Blue Bottle Power supply

[RuudNL]

Does anyone have a schematic of the power supply for a Blue Bottle microphone?
The one I have here only supplies 2 volts of anode voltage...
I do however have about +245 volts right after the bridge rectifier. (So: probably a trasistor or a problem in the regulator circuit.)
Heater voltage starts at about 1 volt and increases very slowly to 5.5 volts.

(The designer must have thought: why do it the simple way if you can do it a more complicated way too!)

 

[RuudNL]

I found that there are four(!) bridge rectifiers... Two with 'fat' diodes, two with small signal diodes.
One 'small' bridge rectifier goes to a 78L05/79L05 stabilizer pair, connected to a 5534.
The 78L05 gives 5 Volts, the 79L05 has an output of 0.5 Volts. Not good!
Is it the 5534 drawing too much current from this voltage, is it a capacitor or is the 79L05 'dead'?
It looks like the +5 V. is going to a 330K resistor with a tantalum capacitor at the other side.
Is this maybe a timer circuit, that should give the 'GO!' signal for the +HT?

 

[bockaudio]

It is a shunt regulator on the B+. Should adjust 120-160v? Some versions did have a timer on the xlr3 as well.
Oddly, the heater is not capable of much current, unless there's a resistor to change....

 

[RuudNL]

After replacing the 79L05 everything seems to work again.
(Strange construction of the power supply by the way...)

 

[Audio1Man]

Does anyone have a schematic of the power supply for a Blue Bottle microphone?
The one I have here only supplies 2 volts of anode voltage...
I do however have about +245 volts right after the bridge rectifier. (So: probably a trasistor or a problem in the regulator circuit.)
Heater voltage starts at about 1 volt and increases very slowly to 5.5 volts.

(The designer must have thought: why do it the simple way if you can do it a more complicated way too!)

This may help

Duke

 

[RuudNL]

Many thanks! Interesting information.
As far as I can see the power supply that I repaired at the time was different.
That one had a 78L12 and a 79L12 regulator, that I don't see in this schematic.
What I find very annoying in the 'Blue' power supplies is that it takes "ages" before the relay clicks and the tube is powered. But maybe that's just me...

 

[Khron]

it takes "ages" before the relay clicks and the tube is powered

"Ages" meaning..?

 

[RuudNL]

More than enough time to drink a coffee... (And even when you come back the tube is still not powered up!)

"se vie iät"

 

[SubSpec]

This may help

Duke

Awesome! Might be good to add this here: Blue Mic

There seems to be two Blue tech docs threads, but that one is the earlier. Both only have Robbie to this point, would be cool to see more there.

 

[Nele]

I have one on my bench here. The problem is the output signal keeps getting weaker when turned on. This takes a few hours.
My first idea would be a dying tube. I'm waiting for some new ones to arrive. Or maybe it's a leaking cap somewhere?

I was a bit surprised to see the flimsy flat cable they used to connect the connector to the pcb inside the mic.

If anyone has the schematic of the mic itself it would be a great help.

Also, does anyone have an idea what the variable voltage (E) is doing? I understand that it is used to modify the gain of the mic but wouldn't you do this with your preamp? Or is this to adjust for different capsules?

Here's the pinout of the connector on the power-pcb going to the mic:

1: GND
2: 6.1V Heater
3: 120V B+
4: XLR 2
5: XLR 3
6: E (variable voltage)

 

[Khron]

Also, does anyone have an idea what the variable voltage (E) is doing? I understand that it is used to modify the gain of the mic but wouldn't you do this with your preamp?

As i understand, that's just the adjustable capsule bias voltage. Think of it as a continuously variable pad / attenuator.

 

[Nele]

Yes, just found the manual and it's a variable polarization voltage which they use to adjust the gain:

The Power Stream offers a nine step polarization switch for sensitivity selections. Set at the top (zero) the microphone capsule is set at 60 volts for the suggested performance. When the switch is tuned counter fully clockwise, the polarization voltage is reduced to deliver a 6dB lower output for louder signal sources. When turned fully clockwise, the polarization voltages are increased delivering up to 4dB more output providing more sensitivity for quieter sound sources.