Yes, indeed. Soldering would belong in our Electronic Construction Techniques chapter (chapter 12 in AoE II).
AoE-III has much more material than AoE-II, thanks to larger pages, wider columns, a smaller font, editing to fit most figures into a single column, etc., but with the huge amount of mostly new material, we were forced to leave out many excellent chapters from the 2nd edition. That's one reason why we suggest that folks keep their 2nd edition (or go buy a used one).
I'd vote for that! Except that the gate lead should hit the middle of the gate, not the end.
The 16 volt cap, and the heatsink, are both good ideas. Signal tends to make "soft" transformers, so the unreg voltage could be high.
On a sunny day (Thu, 05 Mar 2015 10:37:26 -0800) it happened John Larkin wrote in :
mm, for that big an electrolytic... wires may be long, bad ESR?, there should also be a 100 nF decoupling close to the LM317. Says the datasheet.
Thanks for the link, and for both previous editions of the book from which I have learnt a lot.
In your sections on Safe Operating Area on pages 627 and 702 and also in the discussion of high voltage regulators on page 696, it might have been worth mentioning that nowadays not all MOSFETs can be run up to their power rating at high VDS. The phenomenon in newer MOSFETs intended for switching operation, wherin at lowish current densities the drain current has a positive tempco for a given VGS due to the negative tempco of Vth dominating, can result in hotspots and destruction within the power rating and below the maximum VDS and ID ratings. Therefore nowadays when high voltage linear operation is required, it is worthwhile looking for a MOSFET with a DC SOA graph. Infineon, irf and others have some application notes about this, e.g.:
Chris
I don't understand how people get away with replacing motherboard caps with new ones that are too big in diameter, so they just leave the leads long.
Performing good soldering on a 16 layer PCB is not easy either.
And all ther personal time spent.
It is like a watch. It fails... do you take it to the shop? Hell no, you go buy a new one.
How much is your personal time worth that you have to waste it sitting with a broken motherboard and soldering iron? What a sad life you have that you would think that task to be constructive.
What's the SRF of the caps they're replacing? Probably not very high (leads don't matter?).
That's Great! I'm certainly looking forward to my copy. It's cool my old editions still have value... not that I'm selling.
George H.
Thanks, Chris. I'm been aware of how much better older MOSFET versions are than newer ones for linear power issues - largely due to larger die area, higher thermal mass, and lower thermal resistance. But I wasn't so much aware of the SOA problems developing in the last 15 years with newer revisions of older MOSFETs, and with new parts. Nor the body of literature that's sprung up dealing with this issue. Well, this is all material for Chapters 3x and 9x, but we'll say something in Chapter 9.
My experience is that as I go looking for production (or "replacement") caps, I consistently find smaller physical sizes (not larger) for the same cap and voltage rating.
Perhaps, but there is nothing magic about (most of) the values.
In the case of motherboards the reason they go bad is sometimes because the voltage rating was too low.
Wouldn't longer leads give it a higher inductance and hence change the SRF? Isn't that just another way of saying that the leads should be short? But it seems to work, maybe because there are more caps than necessary. Maybe there are SMT caps that take care of the higher frequencies. But I've never seen the book or app note that says it's ok to have bypass caps with long leads.
A motherboard has a dedicated plane for VCC and GND. The high frequency impedance of the plane is excellent and the lower SRF of the cap is not important
Cheers
Klaus
As long as we're talking about electrolytics, their ESR is too high for the value to resonate with such small inductances.
The cutoff is: L < ESR^2 * C. For typical values of, say, 50mohm and
1000uF, figure 2.5uH being a problem. That's two meters of cable!Aluminum polymers, however, do have this problem -- essentially being the low voltage equivalent to film capacitors, in terms of ESR, density, etc.
Tim
Or maybe the SRF just isn't an issue in this case?
Color me sad.
6 or 7 years ago I replaced 8 or 10 caps on a computer I had. I did it after supper and before bed, so it was less than four hours total. It lasted a few more years before a HD problem drove me to build a new computer. Oh that's probably just more evidence of my sadness. :-) I got the caps from badcaps.net. He has a page about bad caps and reasons FWIW.Mikek
My $1200 (2200 after the loan) Pioneer Laser Disc player was just under their top of the line model, and lasted me 18 years before it puked.
I am willing to bet that the full optical bench style laser set-up and HV supply only needs to have those EL caps in the front end of that HV supply replaced, and maybe some on the main board.
THAT item would be worth it.
ALL of my old PCs are graveyard devices, and ANY time one breaks, if it is more than a couple years old, a new one is usually easier, and far better on the brain in the end.
I even have an i5 where it has startup issues, and I have yet to get back to that fix it job but have bought a few computers and even touch screens since.
One day, that i5 ITX box WILL get revived, because THAT machine is worth it.
A shitbox "Celeron" level box, especially a store bought, non-user built machine is hardly worth it. They are years old right on the store shelf.
The point is that the SRF of the cap is (likely) low enough that any extra leads are meaningless.
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