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Circuit building: stop using antique parts (2014)

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Re: Circuit building: stop using antique parts (2014)

#161

Post by cr0sh »

WalterBright wrote: post #149
cr0sh wrote: post #61

Earlier quoted context omitted.

> I doubt side by side they sound noticeably better but if you're building vintage it only makes sense to keep the 'tronics true to the time period. In vintage radio repair, they sometimes will replace old caps (usually electrolytics) with new ones, but put the new ones inside the old cans - to preserve the look of the device. Obviously, though, this won't work with all parts...

Old car dash instruments are often upgraded the same way. They use new parts to drive the original indicators so it all looks correct, but is actually accurate. There are even kits to replace the guts of old car radios with modern stereos while preserving the controls and dials and their function.

Speaking of cars, I know I've heard of people who restore old tube-based car radios replacing the "buzzer" (or whatever it's called) that boosts the battery voltage up to the "B" voltage (I think that's right) with something more "modern" (probably a 555 oscillator and some other parts); the metal can for the original part is more than roomy enough for the replacement, and the new stuff is more reliable.

Re: Circuit building: stop using antique parts (2014)

#162

Post by cr0sh »

jacquesm wrote: post #77
cr0sh wrote: post #62

Earlier quoted context omitted.

> before you overcome the housings capacity to get rid of the heat. The thing is, most of these larger BJT parts were designed to be used with heatsinks, not usually standalone. IMHO, there's nothing wrong with dropping some voltage and dumping some heat. Sure, it isn't efficient, but if you size everything properly, and your project can accommodate the heatsink - then where's the problem? Heck, a long time ago you c…

> outside of the L298's weird footprint, and the fact that heatsinks for them are almost unobtanium In a pinch: any piece of aluminum U profile will do, just drill a hole in it and use some heat conducting paste.

True, but there were some nice finned Multiwatt-15 heatsink profiles out there back in the day that looked nice. Sometimes they can be found NOS - but it's rare...

Re: Circuit building: stop using antique parts (2014)

#163

Post by fr0sty »

cr0sh wrote: post #161
WalterBright wrote: post #149

Earlier quoted context omitted.

Old car dash instruments are often upgraded the same way. They use new parts to drive the original indicators so it all looks correct, but is actually accurate. There are even kits to replace the guts of old car radios with modern stereos while preserving the controls and dials and their function.

Speaking of cars, I know I've heard of people who restore old tube-based car radios replacing the "buzzer" (or whatever it's called) that boosts the battery voltage up to the "B" voltage (I think that's right) with something more "modern" (probably a 555 oscillator and some other parts); the metal can for the original part is more than roomy enough for the replacement, and the new stuff is more reliable.

"Buzzer" = Electromechanical Vibrator

https://en.wikipedia.org/wiki/Vibrator_(electronic)

Re: Circuit building: stop using antique parts (2014)

#164

Post by clarry »

zw123456 wrote: post #100
TD-Linux wrote: post #79

Earlier quoted context omitted.

You might only need to spin the motor in one direction.

Yes, but even so, they also have half bridge chips, all the biasing and compensation, the correct diodes etc. The point is, a motor controller chip is more modern way that the old transistor or MOSFET way. unless you are designing some cheapo thing that will be produced in the millions and have to scrape every penny out of the design, it is better and easier to simply use a motor controller chip in my view.

Maybe you have a box full of transistors and diodes in the closet, because they're kinda needed for everything or at least very useful to have around. You can start building yesterday.

If you want that special bridge chip, you start looking through online stores and datasheets (what a chore, why do they have to suck so hard?), trying to find the chip that has the availability, a reasonable price, the right specs and appropriate package for your use. Then you pay the shipping cost on top of the component, which might be more than the component itself. Then you wait a week or two for the thing to arrive. Then you pray it is intact and you can maybe start building. Hope you ordered the right part and didn't make a mistake in reading the specs.

Re: Circuit building: stop using antique parts (2014)

#166

Post by WalterBright »

cr0sh wrote: post #161
WalterBright wrote: post #149

Earlier quoted context omitted.

Old car dash instruments are often upgraded the same way. They use new parts to drive the original indicators so it all looks correct, but is actually accurate. There are even kits to replace the guts of old car radios with modern stereos while preserving the controls and dials and their function.

