Any way to verify as you go with Multimeter?

Started by Fndr8875, February 26, 2016, 07:23:57 AM

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Fndr8875

im just getting frustrated, ive only got a couple simple things to work, and im prob on my 20th project. My soldering is good, but ovbiously not great or id have had more success. Im normally optomistic because things look good, shiney joints, no solder bridges but there has to be shorts , burned up compoemts, or my inability to follow layouts 100%

blackieNYC

#1
I do go though everything with an ohmmeter when I start to solder. I leave out the op amp and the transistors (but sockets are always used) and measure everywhere. Mine has a cap meter as well. Things like this are more complicated when the op amps and transistors are in-circuit, and you can generally assume that the part itself was properly assembled.  So leave it out until you e metered everything.

Another thing I've been doing lately - the wires I attach to the board, which go to input, output, ground, and maybe switches and pots - before I put them in an enclosure, I tack-solder some resistor lead cuttings to the dangling end of the wires. Now I can poke all the wires back into the breadboard and test again.
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Mark Hammer

Stuff you look for, as you go, is pretty much the same stuff you'd look for post-build troubleshooting.  So, you look for signs of continuity (does the AC voltage at the input pin, when I strum, look like the signal is at least reaching the input of that device?).  You check to make sure all biasing is correct (does that Vref pin or resistor read 4.5Vdc?) and of course you check to make sure that V+ is going everywhere it should.  Use your continuity tester function (beeper) to verify that everywhere that ought to be in contact with ground IS, in fact, tied together.

MrStab

#3
i find instead of verifying with your multimeter throughout the build, you can verify against a coupla other things. first and foremost if you have as in-depth an understanding of a circuit and all its different paths as possible then you can occasionally look at stuff and go "hmm, that seems wrong". when i'm using stripboard, most of the time that's how i spot my errors.

another method is physical reference points: checking that each component you're putting in is the right distance (in rows/columns) from nearby trace cuts or the edges of the board.

i've noticed things like stripboard/veroboard and perfboard may be more prone to solder bridges than PCBs as all the rows or pads are constantly close together. a cheap desoldering pump is a handy way to clear up between traces and avoid burning components. you could also try to put in ESD and more heat-sensitive components towards the end.

(i came up with these methods and inner-monologues through a chronic series of stripboard failures myself!)
Recovered guitar player.
Electronics manufacturer.

anotherjim

I do like Blackie does.
DMM on diode/buzzer range.
Get a clean copy of layout/schematic. Have a couple of colour pens ready.
Use eyes to confirm a connection - mark a check/tick.
Use meter to confirm it's electrically connected - Then check to adjacent parts that it shouldn't be touching - then mark different colour check.
Check on the component symbol also that it's the right value/type and in the right way around.
Check from a wire connected leg/pin on the board to sockets/pots/switches. For sockets, put a plug in an check to the connections on that.
Check your switches route the connections as they should.
Check your pots really do change resistance from the wiper when you turn them.

After that, if it's a confirmed scheme you work to, it has a very good chance of working first time. If it don't, suspect something dumb before tearing it apart -  like a bad cable/power supply/battery or amp not switched on etc...

IC sockets empty. Apply power. Have some idea what voltages to expect on the pins referenced to ground. Eg, dual opamp as amplifiers or filters, you could well expect-
1 = 0v
2 = 0v
3 = Vref  +4.5v
4 = 0v
5 = Vref
6 = 0v
7 = 0v
8 = +9v
Power off, fit chip. Now pins 1,2 and 6,7 should now be Vref too.


Kipper4

#5
True that Jim.
Unless your meter loads down like in this post


http://www.diystompboxes.com/smfforum/index.php?topic=113359.0

Edit
If it's a more complex build I will sometimes tick off componants on the schematic as they are soldered in
Ma throats as dry as an overcooked kipper.


Smoke me a Kipper. I'll be back for breakfast.

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R.G.

Quote from: Kipper4 on February 26, 2016, 10:07:33 AM
If it's a more complex build I will sometimes tick off componants on the schematic as they are soldered in

I print the layout and the schematic both, and mark them off on the schemo and the layout as I solder them in. Double-entry bookkeeping helps.

