On Thu, 28 Jan 2016 09:05:13 -0800, John Larkin <jjlarkin@highlandtechnology.com> wrote:>On Thu, 28 Jan 2016 08:46:47 -0800 (PST), Lasse Langwadt Christensen ><langwadt@fonz.dk> wrote: > >>Den torsdag den 28. januar 2016 kl. 17.02.32 UTC+1 skrev John Larkin: >>> On Thu, 28 Jan 2016 09:49:23 -0500, Ecnerwal >>> <MyNameForward@ReplaceWithMyVices.Com.invalid> wrote: >>> >>> >In article <n8bdnh02ck1@drn.newsguy.com>, >>> > Winfield Hill <hill@rowland.harvard.edu> wrote: >>> > >>> >> SMD resistors take far less space than >>> >> 1/4-watt axial-lead parts. But mixing >>> >> 0805 in among TO-92 makes hand assembly >>> >> a pain. Solder the 0805s first, yes. >>> >> But when coming back to change the value, >>> >> it's hard to get to with the iron tip. >>> > >>> >IMHO 1206 is plenty space saving and fiddly for hand assembly. >>> >>> 0805s are starting to look huge to me now. >> >>yeh, and 0603 isn't that much smaller >> >> >>-Lasse >> > >I'm used to 0603s now. 0402 still looks tiny to me, hard to solder. >Manufacturing doesn't like them either.Your P&P machine shouldn't have any trouble with 0402 (or 0201, for that matter). Rework can be an issue but tell them to suck it up. That's life in the fast lane. I have no problems with 0402s, as long as I have my Mantis. Even 4x or 6x OptiVisors work in a pinch.> >We like to screen reference designators, so going smaller than 0603 >doesn't save much room.We have screened reference designators for all components, too. It's not always possible to get them right at the component but it's not too bad. Sometimes there is a list of parts, off to the side of a row of resistors and caps.
TO-92 vs sot-23 transistors for power
Started by ●January 27, 2016
Reply by ●January 28, 20162016-01-28
Reply by ●January 28, 20162016-01-28
On Thu, 28 Jan 2016 10:56:25 -0600, Tim Wescott <tim@seemywebsite.com> wrote:>On Thu, 28 Jan 2016 09:49:23 -0500, Ecnerwal wrote: > >> In article <n8bdnh02ck1@drn.newsguy.com>, >> Winfield Hill <hill@rowland.harvard.edu> wrote: >> >>> SMD resistors take far less space than 1/4-watt axial-lead parts. But >>> mixing 0805 in among TO-92 makes hand assembly a pain. Solder the >>> 0805s first, yes. But when coming back to change the value, >>> it's hard to get to with the iron tip. >> >> IMHO 1206 is plenty space saving and fiddly for hand assembly. 2512 is a >> lot nicer to handle and doesn't just vanish when you look the other way >> for a second, but is 4 times the real estate. AADE won't admit that >> either is an inductor so no handy numbers there to report (fancier >> equipment might manage to report something, though I can't imagine >> there's a lot of inductance to a ceramic chip type resistor.) >> >> I'll self-inflict 0805 caps at times, which are at least thick enough >> that the size is not utterly maddening (easy to tweeze), but for the >> sake of my own sanity I try to stick to 1206 or larger resistors. All >> hand assembly around here. > >For hand assembly with a microscope (generic stereo 10x) I go down to >0603 no problem, and 0402 if I'm feeling motivated to be teeny. The >microscope makes far more difference than you'd think possible.0402 is our standard size passive. A few designs have used 0201 decoupling caps for large BGAs but they're not qualified my manufacturing or QA so they're not used often.
Reply by ●January 29, 20162016-01-29
On 29/01/16 16:41, Phil Hobbs wrote:>> As my eyes get less flexible I find more need to resort to a microscope >> for reading part numbers (or part "markings" & good luck finding an >> actual part number to map to it these days on little parts, if they even >> are marked.) I don't have good one for working under. > > Some of the Chinese ones are actually pretty decent for the price. Check out Amscope on the slightly higher end, or Andonstar for a cheapie webcam version: > <http://m.ebay.com/itm/2MP-USB-Digital-Microscope-Video-webcam-Magnifier-Camera-Stand-Cam-Andonstar-LW-> > > I used my Andonstar earlier today to help with aligning infrared beams on really small (60 um) photodiodes. Good medicine for $50.Beware that Andonstar have a 1MP and a 2MP version that look otherwise almost identical. I got the right one, but could have missed it. I find it a little annoying that tweaking the focus knob makes the mounting rotate slightly, which moves away from the thing you were trying to focus on. Do you (or anyone) have a cure for that Phil? Clifford Heath.
Reply by ●January 29, 20162016-01-29
In article <7rudncBh-sqk1TfLnZ2dnUU7-X-dnZ2d@giganews.com>, Tim Wescott <tim@seemywebsite.com> wrote:> For hand assembly with a microscope (generic stereo 10x) I go down to > 0603 no problem, and 0402 if I'm feeling motivated to be teeny. The > microscope makes far more difference than you'd think possible.I typically use +5 diopter glasses (my prescription, +5 diopters - something with longer working distance would be nice, but spendier), which also make a big difference - but what size I can do and what size is comfortable (and thus quick) are not the same. I have done 0603, and godawful nasty little feedthroughs with contacts on both sides in the middle as well as the ends at either that size or 0805 - but I prefer not to, and don't find any particular joy in miniaturization for miniaturizations's sake. As my eyes get less flexible I find more need to resort to a microscope for reading part numbers (or part "markings" & good luck finding an actual part number to map to it these days on little parts, if they even are marked.) I don't have good one for working under. -- Cats, coffee, chocolate...vices to live by Please don't feed the trolls. Killfile and ignore them so they will go away.
