EEVblog #828 - Siglent SPD3303X precision Lab PSU Teardown

[blueskull]

Recessed banana sockets are a compromise -- they're less versatile, but you're nominally safe from touching the terminals. If the terminals can't reach a dangerous voltage, then that's a fail, they're less versatile, but __________________.

Could the output be floated at a high voltage? For example, you could use a 15V bench supply to run the gate drive circuit for a motor drive that is running from a mains level supply.

That's stupid and dangerous. I usually use a known good isolated power module, such as a dcp020512u, to do this. I don't want to fry myself by accidentally touch some loose "signal and low power" wires.

[c4757p]

Instead of having to be "protected" from your banana jacks, how about, y'know, not touching them? This isn't handheld equipment. Just don't bloody touch them while it's turned on. We can save the stupid recessed jacks for handheld devices and the Hello Kitty editions.

[SL4P]

go have a coffee, while a trainee or your kids come into your work area.

[c4757p]

So? Your kids could stick their fingers in a toaster or lamp socket too. Don't be a fool and leave things powered up while you walk out, if you're working with dangerous voltages.

As for the trainee... what are you training for, the circus? If he doesn't understand not to touch bitey voltages he needs to repeat school, or otherwise learn the hard way

[Brumby]

My take on all these 'protective protocols' is that it is not intended to protect from deliberate stupidity, but to minimise the risk of accidental contact.

For example, I have never in my life ever known of an instance where something conductive has slipped between a mains plug and a wall socket shorting out the active and neutral - but obviously there have been.  So we now have insulated active and neutral pins.  I don't really mind this because it makes sense AND that it doesn't affect usage (unlike the earlier 'shroud' on line sockets, which caused me problems with a couple of things.)

My only gripe about recessed sockets is that you don't get the terminal post option, useful for securing bare wire connections.  If they are trying to say we should only use 'properly terminated' cables, then I would be miffed.  Trading off significant functionality for an incremental improvement in safety really rubs me up the wrong way.

[Brumby]

Oh, if anyone is still unsure about the question of a shorted turn on the toroidal - here's a snapshot from Dave's video:



I see what looks like a nylon spacer with a moulded rim to ensure the washer nut is kept centred and right away from the mounting disc.  I suspect this spacer will have a cylindrical protrusion at the rear, separating the bolt shaft and any other metalwork.  In short, there is no shorted turn.

Dave did point this out.

[madires]

I see what looks like a nylon spacer with a moulded rim to ensure the washer nut is kept centred and right away from the mounting disc.  I suspect this spacer will have a cylindrical protrusion at the rear, separating the bolt shaft and any other metalwork.  In short, there is no shorted turn.

Yup, you're right! But it would be still an interesting experiment to find out what the impact (in numbers) of a shorted turn in the middle of the toroid would be.

[Kleinstein]

The recessed safty conectors are useful (and in the EU required for a lab supply that deserves it's name) for low voltages too.
Its not about isolation of the connectors itself, but compatibitly with new safety plugs with a fixed insulation tube.

So even if the supply is low voltage this alows you to use the better cables as well and thus no more need to have the unsafe old style banana plugs or the plugs with movable shield.

[SeanB]

I see what looks like a nylon spacer with a moulded rim to ensure the washer nut is kept centred and right away from the mounting disc.  I suspect this spacer will have a cylindrical protrusion at the rear, separating the bolt shaft and any other metalwork.  In short, there is no shorted turn.

Yup, you're right! But it would be still an interesting experiment to find out what the impact (in numbers) of a shorted turn in the middle of the toroid would be.

low voltage high current 1 turn transformer?
primary overheat, insulation breakdown, etc = electroboom?

About 10 seconds after turn on the metal will be hot enough to start melting the outer insulation, and after around 20 seconds the transformer will do an impressive arcing smoke emitting death as the primary windings short together from the inner insulation overheating and melting off. Followed by either a fuse blowing, the mains breaker tripping or the input primary wires burning out.

Generally something to avoid if you can. If it is a higher than 500VA toroid it might only do all thin in under 1 second, leaving the smoking remains and a red hot metal chassis as well.

If the case is aluminium it might just melt out the bolt as well with the flames and arc, and if you are lucky the anodising will provide insulation so nothing happens for a while till the oxide is punctured for some reason.

[Fungus]

About 10 seconds after turn on the metal will be hot enough to start melting the outer insulation, and after around 20 seconds the transformer will do an impressive arcing smoke emitting death as the primary windings short together from the inner insulation overheating and melting off. Followed by either a fuse blowing, the mains breaker tripping or the input primary wires burning out.

Generally something to avoid if you can. If it is a higher than 500VA toroid it might only do all thin in under 1 second, leaving the smoking remains and a red hot metal chassis as well.

If the case is aluminium it might just melt out the bolt as well with the flames and arc, and if you are lucky the anodising will provide insulation so nothing happens for a while till the oxide is punctured for some reason.