Then I go back through after all components are placed and check them off in a different color marker.

It seems like a pain, OK, but contrast this time spent against easter-egging through the circuit trying to figure out what doesn't work.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

Beo

Audio probe works better than trying to ohm out your circuit once everything is soldered.

One pitfall they I fell into in the early days: when testing outside the enclosure, make sure both the input and output jacks have ground connections. In the box, I usually let the box provide ground to the output jack and only ground wire the input jack. But take the circuit out of the box, and your output jack has no ground reference.

Fast Pistoleros

Quote from: Beo on February 26, 2016, 12:07:32 PM
Audio probe works better than trying to ohm out your circuit once everything is soldered.

One pitfall they I fell into in the early days: when testing outside the enclosure, make sure both the input and output jacks have ground connections. In the box, I usually let the box provide ground to the output jack and only ground wire the input jack. But take the circuit out of the box, and your output jack has no ground reference.

i dont ground my output jack either ..saves on wire lol

Fndr8875

Thanks guys for all you replies. This is a really awesome site with alotta smart guys. Another thing that im frustrated with right now is basically im broke, I spent about 100 bucks about two months ago and got a bunch of capacitors, resistors, leds, diodes off ebay, and some ICs, trannys , jfets, sockets from small bear. I do not have an amp right now, i have a Irig HD from ikmultimedia, and a pair of bose desktop speakers, So when i go to test something i have to use a 1/4th inch stereo adapter connected to 1/8th inch stereo cable out to bose speakers. I have had several times where using a breadboard i get no sound. I stripped a cheap guitar cable where i can plug one end directly into breadboard, and a stereo cable and just use one half of the two lines that i also p;ug directly into breadboard. Seems like that meathod will work when the circuit is right, ANy ideas why id have such hit and miss results, seems like the quater inch adapter way would just give me audiio on one channel. I try to research my questions as much as i can before i post, but unfortunatly im still at a point where i struggle to understand concepts and the how and why, so i pretty much count on finding verified pad per hole layouts for something i am trying to build. R.G, your a freaking genious and i looove your pedals, i used to have a Luna od/distortion and a 4 know compressor, they were sweet and i wish i didnt have some unfortunate circumstances that caused me to have to get rid of all my nice gear.

wavley

Quote from: R.G. on February 26, 2016, 11:26:10 AM
Quote from: Kipper4 on February 26, 2016, 10:07:33 AM
If it's a more complex build I will sometimes tick off componants on the schematic as they are soldered in

I print the layout and the schematic both, and mark them off on the schemo and the layout as I solder them in. Double-entry bookkeeping helps.

Then I go back through after all components are placed and check them off in a different color marker.

It seems like a pain, OK, but contrast this time spent against easter-egging through the circuit trying to figure out what doesn't work.

This is pretty much what I do too.  In addition I leave a set of meter leads taped to the bench so I can drop resistors on them to make sure I read them right.
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Kipper4

Similar Wavley
But I use a cheap Chinese componant tester as well as DMM.
Ma throats as dry as an overcooked kipper.


Smoke me a Kipper. I'll be back for breakfast.

Grey Paper.
http://www.aronnelson.com/DIYFiles/up/

Jdansti

I do what RG does, and after I clean the flux off, I look at every solder joint with a magnifying glass. I then correct the solder bridges and partially soldered leads. If there's any question, I bring out the DMM.
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blackieNYC

+1 on enhanced optics. I use an 8X loupe (backwards).  I happen to go straight to the DMM before powering the thing up.

Another cheap trick - a tone generator phone app.  That and a homemade audio probe, for after the continuity, resistance, in-circuit capacitance(better meters only) and lastly- DC voltages test. My perf layouts end up very complex and a bit of a mess, so I really have to go thru every solder joint with a magnifier.  It takes me an eternity to put a pedal together.  Granted, I make them too complex. But many hours, many weeks.  Even when I don't have to desolder some mistakes.
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Tapflo filter, Gator, Magnus Modulus +,Meathead, 4049er,Great Destroyer,Scrambler+, para EQ, Azabache, two-loop mix/blend, Slow Gear, Phase Royal, Escobedo PWM, Uglyface, Jawari,Corruptor,Tri-Vibe,Battery Warmers