JohnRoberts

Re: DIY is starting to be a PITA!
« Reply #20 on: November 04, 2019, 09:37:48 AM »
OT again. I wonder if we should have a metal work accident log a bit like the shock log. Worst that I have ever done was hand drilling a 4mm hole into mild steel. Snapped the drill bit with too much pressure and jammed the broken stub straight into the middle of my thumb nail, punched a hole clean straight through. I always seem to leave a bit of blood somewhere in a chassis. I agree with using Greenlee punches and nibbler, those tools go a long way. I have cut out nice round meter holes with just those tools.
Of course you need to be careful around power tools. I had a co-op job back in the 60s working quality control for a sintering operation. They had a side business involving using cut off saws and the like to make lots of small pieces from fewer large ones. In the bad old days workers were paid piece-work (i.e. paid for their units completed). This motivated them to defeat safety measures to generate more output faster. 

I recall seeing several older workers back in the cut-off area missing fingers, from their adventures in defeating safety measures. One common trick when a machine had two buttons that needed to be pressed to operate, presumably insuring both hands are safely out of danger, was to hold one button down with an elbow, freeing up the hand to feed parts faster.

By the 60s I never caught any workers cheating the safety measures, but plenty of evidence of earlier accidents.

JR

PS: I broke a drill on a drill press in HS shop class (cut my hand but not that bad). I spent two summer vacation breaks during HS working in an actual machine shop and they were pretty safety conscious, but the machines lacked safety measures like production environments. Legally I was too young to operate the machinery, but by the second summer I was doing major projects using pretty much all of the machinery.  I had some drama one time when I broke an end mill on a milling machine (using too fast of a feed speed). The flying end mill remains punched a small hole in a cinder block wall, so that could have really stung.  :o
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.


Matador

Re: DIY is starting to be a PITA!
« Reply #21 on: November 04, 2019, 10:24:31 AM »
IMHO SMD is far easier and quicker.  Given how inexpensive and fast prototype PCB's are these days (check out PCBShopper, which takes your basic requirements and checks many PCB sites for the best deals, including specials), there are fewer and fewer reasons to prototype with bare wires and through-hole components, even for one-offs or experiments.

scott2000

Re: DIY is starting to be a PITA!
« Reply #22 on: November 04, 2019, 10:48:17 AM »
 :-\

I just got that sinking feeling that I used to get when a new version of software comes out.....

I guess the bright side is the price of the chase is in reverse.....

Re: DIY is starting to be a PITA!
« Reply #23 on: November 04, 2019, 11:27:27 AM »
I've been out of the game for about the same length of time (10 years) and there are for sure a few things I have a hard time finding.
I don't have an issue as such with using smd, other than the sometimes inability to identify the part in hand (tweezers) with my older naked eyes.   I still prototype with through-hole for that reason and also because I prefer to work on circuits in 3 dimensions, and the component leads provide somewhat better stability to the eventual rat's nest


There are a couple of decent smd alternatives to the defunct Toshiba K170 J-Fets, albeit with lower dissipation/PD, but there are no smd subs for J74  P channels that I'm aware of.   The Linear Systems LSJ74 is one T.H. alternative but it's an expensive and hard to get part.
Also, with the demise of CRT technology, we lost a lot of the high Ft driver transistors that work wonders in place of the VERY long in the tooth BD139 et al. slugs that they left us with.

Forgot: Low Rbb, high Hfe devices are much thinner on the ground, as are matched devices.   And thermally coupling devices is not easy with smd, in fact, I don't know how I'd actually go about it?


« Last Edit: November 04, 2019, 11:34:49 AM by Winston O'Boogie »
If you want to sound crazy please tell me about THE DEEP STATE.

Matador

Re: DIY is starting to be a PITA!
« Reply #24 on: November 04, 2019, 11:51:03 AM »
And thermally coupling devices is not easy with smd, in fact, I don't know how I'd actually go about it?
Perhaps a dual-BJT in an SOT package?  That's about as thermally coupled as one can get.

