I have damaged my Topping TP30 amp/dac with over-voltage

[MikeG]

I have blown my Topping amp that I use for my laptop sound. Had it connected to my bench supply and for some crazy reason I reached to the bench supply to turn up the volume. Ho Hum. It is designed for a 12 volt supply and must have gotten close to 30 volts when it blew. I only have a basic electronics understanding and some soldering skills.

I understand this amp to be a T class unit. It has an on-board DAC to connect to my laptop's usb port. After blowing it I am measuring a permanent short across positive and negative input of around 3 ohms and this is not polarity dependant. I have disconnected one leg from a couple of surface mounted Schottky diodes and couple of electrolytics that looked shorted when in circuit, but these were red herrings. The DAC chip is an OPA 2134PA and the amplifier is a TA 2024.

I cannot find a circuit diagram on the net and trying to work out what is connected to what on this double sided pcb is well beyond my capability. I don't understand how this amp works and wonder if anyone could steer me in the right direction as to the most likely component(s) that could have blown due to my abuse and that would result in such a low ohms short?

Any guidance at all would be great, else it will have to go in the bin

Many thanks.....Mike

 

[tunedwolf]

Begin by replacing this wee chappie...

 

[4pyros]

Begin by replacing this wee chappie...

View attachment 89902

Thats just a revers polarity diode.

 

[4pyros]

You could have killed all kinds of stuff.
Its to small for a boat anchor.
Start with the tripath.

 

[tunedwolf]

Thats just a revers polarity diode.

I suspect that it is a tvs diode, also providing a modicum of overvolts protection. It's prolly a p6ke15 or something of that order. It's also highly possible if it burnt open circuit, that everything on the board was exposed to the high input voltage, likely killing other components. Just removing the component I marked will tell you instantly if the short is gone or not.

 

[KeepItSimpleStupid]

it depends a lot on what D9 is and how it's wired. Series/parallel? What markings can you make out?

 

[4pyros]

Not much on the web on these cheep Chinese amps, not even in the audio boards.
I am still willing to bet that's a reverse polarity diode.

 

[Nigel Goodwin]

Not much on the web on these cheep Chinese amps, not even in the audio boards.
I am still willing to bet that's a reverse polarity diode.

I would agree - almost certainly just a reverse polarity diode, and the OP has most probably killed the amp chip.

 

[4pyros]

I would agree - almost certainly just a reverse polarity diode, and the OP has most probably killed the amp chip.

Yes and seeing how the amp chip is surface mount its going to be a bear to repair.

 

[Nigel Goodwin]

Yes and seeing how the amp chip is surface mount its going to be a bear to repair.

Order a new amp from China

 

[MikeG]

Hi everyone and thanks for your replies. D1 (marked M7 mic) is in fact wired across the supply line and it is one of the diodes that I lifted a single leg of. I have just tested it and it has been destroyed open circuit. I also disconnected D1 and C33/34 which are in amongst the 4 centrally mounted inductors. The short still remains however. I guess the amp chip is probably fried but there is one more component that looks to be in the non-dac area and that is a H1117C which is very close to the headphone jack on the right hand side of the picture. I have looked this up and it appears to be a voltage regulator. Could this have possibly taken the brunt of my abuse and protected the amp chip? I might be able to remove this with my small proxxon hot air gun.
Many thanks and a Huge MERRY XMAS to EVERYONE

 

[KeepItSimpleStupid]

The HA1117 looks like a relay for speaker protection. 12 VDC coil, rated at 3 A 120 VAC contacts.

The diode could be removed and the system powered up. It's there for reverse polarity protection. If it's a TVS diode, it could have the ability to protect against over voltage as well.

So, the suggestion is, to remove the diode and connect verified correct power.

 

[4pyros]

Your amp chip most certainly runs directly of the supply voltage and because it is a power device, the most likely to blow.

 

[tunedwolf]

It's unfortunate that the protection diode opened before you caught the problem. U5 &U6 are both voltage regulators, but even if they are blown, the issue now will almost certainly begin with the main amp chip, as has been mentioned, it will be sitting right across the incomming supply. However, just in case you were amazingly lucky, check the regulators and any little decoupling capacitors, one of them might just have failed short and saved your bacon. If not them, pull the amp chip

 

[MikeG]

Hi All
Many thanks for all the replies. I have de soldered the regulators and they are not the source of the problem. On a positive note this is the first time I have managed to remove anything with more than 2 connections without destroying the board, so a new skill using hot air has been acquired...... Removal and replacement of the amp is just beyond what I can muster, so I guess I am the proud owner of an undersized boat anchor/small project case.

As it's xmas time I guess a further spend is in order.........choice between another similar or upgrade to a decent headphone amp/dac and separate power amp.

Hope you all have a good new year

 

[4pyros]

Hi All
Many thanks for all the replies. I have de soldered the regulators and they are not the source of the problem. On a positive note this is the first time I have managed to remove anything with more than 2 connections without destroying the board, so a new skill using hot air has been acquired...... Removal and replacement of the amp is just beyond what I can muster, so I guess I am the proud owner of an undersized boat anchor/small project case.

As it's xmas time I guess a further spend is in order.........choice between another similar or upgrade to a decent headphone amp/dac and separate power amp.

Hope you all have a good new year

Its in a nice box. LOL Happy Holidays