Megatron Electrostatic Headphone Amplifier

[sorenb]

1 minute ago, JoaMat said:

Emission Labs 20B and 300B, is that the 4 pins socket or the octal socket with center tap filament?

20B octals
300b UX4

I got inspired from your Octal/UX4 pattern ;o)

[JoaMat]

Great work - more Sort Guld.

[Faust]

-resolved-

[Justaguy]

I'm looking at the 300V power supply for the Megatron XL (megatronpowersupply300v2xl in the drive) and it looks like pin 5 on the pcb has an unlabeled component connected to the +300V line. Looking at the schematic (megatronps300.pdf and megatronschem2.pdf in the drive) have a 22 ohm R27 connecting pin 5 to ground.

I'm very much a novice, but I don't think connecting a heater pin to the output line is right.

[jamesmking]

41 minutes ago, Justaguy said:

I'm looking at the 300V power supply for the Megatron XL (megatronpowersupply300v2xl in the drive) and it looks like pin 5 on the pcb has an unlabeled component connected to the +300V line. Looking at the schematic (megatronps300.pdf and megatronschem2.pdf in the drive) have a 22 ohm R27 connecting pin 5 to ground.

I'm very much a novice, but I don't think connecting a heater pin to the output line is right.

22ohm to ground on the heater/filament looks like its there to stop the heater floating and might reduce hum and is therefore probably optional. It looks like this resistor is not present in the megatronpowersupply300v2xl gerbers. It also looks like there is a 221 ohm resistor between the anode and G2 of the el84 in the gerbers which is not present in the megatronps300.pdf.  I am afraid I did not build this power supply so I can't comment on which is the more up to date or preferred version. But in general its the Gerbers which people get pcbs made from and therefore is assumed to be correctly functioning unless the threads on headcase say otherwise.

[Justaguy]

On 3/24/2023 at 12:53 PM, kevin gilmore said:

Power supply #3   tube rectified lc filtered 4 x 6l6gc fully regulated voltages. 300 volt tube rectified and 6bq5 regulated power supply. solid state regulated bias

Referring to my last post, I saw the images of the Felista audio repair and that region of the board is unpopulated.

So another question:
Is there a board for Power supply #3? (reference quote above)
megatronpowersupplyxl has the gz34 tubes and the LC filter, but no 6l6gc tubes. The 300V supply has a el84, which is the 6bq5 quoted. This theoretical full tube build would be 3 on the 300V PSU,  6(?) on the 400V supply and 12 on the amp? That would certainly be something to look at.