Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: joesatch on March 31, 2024, 11:35:25 am
-
i usually use a fwb but in this case my PT is center tapped and the CT must be grounded as this CT is the HT that i will use with 2 phase . I will show the PT i'm working with. What i want to do is use the yellow secondaries which measure 24vac (with CT grounded) for a dc heater circuit. I have tested rectifying these yellows with a two phase rectifier and the dc result is 10vdc. Now the valve wizard says i'm supposed to get Vdc = 1.3 × Vrms. Which is obviously incorrect. What rectification must i use to get this yellow wind eventually into a 7812 regulator for 12vdc heaters?
-
... What i want to do is use the yellow secondaries which measure 24vac (with CT grounded) for a dc heater circuit. I have tested rectifying these yellows with a two phase rectifier and the dc result is 10vdc...
Show the exact circuit you used and note what and where the AC and DC voltages you measured.
-
The valve wizards numbers are correct. The fact that you only get 10vdc tells me that you did not connect a filter cap to your rectifier output. Use a filter cap and you will see the voltage magically increase to about 16.8vdc.
Having said that, if those 24vac taps are really part of the high voltage winding as shown in your pic, there will likely not be enough current capacity to properly light up a filament string.
-
ok thanks for your input i will scrap this plan and use a separate PT for the dc heaters. Was hoping to avoid the extra weight in the amp
-
ok thanks for your input i will scrap this plan and use a separate PT for the dc heaters. Was hoping to avoid the extra weight in the amp
Show us a schematic for your amp. There may be a way to do dc filaments without an additional transformer.
-
i dont have a schematic. i'm using this PT to build a 2204 circuit. The original schematic from the PT pulled is this one.
-
The original 2204 worked just fine with AC filaments.
-
The original 2204 worked just fine with AC filaments.
i'm adding some relays to make it channel switchable 2 masters and 2 gains plus i have some mods to make it more high gain. . Gonna go with a separate PT