorrow.

It's not a simple repair. The vertical board has to come out plus the bracket assembly behind it. Those 2 circular assemblies up top are the backside of the vertical output transistors.



 

[mnementh]

and a little mysterious TE thingie:   

It's a under-load cell tester for old-school Lead-Acid batteries with exposed bus bars between the cells. Grand-dad had one; also had such a battery in Miss Allis (old diesel tractor ~110HP or so).

mnem
 

AKA the crackle tester, so named for the noise it makes when you stab the probes onto the battery terminals. Make sure it's a 12V and not a 6V one before you test it on your car battery, as these things get HOT under nominal voltage; put a 6V one on a 12V battery and the resistive element may well melt before you can disengage it, as the probes have a tendency to weld themselves to the battery terminals.

Ummm... not quite. This particular version is used to measure individual cells; while the poky bits will sizzle a tad, especially if the bus bars under test are a bit crusty, we're talking typical 1.5-2.5V here. Terminal battery voltage makes no difference measuring cell-by-cell.

mnem
 

Oh, sweet cheese and crackers...       ...a page and a half later and still going...? Seriously?

mnem
*toddles off to buy some batteries I can lick*

[Neomys Sapiens]

Yeah .2v which is in spec now 

Have fixed the loose CRT and var knobs now as well. Reassembly in progress.

Robert deserves the jammy git award for that 8640B 

And my eternal envy -- for I desire a 8640B. Or any boat anchor RF gen. When I've got that, all i need is a SA. Or so I think.

Meanwhile, neither the repair queue nor the project stack are shrinking, but it is funnier to put them off and dream of gear...

Did a somewhat deep dive (deep since it did require me swimming in pretty uncharted waters of knowledge) into a 3-phase motor yesterday, for my neighbour. He's had it rewound by a winding shop but it does not work. We tried to find out if the winding shop had put it together correctly or not.

At any rate, it was moot, because something he's done to it -- perhaps as a consequence of faulty rewinding, perhaps not, it is thoroughly roasted. Again. We first tried to make sense of it by measuring ohms, but that did not help. Then I tried inductance (DE-5000  ). Made more sense, but not enough.  Finally, cracked it open, just to reveal a blackened winding.

It is called Dahlander circuit or -winding.
Some info in the pictures. Now the control circuit for the mains contactors shown depends on which transitions between speeds you want to allow. For this, all combinations do exist, so that you might switch only up, only via off, directly into both, up and down, etc.

And guess what? That guy was Swedish!

[med6753]

Yeah I misread it. I thought it was the battery being referred to and not the tester, but the tester is in fact as Mnem and I called it, a cell tester to be used on the old vintage batteries that had all the cell connections exposed and as such the battery voltage does not matter, 6V or 12V, the cell voltage is always going around 2.5V on a fully charged battery.

Take another look at the actual meter on that tester and you will see that reads -2.5V 0V +2.5V so its not a requirement to observe the polarity when testing a cell on old vintage batteries like these.

I just wish I had £1 for each time I have used these testers on bus batteries while doing my apprenticeship.

A Lucas battery? Why bother testing it. It will always be dead. 

[Specmaster]

No they won't, its a myth, they were in fact very good batteries.

[factory]

Another of those hp logic dart testers has appeared on ePay (US only), with a working screen this time. 


https://www.ebay.com/itm/224556878202

David

[BU508A]

and a little mysterious TE thingie:   

It's a under-load cell tester for old-school Lead-Acid batteries with exposed bus bars between the cells. Grand-dad had one; also had such a battery in Miss Allis (old diesel tractor ~110HP or so).

mnem
 

AKA the crackle tester, so named for the noise it makes when you stab the probes onto the battery terminals. Make sure it's a 12V and not a 6V one before you test it on your car battery, as these things get HOT under nominal voltage; put a 6V one on a 12V battery and the resistive element may well melt before you can disengage it, as the probes have a tendency to weld themselves to the battery terminals.

Ummm... not quite. This particular version is used to measure individual cells; while the poky bits will sizzle a tad, especially if the bus bars under test are a bit crusty, we're talking typical 1.5-2.5V here. Terminal battery voltage makes no difference measuring cell-by-cell.

mnem
 

Oh, sweet cheese and crackers...       ...a page and a half later and still going...? Seriously?

mnem
*toddles off to buy some batteries I can lick*

What do you expect? You are dealing with engineers here. Everyone wants to be at least a little bit right.

