[lupoal]

I can send you the pin details if it will help

yes please,
how do you measure the heater voltage? do you remove valve and measure inside the socket (I mean the adapter) or do you opend the LD and measure it on the pcb soldering point? (much more dangerous)

 

[lupoal]

... so here...

between 7 and 8... so, looking at from the bottom to the valve the first two pins moving in counterclowise direction... right?
unfortunately no way to measure each heater inside as they are in parallel on noly two pins (and two resistors in parallel... well the gap in the values could be higher then evaluated via multimeter)

 

[TrollDragon]

If the tubes sound good I really wouldn't worry about one filament brighter than the other.

 

[lupoal]

in the mean time I've measured the voltage at the heater... it is roughly 6,7Vac (the voltage at home is 240Vac instead of the nominal 220Vac)
I've tried also to get the value of resistance between pin 7 and 8 but no way... I always get 0... tested both Tungsl and both Sylvania... always 0 but there is electrical continuity as testing for that I get a nice "beeeep" from multimeter

 

[Datun Walnut]

yes please,
how do you measure the heater voltage? do you remove valve and measure inside the socket (I mean the adapter) or do you opend the LD and measure it on the pcb soldering point? (much more dangerous)

I'll put something together for you. Do you have a multimeter?

 

[lupoal]

Datun... please read two messages above... I've measured the voltage and is 6,7Vac... no way for the heater impedance, between 7 and 8 always 0

 

[gibosi]

my two tungsol 6SN7GTB, are driven by two CV4014 (thank you Datum Walnut!) and... they sound really fine but... the two tubes seems to have (well, I think they have) a quite different operating temperature, I swipped the tubes between the two position and the hotter one is always the same (tube, not position), I've done the same with the CV4014 (thinking could be from differences in those but no, the hotter 6SN7 remain unchanged)...here is a picture, what do you think about? all normal or one of the tubes is fault?

How do you know that they have quite different operating temperatures? Have you measured the temperature? Or is it that one is brighter than the other?

 

[Datun Walnut]

Sorry, I was in the pub . I'd say that sounds ok to me too

 

[cddc]

... so here...


between 7 and 8... so, looking at from the bottom to the valve the first two pins moving in counterclowise direction... right?
unfortunately no way to measure each heater inside as they are in parallel on noly two pins (and two resistors in parallel... well the gap in the values could be higher then evaluated via multimeter)

Look at the tube from the bottom (as in the pic above), you should count pins clockwise (instead of countclockwise).

I guess you measured wrong pins, and that's why you got zero reading.

 

[cddc]

in the mean time I've measured the voltage at the heater... it is roughly 6,7Vac (the voltage at home is 240Vac instead of the nominal 220Vac)
I've tried also to get the value of resistance between pin 7 and 8 but no way... I always get 0... tested both Tungsl and both Sylvania... always 0 but there is electrical continuity as testing for that I get a nice "beeeep" from multimeter

The tube on the right does look much brighter than the one on the left.

You can measure the temp with a laser gun or some DMM with temp function.

But I think measuring the heater resistance should be much easier. You can find if there is any short or problem which could possibly lead to the difference in resistance or brightness.

The 2 filaments inside 6SN7 are indeed wired in parallel, so it's impossible to measure only one of them, you can only measure the overall combined resistance.

 

[cddc]

Datun... please read two messages above... I've measured the voltage and is 6,7Vac... no way for the heater impedance, between 7 and 8 always 0

Also, make sure when you measure the resistance you need to unplug the tubes, and then measure them. You can not measure the resistance when they are still sitting in the sockets.


Edit: also make sure your DMM is set on the right range (e.g. 20 ohms). I have measured 6SN7 filaments before, it's somewhere between 1 to 3 ohms, I think. If you set your DMM on the 20K or 2M ohms range or on the continuity range, you will definitely get a zero reading.

 

[TrollDragon]

I guess you measured wrong pins, and that's why you got zero reading.

No combination of pins would give him 0 ohms unless the tube was shorted. I think the scale was too high on the meter.

 

[cddc]

No combination of pins would give him 0 ohms unless the tube was shorted. I think the scale was too high on the meter.

lupoal was asking if he should count the pins countclockwise, so I was telling him that this is the wrong way of counting and getting the wrong pins is a possibility if using the wrong way.

Now, how to display an open circuit on different multimeters would be tricky. Some may show OP and lupoal thought it's a zero with a suffix P, this could be a possibility; or some may show the infinity sign which looks like 2 zeros, this is also a possibility; or some just use 0 to show open circuit, it is also a possibility.

We can't conclude anything from what lupoal told us. So we can only give him the possible reasons.

 

[cddc]

Anyway, I've told lupoal all the possibilities. It is not rocket science, I think he should be smart enough to figure it out.

 

[lupoal]

How do you know that they have quite different operating temperatures? Have you measured the temperature? Or is it that one is brighter than the other?

just because it looks brighter (as you can see in teh picture)... well, to be nore precise, one is orange (hot) the onther tube is almost grey/metal that should means much colder