I've never seen anything like that, but I'm in the UK where our mains wiring, mains switches are significantly more sturdy than most.

I'm guessing at it's function - does that give you power on/off control for a set of AC sockets at the back there?

Connecting multiple ground wires and the metal case with a rivet is probably not allowed in some countries.

megatron-uk wrote on 2023-01-14, 09:41:

I've never seen anything like that, but I'm in the UK where our mains wiring, mains switches are significantly more sturdy than most.

I'm guessing at it's function - does that give you power on/off control for a set of AC sockets at the back there?

Yes, these were actually fairly common in the US for many years. Mostly in office or home office environments.

I like big chonky toggle switches and I like to be able to cut power to specific devices that I'm not using, so I have been using them for many years... more specifically on my retro setups over the last 8 years or so. I have a really neat looking black one with green and red led switches hooked up to my MIDI stack. You can bet I'll be cracking that thing open ASAP though... I'd be mortified if my garage sale power center fried an MT-32, CM-64, SC-55 and TG-100 all at once while also starting a house fire. 😢

majestyk wrote on 2023-01-14, 14:07:

Connecting multiple ground wires and the metal case with a rivet is probably not allowed in some countries.

Yeah, I can't really comment on the soundness of the overall design because that's just not my area of expertise. There was definitely more than one thing wrong with this unit though, despite it looking solid and well built from the outside.

Also on the warning list, I've run into a PC power cable that swapped live and neutral. Gave me some serious problems that were very difficult to diagnose with a PID controller project.

RussD wrote on 2023-01-15, 05:14:

Also on the warning list, I've run into a PC power cable that swapped live and neutral. Gave me some serious problems that were very difficult to diagnose with a PID controller project.

Yep, one of these beauties came with my ZD-985 desoldering station. I believe this was a known problem with that unit. Funny thing is I never used the cable because I have two or three PC power cords permanently attached to one of my power centers (with a CRT on top), and I just switch the cables on as needed. When I read about the issue several months later I dug through my power cords and found the one that had come with the ZD-985, tested it, and sure enough it was backward.

Scary stuff!

Ozzuneoj wrote on 2023-01-14, 19:46:

megatron-uk wrote on 2023-01-14, 09:41:

I've never seen anything like that, but I'm in the UK where our mains wiring, mains switches are significantly more sturdy than most.

I'm guessing at it's function - does that give you power on/off control for a set of AC sockets at the back there?

Yes, these were actually fairly common in the US for many years. Mostly in office or home office environments.

I like big chonky toggle switches and I like to be able to cut power to specific devices that I'm not using, so I have been using them for many years... more specifically on my retro setups over the last 8 years or so. I have a really neat looking black one with green and red led switches hooked up to my MIDI stack. You can bet I'll be cracking that thing open ASAP though... I'd be mortified if my garage sale power center fried an MT-32, CM-64, SC-55 and TG-100 all at once while also starting a house fire. 😢

These type of things are also quite common in the UK, but they're significantly more durable and made to much higher standards:

You can get them in all kinds of form factors - trailing extension leads like the above are very common, but there are also desk mounted items, towers etc. It is very common to have individual switches on the sockets - all of our mains sockets are also individually switched in the UK. In a previous job I used to run the IT systems for a Computing department in a large UK university; the thought of having electrical equipment like that is absolutely terrifying - one thing I used to have my team do regularly was patrol for international students in our labs who had brought in their own extension cables, chargers etc. The idea of having equipment made to standards (if you can call them standards!) like that plugged in to labs with hundreds of thousands of £ worth of equipment in is crazy.

So the burnt/overheated part with the resistors and diodes, does anyone know exactly what's going on there?
My first guess would be that the voltage being fed in is higher than what was designed for, so the resistors aren't limiting the current to "safe" values...

jmarsh wrote on 2023-01-15, 20:58:

So the burnt/overheated part with the resistors and diodes, does anyone know exactly what's going on there?
My first guess would be that the voltage being fed in is higher than what was designed for, so the resistors aren't limiting the current to "safe" values...

Without seeing the traces I can't be sure, but I think it's even worse...

Normally if you want to turn AC into DC you first use a transformer to get AC voltage near what you want DC, use a bridge rectifier (network of four diodes) to turn the AC into bumpy DC, then add a big cap to smooth that into nice DC. You then use a voltage regulator on the DC to drop it down to exactly the desired voltage, either a linear regulator (which 'burns' off excess power) or a more elegant PWM regulator, with another cap to smooth out the pulses.

Here there's no transformer (that little coil certainly doesn't count as one) but worse: unless there's some interesting wiring underneath, there's no rectifier. Mains VAC is going straight into those rectifier diodes. They are chopping half of it off and the resistor after it is acting as a ghetto regulator to drop it from mains to whatever the LEDs take without blowing them out with too much current. With the imperfect lighting and discoloured resistors I can't exactly figure out their value, or even if they originally would have all been the same. That output in all its pulsing half-sine glory gets fed to the connector and the LEDs. That also means that these diodes and resistors are likely to get rather hot, which over time can cause things to go black.

These poor designs is rather common. Even the newest power bars are poorly designed, Contacts made of thin tree-like fingers weak stamped from brass sheet.

Finding quality one is not easy than you think.

Cheers,

Hmmm, I gots one of those with a different badge on... I wonder why one of the buttons/sockets on that seems dead... complete mystery obviously.

Before getting my MIDI stack hooked back up I disassembled the power center I intended to use for that. It doesn't look like a work of art inside, but thankfully, it looks to be a bit better quality than the other one. At least nothing is burnt, the outlets on the back are assembled similarly to a real surge protector, and it smelled like new electronics inside when I opened it - rather than burnt electronics. It is manufactured for\by National Lighting and seems to still be somewhat easy to find online. Interestingly, despite it's retro-look, it has a website address printed into the plastic on the bottom, so I would guess it is less than 20 years old.

Also, one more thing worth mentioning...

I was a bit surprised when I looked more closely at the big foil label on the "PC Concepts" one I originally posted about. It was playing double duty as a tamper-evident seal and the only date written on it was 1991... which really CAN'T be the date that the thing was manufactured. It had to have been just some arbitrary copyright date, either for the label or for that particular design. It was kept in an office with fluorescent lighting and windows, so the plastic front would definitely have been bleached if it was 30+ years old.

Two more pictures of this power center, and the neat retro-glow the fits so nicely with a MIDI stack.

Each device is connected to a switch. The mixer is switch on with the red Master switch. The rest are switched on in order from right to left, top to bottom. Very satisfying to switch them on this way, and I don't have to reach to the back for the MT-32.