LM317 Minimum

Linear tech/ADI parts have a premium price so one has to evaluate if they are necessary. Also using second source parts have advantages of availability.
I routinely use ST LM217T-DG for the extra pennies they cost, it has slightly better specs than the regular lm317
 
It beats me why anyone would want to use a LM317/337 regulator when newer, better spec'd, linear, through hole mountong devices exist
The fact that TI (and others) keep making them should tell you something about the market demand for these ICs. The LM317 first saw the light of day in 1976 if I recall correctly. I'm sure it's been ported to newer semiconductor processes at least a half-dozen times by now.

Tom
 
I once had a circuit that sometimes worked fine and sometimes produced an annoying high-pitched beep. It turned out to be due to me using only X5R ceramic decoupling capacitors at the output of an LM317; the LM317 was at the edge between oscillating and not oscillating, and when it oscillated, the X5R capacitors worked as piezotweeters. I connected an ordinary aluminium electrolytic capacitor across the output and since then, it's always been silent.
That's cute. 🙂

I built an LM317/337 regulator with ceramic output caps at one point too. The LM317 was stable (or at least I didn't observe any instability) but the LM337 definitely did not like a ceramic output cap. I've used plain electrolytic caps ever since then.

Electrolytic capacitors also have the advantage that they provide the capacitance that's marked on the can even with significant DC bias. Sadly the same cannot be said for X5R/X7R.

Tom
 
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BBB.jpg


Here's my first revision of the BBB (Best Basic for a Beginner) circuit. It's handle a range of VA's and voltages. BOM and PCB to follow. C1 is Tantalum.

Regards,
Dan
 
I'd up the 470 uF to 1000 uF for three reasons: 1000 uF tends to have better availability, it is often cheaper, and it'll result in lower ripple voltage. Better performance, higher availability, lower cost. That's a rare find. Take it! 🙂

Tantalum is polarized, so you'll want the schematic to reflect that. Personally I'd use an 1 uF, X5R or X7R ceramic, but that's me.

You could make it even more useful for audio by making a split/bipolar supply out of this. One could also consider board options to allow the transformer primary to be configured for 230 V for more international appeal. Just suggestions...

Tom
 
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I'd up the 470 uF to 1000 uF for three reasons: 1000 uF tends to have better availability, it is often cheaper, and it'll result in lower ripple voltage. Better performance, higher availability, lower cost. That's a rare find. Take it! 🙂

Tantalum is polarized, so you'll want the schematic to reflect that. Personally I'd use an 1 uF, X5R or X7R ceramic, but that's me.

You could make it even more useful for audio by making a split/bipolar supply out of this. One could also consider board options to allow the transformer primary to be configured for 230 V for more international appeal. Just suggestions...

Tom
As time permits I'm going to implement all of your suggestions. The first two (1000uF and XR7) were easy and are done already. I'm going to build and test the first board and then move on.

Regards,
Dan
 
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Or maybe you didn't run them near 100% of their rated voltage. As noted in the KEMET document linked to above, running them below 80% of their rated voltage (or 90% for ≤10 V) makes them last much longer.

With the high-k dielectrics in, say, X5R, X7R, etc. ceramic capacitors you also have to derate the voltage rating. Not for reliability, but rather because of the rather horrid voltage coefficient of those dielectrics. Commonly the 'good' (Class 2) high-k dielectric capacitors are down to ~20% of their marked capacitance at the full rated voltage. Physics is annoying sometimes.

Tom