[JN] 845 Woes

TubeGarden at aol.com TubeGarden at aol.com
Mon Jul 26 10:49:40 CDT 2010


Yes, both speex suggests the PS has a cool solder puddle, somewhere.
 
If the same 2A3 amp is being used, it is likely in the 845 filament or HT  
section.
 
If not, try disconnecting your source component. If the static goes away,  
you have system ground issues. More fun!
 
Happy Ears!
Al
 
 
 
In a message dated 7/26/2010 10:42:40 A.M. Central Daylight Time,  
christian at rintelen.ch writes:


do i  understand you correctly that you've only changed the 845 output 
tubes  whilst chasing gremlins? how about changing the driver tube/s and 
the 2a3?  otoh the 10 minutes after power-up suggest a cold solder joint 
or  something else that heats up and expands slowly and leads to an  
intermittent contact. have you checked all solder  joints?

©

> Some years ago, I built a nice single-ended 2A3  amp. Wanting more power, 
I decided to use it to drive an 845 via a Lundahl  interstage transformer. 
After the usual debugging and grounding  experimentation (lots of experience 
there!) all was great - for a few weeks.  Then, 10 minutes after turn on, a 
'ststic' noise would come from the speakers.  I spent many hours trying to 
chase this down with no success, finally deciding  it was caused by the 
845's (Valve Arts) even though it came through both  speakers. I bought a pair 
of Shungang 845B's and was in musical bliss once  again - for an hour. The 
static returned and now it developes once again 10  minutes after turn on. I 
even bought a Zerostat and zapped everything to no  avail. I am now back 
listening to the original 2A3 amp so that I can listen to  music 'till I get 
this figured out. Has any had any experiences like this?  Thanks!
>  Mark

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