C-1000t phonostage thumping

[bwilson51]

I am getting a thumping sound out of my left channel ,I have been playing it all day and went from phono to cd and then when I switched back I am getting that sound.Could one of the tubes going bad cause this.

[miner]

Yes it does appear to be a tube issue. I would change all tubes to have a fresh benchmark for a time zero measurement.

[keef]

^^^tubes.

[bwilson51]

Thanks I will swap them out tonight

[bwilson51]

The phone tubes are in the center,of the 4 tubes which ones are for the mc phonostage.

[bwilson51]

I swapped out the tubes today and that took care of the thumping sound, I tested the preamp with the top cover off and everything was fine.
I put the 2 bars with the rubber rings on both sides careful to only have the rubber rings touch the tubes.I put the top back on and installed the preamp back in my system and not the left channel has not output.I checked both fuses on the other part of the preamp and they look fine.Any idea what could cause this

[Formerly YB-2]

You may have a pin not making contact with the socket. Just wiggle all the tubes and see if the sound comes back. Not unusual for a little surface corrosion to create such a problem. Also, check to see that the filaments in all the tubes are glowing.

[bwilson51]

All tubes are glowing and when I go from stand by to on the left meter moves a couple of times and then when it goes into operation mode it does nothing.Right channel music and meter moving, left channel no music or meter movement.I made sure the pins line up with the correct slots .I will look again.No issues until last night with the left channel making the original noise.I am confused,but that’s nothing new

[W9TR]

Sometimes brand new tubes fail in the first hours of use - infant mortality. Swap the left and right channel tubes and see if it follows the tubes. If not there is something else wrong.

[bwilson51]

I had a thumping in the left channel before I swapped tubes and after getting suggestions from member here I decided to swap tubes.The preamp was in standby when I removed the main wires from the power section into the tubes I thought this is not good so I removed the power cord from the preamp and changed the tubes leaving the top off I put the preamp back in my rack and hooked everything up.Everything worked fine.I powered everything down to to the tube dampers back and put the top back on.I hooked everything up and went to play a cd and now no music from the left channel.I am beginning to think that maybe the thumping was not a tube issue.I have done a factory reset and same problem.I looked in my manual and can see nothing that helps.I will call MCINTOSH or audio classics on Monday.