Stereo Amps From China;

[tblo163]

I`ve bought a couple of these from ebay,180W+180W Stereo amplifier,for MP3 Playback.After 5 minutes of use,they both failed.The units have Volume,Bass &Trebble pots(47K).They use a TDA7057AQ Amp & a NJR4558D J-FET for the Pre-Amp.The units are not drawing any current(apart from 0.03amps for the rainbow LED)The Amp IC is getting 12v & all Grnd connections are o.k.The Pre-Amp is getting 12v@pin8,Grnd@pin4, 5.53v@pin1, 6.64@pin2, 7.46v@pin3, 5.34v@pin5, 6.56v@pin6, & 5.42v@pin7.The TDA7057 is getting 1volt@pins1&7=VCI&VC2-DC-VOL-CONTROL,so the amp should not be in mute mode,The voltage to Vol-inputs 1&2(pins#3&5,look suspect,reading 0.19 & 0.09 respectively.I`m sure they should be more like 1.2v.That`s as far as I`ve got,I`m looking to find out what controls the Input voltges & which component is likely to have failed.The circuit boards look pretty well built,but I should have known better than to buy cheap products from CHINA.Thanks for any suggestions Terry,

 

[audioguru]

but I should have known better than to buy cheap products from CHINA.

Yes, you said it.
Datasheetarchive.com has never heard of the TDA5057 which is probably a counterfeit. 180 Whats is not anywhere near 180 watts. Maybe 18 watts.

 

[tblo163]

Thanks for the reply,I`m still investigating this piece of junk.The only thing I`ve found so far is the main cap is marked on the board as 1500uF 25V,But the one fitted is 2200uF 16V.I`ll keep trying.I`ve got the data sheet for the TDA7057AQ.I will gladly upload it to you,if you want it.

 

[audioguru]

The main filter capacitor has a small value for a low power amplifier.
I still cannot find a datasheet nor listing for a TDA5057. Please upload its datasheet.

 

[tcmtech]

Does it even have a switching power supply of some sort? Toroid transformer or mini hf transformer?

I picked up a junker from a friend years ago that was rated at 230 watt per channel.
Big aluminum heat sink body and a piar of 30 amp fuses on one end too!
Got home and took it apart and all it had was a pair of 16 watt audio amp IC's at one end. AND a pair of 50w 4 ohm resistors attached to the side of the body!
The resistors came on with a relay when the power up signal was activated!
Warmed the amp right up and gave the illusion that its really working hard too!
the other 90% of the inside was emty!

 

[tblo163]

I`ve been looking for a way to send you the data sheet,for the TDA7057AQ, There doesn`t seem to be an option to do this on this forum.SO I need an address to upload it to Securely by yousend it.com. will send it to you with pleasure Terry

 

[tblo163]

data sheet

I Think This Should Get To You O.k. Let Me Know If It Works Terry

 

[audioguru]

I`ve been looking for a way to send you the data sheet,for the TDA5057AQ, There doesn`t seem to be an option to do this on this forum.SO I need an address to upload it to Securely by yousend it.com. will send it to you with pleasure Terry

Simply click on Go Advanced, Manage attachments and attach the datasheet to your reply like this:

 

[Nigel Goodwin]

Explains why we couldn't find a datasheet for it - a completely different number!.

Assuming it's the chip that you've posted the datasheet for, it's only an 8W ampliifer, and that's with a 15V supply, dropping to 5.3W on only 12V.

What supply are you running them on, and what impedance speakers were you feeding from them?.

 

[tcmtech]

I would like to see a picture if you could. external and internal shots.

 

[mneary]

So, is the amplifier really a TDA5057AQ or a TDA7057AQ?

 

[tblo163]

Yes it`s definately a 13pin TDA 7057 AQ,I`ve ghecked the markings on it,it`s made by .JRC (Japan Radio Co.) it worked perfectly for 5mins.at 12volt input with 8ohm speakers.

 

[audioguru]

Assuming it's the chip that you've posted the datasheet for, it's only an 8W ampliifer, and that's with a 15V supply, dropping to 5.3W on only 12V.

The graph shows it at 5.3W with a horrible-sounding 10% clipping distortion. Another graph shows that it begins clipping at an output of only 3.5W.

The Chinese say its power is 180 + 180 Whats?

 

[tblo163]

AMP or Chinese Junk?

O,K. Here`s what the little B#####d looks like.Very pretty,shame it doesn`t work.

 

[tcmtech]

I think they ment to rate it in joules! It just got miss translated.

Hope you did not pay to much!

I have been around enough of the higher end chinese designed and built stuff to say that end of the spectrum often beats our american stuff hands down!

But then you get junk like this and it just hurts them on the world market.
Oh well their loss!
Sorry you got took.

 

[tblo163]

13.5volt supply with 8 ohm speakers.The sound quality was very good,for the short time it worked.response from volume,bass & treble were exellent.I usually make my own units, AMPS,PMWs,EFIEs ect.,& never had any problems, I just can`t get my head round this one.

 

[tblo163]

O.K. Thanks for cheering me up, it only cost $8.post free.it`s worth that for the three 47K Pots & spare parts.Pretty box though. Cheers.

 

[mneary]

Could you share with us the reason you posted the data sheet for the TDA7057AQ? Now I'm really confused.

 

[Mikebits]

Did you really think you could get 180 Whats amp for 8 bucks.

 

[tblo163]

Could you share with us the reason you posted the data sheet for the TDA7057AQ? Now I'm really confused.

The data sheet was meant for audioguru & Nigel Goodwin,they couldn`t find it,so I sent it to them from my files,while ever it`s on the forum anyone can view it or save it .
cheers Terry