Test Equipment Anonymous (TEA) group therapy thread

[mnementh]

Okies... I picked up one of these cheap BT receiver modules because the feature-set is exactly what I wanted for a headphone receiver to pair with the FireTV, and it's still BT4.0 so it does pair properly with this older STB. Only problem is the final output is a PAM8403 2-ch Class-D amplifier, which does not play well with headphones due to common-GND wiring.

I was thinking of dumping the output across a couple of 10-100Ω pots in L-Pad config; then capacitive-coupling the (-) side for the return. Problem is, nowhere can I find any suggestion as to what the minimum loading is on this IC should be, and I'm worried aboot oscillation due to the RC filter I'm essentially making.

The board uses some random BT Chip (AS20BP01360-25A4) I couldn't find any documentation on, so no idea how much it can drive directly; worst case I can try tapping at the PAM8403 inputs and see how it works, but from prior tinkery I expect a lot of digital noise.

 Anybody here done any experimentation with the PAM8403?


mnem
 

[AVGresponding]

Just a heads up for international bidders: never buy an HPAK E36xx supply from the US. Some of them can't be converted to 230v.

Sure they can, you just need a big enough transformer 
BTW take care if using the yellow "110" worksite tool transformers. They are actually 55-0-55 volt with the center tap connected to ground. Some equipment does not like it's neutral being 55V below ground.

Not always. There's some marginal penny pinching bastard stuff that doesn't like 50Hz out there. Heathkit comes to mind

Good call with the tool transformers - never knew that. Makes sense though as it keeps the earth potential low enough that it's just going to wake you up a bit at 50V AC or so. Last time I did anything on 110V I was using my scariac to do the job which is definitely tapped at neutral and 110V.

It's a simple matter to remove the link that connects ground with the secondary centre tap. I can't recall ever seeing one where the ct is directly connected to the trafo chassis but I suppose it's possible, which would make it more tricky. Still all it would require is connecting the ground directly through, bypassing the trafo which is inside a sturdy case anyway.

Other things to be aware of is the VA rating. The headline rating will almost certainly be the intermittent maximum, the constant rating is usually around 33-66% of that.

I think there are filters in these PSUs that have components selected for 50 or 60Hz though? Might get more noise than you want if so, without swapping them.

[med6753]

Here is Larry all stripped down just to get to the defective Timing Switch board. 2nd pix shows the offender. Some Gorilla did indeed break it. Under the switch shield you can hear something rattling around and sometimes the switch would jam. The known good board out of Curly is silent and no jamming.

To keep my sanity and insure accurate work I just do a little bit of this mess each day and put it aside. And lots of pictures and written notes on how it all goes back together. And of course take my time. I don't want to have to go back in there for some stupid mistake.




Here is everything staged to go back in. That's tomorrow's agenda.   

[Robert763]

Just a heads up for international bidders: never buy an HPAK E36xx supply from the US. Some of them can't be converted to 230v.

Sure they can, you just need a big enough transformer 
BTW take care if using the yellow "110" worksite tool transformers. They are actually 55-0-55 volt with the center tap connected to ground. Some equipment does not like it's neutral being 55V below ground.

Not always. There's some marginal penny pinching bastard stuff that doesn't like 50Hz out there. Heathkit comes to mind

Good call with the tool transformers - never knew that. Makes sense though as it keeps the earth potential low enough that it's just going to wake you up a bit at 50V AC or so. Last time I did anything on 110V I was using my scariac to do the job which is definitely tapped at neutral and 110V.

I was thinking specifically of the E36XX units, but you are correct, a lot of cheap NA transformers don't like 50Hz even ones with dual 115V primaries. Power thansformers have a minmum volt/hertz product related to the core size. You need more Iron in the core at lower frequencies (This is why aircraft use 400Hz, the core is about 1/8th the size of a 50Hz one saving weight) So if you have a 50Hz 230V transformer ( 4.6V/Hz) you can run it at 276V 60Hz (insulation assumed to be OK) but one rated at 2 x 115V 60Hz (3.8 V/Hz) would only be good for 192V at 50Hz. So a lot of cheap 60Hz transformers run hot on 50Hz.

