- TIP: avoiding dried up/blocked ink-jet carts - 1 Update
- Heat sink grease - 4 Updates
- What resistor to use for a single LED - 4 Updates
| etpm@whidbey.com: Apr 13 09:42AM -0700 >different colour calcium based chemical formulation at different times >building up the patterning, clever stuff. Millions of years before >Epson,Canon, HP etc That is so cool. I had no idea that was how the eggs got that look. Thanks for posting. Eric |
| Jeff Liebermann <jeffl@cruzio.com>: Apr 13 08:02AM -0700 On Thu, 12 Apr 2018 22:34:41 -0500, Fox's Mercantile <jdangus@att.net> wrote: >> and gouges run. Apply a tiny amount of thermal goo to the >> heat sink. Use a plastic razor blade: >As the original Jeff-1.0, I have to agree with Mr. Liebermann. Nobody agrees with me. Something must be wrong. >Originally, I was in the "blob and clamp" group. But, aside >from the mess that tends to make, I learned that really was >not the right method. I should start posting photos of CPU heat sink installations on some of the machines I've seen in my palatial office for repair. I'm now buying alcohol by the gallon and Q-Tips by the Costco box. >until I have a very thin layer spread over the entire part. >Then clamp it together. It may not be quite as right, but it's >a hell of a lot messy and I haven't had any overheating failures. Yeah, that works, except that the solvent used in some tubes of thermal goo seems to remove the decals and painted letters on my keyboards. I find it necessary to wash my hands after working with thermal goo. Let's see what the MSDS says: <https://www.chempoint.com/products/download?grade=51854&type=msds> This is cute: Page 6: Hazardous decomposition products Thermal decompositions: Formaldehyde That's odd. It's 50-70% zinc oxide, but the MSDS sheet does not specify what the remaining 50-30% might be. No odor, so it might be water, but that should be specified. >As in all things in life, there's a right way to do things, then >there's the internet, which will teach you all the other 101 ways >of doing it wrong. Welcome to IoT, the Internet of Things (that are wrong). The best part is that for every wrong way to do something, there are large numbers of people (like me) who will blindly redistribute the wrong way when asked. Things tend to look more authoritative when formatted in HTML than with badly formatted ordinary text using broken English. Never mind Fake News. Deal with the fake instructions crisis. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Apr 13 08:25AM -0700 Silicon pads. No thinking involved. No grease. No smear. Why not? 25 posts on the quantity of angels and pinheads involved. What a waste. Peter Wieck Melrose Park, PA |
| Jeff Liebermann <jeffl@cruzio.com>: Apr 13 09:13AM -0700 On Fri, 13 Apr 2018 08:25:20 -0700 (PDT), "pfjw@aol.com" >Silicon pads. No thinking involved. No grease. No smear. Why not? W/m*K Diamond 1000 c-BN 740 (Cubic Boron Nitride) h-BN 600 (Hexagonal Boron Nitride) Silver 406 Copper 385 Gold 314 AlN 285 (aluminum nitride ceramic) Aluminum 205 Graphite 200 Carbon 150 SiC 120 Brass 109 Indium 86 ZnO 50 (zinc oxide) Al2O3 25 (aluminum oxide ceramic) Pastes 4.0 Sil Pad 2000 3.5 Circuit Works 1.84 Dow Corning 340 0.67 Sil Pad 2000, which is one of the better silicon impregnated pads, has a fairly lousy thermal conductivity. The big advantage is that they don't use thermal goo: <http://www.henkel-adhesives.com/product-search-1554.htm?nodeid=8806349996033> For non-critical applications, such as those encountered by most of those in this newsgroup, they're just fine. There are ways to install them incorrectly. If they have a problem, it's that performance varies with the amount of pressure applied. >25 posts on the quantity of angels and pinheads involved. What a waste. Really? I got most of my experience with thermal management at a company that made various RF power products. I think the biggest was a 2-30MHz 1000 watt PEP power amplifier. To do that with BJT devices required careful balancing of the devices used in Class AB, which included careful mechanical balancing. To remain competitive, the power products