Hi this is my first post.
I am currently repairing a Beomaster 8000, the original fault being that the power amplifier would not switch on, the relaysnot clicking into operation. This was traced to dry joints on through hole joints in the computer module.
Having repaired this, I have faults in the preamplifier in which it would appear that all three switching IC's have failed. For instance when TP1 is selected there is signal on R206 where it connects to the preset pot but nothing on the end of R206.
Similarly there is signal (FM and TP2) on one end of R223 and R224 but not where it connects to the IC's.
I have checked the relevant supplies and they are present and correct.
The IC's are AD10/278 & AD10/192
It seems that these IC's are no longer available. Ihave found an equivalent for AD10/192 http://uk.rs-online.com/web/p/products/5229206/ but cant find an equivalent for AD10/278. The best I can do is to build two submodules to take new 4 channel chips.
Has anyone any idea as to why these IC's have failed?
Does anyone know where I can get replacements or doI fit the ones from RS with some modifications?
Thank you
Michael