Troubleshooting as a noob?

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L!mbo
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Troubleshooting as a noob?

Post by L!mbo » Fri Jul 08, 2016 5:00 pm

Hey guys.

I finally have a module that I have to troubleshoot (all parts placed correctly) to see if I have a failed part of some sorts. I know how to measure resisters but other than that, i'm pretty green.

Any videos or guides you recommend?

The module i'm troubleshooting is a radio music that won't power on.

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EATyourGUITAR
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Post by EATyourGUITAR » Fri Jul 08, 2016 7:37 pm

Check the supply voltage. If ok check power pins on all the IC. If ok, run a sine wave throught it. If this is a logic, run gates, if this is a vco it should make sound. What kind of module is it?
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L!mbo
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Post by L!mbo » Fri Jul 08, 2016 8:11 pm

EATyourGUITAR wrote:Check the supply voltage. If ok check power pins on all the IC. If ok, run a sine wave throught it. If this is a logic, run gates, if this is a vco it should make sound. What kind of module is it?
Radio music sampler from music thing. I'm trying to find out where i need to put the ground and the posititve to test the voltage, which is why I kindof wanted a crash course video. Haven't found any yet but i'm still looking.

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sixty_n
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Post by sixty_n » Fri Jul 08, 2016 9:00 pm

You can use any of the middle six power pins as ground. First check there is no connection between these and the two pins for +12 and -12 at either end but there probably isn't as that would have messed up your other modules and your power supply.

To check the voltage is correct at IC sockets google the chip name + pinout e.g. "tl074 pinout" and look which pins are labeled V+ or Vcc. You can check the voltage with your multimeter between this pin and the ground from the power header

I'd check the diodes and electrolytic capacitors are the right way round first and make sure the teensy pins are connecting properly (multimeter though each socket pin from on top of the teensy to the bottom of the pcb). Also I had some problem with mine where the card was read only or something like that and nothing worked but I can't remember exactly what it was. I think one led flashed once when I turned it on but nothing else happened

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tony d
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Post by tony d » Fri Jul 08, 2016 10:10 pm

Read through this, it is a pretty comprehensive list of things to look at when troubleshooting.

http://www.musicfromouterspace.com/inde ... 70&VPH=513

Good luck! The best moments i've had in synth diy are finally figuring out what i did wrong and having a module come to life

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infovore
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Post by infovore » Sat Jul 09, 2016 8:48 am

Get a copy of the schematic. All the Music Thing modules are open-source, so that's easy to find. The MTM modules are designed in EAGLE - you can get a freeware copy of that easily.

And then, follow the signal around. Obvious things for starters are:

* continuity - with the power OFF, look at your solder joints. Are any dodgy? If they're dodgy, put a multimeter into continuity testing mode and touch the suspect joint to a point you know it should be connected to. Does the continuity tester beep? If not: not connected. Re-solder the joint. Also, everything that should be connected to ground should have continuity with anything else - so an obvious one is checking the ground pins on the euro power supply to, say, IC ground and confirming that's working. Whilst you're at it: if you see blobby solder that looks like it might be joining two pads that aren't, again, continuity-check them to confirm if they're touching or not.

* Direction: are all components with directionality in the right place? That means: diodes, electrolytic caps, voltage regulators, transistors, ICs. You can do this with an eyeball.

* Voltages. Make sure when you're testing voltages not to short circuit anything. But: with power running through the device (and ideally, no other modules in your system - so just connect the module alone, or, alternatively, use a module-tester of sorts for power), check that things have the power they require. You measure voltage across points. So, put the multimeter into Voltage DC mode, and put the black test probe onto a GND source. Then, put the red test probe onto something that should have ~5V DC. Does it have about 5? (Anything from 4.9 to 5.1, basically). If not: well, that's an issue. Obvious things to test here are the voltage inputs to the ICs on the radio music. Be particularly careful around the Teensy - microcontrollers are more fragile to unexpected voltage than discrete components.

If everything that should have power is getting the power it needs, and you've got no suspect shorts, and no duff solder joints... then it's time to bash heads with more forumites!

Also: don't just _measure_ resistors. Confirm that each part is in the correct location - the schematic will tell you which resistor ("R4") has which value. You can double-check the board layout for where they should be, and just work through them one at once. If it helps, take a photo of the board and annotate it in a graphics package.

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sduck
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Post by sduck » Sat Jul 09, 2016 9:19 am

Do you have a DMM?
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L!mbo
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Post by L!mbo » Sat Jul 09, 2016 7:21 pm

What is a DMM?

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qfactor
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Post by qfactor » Sat Jul 09, 2016 8:51 pm

Well, it's definitely NOT a "Drum Machine Module" but a Digital MultiMeter!! :guinness:

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EATyourGUITAR
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Post by EATyourGUITAR » Sat Jul 09, 2016 9:37 pm

I would say that 4v on the 5v rail is within spec for most logic modules. voltage drop on a flying bus connected to a flying bus in an extension cabinet can be anything and the gates are still gates. very few modules are using power 5v as a voltage ref or voltage follower I think. most of them are little $7 computers crunching binary and running a DAC. there are some modules that draw 500ma on 5v to a DC DC converter for a tube power supply. this is totally no problem on a power one or condor power supply, they usually have 2A 5v and 800mA 12v. it would also explain the voltage drop but it won't have any adverse affect on the DC DC converter.

if 4v is a fail then show me the module that fails it.
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sduck
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Post by sduck » Sat Jul 09, 2016 9:51 pm

Get a DMM. Spend some quality time learning some basics with it - measuring voltages, resistance, continuity at least. Get back to this when you've done this. You can't really do any meaningful trouble shooting without a DMM and some basic skills using it.
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L!mbo
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Post by L!mbo » Sun Jul 10, 2016 9:51 am

I just got a DMM but I've used fluke meters before at work so I know a little about them. When I get home i'll try some of the things you guys mentioned and see if it helps. Thanks a lot for the tips and the MFOS website referral.

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Post by pfzzz » Sun Jan 10, 2021 2:45 pm

tony d wrote:
Fri Jul 08, 2016 10:10 pm
Read through this, it is a pretty comprehensive list of things to look at when troubleshooting.

http://www.musicfromouterspace.com/inde ... 70&VPH=513

Good luck! The best moments i've had in synth diy are finally figuring out what i did wrong and having a module come to life
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