[Robert763]

Just a heads up for international bidders: never buy an HPAK E36xx supply from the US. Some of them can't be converted to 230v.

Sure they can, you just need a big enough transformer 
BTW take care if using the yellow "110" worksite tool transformers. They are actually 55-0-55 volt with the center tap connected to ground. Some equipment does not like it's neutral being 55V below ground.

Not always. There's some marginal penny pinching bastard stuff that doesn't like 50Hz out there. Heathkit comes to mind

Good call with the tool transformers - never knew that. Makes sense though as it keeps the earth potential low enough that it's just going to wake you up a bit at 50V AC or so. Last time I did anything on 110V I was using my scariac to do the job which is definitely tapped at neutral and 110V.

It's a simple matter to remove the link that connects ground with the secondary centre tap. I can't recall ever seeing one where the ct is directly connected to the trafo chassis but I suppose it's possible, which would make it more tricky. Still all it would require is connecting the ground directly through, bypassing the trafo which is inside a sturdy case anyway.

Other things to be aware of is the VA rating. The headline rating will almost certainly be the intermittent maximum, the constant rating is usually around 33-66% of that.

I think there are filters in these PSUs that have components selected for 50 or 60Hz though? Might get more noise than you want if so, without swapping them.

I have done this at a pinch, but have also seen units where the CT connection was under the potting. You MUST also change the output connecectors to a NEMA type or similar so that it can't be used for power tools as that would be unsafe.

[AVGresponding]

I have done this at a pinch, but have also seen units where the CT connection was under the potting. You MUST also change the output connecectors to a NEMA type or similar so that it can't be used for power tools as that would be unsafe.

Obviously (to me).

You wouldn't believe how many times I've had to cut couplers off the end of 110V festoon cable on sites. Telling people why it's a no-no is a waste of time, they just don't care.
Maybe I should let them have a nasty electric shock, they might be more inclined to listen at that point. Of course, then it would be my fault, for not protecting these Darwin award contenders from themselves...

[mansaxel]

BTW take care if using the yellow "110" worksite tool transformers. They are actually 55-0-55 volt with the center tap connected to ground. Some equipment does not like it's neutral being 55V below ground.

In my mind, that can't be to code. Of course, if the designer was a cheap bastard and cheated, then it's a problem, of course. But then said device would be prohibited to connect, and I don't think it would pass a PAT test.

Think of Norway, which is 220/127V with only the 3 phases and ground cabled most of the time, or perhaps someone running a computer or other device off of two phases of an US or avionics 208/120 net -- an AC supply that has both legs off of ground is not uncommon! Every ship with a three-phase mains system on it has the same situation. (you don't want current in the hull (if you want a hull that still is a hull after some time in electrolyte, ie. sea water), so you run delta-mains)

[AVGresponding]

BTW take care if using the yellow "110" worksite tool transformers. They are actually 55-0-55 volt with the center tap connected to ground. Some equipment does not like it's neutral being 55V below ground.

In my mind, that can't be to code. Of course, if the designer was a cheap bastard and cheated, then it's a problem, of course. But then said device would be prohibited to connect, and I don't think it would pass a PAT test.

Think of Norway, which is 220/127V with only the 3 phases and ground cabled most of the time, or perhaps someone running a computer or other device off of two phases of an US or avionics 208/120 net -- an AC supply that has both legs off of ground is not uncommon! Every ship with a three-phase mains system on it has the same situation. (you don't want current in the hull (if you want a hull that still is a hull after some time in electrolyte, ie. sea water), so you run delta-mains)

It does indeed comply with both BS7671 and IET PAT regulations.

The purpose is to ensure the potential is only ever 55V away from ground, which is a low enough voltage that even in worst case scenarios ensures current flow through a human body is minimal.

[med6753]

I've seen some 208V 3 phase breaker boxes here that have a label on them "No neutral". My assumption with that arrangement is that you can't have 120V service out of them.   

