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

[neopl]

Hi

So I've done something very very daft.... I soldered one of the black diodes from the power section the wrong way around... despite clear markings on the board

I connected the module and the whole system started to flash on and off... At that point I investigated and realized my mistake, I have since de-soldered the diode and put it the right way around, now my system no longer flashes like mad when I power it on, but the Radio Music does not seem to be working. I get no lights on the module, and no output is coming out.

I don't know the first thing about troubleshooting electronics, all my builds thus far have been free of mistakes. Any ideas what could of gone wrong?

Thanks !


Also, I tried reloading the Teeney to see maybe the fault is there, and I cannot get my computer to recognize it anymore. Did i cut the correct trace? In the build doc I was debating if it is the one I cut, which in the doc was being covered by the knife, or if it is the trace I didn't cut that is more toward the tip of the knife.

trace.jpeg (50.39 KiB) Viewed 473 times

[SphericalSound]

Putting a power diode in reverse should not screw a circuit unless you also power it in reverse.

So the obvious thing is to cut this diode and solder another with the correct orientation.

The teensy cut is correct. You can just bridge with a blob of solder for the computer to recognize it but first I would try to put the diode correctly and power it again

[gtrmstr53]

i'd second SphericalSound's advice. if you're able to, test it with a new diode. if that doesn't fix it, try connecting the teensy to a known good computer. if neither the diode nor the teensy are the issue, i'd start looking for any burnt resistors or anything like that?

[EATyourGUITAR]

assuming this is the schematic for the version of the PCB you have.
https://raw.githubusercontent.com/TomWh ... 20Rev2.pdf

installing a diode backwards will suck enough power from your power supply to bring the rails down temporarily and heat up the diode. %95 of power supplies will simply output less voltage with no permanent damage to the power supply. the power supply may turn off and on rapidly as it tries to supply power to the short circuit. this is why your lights were flipping on and off on other modules. I don't think you damaged any components on the radio music since the short is closer to the power supply than the components on the module. if you installed some diodes backwards AND you reverse powered the module with a backwards power cable then you could possibly reverse power the module with no reverse power protection. the reverse power protection on the module only protects the module if those diodes are the right way around.

[batchas]

Also, I tried reloading the Teeney to see maybe the fault is there, and I cannot get my computer to recognize it anymore. Did i cut the correct trace? In the build doc I was debating if it is the one I cut, which in the doc was being covered by the knife, or if it is the trace I didn't cut that is more toward the tip of the knife.

When this trace is cut on the Teensy, than you need to power the module as well in addition to the USB connection to get the firmware upload working.

Or like SphericalSound mentioned, you bridge the 2 pads, so they are connected together again and you don't power the module.

[neopl]

Thank you for the invaluable help so far! It is comforting to know that the module is probably not broken beyond repair. Is it likely that the diode is toast and need to be replaced with a new one? I reversed it so it is now placed the correct way around, but the module does not seem to power on at all now. I visually triple checked the other components and the boards and all looks fine to me. I'll be buying another diode keeping fingers crossed that is the issue.

In the meantime, I do have a Brymen BM 867M multimeter, so I'll go about learning as to how it can be used to test the diode to see if its fried or not.

Edit: I just did the Diode test as explained here https://www.fluke.com/en-gb/learn/blog/ ... est-diodes
In one direction is shows .53v when I swap the multimeter test prongs (what are the called? ) the Multimeter shows OL. So it would appear the the diode is fine? Although mind you, I have not removed the diode from the PCB before doing the test.

[EATyourGUITAR]

the diode is fine. the problem is somewhere else. check the power pins of the teensy to make sure you have power. check the 5v regulator.

[neopl]

the diode is fine. the problem is somewhere else. check the power pins of the teensy to make sure you have power. check the 5v regulator.

Ok, cool, now maybe a daft question. But just to be clear I understand it... that to test the 5v regulator I must have the module plugged in? Same goes for testing the power pins (3.3V +GND) on the Teensy? Obviously going to be extra careful to not touch any other components, but I rather ask this questions now in case what I’m about to do is a no no!

