Why need 2 LM317 to operate one filament?urgent!
Because the author drew his schematic this way ? Each regulator delivers cca. 145 mA, tube requires 300 mA to operate. Perhaps he wanted to spread the heat around ... who knows. With decent heatsink you can easily use just one LM317 (and change value of 20R and 15R resistors, of course, to get parallel resistance of cca. 4.16R).
My first impression was "will never flight" !
But, at a second look it seems to me that each LM317 is used as pull down for the IRF610 source followers.
Don't be confused by the "+Bat-1" and "+Bat-2" labels which are indeed the anode connections to each active load (2SK30) wich each drive an IRF610.
If so, each source follower draw near 150 mA.
My two pence.
Yves.
But, at a second look it seems to me that each LM317 is used as pull down for the IRF610 source followers.
Don't be confused by the "+Bat-1" and "+Bat-2" labels which are indeed the anode connections to each active load (2SK30) wich each drive an IRF610.
If so, each source follower draw near 150 mA.
My two pence.
Yves.
It appears that those ccs both control the current through the output devices on each channel and each one also provides half the filament power. (current sources sum directly [Norton]) It is actually rather clever and obviates the need for a separate filament supply and also reduces the dissipation across each LM317 as the voltage across them is reduced by the amount of the filament voltage.
This works well because the swings required at the output are small as compared to the available supply voltage, the ability to swing in the negative direction is compromised by the voltage drop of the filament.
This works well because the swings required at the output are small as compared to the available supply voltage, the ability to swing in the negative direction is compromised by the voltage drop of the filament.
Check the value of the resistors, and make sure that the LM317 that is running hot is properly attached to its heat sink.
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