Hi,

I am using a homemade EF86 preamp, triode connected. Lately it is making
noise like static in one the the channels. I swapped the tubes and the noise
has gone to the other channel, so the problem is on the tube. Is there
anything that I can do to fix it?
I am using a 12VDC regulated supply on the heaters, in series. so this tube
has been for a while with a heatr voltage from 12VDC to 6 VDC, while the
other has 6 to 0 VDC. Can this be the problem?
V+ on the anode is 180VDC, regulated.

Thanks

Miguel

LMMP wrote:

Hi,

I am using a homemade EF86 preamp, triode connected. Lately it is making
noise like static in one the the channels. I swapped the tubes and the noise
has gone to the other channel, so the problem is on the tube. Is there
anything that I can do to fix it?

It seems you have a crook tube, so replace it with a new tube,
and put the old one in the bin.


I am using a 12VDC regulated supply on the heaters, in series. so this tube
has been for a while with a heatr voltage from 12VDC to 6 VDC, while the
other has 6 to 0 VDC. Can this be the problem?

Nope, if the heater is 6v across the filament, it should be fine.

Patrick Turner.


V+ on the anode is 180VDC, regulated.

Thanks

Miguel

On Wed, 17 Sep 2003 13:30:44 +0100, LMMP wrote:

Hi,

I am using a homemade EF86 preamp, triode connected. Lately it is making
noise like static in one the the channels. I swapped the tubes and the noise
has gone to the other channel, so the problem is on the tube. Is there
anything that I can do to fix it?

Nao. Quando uma valvula esta defeitoso nesse maneira,
nao e possivel reparar.
Muito triste,mas esso e o fato.
Voce tem que repor a valvula.

I am using a 12VDC regulated supply on the heaters, in series. so this tube
has been for a while with a heatr voltage from 12VDC to 6 VDC, while the
other has 6 to 0 VDC. Can this be the problem?

Nao e possivel que esso e a causa do problema.

--
Ned Carlson Triode Electronics
5633 W Irving Park Rd Chicago, IL, 60634 USA
http://www.triodeelectronics.com/

LMMP wrote:

Hi,

I am using a homemade EF86 preamp, triode connected. Lately it is making
noise like static in one the the channels. I swapped the tubes and the noise
has gone to the other channel, so the problem is on the tube. Is there
anything that I can do to fix it?
I am using a 12VDC regulated supply on the heaters, in series. so this tube
has been for a while with a heater voltage from 12VDC to 6 VDC, while the
other has 6 to 0 VDC. Can this be the problem?
V+ on the anode is 180VDC, regulated.


That heater voltage won't bother a good tube. In fact, an old trick to
reduce hum
from AC on heaters is to elevate the heater about 30VDC above what the
cathodes
voltages are.

It's just a bad tube, toss it. Last resort, try smacking it on a wooden
(or similar
softer than metal or concrete material) to possibly jar particles that
might be
causing a partial short. Odds are long here, though.....

Thanks guys.
I replaced the tube and everything is back to normal. I am using quite old
Phillips EF86s I scraped from old equipment, so this is not really a
surprise for me.

Miguel



"Robert Casey" escreveu na mensagem
...
LMMP wrote:

Hi,

I am using a homemade EF86 preamp, triode connected. Lately it is making
noise like static in one the the channels. I swapped the tubes and the
noise
has gone to the other channel, so the problem is on the tube. Is there
anything that I can do to fix it?
I am using a 12VDC regulated supply on the heaters, in series. so this
tube
has been for a while with a heater voltage from 12VDC to 6 VDC, while the
other has 6 to 0 VDC. Can this be the problem?
V+ on the anode is 180VDC, regulated.


That heater voltage won't bother a good tube. In fact, an old trick to
reduce hum
from AC on heaters is to elevate the heater about 30VDC above what the
cathodes
voltages are.

It's just a bad tube, toss it. Last resort, try smacking it on a wooden
(or similar
softer than metal or concrete material) to possibly jar particles that
might be
causing a partial short. Odds are long here, though.....