[Robert763]

BTW take care if using the yellow "110" worksite tool transformers. They are actually 55-0-55 volt with the center tap connected to ground. Some equipment does not like it's neutral being 55V below ground.

In my mind, that can't be to code. Of course, if the designer was a cheap bastard and cheated, then it's a problem, of course. But then said device would be prohibited to connect, and I don't think it would pass a PAT test.

Think of Norway, which is 220/127V with only the 3 phases and ground cabled most of the time, or perhaps someone running a computer or other device off of two phases of an US or avionics 208/120 net -- an AC supply that has both legs off of ground is not uncommon! Every ship with a three-phase mains system on it has the same situation. (you don't want current in the hull (if you want a hull that still is a hull after some time in electrolyte, ie. sea water), so you run delta-mains)

I assume you meen the equipment not the transformer or supply?
Note that this only applies to 115V equipment and it is an indication of poor design. Symptoms are mains frequency noise issues or premature PSU failure.

EDIT, Actually I have seen one case of it in the USA where somone connected a 240V item across the 220V split phase domestic supply. This put the power supply neutral 110V below ground.

[Robert763]

I've seen some 208V 3 phase breaker boxes here that have a label on them "No neutral". My assumption with that arrangement is that you can't have 120V service out of them.

Correct. Probably fed from a Delta transformer secondary. Delta windings use less copper than Star becuase the current is lower for the same power. Can also be because they only used 3 core and Earth cable instead of 4 core +E. You an always get 115V between a phase and ground.......

[mansaxel]

BTW take care if using the yellow "110" worksite tool transformers. They are actually 55-0-55 volt with the center tap connected to ground. Some equipment does not like it's neutral being 55V below ground.

In my mind, that can't be to code. Of course, if the designer was a cheap bastard and cheated, then it's a problem, of course. But then said device would be prohibited to connect, and I don't think it would pass a PAT test.

Think of Norway, which is 220/127V with only the 3 phases and ground cabled most of the time, or perhaps someone running a computer or other device off of two phases of an US or avionics 208/120 net -- an AC supply that has both legs off of ground is not uncommon! Every ship with a three-phase mains system on it has the same situation. (you don't want current in the hull (if you want a hull that still is a hull after some time in electrolyte, ie. sea water), so you run delta-mains)

It does indeed comply with both BS7671 and IET PAT regulations.

The purpose is to ensure the potential is only ever 55V away from ground, which is a low enough voltage that even in worst case scenarios ensures current flow through a human body is minimal.

Yes, indeed it is to code to keep the ground at a CT. Not liking it is what I thought couldn't be to code.

[mansaxel]

BTW take care if using the yellow "110" worksite tool transformers. They are actually 55-0-55 volt with the center tap connected to ground. Some equipment does not like it's neutral being 55V below ground.

In my mind, that can't be to code.

I assume you meen the equipment not the transformer or supply?

Yes.

Note that this only applies to 115V equipment and it is an indication of poor design. Symptoms are mains frequency noise issues or premature PSU failure.

EDIT, Actually I have seen one case of it in the USA where somone connected a 240V item across the 220V split phase domestic supply. This put the power supply neutral 110V below ground.

Yes, I think we agree. I certainly expect to be able to run proper gear off of a Norwegian outlet, or off-shore.

[Specmaster]

BTW take care if using the yellow "110" worksite tool transformers. They are actually 55-0-55 volt with the center tap connected to ground. Some equipment does not like it's neutral being 55V below ground.

In my mind, that can't be to code. Of course, if the designer was a cheap bastard and cheated, then it's a problem, of course. But then said device would be prohibited to connect, and I don't think it would pass a PAT test.

Think of Norway, which is 220/127V with only the 3 phases and ground cabled most of the time, or perhaps someone running a computer or other device off of two phases of an US or avionics 208/120 net -- an AC supply that has both legs off of ground is not uncommon! Every ship with a three-phase mains system on it has the same situation. (you don't want current in the hull (if you want a hull that still is a hull after some time in electrolyte, ie. sea water), so you run delta-mains)

It does indeed comply with both BS7671 and IET PAT regulations.