 

[Specmaster]

Or as we Brits and Mericans call it a star delta connection and the circuit shown is only for the power, the control circuitry has been omitted.

If all three coils are energised at the same there will be a big flash as K93M will present a bolted short circuit to the incoming 3 phase supply. In a correctly connected starter system for such a configuration, there should only ever be 2 contactors energised at any time.

To start it should be in star mode with K91M and K93M energised to place the windings in star fashion to reduce start up inrush current and once the motor has run up to speed and the current has dropped to a manageable level, K93M must de-energised and K81M energised to reconnect the motor windings in delta fashion. When in delta mode, both K91M and K81M contactors are closed.

[med6753]

No they won't, its a myth, they were in fact very good batteries.

Compared to what? This? 

[Robert763]

Just to tickle the dragon...
The risk of a hydrogen explosion is the same for testing 1 cell or the whole battery. While 2V will not make an arc, it will spark. The energy is low and unlikely to ignite petrol for example, the very low ignition energy of hydrogen (20uJ) and wide iginable mixture range meens ignition is likel even at 2V.

Of course you only get H2 evolved during charging and you should not test immediately after charge anyway.....
I once witnessed a lead acid battery explosion. It was a 24V trolley accumulator used for aircraft ground power. The line engineer had put it on charge earlier and then turned the charger off and went for his tea break before disconnecting it. He was fully aware of the danger, hence the break. After his break he dsconnected the lead and one battery exploded. He was very lucky. Was wearing prescription safety glasses so eyes were OK but a battery vent plug left a nasty cut on his forehead. He also needed new overalls.
Someone else had turned the charger back on thinking they were being helpful.

[Robert763]

Or as we Brits and Mericans call it a star delta connection and the circuit shown is only for the power, the control circuitry has been omitted.

If all three coils are energised at the same there will be a big flash as K93M will present a bolted short circuit to the incoming 3 phase supply. In a correctly connected starter system for such a configuration, there should only ever be 2 contactors energised at any time.

To start it should be in star mode with K91M and K93M energised to place the windings in star fashion to reduce start up inrush current and once the motor has run up to speed and the current has dropped to a manageable level, K93M must de-energised and K81M energised to reconnect the motor windings in delta fashion. When in delta mode, both K91M and K81M contactors are closed.

No, the circuit referred to is not Star/Delta. Star Delta is single speed and used to adjust voltage or lower current for starting. The
Dahlander is dual speed. It changes the number of poles in the motor by having two setsof windings and wiring each set either to the same phase (N poles) or next phase (2N poles).
I've not seen it drawn like that before so did not recognise it.

[BU508A]

Another arrival today: SMD prototype PCBs in fancy blue.

I've bought them here (NAWTS): https://www.ebay.com/itm/264795754351

Picture of them. They are two-sided cards that can simply be broken in half. The holes are plated through.


Detailed view with a scale:

[Cerebus]

...nasty cut on his forehead. He also needed new overalls.

And new trousers!

[Specmaster]

Just to tickle the dragon...
The risk of a hyrogen explosion is the same for testing 1 cell or the whole battery. While 2V will not make an arc, it will spark. The energy is low and unlikely to ignite petrol for example, the very low ignition energy of hydrogen (20uJ) and wide iginable mixture range meens ignition is likel even at 2V.

Of course you only get H2 evolved during charging and tou should not test immediatly after charge anyway.....
I once witnessed a lead acid battery explosion. It was a 24V trolly accumulator used for aircraft ground power. The line engineer had put it on charge earlier and thn turned the charger off ad went for his tea break before disconnecting it. He was fully aware of the danger, hence the break. After his break he diconnected the lead and one battery exploded. He was very lucky. Was wearing prescription safety glasses so eyes were OK but a battery vent plug left a nasty cut on his forehead. He also needed new overalls.

It was me who said that, not the dwagon 

That is all very true and is why all new battery testers do the switching of the load from a safe distance on the end of some suitable leads, so that when connecting the leads to the battery, it is done so with nothing connected to cause a spark. These testers can do so much more as well.