Common Parts That Are Not So Common :/

[steveyraff]

15uf electrolytic capacitors. All I can get these days is either ginormous 400v's, or way over priced singles. Just 2 months ago I bought a pack of 50 for about a fiver.

250k trimmers. Few months ago spend about £2 on 20. Last week I had to order 2 from Latvia for £25.

Uuuuuugh. Not any real point to this post other than to vent my frustration lol Thanks.

[ElectricDruid]

I never needed a 250K trimmer, but 15uF caps would often be very helpful. But caps in decent ranges (and 15 is only an E6 value!) and reasonable tolerances are very hard to find at sensible prices. Unless you go to the manufacurer and order 100,000 I expect. Then you can probably get whatever you like.

[puretube]

10uF+4.7uF comes close enough ... ("piggyback") 

[StephenGiles]

I never needed a 250K trimmer, but 15uF caps would often be very helpful. But caps in decent ranges (and 15 is only an E6 value!) and reasonable tolerances are very hard to find at sensible prices. Unless you go to the manufacurer and order 100,000 I expect. Then you can probably get whatever you like.

I would have thought that tolerances are irrelevant with caps.

[Fancy Lime]

Not irrelevant but for electrolytic caps the tolerances are usually huge. Like "-50%, +100%" huge. There are product lines with tighter tolerances but capacity of electrolytics is also a strong function of the DC bias across them and, worst of all, the age of the cap. That's why electrolytics are not used in anything where tolerances are an issue at all, unless there really is no other way. And also why you mostly only get E3 series values (1.0, 2.2, 4.7, 10, 22, 47...uF). A nominal 15u cap may in actual fact have 7.5u or 30u. So even E6 values are a bit pointless. If you really need 15u precisely, you don't want an electrolytic cap. 4.7u film box caps are quite readily available and not too expensive. Or they were last I checked but that was a year ago or so, so who knows. Just get three of those in parallel, if they are still available.

Andy

[pacealot]

Tolerance can certainly be an issue for LFOs, which is why one of my most frequently postponed projects is recapping the tremolo in my Sunn Coliseum Lead amp. It has three 1.6µF (!!!) axial 'lytics in the LFO, and I'm sure 1.5µF would be fine and are theoretically available, but making the various options/combinations both oscillate and fit comfortably on the PCB is the major hurdle. I can get 1.5µF axial film caps at Mouser (albeit for nearly $2 each), but they're over an inch long, and it's a tight board. Either that or splash out 5 bucks each for Sprague 'lytics which will fit, but are still 'lytics. That's why I haven't quite gotten the gumption up yet...

[Andon]

25K pots are surprisingly uncommon when I'm looking for them - they can be found, but usually not in the taper I'm needing at that moment.

[StephenGiles]

25K pots are surprisingly uncommon when I'm looking for them - they can be found, but usually not in the taper I'm needing at that moment.

There was an circuit in a French electronics magazine back in the early 80s, which used a FET + other components to change the taper of a linear pot.

[davent]

15uf electrolytic capacitors. All I can get these days is either ginormous 400v's, or way over priced singles. Just 2 months ago I bought a pack of 50 for about a fiver.

250k trimmers. Few months ago spend about £2 on 20. Last week I had to order 2 from Latvia for £25.

Uuuuuugh. Not any real point to this post other than to vent my frustration lol Thanks.

Mouser shows 55 different 15uF flavours 63v or less listed as in stock, starting at 19 cents cdn for minimum one purchase.

https://www.mouser.ca/c/passive-components/capacitors/aluminum-electrolytic-capacitors/?capacitance=15%20uF&termination%20style=Axial~~Radial&voltage%20rating%20dc=16%20VDC~~63%20VDC&instock=y&rp=passive-components%2Fcapacitors%2Faluminum-electrolytic-capacitors%7C~Voltage%20Rating%20DC%7C~Termination%20Style&sort=pricing

250k trimmers

https://www.mouser.ca/c/passive-components/potentiometers-trimmers-rheostats/trimmer-resistors-through-hole/?resistance=250%20kOhms&instock=y&sort=pricing

[amptramp]

Tolerance can certainly be an issue for LFOs, which is why one of my most frequently postponed projects is recapping the tremolo in my Sunn Coliseum Lead amp. It has three 1.6µF (!!!) axial 'lytics in the LFO, and I'm sure 1.5µF would be fine and are theoretically available, but making the various options/combinations both oscillate and fit comfortably on the PCB is the major hurdle. I can get 1.5µF axial film caps at Mouser (albeit for nearly $2 each), but they're over an inch long, and it's a tight board. Either that or splash out 5 bucks each for Sprague 'lytics which will fit, but are still 'lytics. That's why I haven't quite gotten the gumption up yet...

You might consider raising the R values in the circuit to allow you to use 1 µF capacitors that are available as small film capacitors in low voltage ratings.  In a typical tremolo circuit, the capacitors pass AC, so you need something that is capable of doing that or the capacitor life may be short.

[Fancy Lime]

[...]  In a typical tremolo circuit, the capacitors pass AC, so you need something that is capable of doing that or the capacitor life may be short.

Could you elaborate on that? I was under the impression that all caps can pass AC.

[PRR]

...impression that all caps can pass AC.

Yes, for a while.

Standard electrolytic will not do well with reverse voltage. In the phase-shift oscillator the voltage on the speed caps does reverse. If there was any power behind it, they would burst. In an LFO they will just go leaky and quit oscillating.

[steveyraff]

Mouser shows 55 different 15uF flavours 63v or less listed as in stock, starting at 19 cents cdn for minimum one purchase.

£17 for delivery? Umm... no thanks. That's exactly why I am never able to use Mouser, unfortunately.

[FiveseveN]

But shipping is free for orders over 90 EUR (I remember it being lower). For Digikey it's $60 and other distributors have similar offers.

[steveyraff]

But shipping is free for orders over 90 EUR (I remember it being lower). For Digikey it's $60 and other distributors have similar offers.

Yea, I don't need £100 worth of 15uf caps to finish this pedal lol

[marcelomd]

Somehow my projects always need 1-2 units of the ONE part I don't have. And I explicitly don't use rare parts made of unicorns or something.

Always.

[antonis]

parts made of unicorns

Excellent insulator..!!
(by far superior to mica or porcelain..)

[amz-fx]

Common Parts That Are Not So Common: NE570 in a DIP, or even in smt

It was everywhere for many years but seems to be discontinued, and out of stock at the usual sources.

regards, Jack

[R.G.]

There was an SE570 and a couple of SE57n's available at one point. Don't know if they still are, but if so, they were in DIP and SO.. packages and had equivalent function. Google may help.

[GGBB]

Common Parts That Are Not So Common: NE570 in a DIP, or even in smt

It was everywhere for many years but seems to be discontinued, and out of stock at the usual sources.

regards, Jack

I'm sure I'm not the only one?



I don't know what to build with them.