The purpose is to ensure the potential is only ever 55V away from ground, which is a low enough voltage that even in worst case scenarios ensures current flow through a human body is minimal.

Absolutely nailed it, it's all about reducing the shock risk to people which is very important on site work given the high risk of the power leads sustaining damage.

[AVGresponding]

3rd relist, and the opening price has dropped from £4k to £500. I still think that's too high, given the HDD has been erased meaning you need a new OS from Keithley, no doubt not cheap, before you can even do self-tests to see if any of the hw is borked.

Then add to that there's no test fixture, which it likely needs, looks to use triaxial cable, and is also likely expensive and/or hard to find. Looks to be some annoying damage to some of the connectors too.

https://www.ebay.co.uk/itm/Keithley-4200-Semiconductor-Characterization-System/353376546157

[bd139]

3rd relist, and the opening price has dropped from £4k to £500. I still think that's too high, given the HDD has been erased meaning you need a new OS from Keithley, no doubt not cheap, before you can even do self-tests to see if any of the hw is borked.

Then add to that there's no test fixture, which it likely needs, looks to use triaxial cable, and is also likely expensive and/or hard to find. Looks to be some annoying damage to some of the connectors too.

https://www.ebay.co.uk/itm/Keithley-4200-Semiconductor-Characterization-System/353376546157

That's worth about -£5 i.e. WEEE disposal. It's a PC with some acquisition cards in it. You'd need the cables, the software, the licenses, the cards repaired. If you have one already it's probably worth £100 or so for the bits and that's about it.

[beanflying]

All the better to pre choppy choppy stock for the Laser. Between this big boy and the Tracksaw I can't see me ever needing a Table Saw was part of the reason to go this size. Added feature is added likelihood of retaining the number of digits I was born with   

You think?

Proportion of YouTube videos watched involving stand-alone mechanical saws that make me wince expecting digits or limbs to go flying:

Horizontal bandsaws	10%
Table saws	20%
Vertical bandsaws	90%

Kickback or getting dragged into Tables saws is more like the 90% partly due to blade angles and also fence issues. Good pushsticks and methods are needed with all of them regardless

[AVGresponding]

That's worth about -£5 i.e. WEEE disposal. It's a PC with some acquisition cards in it. You'd need the cables, the software, the licenses, the cards repaired. If you have one already it's probably worth £100 or so for the bits and that's about it.

Haha I knew it wasn't worth what they were asking (to be fair they really have no idea on this stuff), but I didn't realise it was so bad.

Good thing I wasn't planning to bid on it!

[tautech]

All the better to pre choppy choppy stock for the Laser. Between this big boy and the Tracksaw I can't see me ever needing a Table Saw was part of the reason to go this size. Added feature is added likelihood of retaining the number of digits I was born with   

You think?

Proportion of YouTube videos watched involving stand-alone mechanical saws that make me wince expecting digits or limbs to go flying:

Horizontal bandsaws	10%
Table saws	20%
Vertical bandsaws	90%

Kickback or getting dragged into Tables saws is more like the 90% partly due to blade angles and also fence issues. Good pushsticks and methods are needed with all of them regardless

Yep, little stuff is where the highest risk is but often we're too lazy to mitigate risk. 

I used to have a evenings piece work sideline cutting a range of wedges for wedging the treads and risers in wooden stair construction and cut some 5 different sizes by the drum full. 
First cut was a 35mm wide wedge then split in half which was were real risk was and we had a tunnel covering the blade so to not wear any from the rear edge of the saw and anti kickback fingers on the inlet to the tunnel but it didn't stop one little swine one evening and flicked the sharp cornered little mongrel into the soft web between my thumb and forefinger to punch a good triangular divot and leak the red stuff big time. Put a funny look on my face I can tell you !   

[Tomorokoshi]

All the better to pre choppy choppy stock for the Laser. Between this big boy and the Tracksaw I can't see me ever needing a Table Saw was part of the reason to go this size. Added feature is added likelihood of retaining the number of digits I was born with   

You think?

