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-   -   SMSL T-AMP problem (http://www.diyaudio.com/forums/class-d/227079-smsl-t-amp-problem.html)

erictioh 5th January 2013 07:47 AM

SMSL T-AMP problem
 
Hi i have a SMSL T-AMP model SA-50. I just accidently touching my RCA + plug with the speaker output of the AMP, i heared a little pop sound from my speaker.

Then i notice my left speaker volume is much softer than right side, it is very much lack of low frequency (less bass and deep vocal).

1. It is not speaker issue because i have swap left and right and the problem is still on the left.
2. It is the problem on the left speaker output

Can anyone point out which part of the amp possibly spoil and is it possible to repair? or i just get a new one.

Mooly 5th January 2013 04:53 PM

:captain:

Moved to Class D

:)

Mooly 5th January 2013 05:01 PM

Looking at the data sheet for the TDA7492 I suspect you have zapped the chip. Although it claims to be short circuit proof I'm not so sure about a short to ground (with it being a bridge type output) which is probably what happened with your RCA short. I can't see any of the output chokes going OC but I guess you should do some basic checks.

The circuit should be very similar to this,
http://www.st.com/internet/com/TECHN...CD00205863.pdf

erictioh 6th January 2013 03:16 AM

So in short it is something wrong in the tda7492 chip which is better for me to get new amp or am I able to just replace the chip ? Can recommend where to get such replacement part ?

I'm no experience in amp diagnose, but I have an oscilloscope can you show me some guide ?

Mooly 6th January 2013 06:48 AM

The chip should be widely available. The problem will be whether you are able to replace an SMD device successfully,

TDA7492 - STMICROELECTRONICS - IC, AMP, AUDIO, CLASS D, 36POWERSO | Farnell United Kingdom

All you can do for faultfinding is check that your accidental short hasn't caused any print to go open circuit or one of the coils to go open.

erictioh 6th January 2013 09:18 AM

I just found out that the prob is not with my amp, but the apple airport express that I use to connect to the amp.

Looks like the short circuit protection is real but it is the airport express doesn't have protection. Ill send for warranty then. Thanks Mooly for your expert thought

Mooly 6th January 2013 10:00 AM

So it's zapped the source, an unusual issue.

erictioh 6th January 2013 10:57 AM

Because I use rca splitter to subwoofer. When I took out one of my speaker wire and accidentally touching a rca cable and that goes my airport express.

So lesson learn, power off everything before dismantle anything

erictioh 7th January 2013 02:01 AM

I confirm out this by using my iphone or ipod as source and the sound is balanced and work perfectly like before.

Now the problem is in the airport express, howeve when i plug an earphone to the express i can't detect any problem, vocal is just centered and sounded good.

It only happened when i plug to smsl amp and earphone pick up the signal nicely, can anyone explain why ?

One of my guess is the airport express line out lost of some power on left side which to earphone still sufficient enough ? am i correct ?

Mooly 7th January 2013 06:40 AM

My guess is you zapped either an opamp output in this airport express do-dah or zapped a series output feed component. You would have to open it up and look.


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