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.
guycom
Guy this is so easily fixed. All you need to do is burnish the relay's normally open contacts, which are now dirty & degraded from the years of use. Go to Radio Shack or check their website for a relay contact burnishing tool. These are like a very fine nail file, but are coated with diamond dust on both sides. You simply insert the spatula end in between the contacts, then apply finger pressure to the relay armature to hold the contacts against the tool, then file with an in/out motion. If both sides of the tool aren't abrasive (some are / some aren't) then turn it over & do the opposite contact. Spray or hand apply some good oilfree contact cleaner afterwards. Crocus cloth (a very fine abrasive) found in better hardware stores will also do a good job, & is cheaper too.
Update- crocus cloth worked. Also corected a low left channel at slight volumes. Thank you both for the advice regards, Guy
Not sure anyone will respond but...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. Sounded like a relay problem. So I opened up the relay, blew some contact cleaner and that did not help. The contacts look to be gold plated so they shouldn’t even be dirty. I removed the little spring (see the pics) and sure enough, the contacts look very clean. Next test was to see if there was any sound - so I added a source and listened through earbuds. No sound. However, if I manually (using insulated pliers) flip the contacts in the relay so that they make contact, I get good sound out of the earbuds. So for some reason, the relay will not flip. It does not seem to be because of a problem in the circuit, as I get good sound out of it. So either the relay is gone or something upstream of the relay is gone. Any ideas?