[EATyourGUITAR]

Plug it in. Test voltages. Make sure the teensy has power. I didn't look if it is a 5v regulator or 3.3v regulator. Maybe there is a LDO 3.3v regulator on the teensy that converts 5v to 3.3v.

[neopl]

Plug it in. Test voltages. Make sure the teensy has power. I didn't look if it is a 5v regulator or 3.3v regulator. Maybe there is a LDO 3.3v regulator on the teensy that converts 5v to 3.3v.

Ok cheers, so I powered on the case with the module plugged in, switched my multimeter to DC and tested the 5v regulator on the PCB. I tried every permutation of touching the 3pins, and the most i got was between 0.07 to 0.1V (I understand that I should be getting 5V on the Regulator?)

I wanted to test the Teensey as well, but I'm not sure which pins I should be touching. I'm trying the Pins labeled AGND and 3.3V (250 mA max) as shown on the diagram below, but I am not getting any output on the multimeter. The pins on the right side, 3.3V and GND are not soldered according to the Radio Music manual.

Could this mean that the 5V Regulator needs replacing?

EDIT: So I'm pretty sure I am measuring the 5V Regulator correctly. I just opened one of my previous builds and tested a regulator in there (a L79L12) and depending on which pins I was touching I was getting a solid 12V, 13V or -13V . Another Regulator I tested in that build - a 7812ACT and again am getting either 12 or 15V. All a far cry from the .07 to .1V on the radio music.

[synthetek]

Pull the teensy out and check the voltage on the radio music pcb also try the teensy by itself and see if the computer/teensy loader can see it.

[neopl]

Pull the teensy out and check the voltage on the radio music pcb also try the teensy by itself and see if the computer/teensy loader can see it.

I pulled the Teensey out, I checked the PCB pins with the multimeter where 3.3V and GND of the Teensey should be and I got nothing. I also got nothing at the 5v voltage regulator on the PCB.

I bridged the cut trace on the Teensey so that I can power it over USB to see if I can and alas, I can no longer get my computer to recognize it. I also tried testing the 3.3V and GND pins on the Teensey when connected over USB, and still got nothing.

So what can we surmise from this? The 5V Voltage regulator needs replacing and I also need a new Teensey from the looks of it.

[synthetek]

So what can we surmise from this? The 5V Voltage regulator needs replacing and I also need a new Teensey from the looks of it.

Probably, did you use the poly fuses in your build and have you checked them for continuity? and checked after the ferrites that you are getting +12/-12v ?

[neopl]

So what can we surmise from this? The 5V Voltage regulator needs replacing and I also need a new Teensey from the looks of it.

Probably, did you use the poly fuses in your build and have you checked them for continuity? and checked after the ferrites that you are getting +12/-12v ?

I used whatever fuses there were with the kit ''200ma PTC Poly Fuse'' https://www.mouser.co.uk/ProductDetail/ ... 2Bmg%3D%3D

There are two fuses, I checked them both without removing from the circuit, and got no continuity. Would this mean the fusees are also toast, or do I need to remove one of the legs from the circuit and check again?

There are two big ferrites in the power section, but I'm not sure what am I suppose to touch to test for -12 / +12. Do I touch both legs of the single ferrite, or do I touch one leg of each ferrite? I don't want to short any more than is shorted already! Cheers!

[synthetek]

You should power it and test from gnd to to the upper leg on the ferrite, one should be +12 one should be -12. The fuses should have continuity you dont need to remove them to test it.

[neopl]

You should power it and test from gnd to to the upper leg on the ferrite, one should be +12 one should be -12. The fuses should have continuity you dont need to remove them to test it.

Looks like the fuses are toast as I get no continuity. (So far I ordered the Fuses, the 5v regulator, and the Teensey.) Hoping that will be enough to rectify my silly mistake :(

Going back to the to testing the +12 / -12 on the ferrite, when you say GND, you mean one of the GND pins from the 10 pin power connector? And also the upper leg of the ferrite would be the one closer to the 10 pin power connector?

