Doc, the most common causes are grounding and electrical interference on the cables in the amp from other components in your set up or even other components within the amp. Does the amp give out the noise even when all input cables are pulled out and only the speakers are connected? For starters, you could try:
1.Connect the amp power cord of the amp to the same power outlet/wall socket distribution board as your other components that may be connected to the amp, like preamp, source of music, etc.This should eliminate any ground loop.
2. Ensure that the signal cables to and from the amp do not go very close to the power board or power cables.
3. Try opening the amp cover and use a small blower or vacuum cleaner to blow away dust and cobwebs, if any. Then try pushing aside the signal cables away from the transformer, carefully so that all connections remain intact.
4. If the above steps don't help, get an electronics guy to check the sockets on the amp
5. Search the net... there are many discussions on several forums on this subject.
My Cary power amp had this issue which was totally eliminated by pushing aside the cables inside the amp.
The white noise "Hiss" appears only when using preamp along with power amp.
If I use only power amp by pulling out the jumper then there is no noise.
There is noise even in absence of any source.
The noise is affected by Bass and treble controls.
The noise is present even at zero position of the volume control ,but becomes louder by turning up the volume.
This indicated the problem area is in the preamplifier section before the tone and volume control.
It also increases with the time.
May be leaky caps.
Consulted two repair shops in Kolhapur , unfortunately both the shops failed to notice the noise.
Will need to search some other shop.
Learned about FM Akshay ,whose special interest is in Sansui Amps.
Will take appointment and see.
1.Try to find leaky capacitors which may be cause of noise and replace them. If possible, recap the whole preamplifier section with Nichicon FG or Nichicon MUSE Capacitors available on mouser or digikey.
2. Also the 2SC458 Transistors are always the cause of noisy in Vintage Triple Series Sansui Amplifiers. Replace all 2SC458 transistors with KSC1845FTA transistors available on digikey.
3. Deoxit/Clean all pots/controls with proper solvents like Deoxit or Isopropyl alcohol.
Raj12345,you are wonderful.
Replaced the caps.
Noise came to half
Replaced all 2sc458 and the noise disappeared.
Then probed thr amp more and bass ,treble and volume control was found replaced by the seller.changed 50 k vc to 100 k and the sound from amp.became supersweet.
Could not get the proper caps and the transister.replaced with local available matching one.
Will wait for nichicon caps and transisters from mojer
Its nice that your problem is solved.
You can get KSC1845FTA from an indian website element14.com
Also if you replaces capacitors with local one, the music quality of au555 wont be up to mark. Also extra noise may be added by local caps/transistors.
So please purchase original made in japan/america capacitors to ensure u getiing original hifidelty sound from au555.
Ordered nichikon from amazon.
Will explore indian website today.
Few off the sc458 were already exchanged by the company with some other model.I will physically check all the 458 and will order them.will tell here which transister were used as a replacement by the company.
Look at the manual of au555 and locate all 2sc458 transistors. Wich already present in your boards in place of 2sc458 u will hv to write here tgen only we can suggest weather good or not. In general u can replace all 2sc458 with KSC1845FTA w.r.to service manual. Also change leaky caps anywhere located. U can check resistors for value change and replace appropriately.