Blown amplifier chip. - UK Vintage Radio Repair and Restoration Discussion Forum

Tractorfan · 11th Feb 2019, 3:26 pm

Hi,
I have a couple of Philips wireless speakers which operate on 433.2 MHz from a transmitter connected to the Humax STB. Really handy to listen to the radio around the house.
One of them had stopped working and I investigated the problem only to find that the integrated audio amp chip had exploded. Of course, it's obliterated the type no. (naturally

).
I fitted an extension speaker socket to the unit a while ago so that I can keep it in range of the transmitter, and take the extension speaker further afield.
Would a shorted speaker lead be enough to cause total destruction? I thought that would just 'kill' the chip, not blow it apart!
I'll also check the 'wall wart' PSU in case that's thrown a wobbly and over volted it.
Cheers, Pete.

paulsherwin · 11th Feb 2019, 3:35 pm

It's certainly an impressive failure.

I would just replace the amp section with one of the amp modules from China which cost under £1. There are a range of options available, depending on the supply voltage and output required.

barrymagrec · 11th Feb 2019, 4:08 pm

Could you look at the other unit to ID the chip?

snowman_al · 11th Feb 2019, 6:20 pm

Most likely a TDA7056A.

It should be short circuit protected so check volts etc. before replacement and switch on.

Alan

What impedance are the extension speakers and do you use both the extension and the internal speaker at the same time?

Tractorfan · 11th Feb 2019, 6:47 pm

Hi,
Now, why didn't I think of that?

I have a second one that I could open up and have a shufty within.
Although they are mono units, they can be switched to relay either 'left, mono, or right' and used as a stereo pair.
Cheers, Pete.

Sideband · 11th Feb 2019, 9:26 pm

Quote:

Originally Posted by Tractorfan

Would a shorted speaker lead be enough to cause total destruction? I thought that would just 'kill' the chip, not blow it apart!

Depends on the chip.....'killing' the chip and 'blowing it apart'.....the end result is the same. Check the output of the wall wart first, then check the condition of connecting leads.

tri-comp · 11th Feb 2019, 10:12 pm

Pete,
It would make it sooo much simpler, if you would just write the typeno. of the Philips speaker.
I have loads of Philips service-manuals and perhaps also the one covering your speaker.

Rgds,

/Torben

Alistair D · 12th Feb 2019, 10:37 am

I have seen similar devastation in a couple of Marshall amps that use the 7056 chip. Neither of the chip's speaker output connections is at ground potential so what I suspect has happened is that since the speaker output is a 1/4 inch jack socket someone has thought that it was possible to connect the output to either an external PA or recording equipment. Plugging in earthed jack plug into the speaker socket is what caused the problem.

Is it possible that one of the extension speaker wires has been shorted to earth or, if not earth, one of the input grounds? I am not prepared to test this theory so I could be completely wrong of course.

Al

11th Feb 2019, 3:26 pm	#1
Tractorfan Dekatron Join Date: Mar 2008 Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.) Posts: 3,184	Blown amplifier chip. Hi, I have a couple of Philips wireless speakers which operate on 433.2 MHz from a transmitter connected to the Humax STB. Really handy to listen to the radio around the house. One of them had stopped working and I investigated the problem only to find that the integrated audio amp chip had exploded. Of course, it's obliterated the type no. (naturally ). I fitted an extension speaker socket to the unit a while ago so that I can keep it in range of the transmitter, and take the extension speaker further afield. Would a shorted speaker lead be enough to cause total destruction? I thought that would just 'kill' the chip, not blow it apart! I'll also check the 'wall wart' PSU in case that's thrown a wobbly and over volted it. Cheers, Pete. Attached Thumbnails __________________ "Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."

11th Feb 2019, 3:35 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,965	Re: Blown amplifier chip. It's certainly an impressive failure. I would just replace the amp section with one of the amp modules from China which cost under £1. There are a range of options available, depending on the supply voltage and output required.

11th Feb 2019, 4:08 pm	#3
barrymagrec Octode Join Date: Dec 2017 Location: Morden, Surrey, UK. Posts: 1,560	Re: Blown amplifier chip. Could you look at the other unit to ID the chip?

11th Feb 2019, 6:20 pm	#4
snowman_al Octode Join Date: Dec 2018 Location: Llandeilo, West Wales, UK. Posts: 1,092	Re: Blown amplifier chip. Most likely a TDA7056A. It should be short circuit protected so check volts etc. before replacement and switch on. Alan What impedance are the extension speakers and do you use both the extension and the internal speaker at the same time? __________________ Never Leave Well Enough Alone... Last edited by snowman_al; 11th Feb 2019 at 6:27 pm. Reason: Extension speakers

11th Feb 2019, 6:47 pm	#5
Tractorfan Dekatron Join Date: Mar 2008 Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.) Posts: 3,184	Re: Blown amplifier chip. Hi, Now, why didn't I think of that? I have a second one that I could open up and have a shufty within. Although they are mono units, they can be switched to relay either 'left, mono, or right' and used as a stereo pair. Cheers, Pete. __________________ "Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."

11th Feb 2019, 10:12 pm	#7
tri-comp Heptode Join Date: Oct 2008 Location: Aalborg, Denmark Posts: 903	Re: Blown amplifier chip. Pete, It would make it sooo much simpler, if you would just write the typeno. of the Philips speaker. I have loads of Philips service-manuals and perhaps also the one covering your speaker. Rgds, /Torben

12th Feb 2019, 10:37 am	#8
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Re: Blown amplifier chip. I have seen similar devastation in a couple of Marshall amps that use the 7056 chip. Neither of the chip's speaker output connections is at ground potential so what I suspect has happened is that since the speaker output is a 1/4 inch jack socket someone has thought that it was possible to connect the output to either an external PA or recording equipment. Plugging in earthed jack plug into the speaker socket is what caused the problem. Is it possible that one of the extension speaker wires has been shorted to earth or, if not earth, one of the input grounds? I am not prepared to test this theory so I could be completely wrong of course. Al __________________ I won't tell you how I discovered that.