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TDA1013A vs TDA1013B

I'm trrying to repair an old Sony 21" BE-1 TVC that presents no audio at all. I replaced the IC TDA1013A with a new TDA1013B with the following results: audio now is ok but when TV is off for a long period (several hours) it comes out after severals seconds :(. The second stage of the IC TDA1013A|B (an AF ampli that drives 8ohm speaker) works fine because if I inject the signal on pin 5 sound is ok (the problem is that in this way I bypass the pre-ampli stage that has VAC for volume control). Is There something I can do in order to get IC 1013B compatible with IC

1013A? I'm not able to retreive the TDA1013A in the marketing... Thanks,
Reply to
reario
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There is no electrical difference between them. Check pin7 voltage, 2V = low, 6V = high vol

Reply to
GPG

hi, thanks for your answer. I've checked all voltages on IC and everything seems to be ok. with multimeter on pin pin7 the output ranges from 3V to 6.5V. Mute works fine (when I disconnect RF signal or local video input) voltage on pin7 drops to 2.9V). Our Sony technical supports says that ICTDA1013A and tda1013B have different input and output impedence so the RC network presents in the TVC is optmal for the 1013A model. It is not possible to get a version of IC 1013A in pour market (Italy).

Thanks again, Vittorio

Reply to
reario

On 30 Jul 2006 23:27:28 -0700, "reario" put finger to keyboard and composed:

I found these datasheets:

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The TDA1013A has an input impedance of 100K whereas the TDA1013B has an Rin of 29K. AFAICS, this difference should only be important if the output impedance of the sound IF stage is of comparable magnitude. Even then, the only result would be lower volume levels which you should be able to compensate with the volume control.

As for the output impedances, they are 200 ohms and 60 ohms, respectively. Once again I can't see these as being significant since the Rin of the power amp stage is 100K or so.

- Franc Zabkar

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Reply to
Franc Zabkar

Franc Zabkar ha scritto:

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Yes you are right but the problem is that I really don't know what else look for...I replaced almost all passive component in the input stage without success! I've also connected with a little capacitor the IF signal directly on pin 5 (bypassing the AV switch ) and the sounds flows out fine. As I've written the problem is not in the final part of the IC but only in the pre-ampli part.

This is a link to the electrical diagram of TV.

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thanks for your help.

Reply to
reario

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