Warm Audio - TB12 Tone Beast ORANGE - No Signal

[amplexus]

That is a bog standard linear power supply. 3 x 3 terminal regulators some caps and basic 400* diodes in a full wave bridge configuration- which is why you got diode readings in both directions when you probed them in circuit. Probably also a basic voltage doubler to get the dc for the phantom supply (an issue there could be bringing all the rails down…)

You are certainly not getting correct voltages out of that psu based on your readings- but even at +/-13VDC i would expect SOME signal. At any rate you’ve got a 317 and 337 for audio rails, and probably a TL738 for phantom.

First step- check the ac output of the adaptor where it comes into the psu board. Is it where it should be? Second step, look at the DC voltage on the input pins of each of the regulators (check the datasheets when you confirm which regs are on the board). That DC input voltage should be at least 2-3 V higher than the desired rail voltages, so i’d say you’re likely going to want to see a minimum of +/-18V on the 317/337 and minimally 51-52VDC on whatever the phantom reg is.

If those voltages all check out then the issue is the regulator or forward (output caps), if not its in front. These are very simple linear reg circuits, basically right off the datasheet application notes, so there aren’t a lot of places they can go wrong. If your input voltages to the regs is bad then I might suspect the voltage doubler circuit, if you can trace where the 48V rail is sourcing from and disconnect it by lifting a component leg, then check the audio rails and see if they snap back.

Verifying those voltages at those locations will narrow things down considerably.

 

[TLK]

I would agree with the observation that the power input connector is NOT a mains AC power input. Likely that it requires an external power pack that outputs either an AC or DC voltage source and rest of DC power needs are created on the power supply board. I don't see anywhere in your posts that describe what you been powering this unit up with when testing ??? Do you not have the proper AC mains power adapter it came with ?

 

[pucho812]

Rear shot of a tb12 v1. Note the 24v ac plug…

If your using a dc wall wart, it won’t work.

 

[Nele]

Although this looks like a faulty psu also check the switches. I had one unit in for repair which turned on but passed no audio. After checking everything the owner called WARM and they said to check the switches. They are self-cleaning so clicking them 20 times should clean them.

 

[NoisyIndividual]

It is not uncommon for customers to bring me gear with the wrong DC power supply instead of the correct AC one.
Quite often the DC supply will be able to supply the 5v or whatever for the computing side of things, and often +15v, but not the -15v.

So the unit will power up, lights on and everything, but there is no audio.

 

[pucho812]

It is not uncommon for customers to bring me gear with the wrong DC power supply instead of the correct AC one.
Quite often the DC supply will be able to supply the 5v or whatever for the computing side of things, and often +15v, but not the -15v.

So the unit will power up, lights on and everything, but there is no audio.

I am thinking the same thing, that he is not connecting it with an AC wall wart that outputs 24VAC.

 

[callgrlmusic]

I would agree with the observation that the power input connector is NOT a mains AC power input. Likely that it requires an external power pack that outputs either an AC or DC voltage source and rest of DC power needs are created on the power supply board. I don't see anywhere in your posts that describe what you been powering this unit up with when testing ??? Do you not have the proper AC mains power adapter it came with ?

i am using the adapter it came with. the power adapter IS outputting 24v, as it should. i’ll check the voltage regulators next.

 

[callgrlmusic]

Although this looks like a faulty psu also check the switches. I had one unit in for repair which turned on but passed no audio. After checking everything the owner called WARM and they said to check the switches. They are self-cleaning so clicking them 20 times should clean them.

i also called them and received the same information. it was the last thing i tried before i came to groupdiy with it

 

[callgrlmusic]

i am using the adapter it came with. the power adapter IS outputting 24v, as it should. i’ll check the voltage regulators next.

great news and great catch, all. i was using the power supply MY FRIEND SUPPLIED with the unit, NOT the original. it is, indeed, sending DC and not AC. waiting on a replacement to arrive now and will update. talk about feeling stupid!!!

