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amp and unwanted speaker vibration

I like to seek opinion and advice from  Audiogon members.  When I connect my tube  amp (Lectron HJ50) to  my speakers ( Focus Audio Model  78) , unwanted vibration of speaker cone would occur.even  with all other equipment off.  The simultaneous vibrations from both speakers  would start to occur very rapidly and  consecutively   after I turn on  the amp for about 30 min.  However, when I plug the  amp power cord to a Belkin home theater surge protector 8 outlet extension cord (from Radio Shack), the vibration would start to occur in about 60 min, with initially only about 4 slow consecutive vibrations, then 5-9 slow vibration every 5-10 minutes.  This has been observed repeatedly.  So I think there is something wrong with my amp (it is more than 20 year old), although its performance is otherwise fine.   As the vibration  is delayed and reduced significantly by using the surge protector extension cord to supply the electricity to the amp,  I wonder if my electricity source is a problem. Would more expensive (presumable better) AC power cords on sale at Audiogon  solve the problem.?  
moses189
moses189 OP
15 posts
 
Thanks for the advices from Shadorne and mgreen27. Any thoughts as to why using Radio Shack surge protector to connect amp power cord reduces the problem significantly? If I listen to music only for one hour, then no problem is detected. 
What would be an estimated cost to replace capacitors of the Lectron tube amp?
In reference to kalali, the answer is yes. When I have turntable and preamp on and play music, no woofer vibration initially until about 60min. 

czarivey
4,494 posts
 
Overhaul such as replacement of caps should be in $200...250 range. Large filter caps can be expensive depending which ones you want to choose.

moses189 OP
15 posts
 
Thanks czarivy. A follow up question to seek advice from Audiogon members: since my Lectron HJ50 tube amp is over 25 years old, assuming it has been used 5 h a week for all these years， what other problems would I expect with continue use if I repair what is needed now? Would you advice me to buy another equivalent/ or better and newer amp? If so what would be a suitable commendation for my system (focus audio model 78 speaker,Transcendent 

moses189 OP
15 posts
 
Preamp, Transcendent phono preamp, Linn Sondek LP12). Thanks
jond's avatar
jond
3,400 posts
 
That is by reputation a very good amp you own, to some a classic. I suggest keeping it taking it to a tech getting it looked over and as others have said recapped. You may find its like getting a whole new amp in terms of improved sound quality. To me that makes much more sense than ditching a very good older amp for a new one. Good luck!
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