Speaking of cars, I know I've heard of people who restore old tube-based car radios replacing the "buzzer" (or whatever it's called) that boosts the battery voltage up to the "B" voltage (I think that's right) with something more "modern" (probably a 555 oscillator and some other parts); the metal can for the original part is more than roomy enough for the replacement, and the new stuff is more reliable.

On my '72 Dodge, there's a mechanical device to lower the 12 volt system voltage to 5 volts for the dash instruments. It's a buzzer kind of thingy. Some people replaced it with a modern voltage regulator to get exactly 5 clean volts, and found that the instruments didn't work right.

It turns out that the instruments needed the erratic 5 volts, else they'd "stick".

Re: Circuit building: stop using antique parts (2014)

#167

Post by jwatte »

retrogradeorbit wrote: post #128
jwatte wrote: post #103

Earlier quoted context omitted.

ADC, MCU, DAC, done. Cheaper, too -- I think 50 cent ARMs can do that these days. Any pedal that isn't digital today is just nostalgia (like tube headphone amps and the like.) Digital is the clear better choice even for sound shaping.

Hogwash. There are effects that analogue clearly destroys digital on. And the main one is distortion. Digital is much more suited to time based effects. Analogue to harmonic distortion based effects. You can keep your ADC/MCU/DAC distortion pedal. But if you are ever wondering why your guitar distortion sounds crap, this is it. But maybe you think it's fine. Anything sounds great with cotton-ears. And tube amps only…

I'm more of a recording engineer than a guitarist (member of the AES for many years.)

Shitty digital pedals from 20 years ago sound shitty, I agree!

Well modelled digital effects, however, can these days give you anything an analog pedal can. Most of the time, just run a high accuracy Spice model of the pedal in real time! Modern DSP is so cheap and fast that this is possible and works fine.

Re: Circuit building: stop using antique parts (2014)

#168

Post by Kliment »

moron4hire wrote: post #156
Kliment wrote: post #148

Earlier quoted context omitted.

Hey, I teach SMD soldering to absolute beginners, many of whom have never done ANY electronics. Within an hour and a half they have a working board with "advanced" components like QFNs and 0402 passives attached. Nobody goes without a working board. Only equipment needed is a pair of tweezers, a metal squeegee for paste deposition and a plain off-the-shelf $10 hotplate. No fancy anything. It's not a setup you'd use f…

How do you make the solder paste stencil? How do you make the PCB traces?

You can get PCBs made very cheaply these days (dirtypcbs are an example of how cheap), and for $20-$30 you can have a sheetful of stencils lasered for you so this is mostly academic, but:

PCBs: You can make PCBs by toner transfer, phototransfer, or milling, just like you'd make PCBs for through hole designs, except you don't need the precision drilling you'd need for through hole parts. The transfer methods need an etch stage, which you can do at home with fairly safe chemicals these days, see for instance http://quinndunki.com/blondihacks/?p=835 for a very detailed tutorial. With a bit of care you can do double layer this way, but if you need lots of layer interconnections it's better to outsource PCB production. It's WAY easier to make PCBs for surface-mount designs at home because there is a lot less drilling involved.

Stencils: If you have a laser cutter available, cut them from construction paper. They'll only work once, but you can make a bunch. If you have one of those label cutting machines, those work too. If you're etching your PCBs, you can etch stencils from thin copper sheet, using the same method. Another excellent material that is already the correct thickness is the wall of an aluminium beverage can. Toner transfer works well for these and can give excellent detail. Remember most have a plastic coating on both sides, so file the outside with the image until you get naked metal (check with a multimeter), transfer on that and then etch. You can get presensitized sheets of various metals for phototransfer as well. If you only have a handful of pads you can also plop bits of solder paste on with a toothpick.

What about breadboards? The most common surface mount packages have breadboard adapter boards available. If there isn't one for the one you want, etch a board with a bunch of 2.54mm pitch pads along the edge (no holes, you want the board vertical so you have lots of breadboard space available). Stick any decoupling caps and pullup/pulldown resistors straight on the PCB so you don't clutter your breadboard with them, solder a bunch of header pins sideways, and there you go. You can put a label for the kind of part it is right into the copper.

