Radio Music - soldered one of the big black diodes the wrong way, am I toast?

[EATyourGUITAR]

I should say that all the problems have been corrected and all the current diy kits from music thing do not have this problem as far as I know.

2017. that is the schematic with the problems.

AFAIK, there's no other more recent version of the Radio Music circuit. So I'm curious of which corrected version you do refer to?

ok so I didn't do my research. I don't know why these are still being sold in 2021. they should have been fixed a long time ago. see this is from 2013 with the fuses in the correct location before the diodes. 2013

https://musicthing.co.uk/wp-content/upl ... ematic.pdf

but this one is the same problem as the radio music. 2014

https://musicthing.co.uk/wp-content/upl ... ematic.pdf

no new versions exist? leave the diodes out. not worth damage to the power supply. replace the fuses with 22R resistors. turing machine should be 47R.

[JimY]

Possible there was another problem apart from the diode. One thing to take home from this, is that if any part of the project can be left out (socketed chips/module) then power the board and test voltages first without them. Reduce the chance of damage from power faults. If you get good voltages on the socket power pins, only then is it worth switching off, fitting the parts back and going for the big one.

[synthetek]

The way the power in set up the backwards diode could have sent 12v to gnd in the circuit even if the fuse was blown.

[neopl]

The only other thing might be the TL074 but kind of hard to test that without the teensy, If the lights and buttons work when you replace the teensy but you get no sound then replace the TL074.

I think this is exactly what is happening. I replaced the Teensy and I get the level lights flash on the module, and also the Reset light lights up when I press the button, but I get no sound from the module. Safe to assume it is the TL074 that also needs replacing?

Anyway, thanks for all the help everyone, I learned a lot, and know that for the future, I should leave all the expensive components out and check voltages first! And better yet, not get cocky and rush a build like I did this time around.

--------------------

EDIT So the plot thickens. I actually found a TL074CN laying around, so I swapped them out, but still the same issue. All the lights flash when the SD card is in, but no sound. Totally lost at this stage, any ideas?

I also looked at the SD card to see if the settings file got created, and it has, so it looks like the software side of things is fine for sure.

[synthetek]

did you send a trigger to it?

[neopl]

did you send a trigger to it?

I thought that Radio Music is meant to output sound continuously? But anyway, I just tried sending triggers to all the inputs, and still nothing :(

When I turn up the trimmer on the back all the way I can hear electrical hum noise, but no sound

[synthetek]

you have samples on the SD card? maybe try chord organ firmware to rule out a problem with the sd card/sample format

[neopl]

you have samples on the SD card? maybe try chord organ firmware to rule out a problem with the sd card/sample format

I used the samples from the github page, so they were already formatted in the folder structure readable by Radio Music. Nevertheless, in case I messed up something with the SD card I did do as you suggested and loaded the Chord Organ firmware. I know that loading the firmware has been successful because the CHORDORG.TXT file gets auto created on the SD card. Also the Trigger output works as when I turn the knobs I do get trig out. Unfortunately no audio still. It would appear that everything is working aside from the audio.

[synthetek]

Post pics of front and back sides of your boards, check the other diodes with your meter, test caps and resistors you wont get exact values with them in the circuit but look for anything unusual like shorts or open.

[JimY]

Op-amps are possible to check voltage-wise with nothing else happening. Each amp usually will want to settle with all 3 pins at a "reference" voltage. If its a bi-polar power supply (which this is) that reference will usually be 0v. A reference of 0 is hard to tell anything by (it would be 0 with no power too!) - but if it ain't 0v, then something could require investigating. If it is all at 0v and there is supply volts on the IC power pins, then there's a good chance all is well (well enough to try it all together anyway). At least you will know there is nothing nasty such as applying -12v to an MCU pin!
The connection to reference is usually via a high-value resistor between the reference 0v and the amp +input pin or by having a permanent resistive connection to a preceding circuit that is itself referenced.

Looking at the Rev2 schematic, only IC4a has a 0v reference (via R5). The other 3 amps have no reference! IC4b and IC4c will get a reference when a CV source is plugged in. IC4d never has a reference - it is entirely blocked from any reference by capacitors so its DC voltages are free to wander anywhere within the power supply limits.

I think that in this instance, I'd fit 1M reference resistors between 0v and the +input pins of all amps except IC4a. 1M is high enough to supply a reference without affecting performance.

[twigathy]

I built a pair of Radio Musics recently (+ a Chord Organ, which is the same hardware) - in the build guide there's some notes about the opamp's lack of ground reference here:
https://github.com/TomWhitwell/RadioMus ... -red-thonk

[neopl]

Post pics of front and back sides of your boards, check the other diodes with your meter, test caps and resistors you wont get exact values with them in the circuit but look for anything unusual like shorts or open.

