Hi folks,
I've had this sansui valve amp as my preferred amp for many years. One day, i went off to travel south america and ended up getting married! We came back to visit the family after 7 years and took the amp back with us to Brazil. So it sat unused for years, i tested it out for about 30 minutes and was surprised that everything was fine - great infact (this is before we travelled back).
So we arrived home (Brazil) and i wanted to test it out to check that it survived the journey (checked luggage 'fragile'). All i had were headphones - no speakers. Switched the voltage to 117v (i measured the mains) from 220v. Made sure everything was seated and cranked it on... massive hummm left channel. I thought its got to be a grounding issue as our house is old and doesnt have 3 'pronged' plugs which means no earth.
So i just bought some nice bookshelfs and went to resolve the 'grounding issue'. i ran a line directly from a copper grounding rod to a special 3 pronged socket - just for my little sansui!! BUT, it didn't make a difference while testing with headphones. So i figured i'd just see how it was with the speakers attached... with the speakers, the hum is faint and wouldn't interfere with normal listening - infact, i was thinking its always had that little hum (but this hum renders the headphones unusable).
When i started listening to some music it immediately became apparent that the left channel was very weak. If i compensated for this with the balance control that channel has a bit of distortion (compensated = balance knob almost entirely turned left!).
So i did some reading up...
I tried various sources, fm radio, aux, tape monitor - no change.
I disconnected the ground i made - no change.
swapped power valves around - no change.
With unit off, worked on the swicthes - on/off 20 times etc
Worked the pots - listened to the volume and balance knobs (no music) to try and hear if anything changes - no change.
With music the weakness remains constant through the range of volume pot.
The right channel is perfect.
Its not the speakers (i swapped them)
Never had issue with pots
Never swapped out anything while i've had it.
All the caps and resistors look original.
All the valves glow healthily (its magic isnt it?!) EXCEPT for the preamp valve (12ax7/ecc83). This preamp valve almost looks like theres nothing on - only on close close inspection can i see a couple of 'points' lit up. But it doesnt appear burnt or discoloured.
Maybe i've just answered my own question?! But what do you guys think?
Like i said, i did some reading up and read others commenting that it was unlikely to be a valve issue and more likely to be caps, resistors, or pots etc
What should i try next? I'm no stranger to a soldering iron if need be - and prefer to learn and do things myself. Plus the fact that there wouldn't be a valve specialist for at least 600 miles from where we live!
Any thoughts and advice are greatly appreciated.
Thanks,
Mike
I've had this sansui valve amp as my preferred amp for many years. One day, i went off to travel south america and ended up getting married! We came back to visit the family after 7 years and took the amp back with us to Brazil. So it sat unused for years, i tested it out for about 30 minutes and was surprised that everything was fine - great infact (this is before we travelled back).
So we arrived home (Brazil) and i wanted to test it out to check that it survived the journey (checked luggage 'fragile'). All i had were headphones - no speakers. Switched the voltage to 117v (i measured the mains) from 220v. Made sure everything was seated and cranked it on... massive hummm left channel. I thought its got to be a grounding issue as our house is old and doesnt have 3 'pronged' plugs which means no earth.
So i just bought some nice bookshelfs and went to resolve the 'grounding issue'. i ran a line directly from a copper grounding rod to a special 3 pronged socket - just for my little sansui!! BUT, it didn't make a difference while testing with headphones. So i figured i'd just see how it was with the speakers attached... with the speakers, the hum is faint and wouldn't interfere with normal listening - infact, i was thinking its always had that little hum (but this hum renders the headphones unusable).
When i started listening to some music it immediately became apparent that the left channel was very weak. If i compensated for this with the balance control that channel has a bit of distortion (compensated = balance knob almost entirely turned left!).
So i did some reading up...
I tried various sources, fm radio, aux, tape monitor - no change.
I disconnected the ground i made - no change.
swapped power valves around - no change.
With unit off, worked on the swicthes - on/off 20 times etc
Worked the pots - listened to the volume and balance knobs (no music) to try and hear if anything changes - no change.
With music the weakness remains constant through the range of volume pot.
The right channel is perfect.
Its not the speakers (i swapped them)
Never had issue with pots
Never swapped out anything while i've had it.
All the caps and resistors look original.
All the valves glow healthily (its magic isnt it?!) EXCEPT for the preamp valve (12ax7/ecc83). This preamp valve almost looks like theres nothing on - only on close close inspection can i see a couple of 'points' lit up. But it doesnt appear burnt or discoloured.
Maybe i've just answered my own question?! But what do you guys think?
Like i said, i did some reading up and read others commenting that it was unlikely to be a valve issue and more likely to be caps, resistors, or pots etc
What should i try next? I'm no stranger to a soldering iron if need be - and prefer to learn and do things myself. Plus the fact that there wouldn't be a valve specialist for at least 600 miles from where we live!
Any thoughts and advice are greatly appreciated.
Thanks,
Mike
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