[synthetek]

Check the end of ferrite away from the connector and gnd at the 10 pin connector. If your not getting +12/-12v there you could remove the fuses and bridge where the fuses were and then check for +12/-12 again. The 5V regulator could be working the and just not getting 12V

[neopl]

Check the end of ferrite away from the connector and gnd at the 10 pin connector. If your not getting +12/-12v there you could remove the fuses and bridge where the fuses were and then check for +12/-12 again. The 5V regulator could be working the and just not getting 12V

We're getting closer, thanks for the top tips! I was not getting +12 / -12 but then when I took the fuses out and bridged their connections i got 12 volts between the GND and the ferrite. At this stage I also checked the 5v regulator and I was getting either 12V or 5V depending on which pins I was touching, so it looks like the 5v regulator is fine after all.

So the fuses and the Teensy are toast for sure. Hopefully it will end there. I'm expecting Teensy and the fuses to come in the post by the end of the week.

Is it likely that anything else could of fried? I can do some more tests while I wait for the fuses and the Teensy.

Overall I'm glad I messed up on this built as I think I learned a lot, and I imagine it is easier troubleshooting something smaller like this vs some larger builds I've done in the past.

[synthetek]

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.

[batchas]

I thought till now that the role of the fuses was to protect the further circuit.
I mean if the fuses are dead, then the current should not flow further and harm the Teensy or any other component.
But this is not what is described here, then I'm wondering what are the fuses for. Do you know?

[JimY]

Shouldn't a polyfuse self restore when cool? So if you test while still hot from desoldering you could get an open reading. However, although heating "blows" the fuse, the cool reset time is long and not due to cooling - this can take days to reach the original resistance.
It seems odd to fit the fuses "after" the protection diodes. I would think the purpose of a fuse would be to disconnect everything when wrong polarity is applied. If a powerful power supply was used, it could blow the protection diodes and the fuses would do nothing.

Polyfuse current rating marking is weird. They are in milliamps/10 and shown in 2 or 3 digits. A 200mA is 020 and sometimes reduced to just 20 or 02! Confusion with other possible values is avoided by simply not making those values - there is no 2A rating! The fuse type in the original build doc suggests 100mA.

[EATyourGUITAR]

It seems odd to fit the fuses "after" the protection diodes. I would think the purpose of a fuse would be to disconnect everything when wrong polarity is applied. If a powerful power supply was used, it could blow the protection diodes and the fuses would do nothing.

this problem has been known for years. mistakes were made. I called this out way in the beginning. I think music thing got the message. the newer designs for other modules are correctly designed in the power section. I put forth the criticism that with reversed power connected, this design puts a massive load on the user's power supply which may cause damage to some power systems. while it is unlikely, it is also possible. modules should not damage power supplies. I don't know if the schematic I linked is even matching the latest version of the radio music DIY PCB that is available. probably the PCB is the newer one that is correctly designed. the schematic I linked looks like the old one with problems. it was the first thing I could find in google. 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.

[neopl]

It seems odd to fit the fuses "after" the protection diodes. I would think the purpose of a fuse would be to disconnect everything when wrong polarity is applied. If a powerful power supply was used, it could blow the protection diodes and the fuses would do nothing.

this problem has been known for years. mistakes were made. I called this out way in the beginning. I think music thing got the message. the newer designs for other modules are correctly designed in the power section. I put forth the criticism that with reversed power connected, this design puts a massive load on the user's power supply which may cause damage to some power systems. while it is unlikely, it is also possible. modules should not damage power supplies. I don't know if the schematic I linked is even matching the latest version of the radio music DIY PCB that is available. probably the PCB is the newer one that is correctly designed. the schematic I linked looks like the old one with problems. it was the first thing I could find in google. 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.

For those curious (and for those who can read there, sadly not me, not yet) here are the up to date schematics.

https://github.com/TomWhitwell/RadioMus ... Schematics

I do agree that it is curious that the fuses would not protect the rest of the circuit. I do have a beefy power supply (Pittsburg modular structure ep-420 case) I know it was mentioned that a strong power supply could be a factor.

[EATyourGUITAR]

here are the up to date schematics.

https://github.com/TomWhitwell/RadioMus ... Schematics

2017. that is the schematic with the problems. don't worry though. probably your power supply has protection. it only matters if you connect the radio music with a reverse power cable red stripe and all that. you could replace the polyfuses with metal jumper or maybe 22R resistors to act as a one time fuse.

[batchas]

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?