Proportion of YouTube videos watched involving stand-alone mechanical saws that make me wince expecting digits or limbs to go flying:

Horizontal bandsaws	10%
Table saws	20%
Vertical bandsaws	90%

Kickback or getting dragged into Tables saws is more like the 90% partly due to blade angles and also fence issues. Good pushsticks and methods are needed with all of them regardless

Yep, little stuff is where the highest risk is but often we're too lazy to mitigate risk. 

I used to have a evenings piece work sideline cutting a range of wedges for wedging the treads and risers in wooden stair construction and cut some 5 different sizes by the drum full. 
First cut was a 35mm wide wedge then split in half which was were real risk was and we had a tunnel covering the blade so to not wear any from the rear edge of the saw and anti kickback fingers on the inlet to the tunnel but it didn't stop one little swine one evening and flicked the sharp cornered little mongrel into the soft web between my thumb and forefinger to punch a good triangular divot and leak the red stuff big time. Put a funny look on my face I can tell you !   

Radial Arm Saws: Hold my beer.

[bd139]

Random craziness which Med will find amusing based on his itty bitty moron heritage: Someone is trying to pay me to rewrite a cobol program for processing commissions that has been doing the rounds for 40 years into something “modern”. Looking at it I’ve actually come to the conclusion that they should just leave it the fuck alone and keep their z10. I give in. It’s the right tool for the job.

No TE purchases yet. Very disappointed this month already 

[cyclin_al]

Just a heads up for international bidders: never buy an HPAK E36xx supply from the US. Some of them can't be converted to 230v.

Sure they can, you just need a big enough transformer 
BTW take care if using the yellow "110" worksite tool transformers. They are actually 55-0-55 volt with the center tap connected to ground. Some equipment does not like it's neutral being 55V below ground.

Not always. There's some marginal penny pinching bastard stuff that doesn't like 50Hz out there. Heathkit comes to mind

Good call with the tool transformers - never knew that. Makes sense though as it keeps the earth potential low enough that it's just going to wake you up a bit at 50V AC or so. Last time I did anything on 110V I was using my scariac to do the job which is definitely tapped at neutral and 110V.

It's a simple matter to remove the link that connects ground with the secondary centre tap. I can't recall ever seeing one where the ct is directly connected to the trafo chassis but I suppose it's possible, which would make it more tricky. Still all it would require is connecting the ground directly through, bypassing the trafo which is inside a sturdy case anyway.

Other things to be aware of is the VA rating. The headline rating will almost certainly be the intermittent maximum, the constant rating is usually around 33-66% of that.

I think there are filters in these PSUs that have components selected for 50 or 60Hz though? Might get more noise than you want if so, without swapping them.

The Operating and Servicing Manual for my North American HP E3610A indicates:

Option  Description
0EM:115 Vac ± 10%, 47-63 Hz Input
0E3:230 Vac ± 10%, 47-63 Hz Input
0E9:100 Vac ± 10%, 47-63 Hz Input

So, according to that, 50-60 Hz input should not be an issue whether you use a trafo or install option OE3 (or your own equivalent).

EDIT:  Brain switched on a bit more:  What is the variance ±% on 50 Hz on your side of the pond?

[dl6lr]

Meanwhile in Italy...

And in France:


(All directions vs. other directions)

[med6753]

Random craziness which Med will find amusing based on his itty bitty moron heritage: Someone is trying to pay me to rewrite a cobol program for processing commissions that has been doing the rounds for 40 years into something “modern”. Looking at it I’ve actually come to the conclusion that they should just leave it the fuck alone and keep their z10. I give in. It’s the right tool for the job.

No TE purchases yet. Very disappointed this month already 

If ain't broke.......

[Cerebus]

EDIT:  Brain switched on a bit more:  What is the variance ±% on 50 Hz on your side of the pond?

UK: ±1% (i.e. 49.5Hz to 50.5Hz) The normal operational limits are much tighter at 49.8Hz to 50.2Hz.