Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 3691800 times)

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Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72650 on: October 19, 2020, 11:21:32 pm »
@Cerebus, the input voltage is the same on both 3-5 and 4-5, 11.1Vac.

I did wonder about the accuracy of that required voltage because on other circuits where the voltage was critical I have seen the use of negative regulators, like the 7805 on the positive rail.
« Last Edit: October 19, 2020, 11:24:29 pm by Specmaster »
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Online BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72651 on: October 19, 2020, 11:34:11 pm »
@Cerebus, the input voltage is the same on both 3-5 and 4-5, 11.1Vac.

I did wonder about the accuracy of that required voltage because on other circuits where the voltage was critical I have seen the use of negative regulators, like the 7805 on the positive rail.

The absoulte voltage accuracy of a Zener is usually not that important. More important is the stabilty. For this, the current through the zener must be set to a certain point. For example, if one has a 1N829A the voltage is usually around 6.2V but the current must be set roughly at 3mA to 7.5mA through the 1N829 to get the most stability out there.

Link to the datasheet (NXP/Philips)
 
As for the voltage regulators:
7805 = +5V 1A
7905 = -5V 1A (different! pinout as for the 7805, don't ask, how I know...  :palm: )

Edit: corrected current and added link
« Last Edit: October 19, 2020, 11:39:41 pm by BU508A »
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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72652 on: October 19, 2020, 11:34:35 pm »


$31 or $37 W/Comms at bang-em-good

I'm just gonna leave this here where anybody might trip over it...

mnem
 >:D
 
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Offline Cerebus

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72653 on: October 19, 2020, 11:36:15 pm »
@Cerebus, the input voltage is the same on both 3-5 and 4-5, 11.1Vac.

I did wonder about the accuracy of that required voltage because on other circuits where the voltage was critical I have seen the use of negative regulators, like the 7805 on the positive rail.

That gives us about 15V across C22, and so roughly 32 mA through R59 and D11 => 162 mW dissipation in the diode (if the diode had to sink all that current), so 400 mW is fine. If it's a BZX55C5V1 or similar, they are rated for a voltage of 4.8V to 5.4V at 5mA, allow for a chunk of that 32 mA being used in the circuit proper and that 5.3V sounds completely reasonable.
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Offline med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72654 on: October 19, 2020, 11:38:47 pm »
Here is to be to be peaceful and orderly. Without bad smell due to my old crappy smoke extractor. Now its a covid proof fart extractor?

#1 rule to limit test gear damage: Limit coffee movement, hold coffee in stainless steel screwable mug. Always.

OK, I give up. What exactly are you trying to show in these pictures?  :-//

And I thought my phone took shitty pictures.  ::)
An old gray beard with an attitude.
 
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Online BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72655 on: October 19, 2020, 11:42:36 pm »
Here is to be to be peaceful and orderly. Without bad smell due to my old crappy smoke extractor. Now its a covid proof fart extractor?

#1 rule to limit test gear damage: Limit coffee movement, hold coffee in stainless steel screwable mug. Always.

OK, I give up. What exactly are you trying to show in these pictures?  :-//

And I thought my phone took shitty pictures.  ::)

Only, if it comes to pink brown curtains.   :-DD
The Tek-blue is very fine.  ;D
“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 
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Offline med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72656 on: October 19, 2020, 11:44:00 pm »



Are those solder splashes on the safety glasses?  :o

Many years ago I had a solder ball explode because of a trapped air pocket with similar results.
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Offline Cerebus

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72657 on: October 19, 2020, 11:46:26 pm »
@Cerebus, the input voltage is the same on both 3-5 and 4-5, 11.1Vac.

I did wonder about the accuracy of that required voltage because on other circuits where the voltage was critical I have seen the use of negative regulators, like the 7805 on the positive rail.

The absoulte voltage accuracy of a Zener is usually not that important. More important is the stabilty. For this, the current through the zener must be set to a certain point. For example, if one has a 1N829A the voltage is usually around 6.2V but the current must be set roughly at 3mA through the 1N829 to get the most stability out there.

Beware of that 3mA figure, the fancy 1N829A-1 and 1N829A-1 versions are measured at 7.5mA and that's also the test current for the guaranteed tempco on the fancy ones (5ppm/ºC). I know because I've got a carefully guarded set that I got for a very reasonable price. The stated range is 5.89-6.51V but my set are all within 30mV of the nominal 6.20V figure.
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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72658 on: October 19, 2020, 11:48:08 pm »
Here's datasheets for common Japanese spec MTZ family zeners. As you can see, package markings don't always coincide with nominal reverse voltage, and even nominal voltage is a pretty broad range dependent upon dissipation.

mnem
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Offline Cerebus

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72659 on: October 19, 2020, 11:51:11 pm »
Here is to be to be peaceful and orderly. Without bad smell due to my old crappy smoke extractor. Now its a covid proof fart extractor?

