MUFF WIGGLER Forum Index
 FAQ & Terms of UseFAQ & Terms Of Use   Wiggler RadioMW Radio   Muff Wiggler TwitterTwitter   Support the site @ PatreonPatreon 
 SearchSearch   RegisterSign up   Log inLog in 
WIGGLING 'LITE' IN GUEST MODE

Safest way of testing DIY builds?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Safest way of testing DIY builds?
Daisuk
Hey guys! I'm new to DIY'ing, have built a couple of kits for Eurorack, but have been a bit nervous when plugging the modules into the case for the first time, in case I've done something wrong and will shortcircuit something.

Is there a safe way to check whether a DIY kit works (and won't short circuit and possibly damage other modules) without plugging it into a case? Can you for instance get a single instance of a bus board connection from somewhere?

Possibly some very stupid questions, but here goes. lol
regenbot
i always check continuity between rails and ground before plugging anything. I also use frequency central DIY power for testing purposes.
mush
I build at home. I use a small doepfer beauty-case for PSU. I always check continuity between rails and ground before powering up. And only plug in the new module first. After checking I plug in a couple of "utility modules" I keep at home (a Music Thing Radio Music for audio-rate waveforms and testing triggers and CV, an LFO and a mini speaker). I usually calibrate the module at home. And once it is done I take it to my studio and it usually stays there.
gdavis
In addition to the suggestions above, if you're serious about DIY get a bench power supply with constant voltage and constant current modes. Set the current to a reasonable value and it will clamp down if there is a short or if the module draws too much current for any reason.

I use one of these:
http://www.bocatechinc.com/test-equipment/power-supply

Pretty nice for the price. Not an absolute necessity but it's great to have especially if you do anything outside of synths because of the flexibility. You can find basically the same supply under different names, pretty easy to find on ebay.
valis
Agreed.

Never ever ever power a newly built module for the first time in your main case. Get some sort of bench supply. Additionally, power up your pcb for the first time without the ICs and test the voltages. Make sure they are what you expect before putting in your ICs. Then test again, if the module works then put it in your case.
Altitude909
valis wrote:
.. Get some sort of bench supply. ..


Thirded
ablearcher
Yup, bench power supply. You can find em cheap, I use an elenco xp-581a which has seperate +12v, -12v, +5v, and a variable output, which is perfect for eurorack.
oscarthesquirrel
regenbot wrote:
i always check continuity between rails and ground before plugging anything.


As a noob to DIY..what does that mean in plain English..or in instructions that can be simply understood, assimilated and followed ? eek!
gdavis
oscarthesquirrel wrote:
regenbot wrote:
i always check continuity between rails and ground before plugging anything.


As a noob to DIY..what does that mean in plain English..or in instructions that can be simply understood, assimilated and followed ? eek!


Most multimeters have a continuity check feature. Basically it checks if the points contacted by the meters probes are electrically connected or not (i.e. connected together by a wire). When there is continuity between the probes the meter beeps (you can check this by touching the probes together, it should beep while they're touching).

You want some resistance between +12V, -12V and GND. If you check these points with the continuity feature and it beeps continuously, it means you probably have a short somewhere and that plugging in the power supply will likely result in a blown fuse or magic smoke being released.

If your meter can measure resistance you can use that too. If you have around 500 ohms or higher you're probably ok, but if you're in single or double digits, there may be an issue.

The tricky part is that caps on the power supply lines can cause a short beep or the measured resistance to slowly climb. If it's just a very short beep or the resistance climbs above a few ohms very quickly you should be OK. Continuous beep or resistance staying very low is bad.
qfactor
I DIY'd a Freq Central power supply to be my test PSU. After building a module kit, I would plug it into this PSU to test.

First thing I look at, is around the power area of the PCB. Especially if there's a couple of ferrite bead spots or low resistor values (<20ohms).
I'd switch on the power, then "stare" eek! at the beads/resistor, all ready to flick the switch off the moment I see any smoke forming!
Dave Kendall
Agreed with getting a dedicated bench power supply.

FWIW, a Power-one HAA-15 PSU (common in the USA) will simply shut down in case of inadvertent reverse polarity or a short.

cheers,
Dave
fluffymuff
I built myself a Mutable Instruments module tester which was designed by Olivier for this exact purpose - http://mutable-instruments.net/module_tester. I got mine from Thonk but he's currently out of stock but there are a few people doing small runs of these every so often so you should be able to pick one up soon. The only problem is... how do you test the tester!
Luka
power up with bench supply with no IC in sockets - check rails in each socket and shorts in general
power down
power up with IC loaded
if all is well put in case
Daisuk
Wow, lots of very informative and helpful replies here. Thanks a lot, all of you! smile

I'll be looking to get a bench power supply, if I can find one cheap.