With a bit of luck you can even get a second degree burn on your hands when you grab it to try pull the plug.   

[HKJ]

The recessed safty conectors are useful (and in the EU required for a lab supply that deserves it's name) for low voltages too.
Its not about isolation of the connectors itself, but compatibitly with new safety plugs with a fixed insulation tube.

You can get binding post that works with the shrouded banana plugs. I have that on nearly all my power supplies.

[tautech]

The recessed safty conectors are useful (and in the EU required for a lab supply that deserves it's name) for low voltages too.
Its not about isolation of the connectors itself, but compatibitly with new safety plugs with a fixed insulation tube.

You can get binding post that works with the shrouded banana plugs. I have that on nearly all my power supplies.

I'm after some of those, link please?

[HKJ]

I'm after some of those, link please?

I do not know where you can buy them, but Keithley and TTi uses them.

[Fungus]

I'm after some of those, link please?

I do not know where you can buy them

http://www.ebay.com/sch/i.html?_nkw=banana+shrouded+test++socket

[tautech]

I'm after some of those, link please?

I do not know where you can buy them

http://www.ebay.com/sch/i.html?_nkw=banana+shrouded+test++socket

Sorry, no.
4 mm banana shrouded socket to binding post.

Edit
And with X hole

[c4757p]

The recessed safty conectors are useful (and in the EU required for a lab supply that deserves it's name) for low voltages too.
Its not about isolation of the connectors itself, but compatibitly with new safety plugs with a fixed insulation tube.

So even if the supply is low voltage this alows you to use the better cables as well and thus no more need to have the unsafe old style banana plugs or the plugs with movable shield.

I cut the shrouds off my cables, because they're useless. Then they fit in any banana jack. Shame we all can't just stop selling shit to the EU until they learn not to be so up themselves with regulations.

[Monkeh]

The recessed safty conectors are useful (and in the EU required for a lab supply that deserves it's name) for low voltages too.
Its not about isolation of the connectors itself, but compatibitly with new safety plugs with a fixed insulation tube.

So even if the supply is low voltage this alows you to use the better cables as well and thus no more need to have the unsafe old style banana plugs or the plugs with movable shield.

I cut the shrouds off my cables, because they're useless. Then they fit in any banana jack. Shame we all can't just stop selling shit to the EU until they learn not to be so up themselves with regulations.

Shame we all can't just stop selling shit to the US until they learn to play better with others.

[John Coloccia]

The recessed safty conectors are useful (and in the EU required for a lab supply that deserves it's name) for low voltages too.
Its not about isolation of the connectors itself, but compatibitly with new safety plugs with a fixed insulation tube.

So even if the supply is low voltage this alows you to use the better cables as well and thus no more need to have the unsafe old style banana plugs or the plugs with movable shield.

I cut the shrouds off my cables, because they're useless. Then they fit in any banana jack. Shame we all can't just stop selling shit to the EU until they learn not to be so up themselves with regulations.

Shame we all can't just stop selling shit to the US until they learn to play better with others.

I don't know what I'd do without all that British lab equipment. 

Shrouded connectors on a power supply are a fail, because all that will happen is people will create workarounds which will be far less safe than regular binding posts. No reason you can't have both, which is clearly the safest and sanest path forward in the actual real world, not the make believe world of the bureaucrat.

[Tothwolf]

I cut the shrouds off my cables, because they're useless. Then they fit in any banana jack. Shame we all can't just stop selling shit to the EU until they learn not to be so up themselves with regulations.

Shame we all can't just stop selling shit to the US until they learn to play better with others.

If it would mean an end to the RoHS silliness outside of the EU then I'm all for it.

[Siglent America]

Just a quick note to let everyone know that the Siglent engineering team does pay attention to your comments and suggestions. They have informed us that they are addressing the SPD3303X/X-E internal wiring placement & dressing issues pointed out on Dave's video.

Thanks
Steve

[German_EE]

Fixing that wiring is easy, fixing the front panel issue will probably need a new front panel, one or more new PCBs with the holes 19mm apart and a new supplier of front panel connectors.

[Fungus]

Fixing that wiring is easy, fixing the front panel issue will probably need a new front panel, one or more new PCBs with the holes 19mm apart and a new supplier of front panel connectors.

I think they were referring to "internal wiring", ie. the loose mains wires at the side that were being cut by the sharp metal.

I'm not sure what he means by the "dressing issues".

[nctnico]

Dressing of wires: cable harnesses and / or fixating

[orin]

Just a quick note to let everyone know that the Siglent engineering team does pay attention to your comments and suggestions. They have informed us that they are addressing the SPD3303X/X-E internal wiring placement & dressing issues pointed out on Dave's video.

Thanks
Steve

They really need to address the binding posts - see attached picture of a SPD3303D as it arrived from Tequipment.  Still haven't heard back from then what they intend to do about it...

[orin]

errrr wait a minute, even the screw thread got torn out?

Broke at the wire hole... the holes that Dave criticized for being too small!