Reply by ●January 29, 20162016-01-29
>As my eyes get less flexible I find more need to resort to a microscope >for reading part numbers (or part "markings" & good luck finding an >actual part number to map to it these days on little parts, if they even >are marked.) I don't have good one for working under.Some of the Chinese ones are actually pretty decent for the price. Check out Amscope on the slightly higher end, or Andonstar for a cheapie webcam version: <http://m.ebay.com/itm/2MP-USB-Digital-Microscope-Video-webcam-Magnifier-Camera-Stand-Cam-Andonstar-LW-> I used my Andonstar earlier today to help with aligning infrared beams on really small (60 um) photodiodes. Good medicine for $50. Cheers Phil Hobbs
Reply by ●January 29, 20162016-01-29
>I find it a little annoying that tweaking the focus knob makes the >mounting rotate slightly, which moves away from the thing you were >trying to focus on. Do you (or anyone) have a cure for that Phil?You can preload it with a strategically-located rubber band. I usually use just the pen part, zap-strapped to a gooseneck salvaged from an Ikea desk lamp. The other end of the gooseneck is mounted to a Newport optical post base with JB Weld putty, so it screws into the optical table nicely. The zap straps let me turn the camera easily after it's in position, so the image is the right way up. This alignment job is pretty hard, but would be impossible without the USB scope. Cheers Phil Hobbs
Reply by ●January 29, 20162016-01-29
"Winfield Hill" wrote in message news:n8d39t02s36@drn.newsguy.com...>> http://seventransistorlabs.com/Images/Wideband2N7002.jpg > > And, how well does it work? >18dB gain, -3dB at 50MHz (and -10dB up to 200MHz; it's not a simple gain-bandwidth tradeoff, but as far as I can tell, also not "unlimited speed" as Larkin likes to say). Input matching needs work. I haven't tried beyond the little inductor seen there. I get 12.5dBm output, for 2nd harmonic at -20dB to fundamental (and 3rd harmonic about 13dB below that; so, whatever IM3 intercept that might correspond to). 1dB compression, hellifiknow, I don't have a dual channel spec and CBA swapping back and forth to figure it out. ;-)> Here's the business end of the amplifier, a CPU > server heat-sink and fan bolted to the TO-220 > plate, its thermal measures 0.2 C rise per watt. > https://www.dropbox.com/s/f02nqn6w75xvwgx/AMP-70A_fan.jpg > The enclosure has more fans to exhaust hot air.Guessing, even with those fast output transistors, it's acting fairly class A up there. All that dissipation, it's a feature, this time of year. :-) Looks great! Only quirk I see is, why the staggered TO-220 pins? I like models, so I draw 'em like this... http://seventransistorlabs.com/Images/TO-247-Bottom.jpg (or use a larger screw hole for not mounting PCB + device simultaneously) Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reply by ●January 29, 20162016-01-29
Tim Williams wrote...> >"Winfield Hill" wrote > >> Here's the business end of the amplifier, a CPU >> server heat-sink and fan bolted to the TO-220 >> plate, its thermal measures 0.2 C rise per watt. >> https://www.dropbox.com/s/f02nqn6w75xvwgx/AMP-70A_fan.jpg >> The enclosure has more fans to exhaust hot air. > > Guessing, even with those fast output transistors, > it's acting fairly class A up there. All that > dissipation, it's a feature, this time of year. :-) > > Looks great! Only quirk I see is, why the > staggered TO-220 pins?What, you never got into staggered pins? (BTW, easy to model.) -- Thanks, - Win
Reply by ●January 29, 20162016-01-29
On 1/28/2016 9:00 AM, Winfield Hill wrote:> Chris Jones wrote... >> >> I wonder whether it is already too late for the >> nice fast 300V transistors that used to be used >> in the video amplifiers on CRT neck boards. > > You have to get a lifetime supply. Some Alibaba > sellers, etc., still have some types.I don't feel like I can trust Alibaba sellers. I see too many reports of outright fraud there. I don't know how well Alibaba protects the buyers, but it looks like it isn't good enough. -- Rick
Reply by ●January 29, 20162016-01-29
On Thu, 28 Jan 2016 21:41:12 -0800, Phil Hobbs wrote:>>As my eyes get less flexible I find more need to resort to a microscope >>for reading part numbers (or part "markings" & good luck finding an >>actual part number to map to it these days on little parts, if they even >>are marked.) I don't have good one for working under. > > Some of the Chinese ones are actually pretty decent for the price. Check > out Amscope on the slightly higher end, or Andonstar for a cheapie > webcam version: > <http://m.ebay.com/itm/2MP-USB-Digital-Microscope-Video-webcam-Magnifier-Camera-Stand-Cam-Andonstar-LW->> > I used my Andonstar earlier today to help with aligning infrared beams > on really small (60 um) photodiodes. Good medicine for $50.Your link didn't work, but typing Amscope into ebay's search line got a bunch of good hits. I got mine free from a customer who otherwise robbed me blind (with my collusion -- you can't be ripped off for labor unless you allow the account to climb to rip-offable heights). Having one, I think it'd definitely be worth $500 for another one, getting a cheap Chinese one for 1/3 the price is even better. My one complaint with the thing is neck strain -- if I spend all day populating boards without remembering to put a heat pad on my neck first then I'm very sorry the next day. I wonder if something with a USB camera and a screen that I can look at while sitting in a normal posture wouldn't work better. I suppose that going too far down that road would just have me building a semi-automatic pick & place machine. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
