Basic question about stock HST-11a PSU

[Whoops]

By default, the polarization supply is 120V to match the B+ line.  The backplate of the capsule is 60V (taken from a resistor divider), and the front capsule is grounded.  Hence you have for polarization voltages:

0V = omni mode
60V = cardioid mode
120V = figure 8 mode

Since the stock supply has a 9-position switch, there are 6 extra patterns between those above.  Starting at omni mode, each click of the switch raises the polarization roughly 15V.

Thank you,
in this case the stock PSU has the B+ at 200V,
I measured the B+ in the mic and I have 180V.

So how would it be in this case? 180V for the figure of 8 pattern?

 

[Matador]

This is a stock PSU and stock mike, and measured with the mic attached and working?

 

[Whoops]

Stock PSU, Stock Mic (Heaters in Parallel)
PSU rated for 200V B+ and 6,3V Heaters

Voltages measured with mic attached and working
B+  180V
Heaters 6.3V

 

[Banzai]

I've never seen an Apex 460 with 120v.

All over the place, somewhere between 140 to 200v is standard.

 

[Matador]

Agreed.  It really depends on which Zeners were installed in the microphone, and the actual turns ratio on the transformer, as the parts tend to be all over the place.  Replacing the two Zeners with 1N4759's (62V @1W) is a standard mod for these power supplies.

180V B+ means your polarization is about 90V, which is pretty far above what most manufacturers recommend - most suggest 70V or less.

 

[Whoops]

Replacing the two Zeners with 1N4759's (62V @1W) is a standard mod for these power supplies.

I was under the impression, that people recommended replacing those zener diodes in the PSU to lower the voltage (to 120V) in case you changed the capsule for a C12 type. never seen it recommended for people that keep the original capsule.

Should the voltage be lowered also to 120V if the circuit has the original capsule?

the original capsule is supposed to be an U67 type.

 

[moamps]

+B voltage for U67 is +210V, but the capsule is biased to 0, 60V, 120V.  I believe that 180V at any LDC is too much.

 

[Whoops]

+B voltage for U67 is +210V, but the capsule is biased to 0, 60V, 120V.  I believe that 180V at any LDC is too much.

180v is the B+ on the Apex 460 Mic Im working on, not the polarization voltage.

B+ is Pin1 on the attached schematic
Polarization voltage is Pin 3, I will try to measure polarization voltages, I didn't measured them yet

What I and Matador were referring to is that some people replace the Zenners in the PSU, so that the B+ voltage is decreased from 200VDC (in my case is 180V) to 120VDC, but I've seen that mod performed by people that also replaced the capsule for a C12 type capsule, I didnt find info any info on people suggesting that mod for the stock capsule

 

[moamps]

180v is the B+ on the Apex 460 Mic Im working on, not the polarization voltage.

If B+ is 180V and biasing resistors network is made according to the schematic of Apex 460 posted here, the capsule's stator is biased to +90V, consequently +180V on backplate is needed to get figure 8. So, 180V is polarization voltage. That's too much for LDC, IMO. 

If you do some more research, you will find that the Stellar variant of C12 is biased to about 65 and 130V.