Hi,
I wonder if someone have experienced a ULN-HC78A as regulation element in a heater PSU.
ULN-HC78A Ultra Low Noise Positive Regulator 2.5V~30V Output High Current Type | eBay
Does it perform as it costs???
Thanks in advance.
Victor
I wonder if someone have experienced a ULN-HC78A as regulation element in a heater PSU.
ULN-HC78A Ultra Low Noise Positive Regulator 2.5V~30V Output High Current Type | eBay
Does it perform as it costs???
Thanks in advance.
Victor
It was my first answer to them, they told me that I can order what ever I need, 6,3 or 12,6 V and they shall fix it.
Victor, many commonly used preamp tubes operate at either "6" or "12" V. Building a 12 V. regulated supply is very easy. "Full wave" voltage double 6.3 VAC, using 2X Schottky diodes into a large valued cap. stack. Follow the rectifier setup with a 7812 3 terminal regulator. The AC RMS current capability of the filament trafo should be 4X the 12 VDC draw.
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Half the price, and almost twice the current:
MIC29752WWT Microchip Technology | Integrated Circuits (ICs) | DigiKey
MIC29752WWT Microchip Technology | Integrated Circuits (ICs) | DigiKey
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Hi Victor ,
You do not need to spend USD$ 59.00 (!!!!) to have good regulation and low ripple in a simple "heater voltage regulator" !!! It's a waste of money !!! Use the simple , easy do find and cheap LM317T voltage regulator !!! The circuit use only two resistors , one capacitor and two diodes !!! The circuit is on the manufacturer's datasheet , and you will find it here : Datasheet4U.com - 900,000+ datasheet pdf search and download
You do not need to spend USD$ 59.00 (!!!!) to have good regulation and low ripple in a simple "heater voltage regulator" !!! It's a waste of money !!! Use the simple , easy do find and cheap LM317T voltage regulator !!! The circuit use only two resistors , one capacitor and two diodes !!! The circuit is on the manufacturer's datasheet , and you will find it here : Datasheet4U.com - 900,000+ datasheet pdf search and download
LM317 does not always work, same with LM337. Cold heater inrush current activate overload protection. Not with all tubes, but with some it will happen.
I always thought that well filtered heater supply is better than simple AC. Yes it is more simple with AC and it quite works well with a separate heater in a tube bulb. It also depends on an amplifier topology of course, a hard driven tube can add an intermodulation products etc.
I always thought that well filtered heater supply is better than simple AC. Yes it is more simple with AC and it quite works well with a separate heater in a tube bulb. It also depends on an amplifier topology of course, a hard driven tube can add an intermodulation products etc.
I'm sorry to say that Mindutis , BUT you are completely wrong !!! If you operate the LM317T within their current limits (with conservative values) may be 0,7 Ampére (+/-) at nominal tube heater voltage and nominal tube current demand , the overload protection WILL NOT act !!!! If the current demand is bigger than that you can use 2 separate pcs of LM317T , you will save a lot of money and get a very fiable source of heater voltage !!! ALL of my preamplifiers ( I made them to sell) use this system and NEVER had any kind of problem !!!! Listen to my experience !!! It will work fine !! OK ???
Regardless of which heater voltage is settled on, a 4 A./6.3 VAC filament winding is needed to power the supply. However, if a voltage doubler is employed, a single 1.5 A. version of the 7812 regulator will be adequate, provided it is well heat sinked.
2X of Taiwan Semiconductor's SR510 Schottky diode will easily handle the rectifying chore.
2X of Taiwan Semiconductor's SR510 Schottky diode will easily handle the rectifying chore.
Half the price, and almost twice the current:
The Micrel / Microchip MIC29752WWT regulator linked to in this post is "not recommended for designs" on page 3 of it's own data sheet.
The TO220 versions, one of which is good for 5 amps are not on the endangered species list. I can confirm that one MIC29502 will run a pair of 2A3's with a dropout voltage of about half a volt. The large heat sink to the left of the 2A3's is for the regulator and the smaller heat sink is for the dual Schotkey diode that provides FWCT rectification from a 6.3V CT winding. I haven't tested to see if there is enough headroom for 6.3 volt filaments from 6.3V feeding a FWB yet, since it's not necessary in my application.
The Micrel / Microchip MIC29752WWT regulator linked to in this post is "not recommended for designs" on page 3 of it's own data sheet.
The TO220 versions, one of which is good for 5 amps are not on the endangered species list. I can confirm that one MIC29502 will run a pair of 2A3's with a dropout voltage of about half a volt. The large heat sink to the left of the 2A3's is for the regulator and the smaller heat sink is for the dual Schotkey diode that provides FWCT rectification from a 6.3V CT winding. I haven't tested to see if there is enough headroom for 6.3 volt filaments from 6.3V feeding a FWB yet, since it's not necessary in my application.
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What voltage is available for filaments on the transformer winding?
LM317 is a bit noisy, but ECC82 and ECC83 are a bit noisy either so I think that the LM317 is enough for the task.
I have more than 17 V DC after the rectifier, but I think to take a chance with LT1084
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