what I have learned today.

[Pingu]

Lots of cheese...

[Mr Larrington]

The Renault Zoe one – a Nissan accelerator pedal may have been installed instead of a Renault accelerator – made this Unit smile.

[rafletcher]

Hmmm, a Jumpy Spacetourer, cool name!

[Giraffe]

The Renault Zoe one – a Nissan accelerator pedal may have been installed instead of a Renault accelerator – made this Unit smile.

Saw one today - it's 'lectrick.
I refer you to
https://en.wikipedia.org/wiki/Renault–Nissan–Mitsubishi_Alliance

[Cudzoziemiec]

That the Christian Congregational Church of Jamaica is ultimately governed from... Samoa!

[Diver300]

Kyocera AVX offer 2.96 million types of capacitor.

[Feanor]

Kyocera AVX offer 2.96 million types of capacitor.

I'll give you 10,000 house points to Griffindor if you can find me a source of replacement reservoir caps for the NAD amp I have on the bench.

22000uF 63v 105c.
Form factor: 35mm dia, 70mm tall, snap-in 10mm pin spacing.
The form factor is critical to fit the board.

I can only find these from crappy off-brand JCCON shit on ebay.
I might have to mount the replacements off-board with flying leads.

[Diver300]

Kyocera AVX offer 2.96 million types of capacitor.

I'll give you 10,000 house points to Griffindor if you can find me a source of replacement reservoir caps for the NAD amp I have on the bench.

22000uF 63v 105c.
Form factor: 35mm dia, 70mm tall, snap-in 10mm pin spacing.
The form factor is critical to fit the board.

I can only find these from crappy off-brand JCCON shit on ebay.
I might have to mount the replacements off-board with flying leads.

Electrolytic capacitors haven't improved much in the last 20 years, and oddities like that aren't easy to find.
I would suggest getting as much capacitance as you can in the space, for instance this:- https://uk.farnell.com/multicomp/mcklz063m103p51y/cap-10000-f-63v-alu-elec-snap/dp/2610649
and then adding flying leads to additional capacitor(s) in parallel. I would be concerned about the added resistance and inductance from flying leads. That would be reduced if some of the capacitance is in the same place as before.

[MattH]

I'd also be tempted to see if it genuinely needs 63v, or if the designer specced that because they were cheap/no more expensive at the time. Could even be that that was a part they already had on their system. I've done that in the past.
If it's over-rated, then 50v caps are available that otherwise meet the spec. But you'll need to look at the circuit carefully to be sure.

[rafletcher]

Courtesy of Mr Larrington, that  there’s a “Jump To” thingummy at the bottom left of YACF.

[Mr Larrington]

Er, it’s on the right.  Or at least it is on my fondleslab.

[Mrs Pingu]

Ah, that explains why I didn't understand what he was on about 

[Mr Larrington]

Today I are learning that in addition to that forerunner of the noble bicycle the draisine, Karl Freiherr von Drais also invented the keyboard-equipped typewriter* and the meat grinder.

* Or not, as Wikinaccurate's article on the tripewiter makes no mention of the good Baron.

[Feanor]

I'd also be tempted to see if it genuinely needs 63v, or if the designer specced that because they were cheap/no more expensive at the time. Could even be that that was a part they already had on their system. I've done that in the past.
If it's over-rated, then 50v caps are available that otherwise meet the spec. But you'll need to look at the circuit carefully to be sure.

Oh, it does.
The power supply on this device has a slightly unusual NAD feature, called PowerDrive.
The marketing blurb for this is total tosh ( it's hi-fi, after all ), but what it amounts to is this:

The main transformer has two sets of tappings: 'regular', and 'high voltage' (my terminology)
Each is connected to it's own bridge rectifier.
Under normal load, the 'regular' tappings feed the regular rectifier, and charge the reservoir caps to around +/- 50v.
If the load exceeds a threshold, then a pair of SCRs fire, and the higher-voltage DC from the 'high voltage' tappings and rectifier are switched on to the reservoir caps, pushing them up to slightly over 55v.

