[FEELER] C12 Clone Project
- Thread starter chunger
- Start date
Help Support GroupDIY Audio Forum:
chunger
Well-known member
My leaning is Polished nickel plated. As I understand it, nickel plate finish can vary from batch to batch and all of the microphones I'm importing are bead-blasted matte nickel, so if I do the headbaskets in polished nickel, they will contrast with the matte bodies and there will not be problems with finish mis-match between batches and even between different factories for that matter as I know several factories use this tooling.
chunger
Well-known member
Matador said:
PITCHERS! Lemme get my popcorn.
leadbreath
Well-known member
nice...
HellfireStudios
Well-known member
I'll be painting mine to match the rest of the mic's paint job. Let us know when headbasket prices are figured up. Thanks.
-James-
-James-
tonycamp
Well-known member
Matador said:
I've got my popcorn ready also, you guys so RULE!
Hey Matador, a big sheet of white paper may get your pics 1/2 way there?
Thnx
T
David R.
Active member
I am in for two! So hard to build only one mic...
Matador
Well-known member
Exciting shipment received from the PCB house today! These came in must faster than usual: business must be slow in those parts.
I apologize for the crappy cell-phone pics: I'll take better pictures when stuffing of the boards happens.
Here is the main PSU board:
Main microphone PCB:
Here the two microphone PCB's are set together:
I apologize for the crappy cell-phone pics: I'll take better pictures when stuffing of the boards happens.
Here is the main PSU board:
Main microphone PCB:
Here the two microphone PCB's are set together:
tonycamp
Well-known member
how fun!, totally exciting ;D
iprovlek
Well-known member
I will need one !Great work!
I'm in for 1
Volume11
Well-known member
+2 pcbs here.. Thanks
micaddict
Well-known member
Put me on the list for one, please. 
tonycamp
Well-known member
desol said:
Here you go
http://www.groupdiy.com/index.php?topic=50250.0
chunger
Well-known member
Working on the headbasket but I have run into problems with first choice factory in that they took a look at the design and don't want to build it. I'm following up on factory 2 and 3 now but feel headbaskets may lag behind the rest of the parts. I can get stock HT-11a headbasket manufactured with different grill material without much issue at very reasonable cost, but would much rather just get it all done at once and have the new hoop structure.
Matador
Well-known member
Ok here's most of the PSU build!
The PSU case is removed with 4 screws around the bottom sides. Popping the lid reveals the guts:
Three more screws release the main PCB and reveal the wire connections underneath:
There are a series of 7 wires along the top of the PCB that must be removed:
Once those are disconnected, the power transformer leads (4) must be removed. On my unit, there were gobs of solder, so I hit it with some desoldering braid and then they pulled out:
The last two wires go to the PCB mounted fuse. Once those are removed, the PCB can be removed:
Now for the moment of truth: test fitting the new PCB. It looks like all of the screws line up! Success!
Pulling the PCB back out, I start by stuffing the 10 1N4007 rectifier and protection diodes:
Then all of the 1/4W Vishay resistors:
Next go the two trimmers: one for the heather voltage, the other for the tube bias:
Then the screw connection terminal:
Now all of the small Nichicon caps:
Now for the heatsink. The LM317T regulator for the heater voltage is connected to the heatsink with a heatsink mounting kit:
The order goes: the bolt goes through the insulating washer, then through the LM317T, then through the insulating thermal pad, then through the heatsink. On the other side of the bolt: a washer, then a lock washer, then the nut. After this is loosely screwed together, the whole mess can be placed on the board. The heatsink has two mounting tabs that get soldered to the PCB:
This is tricky to solder due to the high thermal mass. You need a good iron for this! Hold the heatsink, and tack one of the tabs and make sure everything is sitting down on the PCB. Then you can solder the other tabs, the three LM317T connections, and then back to the first tab:
Then you can tighten the bolt snugly (but not tight!). It's just there to hole the regulator to the heatsink. With this mounting kit, the heatsink does not rise up to the output voltage, which is much safer if you monkey around inside the case with a screwdriver.
Now it's time for the large caps. There are four 4700uF heater caps:
Then the 100uF 250V caps for the tube B+ supply:
There's a lot more filtering on my board as compared to the original!
Back into the chassis to make sure everything fits and everything has clearance:
Success!
Next I need to redo the polarization switch with new resistors, then install the 1W 5ohm resistors into the heater supply.
