Maker Pro
Maker Pro

TDA1554 Melting

adamdavies986

Feb 10, 2017
13
Joined
Feb 10, 2017
Messages
13
I have made an audio circuit with a tda1554 (bridged to make two 22W outputs) but the IC keeps melting. It is the same as the circuit on the datasheet but with the signal ground connected the the ground of the volume control potentiometer and the audio cable ground not power ground. I have added a picture of the PCB. The audio cable is connected to a Bluetooth module powered by USB. Please help.
 

Attachments

  • IMG_20170210_204342.jpg
    IMG_20170210_204342.jpg
    227.6 KB · Views: 121

davenn

Moderator
Sep 5, 2009
14,254
Joined
Sep 5, 2009
Messages
14,254
I have made an audio circuit with a tda1554 (bridged to make two 22W outputs) but the IC keeps melting. It is the same as the circuit on the datasheet but with the signal ground connected the the ground of the volume control potentiometer and the audio cable ground not power ground. I have added a picture of the PCB. The audio cable is connected to a Bluetooth module powered by USB. Please help.

your photo is too far away to make out any possible wiring errors
and show a photo of the bottom side of the board as well


Ohhh and what about your power supply ????
what is it, did you build or buy it?
if you built it, you better show pic's of that as well and how you connected it to the amp board
 

adamdavies986

Feb 10, 2017
13
Joined
Feb 10, 2017
Messages
13
My power supply is a converted PC PSU which provides a constant 12V output (checked with a multimeter). I connected it with crocodile clips to the wires shown coming off the PCB in the picture. The other wires were connected two speaker that I know work. Hopefully these photos help, I have taken out the IC to make it cleared.

IMG_20170210_222512.jpg

IMG_20170210_222545.jpg

IMG_20170210_222550.jpg

IMG_20161226_094036.jpg


[mod note -- deleted pix that were too poor to see clearly and embedded the others]
 
Last edited by a moderator:

davenn

Moderator
Sep 5, 2009
14,254
Joined
Sep 5, 2009
Messages
14,254
Where are those twisted red and black wires going to ?

is that 12V coming in on that wire in the lower right of the first pic ?
what is being hidden by the USB stick in that pic ?
you also appear to have missed the 220nF capacitors on the inputs
 
Last edited:

Bluejets

Oct 5, 2014
6,901
Joined
Oct 5, 2014
Messages
6,901
Mixing grounds may well have frazzled the chip.
I'd be laying the circuit out in basic form to begin with.
i.e. leave out the usb with bluetooth
 

davenn

Moderator
Sep 5, 2009
14,254
Joined
Sep 5, 2009
Messages
14,254
i.e. leave out the usb with bluetooth

the output of that doesn't even appear to be connected at this point
in fact it is short circuited
 
Last edited:

adamdavies986

Feb 10, 2017
13
Joined
Feb 10, 2017
Messages
13
Twisted wires connect to a potentiometer, the cables on the right are power and the Bluetooth is just covering a small wire connecting the pins I will later use for a switch. Could the signal ground or missing smoothing capacitors have melted it?
 

Bluejets

Oct 5, 2014
6,901
Joined
Oct 5, 2014
Messages
6,901
the output of that doesn't even appear to be connected at this point
in fact it is short circuited
Anyone's guess just what that USB device might be but it appears to be powered from the pc supply via a regulator near the USB. Without any caps on the input , if that usb device is digital it would have been sending dc of some nature directly into the amp chip. No..??
 

adamdavies986

Feb 10, 2017
13
Joined
Feb 10, 2017
Messages
13
The USB device takes power from the port and outputs music through a 3.5mm headphone jack, it is easier to see on the picture in the original post. When it melted I had just connected my phone to the 3.5mm jack, not the USB bluetooth
 

73's de Edd

Aug 21, 2015
3,613
Joined
Aug 21, 2015
Messages
3,613
Sir adamdavies986 . . . . . . . .

Initial Observations / Considerations

1
You have your Power supply electrolytic at one side of the board and its companion HF/RF ceramic decoupling capacitor at the complete opposite side of the board with all of that inductive foil path between them.

2
Move the units to the YELLOW and RED circle positions RIGHT up near the pwr chip.

3
Might as well move the decoupling capacitors associated with the 3 terminal regulator right up beside its terminals also. Consult the 3 term regulator data sheet as to the preferred and types of capacitors + values.

4
With your choosing of BTL mode your mind must have been oriented to power output and at max power . . . . . that will be requiring one healthy size heatsink for cooling that small footprint PWR IC
and your choice seem adequate.

5
The YELLOW boxing is relevant to what looks like a solder bridging, but was probably created in pulling the PWR IC and will later be corrected.