Basically a crappy solution to a poorly regulated under-spec PSU.
Make the base PSU able to hold up under load!
But there's not a marketing name for that...

[Diver300]

I'd also be tempted to see if it genuinely needs 63v, or if the designer specced that because they were cheap/no more expensive at the time. Could even be that that was a part they already had on their system. I've done that in the past.
If it's over-rated, then 50v caps are available that otherwise meet the spec. But you'll need to look at the circuit carefully to be sure.

Oh, it does.
The power supply on this device has a slightly unusual NAD feature, called PowerDrive.
The marketing blurb for this is total tosh ( it's hi-fi, after all ), but what it amounts to is this:

The main transformer has two sets of tappings: 'regular', and 'high voltage' (my terminology)
Each is connected to it's own bridge rectifier.
Under normal load, the 'regular' tappings feed the regular rectifier, and charge the reservoir caps to around +/- 50v.
If the load exceeds a threshold, then a pair of SCRs fire, and the higher-voltage DC from the 'high voltage' tappings and rectifier are switched on to the reservoir caps, pushing them up to slightly over 55v.

Basically a crappy solution to a poorly regulated under-spec PSU.
Make the base PSU able to hold up under load!
But there's not a marketing name for that...

To give them due credit, it does make the system somewhat more efficient. However, charging GBFO capacitors can't be done quickly, and it's not a big change from 50 to 55 V.

I've repaired power amplifiers with other odd power supply arrangements that improved the efficiency.

One had power rails at ±42V, ±84V and ±126 V (and about £200 worth of capacitors) and it would run power the main transistors from whichever rail would be enough. It would change very quickly, so running at 1 kHz and full power, each output cycle would be created using 8 changes of power rail voltage.

Another had two separate power supplies, which were in parallel but were switched to series for large voltage peaks.

Those used unregulated power supplies with really heavy transformers. Another arrangement that I have seen described is to have a switch-mode power supply, where the output voltage changes in response to what is being amplified, and stays a few volts above the output voltage required, following the waveform. The output transistors then remove the switching noise, but they never have a large voltage across them, so they don't get too hot.

±55 V will give around 1500 W into 4 Ohms if run as push-pull, so there is quite a lot of power to be handled. I've seen quite a few amplifiers where the power transistors have exploded, and anything that can keep the heating down is a help.

[Feanor]

Another arrangement that I have seen described is to have a switch-mode power supply, where the output voltage changes in response to what is being amplified, and stays a few volts above the output voltage required, following the waveform. The output transistors then remove the switching noise, but they never have a large voltage across them, so they don't get too hot.

At that point, you've gone 90% of the way to building a class D amp.
Why not go the rest of the way, and ditch the 'analog' output transistors room-heaters totally.

±55 V will give around 1500 W into 4 Ohms if run as push-pull, so there is quite a lot of power to be handled. I've seen quite a few amplifiers where the power transistors have exploded, and anything that can keep the heating down is a help.

Most amps are not designed or rated to operate in Bridge Mode for exactly that reason!

[Diver300]

Another arrangement that I have seen described is to have a switch-mode power supply, where the output voltage changes in response to what is being amplified, and stays a few volts above the output voltage required, following the waveform. The output transistors then remove the switching noise, but they never have a large voltage across them, so they don't get too hot.

At that point, you've gone 90% of the way to building a class D amp.
Why not go the rest of the way, and ditch the 'analog' output transistors room-heaters totally.

It's very difficult to filter enough of the switching noise to be inaudible. It's a lot easier to leave a few volts across some analog output transistors, and that will remove the switching noise. As there is only a few volts across the transistor, they don't become the serious room heaters that they would if the power supply was turned up to 11 all the time.

[Feanor]

On the subject of PSUs, when I was in my teenage years I would repair old TVs which people had put out with the bins!
With mixed success.
These would typically be based around the Thorn 1400 chassis.

