Originally Posted by vbf
I am recently having an issue with my nova : NO SOUND when I switch on the tube, aka blue light, when playing a music. It was not the case before.
No tube...perfect music
Tube : silence....like if it was in mute mode.
Anybody with the same issue?
This is documented?
Thank you for your help on this sad situation on an otherwise wonderful piece of hardware i have received in July.
What type of tube are you using? Check the fuses to the left of the tube socket about 4".
The 6DJ8 (ECC88), 6922 (E88CC), and 7308 (E188CC) can be found listed in the old data sheets as having differing plate dissipation. Most often, the types are noted as simply being premium versions of one another, however the parameters do differ slightly. The .2w referred to below is in regard to the 7308 vs. the 6922. I did have my Nova blow fuses with a 7308 so I suspect this may relate to the fact that sometimes the Nova powers on out of stand-by with the tube activated, when it should not. 1st time it was like it was muted, and my guess is all 3 (4?) fuses were blown, 2nd time I looked rather than send the unit back in, and a few fuses were blown and with the tube on I had distorted low-volume sound. I'm curious to hear what tube you had in there and wouldn't be surprised if the tube tested fine.
"The 0.2-watt difference in plate dissipation will most likely make no difference at all. It's possible that these are all the same tube really, and it was just a matter of the manufacturers trying to avoid being sued by each other way back when while they were in competition.
You have to be careful about the comparison of plate voltage, because it may be actually comparing "apples and oranges". One of the tube specs I was looking at yesterday indicated a slightly higher plate voltage rating under very low (or zero) plate current. Which is a specification that might only apply as the equipment is warming up, and have no impact at all once it is operating. The same holds true for the 0.2-watt difference in plate dissipation, the higher value may only apply for very low plate voltages."
This difference is small but can make a difference in some circuits depending on the design. when testing all the aforementioned types, I have been advised to use the same test parameters for each, that is how subtly and unrelated to transconductance these differences are. this tube is much more complicated because of its high gain that most know or discuss:
At this point, I think I am seeing an effect of what we discussed before: A combination of high-gain tubes, and imperfect manufacturing repeatability. I don't think there's anything wrong with the way they are being tested (the test setup).
Look at the "initial spread" in expected values for the E88CC in this data sheet:http://www.mif.pg.gda.pl/homepages/f...09/e/E88CC.pdf
It's on page 2 in column II. The plate current is 15 mA +/- 0.8 mA. The transconductance is 12.5 mA/V -2/+2.5 mA/V. This means that for emission, 94.7% to 105.3% is normal. And for transconductance, 84% to 116% is normal.. You can expect to see this wide a difference between tubes, and between the 2 sections of a single tube (in some manufacturers).
ECC88 and E88CC are very slightly different. The E88CC grid voltage is supposed to be 1.3V versus 1.2V for ECC88. Otherwise, they look the same. But with these high gain tubes, 0.1V can make a moderate difference.