Plate voltage on 12BH7 for NRI mod W
10/23/2010 7:58:15 PMMitch(89650:0)
Hello,
Can anyone tell me what the plate voltage should be on this tube for this Mod W?
The rectifier is open and i don't get a good voltage reading.
Thanks,
Mitch
10/23/2010 8:29:04 PMMitch(89651:89650)
:Hello,
:Can anyone tell me what the plate voltage should be on this tube for this Mod W?
:The rectifier is open and i don't get a good voltage reading.
:Thanks,
:Mitch
:
With the diode removed and 120 Vac applied through a Variac the secondary winding is 150 Vac. Will this be the voltage i should see on the plates?
Thanks,
Mitch
10/23/2010 9:11:39 PMWarren(89654:89651)
When you add the diode you should get about half the voltage after the diode. plate will be around 60 volts.
10/23/2010 9:19:04 PMMitch(89656:89654)
:When you add the diode you should get about half the voltage after the diode. plate will be around 60 volts.
:
Warren,
Due to half wave rectifier?
Thanks,
Mitch
10/23/2010 9:19:30 PMMitch(89657:89656)
::When you add the diode you should get about half the voltage after the diode. plate will be around 60 volts.
::
:Warren,
:Due to half wave rectifier?
:Thanks,
:Mitch
:
10/23/2010 9:40:27 PMWarren(89658:89657)
Yes, that's right
10/23/2010 10:11:36 PMMitch(89662:89658)
:Yes, that's right
:
Replaced diode, 3 amp 200 volt. Did not install a resistor (I'm the idiot). Slowly increased Variac to 120 Vac, watched the plate voltage go to -15 Vdc. Not good! 10 secs later 20 Mfd cap melted down, too much current.
I will replace the cap and start with a 60 ohm 2 watt resistor in series with the diode and check for about 60 volts at the plates.
Mitch
10/23/2010 11:28:25 PMWarren(89666:89662)
From what you are saying that sounds like that 20 MFD capacitor was installed backwards. You do know that the cathode of the diode is the positive end, and the anode connects to the AC.
10/24/2010 1:28:23 AMMitch(89680:89666)
:From what you are saying that sounds like that 20 MFD capacitor was installed backwards. You do know that the cathode of the diode is the positive end, and the anode connects to the AC.
:
Warren,
Please look at the schematic if you have availability to it. Not sure of your thoughts on right connections.
Thanks again,
Mitch
10/24/2010 1:48:05 AMWarren(89681:89680)
I don't have the schematic. If you can E-mail that to me.
If this is a convention power supply. The Positive end of that 20 MFD connects to the cathode of the diode. The anode to secondary side of the power transformer.
10/24/2010 11:57:31 AMMitch > Warren Diode reverse(89689:89681)
:I don't have the schematic. If you can E-mail that to me.
:If this is a convention power supply. The Positive end of that 20 MFD connects to the cathode of the diode. The anode to secondary side of the power transformer.
:
Warren,
Observation this morning is Diode is reversed.
You are corret about the power supply. I will replace cap and reverse Diode, will let you know.
Thanks for the help.
Mitch
10/24/2010 1:37:41 PMDiode Man(89694:89681)
Forget all this anode and cathode stuff. The banded end of the diode always goes to the positive end of the filter cap.
:I don't have the schematic. If you can E-mail that to me.
:If this is a convention power supply. The Positive end of that 20 MFD connects to the cathode of the diode. The anode to secondary side of the power transformer.
: