What's that smell?

[BillEpstein]

With recent interest in switching cathode resistors, I thought I'd mention that with Gold Lion KT-88s, I get a burnt smell after awhile.

Visual inspection of the 5Watt 560 Ohm Bias resistors and the other 3Watters shows no burns. No issues at all with EH 6CA7s, Shuguang EL-34s or SED 6550s.

I have 10 Watt WW Vishays on hand and will try the 88s again with'm as soon as I finish a speaker project.

In other news, a Denon 103R arrived before it's step-up transformer parts and I have it playing straight in to my MM phono stage. Volume at 3:00 to get good listening levels and hardly even any tube rush.

Damn, George, that's a quiet circuit!

 

[rknize]

Do you have a choke in the PSU? If not, it might be the series resistor.

 

[BillEpstein]

Do you have a choke in the PSU? If not, it might be the series resistor.

Yup, Choke on board.

 

[rknize]

Well, I guess I'd start by putting a volt meter across each cathode bypass cap to see if Vk is reasonable when these tubes are in operation. If you lean on a KT88 hard enough, you can dissipate up to 4W or more from Rk. It's enough to make a resistor smell a bit, but it should go away after a while.

 

[Tubelab_com]

I have never used any expensive tubes, so I have no knowledge of the Gold Lions. I have seen new octal tubes that have a metal ring around the base smell funny for the first week or so. It seems to be from the glue in the base curing. Do you have another amp to try the tubes in?

You might try pulling the hot tube to see if it smells funny when hot. I must mention the obvious, switch the amp off before yanking. Use something to insulate your hand. I use an "Ove Glove". Don't touch it to your nose!

 

[acceler8]

Don't touch it to your nose!

Is that the voice of experience? Haha, just kidding, of course

 

[rknize]

I don't know if I've ever burnt my nose on a tube, but I have on a hot resistor or two.