The PSU on these involved a 'dropper resistor': a foot-long wirewound resistor with multiple tappings for different voltages.
To say this ran warm would be an understatement.
It sat out on metal arms, where free air could circulate past it to give that 'warm tv' smell.
Common failures were one section going open-circuit, where you could patch a new section in using bus-wire.

Other failures modes were one of the series-connected valve heaters failing open-circuit ( often the line output PL504 ); the Line Output Transformer, or the EHT Tripler, a marvellous Cockcroft-Walton voltage multiplier.

There was also a very particular smell, which indicated that a selenium rectifier had pooped itself!

Happy days.

[TheLurker]

That Inkscape's handy* little "calculate the area enclosed by a path" extension only works correctly if the path is drawn as single circuit to start with.  If you combine sub-sections to create the path it wilfully and incorrectly returns a smaller than correct value.

*There are various simple formulae available for determining whether a tail plane for a free flight model aeroplane is large enough. They rely on knowing the area of of both wing and tail plane and while one can approximate a planform closely with a selection of semi-circles, rectangles, triangles and trapezoids and do the sums by hand it is sooo much easier and quicker to trace the outline and point Inkscape at the problem.

[Cudzoziemiec]

Was told a couple of days ago actually. That the term "Asperger's syndrome" is now officially disused in America and discouraged in Europe, due to the eponymous doctor's Nazism and eugenic involvement. https://en.wikipedia.org/wiki/Hans_Asperger#Nazi_involvement

[ElyDave]

Was told a couple of days ago actually. That the term "Asperger's syndrome" is now officially disused in America and discouraged in Europe, due to the eponymous doctor's Nazism and eugenic involvement. https://en.wikipedia.org/wiki/Hans_Asperger#Nazi_involvement

Autistic spectrum seems to be more widely used these days

[T42]

Was told a couple of days ago actually. That the term "Asperger's syndrome" is now officially disused in America and discouraged in Europe, due to the eponymous doctor's Nazism and eugenic involvement. https://en.wikipedia.org/wiki/Hans_Asperger#Nazi_involvement

Autistic spectrum seems to be more widely used these days

We're all on the autistic spectrum somewhere.

[rafletcher]

That “Roundheads” didn’t refer to the helmets the Parliamentarians wore, but rather likened them to the crop-haired Apprentice boys, or London based hooligans.

[Kim]

That “Roundheads” didn’t refer to the helmets the Parliamentarians wore, but rather likened them to the crop-haired Apprentice boys, or London based hooligans.

This one was covered in the documentary Red Dwarf:

Rimmer : You all think I'm a petty-minded bureaucratic nincompoop who delights in enforcing political regulations because he gets some kind of perverse pleasure out of it. And in many ways, you're absolutely damn right! But that doesn't alter the fact that the only we're gonna down track Red Dwarf and get through this in one piece is with a sense of discipline, a sense of purpose, and wherever possible a sensible haircut.

Lister : [Feeling bored after Rimmer's speech]  I'm going back to bed.

Rimmer : Would it harm you to have hair like mine?

The Cat : I have got hair like yours. Just not on my head.

Rimmer : Well, I'm no stranger to the land of scoff. Perhaps you'd like to explain to me why it is that every major battle in history has been won by the side with the shortest haircut.

Kryten : Oh, surely not, sir!

Rimmer : Think about it! Why did the US cavalry beat the Indian nation? Short back and sides versus girly-hippie locks. The Cavaliers and the Roundheads, 1-0 to the pudding-basins. Vietnam, crew-cuts both sides, no score draw.

Kryten : Oh, for a really world-class psychiatrist!

[Mr Larrington]

Arnold Judas Rimmer BSC SSC has clearly never seen a picture of General George Armstrong Custer, military idiot and bar, who could have easily passed for the singer in a Southern Rock band.



Ronnie van Zant



George Custer