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Amplifier speaker relay problems.

Hi, I am working on an Niko Alpha II amplifier it is an older amp with the two large VU meters on the front. There is a problem when powering up that one chanel may not work. I have tracked this down to a relay that is in the speaker output path and is 24volt dc with two normally open contacts. It is on a printed circuite board and I wish to change it as cleaning did not help and I am afraid it may be degrading sound when working if not providing a good path. I uderstand this relay helps prevent thump on powerup and the sound from dithering out on shut down. Thank You for any advice.
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imhififan's avatar
imhififan
2,258 posts
 
@dsrjohn
A friend has a Sony TA-F3A amp. She says it was acting up - i.e. after powering up, it would take quite a while before she would hear the characteristic click and she would get sound but now it never clicks.

Try replace C308 (100uF 25V) may solve the problem

https://www.manualslib.com/manual/1272547/Sony-Ta-F3a.html?page=5#manual
dsrjohn
8 posts
 
Why that one?
imhififan's avatar
imhififan
2,258 posts
 
the circuit is to charge the C308 to a reasonably high voltage so the Q306 turns ON and energize the relay coil.
dsrjohn
8 posts
 
Thank you. Will look into it.
dsrjohn
8 posts
 
Tried replacing cap C308 with several dif 100 uF caps but doesn't work. What would be the next thing to try? If I manually join the contacts in the relay, I get sound out of the speakers so it is something upstream from the relay. Maybe the relay needs replacing?
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