#1 rule to limit test gear damage: Limit coffee movement, hold coffee in stainless steel screwable mug. Always.

OK, I give up. What exactly are you trying to show in these pictures?  :-//

And I thought my phone took shitty pictures.  ::)

Perhaps it's the amount of smoke in the pictures? It looks a bit thick and pungent if you get my drift - that would explain the, erm, certain lack of coherence.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Online 0culus

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72660 on: October 20, 2020, 12:04:00 am »
Here is to be to be peaceful and orderly. Without bad smell due to my old crappy smoke extractor. Now its a covid proof fart extractor?

#1 rule to limit test gear damage: Limit coffee movement, hold coffee in stainless steel screwable mug. Always.

OK, I give up. What exactly are you trying to show in these pictures?  :-//

And I thought my phone took shitty pictures.  ::)

Perhaps it's the amount of smoke in the pictures? It looks a bit thick and pungent if you get my drift - that would explain the, erm, certain lack of coherence.

 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72661 on: October 20, 2020, 12:16:31 am »
Quote from: mnementh
      

And here it is all finished up. 14V @ 45A of industrial-duty DC power. Yum!




Time to go build me another caveman high-current ballast and do some load testing!

mnem



Are those solder splashes on the safety glasses?  :o

Many years ago I had a solder ball explode because of a trapped air pocket with similar results.

Those were my everyday glasses; that was collateral damage the last time I booty-fabbed a caveman ballast resistor like the one above.

I discovered, much to my dismay while soldering the intermediate twist-joints with my 150W GT7 gun, that tapping the excess solder off the joint caused a recoil due to the springy nature of the thing, sending excess solder right back at my face.  :o

I caught that image quite by accident while taking other pics; it appeared mysteriously on the roll between shots of the coils and connectors on the thing. Only thing I can figure is I must've hit the shutter while setting the camera down. :-//

In related events... Canadian coathangers are too fukkin' good.  :wtf:

I'm right now on coathanger number 7 (7 coil segments like in the wet load above) and still drawing way too much current; the steel wire is too damned fat! The cheap 'merkin coathangers above are nice & thin... only needed 4 to get loading right where I wanted. :-DD

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Online BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72662 on: October 20, 2020, 12:16:42 am »
@Cerebus, the input voltage is the same on both 3-5 and 4-5, 11.1Vac.

I did wonder about the accuracy of that required voltage because on other circuits where the voltage was critical I have seen the use of negative regulators, like the 7805 on the positive rail.

The absoulte voltage accuracy of a Zener is usually not that important. More important is the stabilty. For this, the current through the zener must be set to a certain point. For example, if one has a 1N829A the voltage is usually around 6.2V but the current must be set roughly at 3mA through the 1N829 to get the most stability out there.

Beware of that 3mA figure, the fancy 1N829A-1 and 1N829A-1 versions are measured at 7.5mA and that's also the test current for the guaranteed tempco on the fancy ones (5ppm/ºC). I know because I've got a carefully guarded set that I got for a very reasonable price. The stated range is 5.89-6.51V but my set are all within 30mV of the nominal 6.20V figure.

Yes, thanks. I've already corrected it. I've confused it with the roughly 3mA for a LTFLU-1 which I'm playing around with it here.
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Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72663 on: October 20, 2020, 12:53:25 am »
Ok guys, thanks for bolstering my knowledge of Zeners, so that's another road block then, back to head scratching again for now and retrace my steps in case I've missed something.
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Offline 25 CPS

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72664 on: October 20, 2020, 01:25:12 am »
In related events... Canadian coathangers are too fukkin' good.  :wtf:

I'm right now on coathanger number 7 (7 coil segments like in the wet load above) and still drawing way too much current; the steel wire is too damned fat! The cheap 'merkin coathangers above are nice & thin... only needed 4 to get loading right where I wanted. :-DD

mnem
Every silver lining has its grey cloud.

You need to remember that where Americans use 480 volts, we use 600 up here.  That in turn mandates the heavier coat hangers in order to handle the higher power dissipation requirements.
 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72665 on: October 20, 2020, 01:30:21 am »


mnem
« Last Edit: October 20, 2020, 01:32:45 am by mnementh »
 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72666 on: October 20, 2020, 04:44:36 am »
   

Angry Pixie Soup, anyone...? :-DD

*Linky*

mnem
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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72667 on: October 20, 2020, 05:46:49 am »
How about mine, taken just now nothing, touched or posed.
deplorable state. I think the clear bit on the right  because something fell off

I like the "expansion of horizontal surfaces" trick in which you place things in open drawers. It does bring a total new level of disorder. I can't compete.  :-DD

I wont.

