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betajet
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Re: A logic analyser before a scope ... oh the horrors
betajet   9/14/2013 10:23:33 PM
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I completely agree that a 'scope is far more important than a logic analyzer.  A logic analyzer only works with solid Logic 0 and Logic 1 values, so it's useless for signal integrity problems.  I need to see what's really there, like unexpected cross-talk or ringing.  Besides, with modern SMT, how in the world are you going to hook up more than a few probes?

Ooh, stereo microscopes rock.  It's like looking into a whole new world.

Aeroengineer
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Re: A logic analyser before a scope ... oh the horrors
Aeroengineer   9/14/2013 8:37:40 PM
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I have been a big fan of the combination hot air/solder rework station that I listed in the post.  It has served me well.  I know one other person that purchased it on my recommendation (he got the slightly upgraded model) and he has been very happy with it.

Jack.L
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A logic analyser before a scope ... oh the horrors
Jack.L   9/14/2013 7:17:22 PM
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ersonally I have to put the scope before the analyser, wayyyy before, but that is a personal choice. I have done enough digital boards and have rarely found a need for a logic analyser. The scope, it gets used every single day.

You can find great buys on EBAY for everything. I generally find you are better off with older and trusted versus newer and questionable. I had a quick deliverable that required a power supply outside the range of what I had and I needed something that day. I ended up with a low cost brand .... served its purpose, and other than charging batteries, I don't trust it for much. Digital meter accuracy was terrible after a year, banana jacks cheap, isolation questionable ......   Power supplies and multimeters are two places to never go cheap as you want to debug your creations, not the things powering and measuring them.

The scope I seem to use more than any is a 90's vintage Tek digital. It may be old, but when I need it, it's got more than enough bandwidth and sample speed. Great for catching the smallest glitches. Rated 50V input ... 500V with 10:1 probes, but will take 450V peaks without damage. I also have a 200Mhz analog, but it does not seem to get much use nor the easy to use, but not so fast digital scope.  I could see a Picoscope in my future if I can find one at a reasonable price. There is value in the 12bit input and ease of post processing/signal processing.

My Ungar iron that I picked up at an auction along with about 100 tips is finally calling it quits so I am open to suggestions. Weller's are nice, but quickly add up. Maybe Hakko? Any suggestions?

I am in the market for a hot air or IR rework station. There are some interesting low cost ones out there. I don't have to take off enough parts to justify the thousands for a high end unit, but perhaps $250-500 if anyone wants to suggest anything.

Perhaps my favorite piece of equipment is one that people normally do not think of. It is a stereoscopic microscope that again picked up at a sale I think for $100. It gets used at least once every week. It makes it infinitely easier to work on really fine parts. You can't see under a BGA, but for fine pitch QFP, it works out well.

 

 

 

Aeroengineer
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Re: Don't forget reflow parts!
Aeroengineer   9/14/2013 3:49:58 PM
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Yes, I personally do almost all my stuff reflowed with my hot air rework station.  I usually start working some of the smaller components such as the caps and such.  This helps me to see if I need to turn up the temp or not.  With the QFN parts, I ensure that I have designed the pads such that there is just a bit of the solder pad that is exposed past the part.  This helps me to see if there are any solder bridges or if the part has not yet reflowed.  As for stencils, I have not yet needed any stencils, but I am sure that I will get there.  I generally just use a small sewing needle to help spread the past as needed. 

Frank Karkota
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Rookie
Don't forget reflow parts!
Frank Karkota   9/14/2013 3:42:26 PM
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A year ago, I had to design a 900 MHz receiver, so I designed around the ADRF6601.  When I made the PCB, I did not realize how small the part actually was.  When I got the finished board and the IC, I asked myself, "How the heck do I mount this part?"  I could barely see the part, let alone solder it to the board.

I found a company in Toronto called Proto-Advantage that made stencils and sold special solder for reflow parts.  Once I followed all of the steps to mount the part with the solder on the board, I had to figure out how to heat the board enough to melt the solder.  I ended up using my kitchen stove.  I put a sheet of aluminum on the burner and heated until a piece of solder melted and then placed the PCB on the aluminum plate until I saw the solder flow under the IC.

I am always afraid that I will underheat the PCB causing bad solder joints, or overheat the board destroying the ICs.

Someday, everything will be solder reflow.  A good set of tools will be a must!

TonyTib
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CEO
Re: Home 'lectronix lab
TonyTib   9/12/2013 4:55:33 PM
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Sometime the electric company helps: when I was living in Spain a long time ago, sometimes the electric company would let the grounds float up really hight and then zap!!!


Then there was the electrician who was doing a check on a live 450V system, and to save time had the meter hooked up to one set of probes, with another set of probes ready to go, also already connected to 450V when....OK, you can guess.  Fortunately the tech was OK after his shocking experience.


As far as scopes go, I'd recommend considering reputable used sources.  I've head that some Rigol scopes are "badge-engineered" for at least one major brand.  Mine is a Fluke Scopemeter 190 100MHz dual channel model with a really nice set probe set.   Somehow it feels more like a DMM than a scope, but its isolated channels are pretty handly since I often use it for troubleshooting differential encoder signals.

A couple years ago I got a chance at ESC West to play with the then-new R&S scopes, and all I can say is WOW!   Of course, those are in a different price range...

Aeroengineer
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Blogger
Re: Home 'lectronix lab
Aeroengineer   9/12/2013 7:34:10 AM
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This is too true.  In one of my high school physics classes, our teacher had a very tiny, hand-crank, AC generator.  The demonstration was to have you hold the ends of the output and then have him crank slowly.  It showed the muscles in your arms contracting, and causing your hand to grab the electrode tighter.  Hence the problem with grabbing onto an AC voltage source in that once you grab, it may be difficult to let go.

 

On a side note, I love the innocent curiosity of kids.  How you describe the way you though an electric motor works is just very interesting.  I love it.

zeeglen
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Re: Home 'lectronix lab
zeeglen   9/11/2013 9:18:50 PM
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I built a record-player turntable with my meccano set.  I had this idea that motors worked by the electricity in the wires brushing past a rotating shaft, something like a water wheel.  Plugged the wires into a 220VAC outlet...

Afterthought: Fortunately I survived.  Parents, teach your children well.  If your child shows an interest in electricity, or any scientific study, teach them that playing with electricity can be worse than playing with matches.

David Ashton
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Re: Home 'lectronix lab
David Ashton   9/11/2013 8:56:08 PM
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It is surprising how many electronics types had some contact with mains electricity as kids.  Mine was with a meccano-type construction set and I discovered the axles fitted very nicely in those holes in the wall (then round-pin british sockets).  I reckon it gives you an affinity with electricity for the rest of your life :-)

David Ashton
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Re: Home 'lectronix lab
David Ashton   9/11/2013 8:52:28 PM
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@Zeeglen....very timely advice....a retailer I use has some ATTEN scopes at what seem like give-away prices and I had thought about splashing out on one (even give-away prices require some thought on my part....) but you've persuaded me to hang onto my money for now.  I'll buy another Lotto ticket......

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