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Chip Amps Amplifiers based on integrated circuits

How can I know if ICs are bad?
How can I know if ICs are bad?
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Old 8th February 2018, 12:01 AM   #1
diy1995 is offline diy1995
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Join Date: Jan 2017
Location: Slovenia
Default How can I know if ICs are bad?

Hello,
I would like to repair amplifier from old records player.
One channel is silent (you can hear silent buzz and static), other one is silent too, but it starts to "fart" when volume is over 3/4, I can tell that it`s making sounds to the rhythm of music.
I repleaced all the capacitors and measured that ICs are getting right voltage.
I swapped ICs from one channel to the other, but "farting" stays on the same channel, and other one stays silent.
I tried to apply signal after the pots, but nothing changes.

What can I try else? It`s a very simple circuit but is driving me crazy.

In schematic I marked what part of circuit I`m working on (preamp is not on this circuit).
amp.jpg

Thank you for help
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Old 8th February 2018, 09:55 AM   #2
diy1995 is offline diy1995
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Join Date: Jan 2017
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ICs are bad!
It turned out that I tought that I swapped ICs from one channel to another, but I mixed them up and soldered them back to original places...
Now I swapped them and channel behavior turned around so yes... they are bad.
Anyways do anyone now if there are any substitutes to TBA641B12?
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Old 8th February 2018, 10:27 AM   #3
AndrewT is offline AndrewT  Scotland
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Could you isolate the input to the output stage (chipamp) and insert a new PCB with a modern chipamp?
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regards Andrew T.
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Old 8th February 2018, 10:37 AM   #4
globalplayer is offline globalplayer  Germany
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I found a german shop carrying the IC in question.

German:
TBA641B12 integrierter Schaltkreis - Williges-Elektronik-Service GmbH

English: (Google)
Google Ubersetzer
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Old 8th February 2018, 12:00 PM   #5
diy1995 is offline diy1995
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Quote:
Originally Posted by AndrewT View Post
Could you isolate the input to the output stage (chipamp) and insert a new PCB with a modern chipamp?
Yes, I could, but I would like to fix this one. The records player was sitting in basement for many many years, but I can remember as a kid, this amp sounded really nice, it reached full volume without any distortion and it was loud. Nothing like cheap modern amplifiers...
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Old 8th February 2018, 12:01 PM   #6
diy1995 is offline diy1995
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Join Date: Jan 2017
Location: Slovenia
Quote:
Originally Posted by globalplayer View Post
I found a german shop carrying the IC in question.

German:
TBA641B12 integrierter Schaltkreis - Williges-Elektronik-Service GmbH

English: (Google)
Google Ubersetzer
thank you for the link
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