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

Showing 5 responses by budrew

budrew OP
467 posts
 
OK, I can admit human error : ) Having figured out the trouble I put the NOS 12AX7s back in the preamp and also a pair of the EH 12AT7s. This rounded off some of the gritty edges and I'm back to captivating tube bliss : ) So nice! I'm happy.
budrew OP
467 posts
 
I don't know if I should feel stupid or relieved. I switched speaker cable channels and the problem still occurred in the left channel. I was sure it was not a speaker problem but I checked it out to see what was what. It turns out there is a ficus tree next to the left speaker that had grown a limb between the speaker grill and the bass driver and when the bass driver started thumping some of the leaves were vibrating off of it. Doh!!!

I'll check into the EH KT-88s. My amp is from late last year. I still have the EH tubes and may try them again someday.

Anyway, thanks to you all!
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.
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.
budrew OP
467 posts
 
I'm frustrated because I'm stuck here at work in meetings and all I want to do is trouble shot my tube problem : ( But I suppose we have to earn the money to pay for this hobby, eh.

It occurred to me I can try switching the channels for the speaker connections. This may not help with much but at least it will clarify if in fact it is a speaker problem. I have no reason to believe there could be a problem with the speaker, but it's one more thing I'd like to rule out for sure.
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