 

[pucho812]

great news and great catch, all. i was using the power supply MY FRIEND SUPPLIED with the unit, NOT the original. it is, indeed, sending DC and not AC. waiting on a replacement to arrive now and will update. talk about feeling stupid!!!

we all make mistakes. It happens. I am willing to bet your friend had issues too which is how this all started.
No harm no foul.
For those who wonder why they go wall wart instead of standard IEC our own Paul Stamler wrote a wonderful article on the subject.

https://audioxpress.com/assets/upload/files/stamler2874.pdf

 

[callgrlmusic]

thanks all for your help on this! 24v AC amazon power supply from UpBright came in and she's singing again! I have once again learned the hard way: start with the obvious stuff first

 

[pucho812]

thanks all for your help on this! 24v AC amazon power supply from UpBright came in and she's singing again! I have once again learned the hard way: start with the obvious stuff first

we often overlook the simple stuff because we want to solve the hard issues. It gives such a sense of accomplish that one tackled the hard problem. A lot of times the answer is much more simple as Slingblade said "it don't got no gas in it"

 

[p0p0p0000]

Ok... So i just purchased 2nd hand one of these units (Warm Audio TB12 tonebeast orange model). It came with a 12v DC power supply which i obviously didnt check and plugged it in and got LEDS but no audio. I soon realised my mistake?? noticing the 24V AC clearly printed above the p/s socket, and purchased a 24V 1A AC power supply which arrived today. I plugged it in and audio was working it sounded nice, i was messing around with the unit and noticed terrible noise when i engaged the clean capacitor switch (vintage worked fine), after trying to troubleshoot this for a while i noticed smoke coming from the rear near the power supply. I turned it off immediately. I opened it up and saw at least 1 resistor on the p/s burnt. I would like to know 1. Has using the DC power supply damaged the unit (power supply and or clean channel capacitors)? and or has using a 24V 1amp AC supply instead of what i now see is meant to be a 24V 0.42amp AC supply?? is this an issue (I assumed the unit would only pull the power it needs)... i will provide photos and any info as needed.. i have a decent multimeter but am preety noob... any help greatly appreciated... edit: i forgot to add I'm in Australia and we are on 230V mains i believe.. GDAY mates
the previous owner claims he used it with the 12v DC adaptor he provided and it worked fine?? could the P/S be previously modded to accept DC?? I'm confused like Edison and Tesla. the burnt resistor is at the bottom centre of p/s board 1st pic.
My current plan of action involves identifying, sourcing and replacing the burnt resistor. Sourcing and purchase 24V 0.42A AC adaptor, and hoping someone(s) more knowledgeable replies with there ideas.... update burnt resistor removed its r39..

 

[NoisyIndividual]

It is almost certain the resistor burnt because of some other problem you need to fix, it wouldn't just do that itself.

Connecting a DC supply instead of AC should not have damaged anything, but there wouldn't have been any audio.
Maybe the person who sold it gave you the wrong PSU.

The 1A AC supply is fine to use if it is still working, your assumption that the unit will only pull the power it needs is correct.
However, it is not known what would have happened if the failure had occured with the smaller capacity AC supply connected.
Perhaps the resistor wouldn't have burnt to a crisp, something else might have. It may have blown the smaller AC supply instead, then you would have had 2 dead things.


It's not possible to ID the value of the burnt resistor from your photo. There is a photo earlier in this thread of the same resistor not burnt, but it is not easy to make out the colours and thus its value.

 

[p0p0p0000]

Thank you so much for replying, yes i noticed the resistor in the OP's photo and yeah other than it being cream its hard to tell the colour bands. I'm hoping maybe someone else could check and or supply a clearer photo of working unit. I'm trying to find schematics but no luck so far.. Google says "Yes, putting DC power directly into an AC circuit can potentially damage it, as most AC devices are designed to handle the alternating current waveform and may not function properly or could even be damaged by the constant polarity of DC power; this can lead to abnormal operation, overheating, and potential component failure depending on the device and its internal design". which scares me a bit. I'm hoping the damage is isolated to the power supply. Perhaps someone who knows that resistors purpose could shed some light on what could have happened. The unit did come with a broken knob, like it might have been dropped or knocked around during delivery, i don't know if that could have something to do with it either.. i have just found a pic of the resistor from the mk2 black board and assuming its the same according to an online resistor calculator its 68 Ω ±1% (F)??