6
Do not see any capacitive isolation on each of your AUDIO inputs.

7
Your chip failure could have been attributed to that long inductive foil path and its distant bypassing having that unit operating as a power ultrasonic <--------> RF oscillator.


SCALED AND MARKED UP REFERENCING . . . . .

FLKpkWz.jpg


73s de Edd
 
Last edited by a moderator:

Bluejets

Oct 5, 2014
6,901
Joined
Oct 5, 2014
Messages
6,901
The USB device takes power from the port and outputs music through a 3.5mm headphone jack, it is easier to see on the picture in the original post. When it melted I had just connected my phone to the 3.5mm jack, not the USB bluetooth

Well, we are now getting a few bits more of info that may help.
Same applies though...no input caps.
 

adamdavies986

Feb 10, 2017
13
Joined
Feb 10, 2017
Messages
13
Thank you very much for the ideas, the signal ground isn't an issue then? Also I noticed that one audio input pin on the IC might be loose, would that be enough to melt it almost instantly?
 

73's de Edd

Aug 21, 2015
3,613
Joined
Aug 21, 2015
Messages
3,613
Your now loose pin, may well be related to the meltdown and fracturing of the chip during overload.
MOST importantly, no provision of DC isolation of the audio input of that Chip is being provided by the presence of a set of 0.22 UFD capacitors at its audio input pins . . . . check the provided data sheet.
 

adamdavies986

Feb 10, 2017
13
Joined
Feb 10, 2017
Messages
13
Also, since the chip costs £10 and this is starting to get expensive, would the tda1558 work the same as the pinouts are identical and it is the same power rating
 

davenn

Moderator
Sep 5, 2009
14,254
Joined
Sep 5, 2009
Messages
14,254
Sir adamdavies986 . . . . . . . .

Initial Observations / Considerations

1
You have your Power supply electrolytic at one side of the board and its companion HF/RF ceramic decoupling capacitor at the complete opposite side of the board with all of that inductive foil path between them.

2
Move the units to the YELLOW and RED circle positions RIGHT up near the pwr chip.

3
Might as well move the decoupling capacitors associated with the 3 terminal regulator right up beside its terminals also. Consult the 3 term regulator data sheet as to the preferred and types of capacitors + values.

4
With your choosing of BTL mode your mind must have been oriented to power output and at max power . . . . . that will be requiring one healthy size heatsink for cooling that small footprint PWR IC
and your choice seem adequate.

5
The YELLOW boxing is relevant to what looks like a solder bridging, but was probably created in pulling the PWR IC and will later be corrected.

6
Do not see any capacitive isolation on each of your AUDIO inputs.

7
Your chip failure could have been attributed to that long inductive foil path and its distant bypassing having that unit operating as a power ultrasonic <--------> RF oscillator.


SCALED AND MARKED UP REFERENCING . . . . .

73s de Edd

1) and 2) not good but not going to cause his observed meltdown problem

3) again , not good wont cause the problem ... but should have been better placed

5) he commented on this in his earlier posts ... so not relevant, not causing the problem.

6) I already commented on this and he never responded

7) That is a possibility


@adamdavies98 .... overall the board layout is really poor and needs to be redone before you waste another chip

Also I noticed that one audio input pin on the IC might be loose, would that be enough to melt it almost instantly?

no

The output is the audio cable plugged into it not the data cables

you don't have anything except power connected to it ( the USB port)


So the capacitors on the inputs are very important?

absolutely ........ I commented a few posts ago that you didn't have them, but you didn't respond

Also, since the chip costs £10 and this is starting to get expensive, would the tda1558 work the same as the pinouts are identical and it is the same power rating

why change to a different chip ?

you FIRST job is to design a new board layout .... get places for the missing caps and get the layout done in a way that decoupling caps between positive and negative rails DONT
have to run the full circumference of the board

Dave
 

adamdavies986

Feb 10, 2017
13
Joined
Feb 10, 2017
Messages
13
I have started working on a new PCB, should supply voltage ripple rejection be unconnected?
 

davenn

Moderator
Sep 5, 2009
14,254
Joined
Sep 5, 2009
Messages
14,254
I have started working on a new PCB, should supply voltage ripple rejection be unconnected?

OK hopefully looks more like this ......

IMG_2017021.jpg


this is still not perfect and I haven't even addressed the lower right corner
I really dislike that long run for one of the inputs
But at least the power and USB port area has been addressed
NOTE the USB port has been flipped around so pins are opposite to what you had

The board is only 2/3 the size of your original one .... and could be still made smaller once the audio inputs are sorted out


the supply ripple rej. pin isn't addressed for bridge mode
in normal 4 channel mode it goes to ground via a 100uF electro cap
so for bridge mode, it suggests ( in schematic) leaving it disconnected


Dave
 
Top