Alembic F2B Tube not light up

[wui223]

I build the Alembic preamp, but after i connect everything, the tube is not light up. I tried both 12VDC and AC supply, still nothing happen. I check the voltage of B+ and heater, it is fine. Anyone could point out what would have happened?

[bancika]

how did you wire tube heaters?
measure voltage between pins 4 and 5

[wui223]

12V to pin 4 and 5. Pin 9 to ground. Voltage across pin 4 and 5 is 12V

[bancika]

try replacing tube

[wui223]

Fixed. I messed up the pin out, all reverse in order. Now the tube is light up, but no sound at all, previously there are whinning/humming sound now totally silent.

[JonFrum]

Measure your voltages at each tube socket lug and compare them to what you expect. If you don't know what to expect, list them here.

[The Tone God]

Pin 9 should not go to ground if you are using 12v. Leave pin 9 unconnected.

Andrew

[JonFrum]

Pin 9 should not go to ground if you are using 12v. Leave pin 9 unconnected.

Andrew

Are you sure about that?

[The Tone God]

Are you sure about that?

Pin 9 is the centre tap of the heaters. The ends are pins 4 and 5 with the complete heater running at 12v so you need only pins 4 and 5 when running at 12v. Pin 9 is used if using 6v otherwise leave it open.

Andrew

[rockgardenlove]

Yep, he's right. 

[moosapotamus]

Huh, maybe that has something to do with why I prefer the sound of mine running 6.3V to the heaters instead of 12V.

~ Charlie

[The Tone God]

Huh, maybe that has something to do with why I prefer the sound of mine running 6.3V to the heaters instead of 12V.

Umm...I am kinda slow these days but you are kidding right ?

I think the OP is shorting one triode heater by grounding pin 9 which would explain the no sound but some heater action happening.

Andrew

[JonFrum]

Are you sure about that?

Pin 9 is the centre tap of the heaters. The ends are pins 4 and 5 with the complete heater running at 12v so you need only pins 4 and 5 when running at 12v. Pin 9 is used if using 6v otherwise leave it open.

Andrew

The reason I ask is that Fred's Real McTube schematic shows pin 9 grounded.

[The Tone God]

The reason I ask is that Fred's Real McTube schematic shows pin 9 grounded.

I have not seen the schematic so I cannot comment besides that would also be a borderline threadjack for the OP.

Andrew

[wui223]

Hi Charlie, i saw that you built Alembic preamp also. Could you post the voltage for each pin just for reference?

[puretube]

A., TTG:

http://www.dogstar.dantimax.dk/tubestuf/graphics/mct2ps2s.gif
from here:
http://www.dogstar.dantimax.dk/tubestuf/mctube.htm
taken to there:
http://www.tonepad.com/getFile.asp?id=43

T., PT.

[bancika]

in will work without grounding pin 9 but I think that it should be connected to a reference point, ground or some positive DC voltage (in amps it can be output tube cathode). I read that it can help reduce noise.

[The Tone God]

Thanks PT!

In that schematic they are half wave rectifying a 12v centre tap transformer so really pins 4 and 5 are getting 6v so you would need pin 9 ground to complete the connection.

Andrew

[moosapotamus]

Hi Charlie, i saw that you built Alembic preamp also. Could you post the voltage for each pin just for reference?

Sure. But, I might not be able to get to it until after the weekend. If you post your voltages, I'm sure folks could tell you if anything looks questionable.

BTW, my B+ is ~300V and I actually do like the sound better with the heaters at 6.3V than with them at 12V.

~ Charlie

[The Tone God]

BTW, my B+ is ~300V and I actually do like the sound better with the heaters at 6.3V than with them at 12V.

Okay so that is 6.3v per heater half verses 6v making for a difference of 0.3v. I don't know what kind of difference 0.3v in the heater would make to the conduction of the cathode but I wouldn't count on much. For me I see it as one of those "mojo" things. If you like it that way then by all means go for it.

Just my opinion.

Andrew