Again, unless you're in a hurry or the board is very simple you probably want to outsource PCB production. If you do that, get a stencil made as well. If you can combine a bunch of stencils into one file, they probably won't charge you any extra for a stencil the size of 5 boards compared to one the size of one, so with a bit of planning you can get stencils EXTREMELY cheaply. And you can do tens to hundreds of boards with a single stencil if you take good care of it.

For alignment between stencil and board, if you're getting both manufactured for you, place two holes on opposite corners of the PCB that are exactly 3mm in size, and two identical holes in your stencil. Then you can use normal M3 bolts and nuts to fix them together, and it's super-easy to fine-tune alignment with the bolts in place but not yet tightened. There are pre-made stencils you can buy which have a selection of component footprints, so if you have say a little breakout board with just one difficult component you can apply paste to that with the stencil and do the others with the toothpick method or with a syringe dispenser (safety note: NEVER put solder paste in glass syringes, only use plastic ones).

My point in all this? If you can make through-hole stuff you can make surface-mount stuff, and probably with less effort.

Re: Circuit building: stop using antique parts (2014)

#169

Post by fuzzfactor »

busterarm wrote: post #33
PeanutNore wrote: post #14

I build a lot of guitar effects, and that community is even worse when it comes to attachement to obsolete components. The discontinuation of J201 JFETs (in TO-92 through hole package at least) by Fairchild has caused a lot of upset. My perspective, not widely shared, is that JFETs in general have been made obsolete by depletion-mode MOSFETs, at least in audio circuits. Part of the reason, I think, is that a lot of "…

Guitar d00ds having obscure, nonsensical reasons for things because "mah tones!"? Say it ain't so. I mean, nearly every tube head on the market has an essentially pointless standby/bypass switch because of the mistaken belief that you need to warm up your tubes for some arbitrary amount of time in a modern amp and keep them warm. I forget which manufacturer it was that dropped the switch on one model and saw sales pl…

Non-solid-state electron systems should be expected to have their own idiosyncracies, regardless of whether superstition is building up faster than it is being dissipated.

The regular ordinary procedure for cold-starting high-power vacuum tube systems is to switch on the unit while the tubes are in standby.

This will allow the cathodes to heat to their characteristic glow, fully developing the ability to deliver the current you will soon be demanding.

But no high voltage is applied to the anodes (there will be no sound from audio systems) until removed from standby.

A minute or two later is good.

If the cathodes are too cold when applying the high anode voltage, especially at high current demands, it can strip the cathodes of their ability to provide the full performance when you need it most in the future.

Small tubes, most preamp types, run on lower voltages and currents, don't suffer noticeably, and were cheap to begin with.

It's the bigger more expensive tubes that standby is for.

Shut down by switching to standby while the main unit is still powered on.

After no more than a minute or two, fully power off the unit unless you would otherwise have to cold-start unreasonaby soon afterward. This is about 10 to 20 minutes for popular audio units, or much more if there is a true need for instant-on over a longer term.

24 hour standby is not very good for the tubes either, best fully powered off to save hours, or idling at a reasonable fraction of their ratings.

On standby tubes are still more vibration sensitive than fully cold, so it's seldom a good idea to leave them on standby while there is a source of strong vibration from other sources.

Never leave a tube amp in direct sunlight unless fully powered off. Standby will not save you. If it is allowed to heat up above ambient for any reason, let it cool back down to ambient before powering up. Gear that can run continuously at ambient 100degF can die at 70degF in the sun.

Without the sun, different gear (including differing power bias settings on the same gear) will have different maximum ambient temperatures beyond which only short-term operation is advisable, even for units which are otherwise capable of continuous operation under slightly milder conditions.

For musicians it's the class of thick-cone reinforced speakers that can take 20 or 30 minutes (near their power rating) to break in every time, that can throw you off. Speakers can not be "warmed up" silently, you have to make some noise. After this cranked-up break in, reach into an open-back cab and you feel how hot the magnets are, they were made for this but not in the sun either, especially closed-back cabinets where you can't touch the magnets but you know they're even hotter. But often it's not the warmth of the magnets (or the tubes) that makes a (beneficial) difference in the tone, it's the preflexing of the cones which makes them more articulate afterward. Most amps themselves warm up way faster than that, and can do it silently.

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