Yamaha DSP A 1 cutting off

[Lynyrd]

I desoldered c21 & ic5..... same problem

 

[b4nt]

I found Q340, in the ouput stage of a power amp.

Protection: Q317 to Q376. One of those circuits is perhaps raising a fault condition, compromizing box startup.


One could check so, section after section, if any of such transistors raises an error.

 

[nightrider0614]

Hold the set menu + button and the next button and turn the unit on. It will display the error and post it here.

 

[b4nt]

I desoldered c21 & ic5..... same problem

IC5 is or was the Dolby decoder, a big QFP-100. Why did you do that? 🙂

 

[Lynyrd]

IC5 is or was the Dolby decoder, a big QFP-100. Why did you do that? 🙂

Ic5 is blown..... because C21 leaking

 

[Lynyrd]

Hold the set menu + button and the next button and turn the unit on. It will display the error and post it here.

No possible....shut off after 2 seconds

 

[Lynyrd]

C21 was leaking.Hi is shorted.
Because C21 leaking IC5 is shorted and blown

 

[Lynyrd]

If C21 is shorted,protect mode possible?

 

[nightrider0614]

No possible....shut off after 2 seconds

It will still flash the error and point you in the right direction.

 

[b4nt]

C21?

 

[Lynyrd]

 

[Lynyrd]

It will still flash the error and point you in the right direction.

No possible,the Amplifier shut down very quickly

 

[duncan2]

Amazingly that chip is available from China -YSS214 but obviously its no simple job -128 connections.

 

[Lynyrd]

C21 47000uf 5.5v.
Backup capacitor

 

[b4nt]

I find such a big one on function PCB, not close or related with any IC5 there.


> Amazingly that chip is available from China -YSS214 but obviously its no simple job -128 connections.



It maybe another PCB/IC5, not that one. Would need the model he unsoldered, and the PCB name for clarification.

 

[duncan2]

https://eu.mouser.com/Passive-Compo...s-Ultracapacitors/_/N-5x76s?P=1z0wqf2Z1yo19p6

 

[Lynyrd]

Fonction PCB.
IC5 LC78211.
C21 is near IC5.
С21 it leaked and burned out IC5 because of it

 

[duncan2]

The LC78211 (30 pin ) is available from a reputable source.

Its signal data control and transfer .

 

[b4nt]

I do not see where control pins of LC78211 are connected to. Another chip may have suffered from that burn (in case of short circuit).


Both C21 and that one should not halt the box during startup.

 

[Lynyrd]

Well, how can you bypass the protection system? even if something burns it is not so important. I checked a lot but I don't find anything