had to be better than the competition, while still meeting FCC IMD specifications and without faking the numbers. The competitive edge turned out to be the way heat was removed from the devices, which was my headache. I had to go back to basics because most of the applications engineers working for the heatsink and power device companies were more than happy to make their life easier by accepting mediocre performance. To get what I wanted, I had to start with basics, and work my way up, which soon demonstrated that much of the "no thinking" methods, and understandings of how things worked, were wrong. I don't think it was a waste, but you might if you don't have similar problems to deal with. Should that happen, be advised that I derive considerable sadistic enjoyment watching others reinvent the wheel. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
| etpm@whidbey.com: Apr 13 09:28AM -0700 On Thu, 12 Apr 2018 13:31:11 -0700, Jeff Liebermann <jeffl@cruzio.com> wrote: >cracks and crevasses in the aluminum extruded heat sink, then you're >taking a step backwards. The bulk of the heat is passed by metal to >metal contact. Smallest grain size is 1 micron. Or .0000039 Inches. My best surface plate is flat within 30 millionths of an inch. My best set of gauge blocks, the ceramic ones, are +1 to + 3 millionths in size except for the 4 inch block which is +4 millionths. Eric |
| tabbypurr@gmail.com: Apr 13 05:27AM -0700 On Friday, 13 April 2018 13:15:14 UTC+1, Tim R wrote: > Now I'll ask what is certain to be a dumb question. But maybe I'll learn something. > If we have two LEDs in parallel in reversed polarity, and we put 12 volts across them, aren't we exceeding both Vf and Vr? will they share the current, at some calculable ratio? > Sorry for my ignorance, that electrical circuits class was in the 80s. They both see 12v. Manufacturers only spec them to 5v but IRL they can survive far more. NT |
| Tim R <timothy42b@aol.com>: Apr 13 06:37AM -0700 > > Sorry for my ignorance, that electrical circuits class was in the 80s. > They both see 12v. Manufacturers only spec them to 5v but IRL they can survive far more. > NT Apologies, this is way too elementary for you all, but I'm a manager now, they haven't let me do anything technical for years. Well of course they can both survive, you have a 1k current limiting resistor in the circuit. If the forward biased LED were alone, it would drop 1.6 V, the resistor would drop 10.4, the current would be 10 mA. (Assuming automotive 12 V) If the reverse biased LED were alone, it would drop 5 V, the resistor would drop 7, the current would be 7 mA. When both LEDs are in the circuit, does some current flow through each? or does the 1.6V of whichever one is forward biased limit the other to 1.6V, in which case it will never conduct, so there's no problem. If Radio Shack still existed I wouldn't even ask. I'd just go buy two diodes and see what happened. |
| "jfeng@my-deja.com" <jfeng@my-deja.com>: Apr 13 08:22AM -0700 > Thanks, 1K sounds like a winner. And I will likely use a green one too. If decide to use back-to-back diodes, I would use one of those bipolar red/green lamps instead of sticking with a single color. |
| Fox's Mercantile <jdangus@att.net>: Apr 13 10:36AM -0500 > point (made to puncture wire insulation) and a wire > with a clip on the end. I normally use the wire as the > ground (to any metal part of the car body). As usual,your lack of information with your first post, resulted in a shit load of wild goose chasing by others. If you had mentioned it was just a cheap Chinese piece of shit pencil tester it would have been "1K resistor" and that would have been the end of it. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
| You received this digest because you're subscribed to updates for this group. You can change your settings on the group membership page. To unsubscribe from this group and stop receiving emails from it send an email to sci.electronics.repair+unsubscribe@googlegroups.com. |
No Response to "Digest for sci.electronics.repair@googlegroups.com - 9 updates in 3 topics"
Post a Comment