2. amps-preamps
  3. 1085115335

How to track down bad tube and what can it mean?

I recently changed the tubes in my preamp and all but the driver tubes on my amp, but these tubes didn't work out. I replaced these with the stock tubes which had been good before. Now I get distortion from the left channel which sounds like a buzzing that comes and goes with the music. It increases with the volume. I've checked all the tubes and they are placed OK. At one point with the volume loud but not too loud the system turned itself off which had never happened before. My speakers are efficient and it was not putting out more than 10 wats max when this happend.

So how can I track down a bad tube if I have one? I suppose I could replace the tubes one by one with the new ones I tried, but this is extremely tedious and makes me dream of SS. Any idea what this problem, this sound indicates?

Any help is appreciated. My sick system depresses me. Thanks.
budrew
newbee
4,798 posts
 
I'm facinated with the fact that the hum level varies with the level of the music - the reason is that the tubes in the line stage and amp are constant and merely pass on, amplified, what passes thru them. Question - does this problem occur with any source you select, or just one?
budrew OP
467 posts
 
Thanks folks. I'll have to spend some time this weekend on this detective effort. The sound, a buzz that reminds me of a blown speaker though I did nothing to effect the speakers this way, appears with whatever source I have selected. This morning I switched interconnects between preamp and amp and the sound was still coming from the left channel. I'll try switching the left and right tubes in the amp and see where that goes.

Do you use a Q-tip to clean the tube pins?

If necessary I'll take the amp in for service, but it weighs 100 lbs so it's a freakin pain in the arse.
fatparrot
1,314 posts
 
What did you buy for new tubes, and from whom? Are you still using the new tubes in your preamp, amp, or both? What make is your preamp and amp (monoblocks?)
budrew OP
467 posts
 
I put the stock tubes back in both components and that's when the problem started. The new tubes I tried then removed were Electro-Harmonix purchased from Tubeworld. The amp is the Mcintosh MC2102 and preamp is C2200.
listener57
730 posts
 
At Radio Shack, there are non-shedding replacements for Q-tips so no particles accidentally transfer from tube pins into tube sockets. Another way to go is to use tiny, pointed, non-shedding eye cosmetic applicators from the cosmetic section at any pharmacy. These are what seem to be included with the wonderful Walker Audio SST contact enhancer, for use on tube pins, only after your mystery problem has first been definitely solved. Caig makes contact cleaner-enhancer suitable for tube pins, but other Audiogon members can comment whether there is any type, and concentration, of ordinary alcohol also acceptable for preliminary cleaning of tube pins.
Owning tube equipment is more fussy than transistor equipment, and I have been saved more than once from the sound of silence, by having at least one backup tube of each type used in my components. This is one of the prices paid to stay on the side of the angels.
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