I also didn't like the PCB mounted fuse: I'll be replacing it with a chassis mounted one so that the fuse can be replaced without taking everything apart.
The PSU case is removed with 4 screws around the bottom sides. Popping the lid reveals the guts:
Three more screws release the main PCB and reveal the wire connections underneath:
There are a series of 7 wires along the top of the PCB that must be removed:
Once those are disconnected, the power transformer leads (4) must be removed. On my unit, there were gobs of solder, so I hit it with some desoldering braid and then they pulled out:
The last two wires go to the PCB mounted fuse. Once those are removed, the PCB can be removed:
Now for the moment of truth: test fitting the new PCB. It looks like all of the screws line up! Success!
Pulling the PCB back out, I start by stuffing the 10 1N4007 rectifier and protection diodes:
Then all of the 1/4W Vishay resistors:
Next go the two trimmers: one for the heather voltage, the other for the tube bias:
Then the screw connection terminal:
Now all of the small Nichicon caps:
Now for the heatsink. The LM317T regulator for the heater voltage is connected to the heatsink with a heatsink mounting kit:
The order goes: the bolt goes through the insulating washer, then through the LM317T, then through the insulating thermal pad, then through the heatsink. On the other side of the bolt: a washer, then a lock washer, then the nut. After this is loosely screwed together, the whole mess can be placed on the board. The heatsink has two mounting tabs that get soldered to the PCB:
This is tricky to solder due to the high thermal mass. You need a good iron for this! Hold the heatsink, and tack one of the tabs and make sure everything is sitting down on the PCB. Then you can solder the other tabs, the three LM317T connections, and then back to the first tab:
Then you can tighten the bolt snugly (but not tight!). It's just there to hole the regulator to the heatsink. With this mounting kit, the heatsink does not rise up to the output voltage, which is much safer if you monkey around inside the case with a screwdriver.
Now it's time for the large caps. There are four 4700uF heater caps:
Then the 100uF 250V caps for the tube B+ supply:
There's a lot more filtering on my board as compared to the original!
Back into the chassis to make sure everything fits and everything has clearance:
Success!
Next I need to redo the polarization switch with new resistors, then install the 1W 5ohm resistors into the heater supply.
I also didn't like the PCB mounted fuse: I'll be replacing it with a chassis mounted one so that the fuse can be replaced without taking everything apart.
Matador
Well-known member
Some more progress.
Installed some 1.8 ohm resistors into the heater RC filters that go before the regulator. This should give roughly the correct voltage drop before the regulator.
I will tune these later: the math says, we need roughly 2V top across the regulator. This means that after the rectifier, there should be about 13V. This is a 5V drop across these two resistor at 350mA of heater current. This is about 5 ohms per resistor.
Next I wire up the fuse holder (temporarily, before I drill out the chassis for it) with a 250mA fuse. Don't want to burn down the house!
I plug it in, and flick on the switch, and wait to hear that sizzling that comes right before a cap goes blam....but nothing!
I rig a temporary post to the ground terminal so I can ground my meter:
No-load B+ voltage was way over as expected: the transformer should put out about 280V after full wave rectification:
The heater voltage way very high:
A few turns of the heater adjust pot brings it down:
I installed a 100K test load on the B+ line, and a 20 ohm test load on the heater. B+ dropped to 200V and heater stayed at 6.3V!
Success!
I just need to wire the polarization switch and the PSU is good to go!
Installed some 1.8 ohm resistors into the heater RC filters that go before the regulator. This should give roughly the correct voltage drop before the regulator.
I will tune these later: the math says, we need roughly 2V top across the regulator. This means that after the rectifier, there should be about 13V. This is a 5V drop across these two resistor at 350mA of heater current. This is about 5 ohms per resistor.
Next I wire up the fuse holder (temporarily, before I drill out the chassis for it) with a 250mA fuse. Don't want to burn down the house!
I plug it in, and flick on the switch, and wait to hear that sizzling that comes right before a cap goes blam....but nothing!
I rig a temporary post to the ground terminal so I can ground my meter:
No-load B+ voltage was way over as expected: the transformer should put out about 280V after full wave rectification:
The heater voltage way very high:
A few turns of the heater adjust pot brings it down:
I installed a 100K test load on the B+ line, and a 20 ohm test load on the heater. B+ dropped to 200V and heater stayed at 6.3V!
Success!
I just need to wire the polarization switch and the PSU is good to go!
