Just bought an old Sansui (2900)on Ebay...always wanted one. Not sure how old..80's?..but in good condition...Initially I just wanted to test it and not disrupt my existing system.. so I hooked it up to an mp3 player and a pair of Kef phones. AOK..good sound.It had beeen used for 3-4 hours and then I heard from the next room a crackle ..it was from the phones which were still attached to the amp which was on.. but not being used. I have checked the plug/mains input wire visually etc cant see any loose wires..the sound has subsided to a minor one now but is quite discernible through the phones on both channels with zero volume..and is present whether the volume is zero or full-on..no difference in the volume of "the noise". The amp still works fine on both channels throught the power range. The noise is worse (volume-wise) on initial switch on then subsides..but increases when the amp is switched off??? I know I should try it with speakers..it could be the headphone socket I suppose???..but I dont want to risk damaging my speakers.. Anyone suggest what this may be..never had it before..an I'm no spring-chicken. Some sort of electrical interference?
If the amp has not been serviced in several years, it is far too common for capacitors to go bad in vintage equipment. More than likely the power supply caps have started their journey out of this realm. Possibly a coupling cap is leaking, but either way, you will have to have a qualified technician look at the amp. Put "vintage audio repair" into a search engine to find a qualified, and expect expensive, technician.
This is a danger when buying vintage gear and something that everyone should be aware of before sinking money into an amp they've always wanted. Just like restoring a classic automobile, ownership of vintage audio can be fraught with expensive repairs and unexpected (though predictable) problems. Ah, that audio and cars were more like wine and just sat while getting better with age.
Thanks very much people..yes I thought maybe the amp hadn't been used for a while..and it was perfect when I first hooked it up ...well on the face of it! I guess the AC mains running through it for a few hours has found out some suspect parts. I shall get someone to look at it as it didn't cost much..and as I say with volume at half-whack you cant actually hear the "interference-type sound. Not that I will use it until it's fixed.
Anyone know the vintage of the Sansui AU2900..I think the AU2200 which is better known is 19}70's?