Re: DIY is starting to be a PITA!
« Reply #25 on: November 04, 2019, 12:01:56 PM »
Perhaps a dual-BJT in an SOT package?  That's about as thermally coupled as one can get.

Yep, that would seem to be it.  Sometimes I might want to couple a small signal N to a driver P though, or a bias setting device to output devices.     The only thing I've come up with is to probably keep as much copper (with vias) on the board as possible,  around all the devices and hope to just keep temperature down all round.   
If you want to sound crazy please tell me about THE DEEP STATE.

JohnRoberts

Re: DIY is starting to be a PITA!
« Reply #26 on: November 04, 2019, 12:15:39 PM »
I've been out of the game for about the same length of time (10 years) and there are for sure a few things I have a hard time finding.
I got dragged into SMD 25-30 years ago to remain competitive selling value (price sensitive) SKUs. Peavey was already well along the curve for cost effective through hole technology with machine insertion for radial, axial, and common ICs. The only way to get cheaper was offshore, and big Chinese contract manufacturers used cheap labor to hand insert through hole parts avoiding the capital investment in automation machinery.
Quote

I don't have an issue as such with using smd, other than the sometimes inability to identify the part in hand (tweezers) with my older naked eyes.   
try finding smd parts you drop in carpeting...  :o
Quote
I still prototype with through-hole for that reason and also because I prefer to work on circuits in 3 dimensions, and the component leads provide somewhat better stability to the eventual rat's nest
Unfortunately not possible with many modern components that are only available SMD. A bridge I had to cross over ten years ago with my second generation drum tuner, to use a slick class D audio chip about the size of a wood tick with heat sink on the bottom. Impossible to rats nest prototype (I know I tried).  :o
Quote

There are a couple of decent smd alternatives to the defunct Toshiba K170 J-Fets, albeit with lower dissipation/PD, but there are no smd subs for J74  P channels that I'm aware of.   The Linear Systems LSJ74 is one T.H. alternative but it's an expensive and hard to get part.
Also, with the demise of CRT technology, we lost a lot of the high Ft driver transistors that work wonders in place of the VERY long in the tooth BD139 et al. slugs that they left us with.

Forgot: Low Rbb, high Hfe devices are much thinner on the ground, as are matched devices.   And thermally coupling devices is not easy with smd, in fact, I don't know how I'd actually go about it?
I suspect discrete design is a skill set losing favor within engineering management. Back last century when I was still managing engineers we could cobble together hybrid combinations of IC and discrete that outperformed early canned solutions while also costing less money. But that was then and now I expect the economics have flipped... It will be hard to even buy low Rbb bipolar devices to make mic preamps when off the shelf ICs work so well, if not better.  (My personal favorite low Rbb bipolar went obsolete last century).

Any designs I did requiring thermal coupling*** used transistor arrays (I think my favorite old bipolar array is obsolete now too).

JR

*** bias circuits for analog power amps still generally benefit from physical proximity, but class D technology has mooted old bias issues. 
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Re: DIY is starting to be a PITA!
« Reply #27 on: November 04, 2019, 12:39:27 PM »
I hear ya John.

The last time I had to worry about manufacturability involving solid state was almost 20 years ago ( yikes!) and, luckily, I was allowed a decent budget and given access to great T.H. parts.   
For what I want to do now in that area, I'll probably stick with paying up to half a dollar on eBay for a good T.H. transistor and match them by hand where necessary. 

Forget about finding a part the size of a grain of pepper when it pings off onto the carpet, been there 😄

For rework, smd is great, I helped with that on the first UAD1 cards back at Universal in 2000ish which was my first foray into smd.

I suppose I really should stick my toes into class D waters, along with design of switching supplies. 


I'm yet to get back into valve/hollow state technology but I suspect it's much the same niche area as far as parts are concerned.  If I go there, I'll already have prepared myself to pay accordingly for good parts. 


Cheers.

If you want to sound crazy please tell me about THE DEEP STATE.


 

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