6.3VAC rectified into 14VDC?

[bancika]

yesterday I finished my latest build, kalamazoo model 1 amp. I have wired two color led to show red when on standby and green when fully on. To power it I used heaters ->  bridge rectifier -> 47uF -> 330ohm wired to common anode and cathodes are switched with bypass switch.
The problem is that it doesn't work and I read 14VDC from ground to anode. How can that be? I double checked and wiring is good.
Any ideas?
Tnx

[alextheian-alex]

What is the voltage from - to + lead on the 47u cap?  Do you have your heater supply ground referenced?  What is your AC voltage from lead to lead across the filament secondart?

[bancika]

Well, heaters are referenced at output tube cathode via two 100ohm resistors. Tube heaters are powered with AC (measures 6.3V), bridge rectifier is only for powering LED. Ground side of bridge rectifier for LED is grounded together with ground from HV bridge rectifier.
It just occurred to me, output tube cathode is at 8.4V, maybe it's the reason for increased voltage cause LEDs cathodes are grounded. Does it mean that LED has died? It didn't light up even for a second.
Tnx

[brett]

Hi
if your 6.3 is running just a little over (e.g. 6.5) then it should rectify out to 8.4V.  6.3 gives up to 8.0.  8V and 330 ohms gives 24mA which is a lot for a typical LED.  Maybe switch to a 680 ohm resistor?

[alextheian-alex]

Yeah... what Brett said.  You probably sucked too much current through the LED.  Just adjust the LED current limiting resistor for whatever DC voltag you are running it at.

[alextheian-alex]

Whait a minute... did you say that the heaters are referenced to the output tube cathode?  as in elevated?  if so, then the measurements from GROUND to anode of the LED will be DC + cathode DC voltage.  You could just reference the grounds of the rectifier circuit to the same point on the cathode of the output tube.  for accurate DC across the LED then you measure from the cathode of the tube to the anode of the leD.

[Paul Perry (Frostwave)]

Without referring to the circuit in question, here is the only simple way I know of to make 14V DC from 6.3AC:

Tie one side of the ac to point A.

Run a diode -->|-- to a cap, the other end of which goes to A.

Run a diode- -|<-- to another cap, the other end of which goes to A.

Now you will see about 14V DC across the ends of the caps that don't
connect to A.

Maybe this will help find out what you have done..!

[bancika]

Whait a minute... did you say that the heaters are referenced to the output tube cathode?  as in elevated?  if so, then the measurements from GROUND to anode of the LED will be DC + cathode DC voltage.  You could just reference the grounds of the rectifier circuit to the same point on the cathode of the output tube.  for accurate DC across the LED then you measure from the cathode of the tube to the anode of the leD.

Ok then, can I just adjust LED resistor to work with 14V and reference it to ground?
Tnx