Here are the high resolution pictures of my boards. Just follow the link and click open and in the folder there are four jpgs. For reference I also found two pictures on google of the boards before the components are put in.
https://web.tresorit.com/l/9nUSO#vGJRIXPvbZWUu4Y_g1NBFA

Tonight I will start the long process of checking all the resistor and cap values to make sure they are in the right places, and if that is all correct, I will test them with the multimeter.

EDIT. As to the rest of the diodes - the small ones, I checked them all and they are oriented correctly and all display .24 on the multi meter diode test.

[batchas]

did you send a trigger to it?

I thought that Radio Music is meant to output sound continuously? But anyway, I just tried sending triggers to all the inputs, and still nothing :(

When I turn up the trimmer on the back all the way I can hear electrical hum noise, but no sound

Indeed the Radio Music needs a trig at the RESET input. Also the trimmer in the back needs to be "opened" to let a signal pass. If I were you I'd set it in the middle so you're not "all the way" ans sure it's not fully closed. We never know.

Then it's very difficult to tell from photos because of the light reflections.
I'd reflow these to be sure there is no cold joint (looks like on photo, but again impossible to affirm).

Seems that the attachment is not working so I uploaded a screenshot here: https://postimg.cc/rzBzFVFc

[neopl]

did you send a trigger to it?

I thought that Radio Music is meant to output sound continuously? But anyway, I just tried sending triggers to all the inputs, and still nothing :(

When I turn up the trimmer on the back all the way I can hear electrical hum noise, but no sound

Indeed the Radio Music needs a trig at the RESET input. Also the trimmer in the back needs to be "opened" to let a signal pass. If I were you I'd set it in the middle so you're not "all the way" ans sure it's not fully closed. We never know.

Then it's very difficult to tell from photos because of the light reflections.
I'd reflow these to be sure there is no cold joint (looks like on photo, but again impossible to affirm).

Seems that the attachment is not working so I uploaded a screenshot here: https://postimg.cc/rzBzFVFc

I now am running the chord organ software and that i understand outputs sounds continuously, and adjusting the trimmer at the back i still get no sound.

Thank you for looking at the pictures, I took your suggestions on board and re-flowed some of the solder joins, the ones that appear to be touching in the photo are not actually.

Anyway, I checked every single resistor, if it is in the correct place, but also the values i get with the multi-meter - all correct.
I checked the small diodes as well and they all display .24 on the diode test.
I checked all the capacitors and as far as i can tell (it is a little confusing with all the uFs nFs decimal points and such) they also display correct value on the multi-meter.

The only two capacitors that display either O.L or DISC on the multimeter are the small 1n caps in position C4 and C1 on the board. I even took one of them off and it still display O.L or DISC on my Brymen BM867s multimeter. Could this mean they are busted?

Not sure where to go from here :(

[...]

I still need to digest Jimy's suggestions, but that will require a little more thought as a lot of it is above my level of expertise.

[JimY]

Small value capacitors are difficult to measure. 1nF could be "out of range" for your tester (see the user manual for it). As long as they don't measure a short circuit, they can't kill anything. In fact, I measure resistance instead. So with DMM highest resistance range, check it reads O/L. A capacitor must not pass DC current.
They don't often fail or have a very wrong value and since difficult to measure, we would swap them out if there was a reason to suspect them.

On the DAC output, you have a low-pass filter something like the one top right here. The input comes in at R1 and note there is only a connection "dot" instead of a capacitor.
For the other High-pass example, there is an input capacitor C1, but it has a resistor R2 from +input to 0v. R2 is "referencing this filter to 0v. As it happens, both C1 and R2 are essential parts of this filter circuit while the Low Pass is the opposite and so has no referencing resistor.
Now see the Band Pass filter made by adding the two in series. There is no coupling cap between them because the low pass filter needs DC reference at 0v and it gets this from the preceding stage which is in turn, referenced to 0v by that resistor to 0v.

Note that individual circuit tutorials frequently leave out any mention of what it requires before and after it since it isn't directly relevant to what they are teaching. You do need to know that the +input of an opamp, must have a resistive connection (that can be 0 ohms for inverting circuits) coming from somewhere.

So, in the DAC filter you have, the referencing can be done at the input resistor directly after the input capacitor. Fit a resistor from there to 0v. The resistor can be at least x10 the value of the input resistor.

Note, interestingly, you won't find this "no reference" fault by checking voltage on the opamp pins. Your meter has an input resistance (1M to 20M depending) and with the black probe on 0v, the meter will itself reference the circuit to 0v when you connect the red probe.