Would it be a bad idea to just get a small Monorocket case and use that as a sort of "test-case" though? I would of course potentially fry my DIY module, but at least I wouldn't fry the rest of the big case. Are there advantages to getting a bench power supply over a little test case?
Nantonos
The advantage was already mentioned:
gdavis wrote:
get a bench power supply with constant voltage and constant current modes. Set the current to a reasonable value and it will clamp down if there is a short or if the module draws too much current for any reason.


Testing for dead shorts with a multimeter before powering up (like -12V accidentally connected to GND) helps a lot. But sometimes there is no short, but a mistake means that something on the board will try to draw a lot of current and may blow, or damage other components. Being able to set a bench power supply to, say 50mA means your module can draw up to that and no more. So you can detect that it is drawing more than it should, power down, and fix the problem.
SmartBits
mush wrote:
I use a small doepfer beauty-case for PSU.

I got a used Doepfer mini case for this purpose as well. Was cheaper than anything I could DIY as a n00b...
muffjuiggler
did you guys found a good video on explaining how to messure the contacts...
-what it should show on the display
-where should the black and the red sticks on the meters should held on
-how to see that theres something wrong

i have a problem with two solderingpoints because it seems like that those two are touching each other (resistors 12K and 470K)

i definitly see a market for Moduletesters for diy modules!

but i want to test it before i get the risk of a short or something... is this possible?
MrsWedge
Use a power or power supplies that have both overload protection and a crowbar.

Overload protection will keep the ouput current from rising above a set maximum while the crowbar will disconnect the output if a short is detected and will stay disconnected until the short is removed and the power is cycled. I have done extensive development, breadboard and prototyping work using a pair of 12V 5A open frame power supplies and the crowbars definitely prevented terrible things from happening more than once.
adam
muffjuiggler wrote:
did you guys found a good video on explaining how to messure the contacts...
-what it should show on the display
-where should the black and the red sticks on the meters should held on
-how to see that theres something wrong

i have a problem with two solderingpoints because it seems like that those two are touching each other (resistors 12K and 470K)

i definitly see a market for Moduletesters for diy modules!

but i want to test it before i get the risk of a short or something... is this possible?


have you got a schematic? first thing to check is if the two points connect anyway
muffjuiggler
schematics not available in near time...

i asked on fb muff wiggla too and the problem has been solved because most of em sayed that the two points conected each other should be ok.

but still i miss a good video explaining me how to messure the module for shorts before i put it in the rack

best regards
mskala
Quick sanity check for newly-built Eurorack modules: multimeter on "diode test"/"beep continuity" range. Probe top two pins of the 10-pin Eurorack power connector (+12V) against pins in the middle (0V); middle pins against bottom/stripe pins (-12V); top against bottom. Then repeat in the opposite direction (probes swapped), for six measurements in all.

None of the readings should read zero or beep (except maybe very briefly while a capacitor charges) - that indicates a short circuit and will mean trouble if you apply power.

The reading for "forward" measurements (like red on +12V, black on 0V) varies depending on the module design; for most IC-based modules it's usually about 1.5V to 2.0V, but many smaller and discrete-based modules it's "out of range." It just shouldn't be less than about a volt.

The reading for "backward" measurements depends on how the module is protected from reverse connection. Series diodes, like my own designs, these readings should all be "out of range." Parallel diodes, they'll probably be about 0.6V either of the others to the 0V rail, twice that between -12V and +12V. Modules without reverse protection (tsk, tsk) it's anyone's guess. But again, none of these measurements should be zero.

With practice it takes only a few seconds to make these six measurements and interpret the results; if the module passes, my next step is to attach the module to a bench power supply with current-limiting set a little bit higher than the amount of power I expect the module to draw. But if it passes the continuity test, it's already pretty unlikely to have any serious problems just plugging it into a case. The most common serious build error is directly shorting out the power supply rails, and that's easy to detect with these measurements. (Actually finding where it's shorted may be harder... but the fact that it is shorted is not subtle.)

Quick pokes at the power connector for continuity testing do depend on the module being designed to connect together all pins of the power connection - which is how it's supposed to be done, but I've seen exceptions (traces running to only one pin instead of the whole group) in DIY designs. I'm not sure what can be done about that.
muffjuiggler
great explaining mskala

all the explaining didnt connect to my visuellawardness means i think it will all make a sense for me if i dig deeper...

thank you for taking time for me
Dr. Sketch-n-Etch
In the bathtub, of course.
MUFF WIGGLER Forum Index -> Music Tech DIY  
Page 1 of 1
Powered by phpBB © phpBB Group