Jump to content

Megatron Electrostatic Headphone Amplifier


kevin gilmore
 Share

Recommended Posts

Speaking of power supplies, I tried firing up the BATE power supply (should be same as KGSSHV power supply but without the error amplifier and with an additional fixed bias line [edit: instead of the front end supplies]) for the first time. Fried a 2k resistor because the trace went to the cathode of the 10m90s instead of the gate, so I cut the trace and re-routed that and now the +400V rail and bias works fine but I'm measuring that at some point GND is tied to -430V so the negative supplies don't work. Any of you know where exactly this point is? I looked through all the other traces after the 2k resistor mishap and everything else seems to be right.

Edited by mypasswordis
Link to comment
Share on other sites

I looked at the original files and yup, found the issue.  We updated the layout software around that time and they changed one small detail, the relief for the pins followed when doing copy/paste which is what happened here:

 

prSrh3J.jpg

 

See the yellow rings, they are attached to the plane but really shouldn't be.  I'd just remove the caps and drill into the top, then insulate. 

Link to comment
Share on other sites

I wouldn't remove the 2n3904s unless they're fried. You do need to change the current sense resistors to 10 ohms. Get a new transformer with lower secondaries, replace all fqp8n80c with new ones, and you should off-board them to a large heatsink like eggil did. Don't forget the thermal paste.

 

Edit: Oops, typed too slowly. KG has spoken. Do what he says

Edited by mypasswordis
Link to comment
Share on other sites

Thank everyone.

 

i will order some 10Ohm Resistors and large sinks.

 

But during the Chinese New Year, almost all the shop will be closed. :-[ 

 

I have to delay the project.

 

I'd really recommend going offboard sinks... with the right size heatsinks for the KGSSHV board, the temps are still a toasty 90C after 15 mins. This had the side effect of "killing" my LT1021s (it always made the voltage to +430V over time until I offboarded the cooling) when cased up.

 

It's been close to a year and the whole setup still runs well.

 

EDIT: just realized I listed the wrong IC and double quoted heh

Edited by RiStaR
Link to comment
Share on other sites

Is there a reason why you're still using the ceramic insulators? The fqpf8n80c are insulated... so they actually reduce thermal conductivity. With regard to your balance issue are your tubes matched? Also check your attenuator (I had an issue once where the relays weren't working properly on my attenuator).

 

Also, how do you like the sound? ;) 

Link to comment
Share on other sites

By attenuator, I meant your volume control (pot or relay-based)... but it's likely your tubes especially if they aren't matched. By lazy and temporary, are you saying you didn't use thermal paste between your transistors and your heatsinks or the ceramic insulators? Probably not a good idea there...

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.