Hi
I wonder if any of you recognise this amp. To the best of my knowledge it originates from China and was built in the 1990s.
It's branded 'KONES TA-801' and weighs about 25k. It seems pretty well built.
I bought it used, so I don't have any documentation at all. It developed a fault not long after I acquired it, but from memory it sounded pretty good.
Photo attached. I will post a photo of the innards as a follow up and would be grateful for any comments re design, quality etc (as much as you can tell from the pictures.
Basically, I'm trying to decide whether it's worth fixing......
Cheers
Martin
I wonder if any of you recognise this amp. To the best of my knowledge it originates from China and was built in the 1990s.
It's branded 'KONES TA-801' and weighs about 25k. It seems pretty well built.
I bought it used, so I don't have any documentation at all. It developed a fault not long after I acquired it, but from memory it sounded pretty good.
Photo attached. I will post a photo of the innards as a follow up and would be grateful for any comments re design, quality etc (as much as you can tell from the pictures.
Basically, I'm trying to decide whether it's worth fixing......
Cheers
Martin
Attachments
Heres a really simple idea to try. Sometimes the valves become loose in their holders - try taking each tube out and then use a small pair of pliers to crimp the tags of the valve base a little bit tighter.
Its possible that as the valve heats up the grip on the pins slackens off as the contacting metal expands. It has been the source of some crackle issues in one of my amps. The crackle is the sound of tiny amounts of arcing over at the pins.
Alternatively, upend the amp and use a wooden chopstick to prod the big resistors and see if it effects the noise, try this on the cap pins as well - this should identify dodgy resistors or dry solder joints. This should be relatively safe to try if you have the amp well supported before you start.
DC on the wipers of those pots could also be a source of trouble, is the noise effected by the wiper positions ??
Good luck.
Shoog
Its possible that as the valve heats up the grip on the pins slackens off as the contacting metal expands. It has been the source of some crackle issues in one of my amps. The crackle is the sound of tiny amounts of arcing over at the pins.
Alternatively, upend the amp and use a wooden chopstick to prod the big resistors and see if it effects the noise, try this on the cap pins as well - this should identify dodgy resistors or dry solder joints. This should be relatively safe to try if you have the amp well supported before you start.
DC on the wipers of those pots could also be a source of trouble, is the noise effected by the wiper positions ??
Good luck.
Shoog
Shoog - Belated thanks for your suggestion. You were right! At least, I think you were....problem is now sorted.
Here's what I did:
Just to make doubly sure that it wasn't a valve on the blink, I swapped them all over (left to right). This didn't fix the problem, but did improve sound quality quite a bit. I don't understand why, but it occurred to me that I had swapped the valves over when the problem first appeared, so I had just swapped them back to their original positions. Could it have something to do with the fact that the amp is fixed bias and the power tube bias was upset when I swapped the tubes over first time around?
I then tried removing and replacing each tube several times to see if I could clean off any dirt that might have found its way onto the pins/valve bases. Just for good measure, I gently bent the pins a little to make them a tighter fit in the bases. This didn't completely solve the problem, but things did improve.
Then I realised that the valves were not sitting absolutley vertically in the bases, so I straightened them until they did. The problem became worse again. It transpires that some of the valve bases are mounted a little squint, so the valves need to be slightly off vertical to sit in them properly.
Job done, problem solved, amp working again!!!
Hooray!
Many thanks to all of you for your advice.
Cheers
Martin
Here's what I did:
Just to make doubly sure that it wasn't a valve on the blink, I swapped them all over (left to right). This didn't fix the problem, but did improve sound quality quite a bit. I don't understand why, but it occurred to me that I had swapped the valves over when the problem first appeared, so I had just swapped them back to their original positions. Could it have something to do with the fact that the amp is fixed bias and the power tube bias was upset when I swapped the tubes over first time around?
I then tried removing and replacing each tube several times to see if I could clean off any dirt that might have found its way onto the pins/valve bases. Just for good measure, I gently bent the pins a little to make them a tighter fit in the bases. This didn't completely solve the problem, but things did improve.
Then I realised that the valves were not sitting absolutley vertically in the bases, so I straightened them until they did. The problem became worse again. It transpires that some of the valve bases are mounted a little squint, so the valves need to be slightly off vertical to sit in them properly.
Job done, problem solved, amp working again!!!
Hooray!
Many thanks to all of you for your advice.
Cheers
Martin
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.