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72668 on: October 20, 2020, 05:48:30 am »
3rd time today i see that same desoldering iron.... both your pictures, and my desk :-)

It is such a force enabler in repair. Especially on through-hole or solder lug. Oh, and mine is a gift from the wife ;-)

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72669 on: October 20, 2020, 06:19:02 am »
3rd time today i see that same desoldering iron.... both your pictures, and my desk :-)

It is such a force enabler in repair. Especially on through-hole or solder lug. Oh, and mine is a gift from the wife ;-)

talking about a good merrege  :-+ :-+   good find :)
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Offline battlecoder

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72670 on: October 20, 2020, 06:37:22 am »
Agreed. Somewhere in the vicinity of the oscillator crystal there should be a trimmer cap. Using a plastic driver you should be able to set it within +/-1Hz.

Warm up times: 1 hour is an absolute minimum. For critical adjustments as this example I consider 2 plus hours a minimum. Sometimes I'll even leave an instrument idling for as much as 12 hours before a final adjustment.

That's kinda what I thought I was going to find inside. Will try to do this today after work, thanks! It's great to have some confirmation _and_ guidelines for the procedure.
And yes, the counter IS definitely stable. The frequency drift I mentioned is for the signal generation circuitry. That turned out to go away with some warmup time, but still; you can leave it in a set frequency, and it will start moving up and down within a range (it was originally going just in one direction and just kept going and going... but after warmup it stayed within a range, and does no longer try to escape to infinity). It's not dead stable. I think the datasheet mentioned something like 2% FS per range, which is definitely meeting, though. (Although it was listed under "Precision" in the datasheet? I would have expected something like "stability" but that is nowhere to be found in the specs, so whatever)

Anyway, even if the output is not SUPER stable, it still gives a rather clean signal, and the counter seems to be quite decent, so if I can adjust the offset in the frequency measurements I think I'll be more than fine.

Thanks you both for your input! :D

Forgot to update you all on this (I got distracted by the amount of cool gear you are all getting!):
[attachimg=1][attach=1]

The last digit eventually spends more time in 1 than it does on 0, but it's the best I was able to do (I would have loved that to be the other way around, but oh well). Turns out making the last digit match required almost atomic precision.
Anyway, I'm really happy with the instrument. I think it looks great on the bench 8)
 
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Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72671 on: October 20, 2020, 06:52:26 am »
Are the bridge rectifiers hanging on the transformer lugs ?  :-//
And them little round bridges that give trouble on the PCB in the foreground ?  :scared:

Yeah they're all well overrated for the load.

Anyway :popcorn:  :-DD



 

Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72672 on: October 20, 2020, 06:58:42 am »
It does look a lot better from the front... but all that wirering looks a bit messy, i like that better with the older ET30/2

https://youtu.be/J7_efVmkjYs

but yours...on al other points is much more modern... nice catch!

Yeah I had an E30/2 for a while. Nice supplies but there are three flaws with them which is a problem IMHO. Firstly the edge connector carries mains as well as low voltage and they arc over if there's a problem. Secondly the switches get unreliable and thirdly, there's a little fish paper box over the mains side of the board when you're poking around inside which is somewhat inadequate these days. BUT they are excellent little supplies that run nice and warm and quiet :)

Agree about the wiring although it's probably easier to trace out in its technicolour spaghetti glory  :-DD

Edit: also on the E30's you need to solder a diode across the output terminals and across the pass transistors otherwise if there's a line failure and the load drives the power supply it'll blow the driver transistor  :palm:
 
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Offline Robert763

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72673 on: October 20, 2020, 08:37:17 am »
<SNIP>
[/quote]

Forgot to update you all on this (I got distracted by the amount of cool gear you are all getting!):
[attachimg=1][attach=1]

The last digit eventually spends more time in 1 than it does on 0, but it's the best I was able to do (I would have loved that to be the other way around, but oh well). Turns out making the last digit match required almost atomic precision.
Anyway, I'm really happy with the instrument. I think it looks great on the bench 8)
[/quote]

You will never get the last digit to sit on 0 during calibration. It's inherent in the design of most digital systems that the least significanrt bit will flip between 0 and 1. For a counter it depends on when the input signal switches compared to the counting gate in the counter (noise on the level trigger also contributes but is more noticable on high precision countes). The only way you will get a consistent zero is if the internal oscillator and the signal you are measuring are phase locked, but then you are not actually checking the accuracy of the internal oscillator.
 
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Offline battlecoder

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72674 on: October 20, 2020, 12:34:50 pm »


$31 or $37 W/Comms at bang-em-good

I'm just gonna leave this here where anybody might trip over it...

mnem
 >:D
I had the version without connectivity and it worked fine. And a few months ago I upgraded to the one with USB comm (not a fan of the BT option. That module plus the SMPS that powers it contribute with enough electromagnetic pollution on their own already). Works fine, but the noise/ripple levels are a bit on the high side. Definitely not something I'd use without filter caps if I'm working with a voltage (or noise) sensitive circuit, but it's great to have a cheap power supply that has a decent voltage/current range and can be controlled from the PC.
 


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