Re: Adapting a microphone to remote phantom power

On Wed, 15 Apr 2009 14:47:38 -0700, David Nebenzahl
<nobody@xxxxxxxxxxxxxxx> put finger to keyboard and composed:

On 4/15/2009 1:26 PM Franc Zabkar spake thus:

On Tue, 14 Apr 2009 16:08:57 -0700, David Nebenzahl
<nobody@xxxxxxxxxxxxxxx> put finger to keyboard and composed:

Franc--thanks for taking the trouble to draw this out. I've been looking
all over the schematic, and so far I can't find anything to the left of
IC201 in your "drawing" (the 220 uf cap, zener, etc.) Can't see D301 at
all on the schematic. The only zener I can find is one on the DC-DC
board, but nothing there is labled in the diagram. Help!

(I'm not considering modifying the recorder, just satisfying my
curiosity as to how the "plug-in power" works.)

Look at pins 20, 21, and 22 of IC101 in the other channel. Pin 20 goes
to the zener. Pin 20 of IC201 would also go to the same zener,
although it is not shown explicitly because the two channels are
mostly identical (see the note "R-CH is the same as L-CH"). Pin 22 of
IC101 terminates in a capacitor, and is not used (?), whereas pin 22
of IC201 goes to the mike's power circuit and to the LED board.

Thanks again for the quick reply.

I'm stumped. I must be making some really dumb mistake. Looking at the
schematic, pin 20 of IC101 (left channel) goes across and down to an
unspecified pin in IC201, connecting to C138 and C305 on the way. I
don't see any zener nor any connection to one. I do see the capacitor on
pin 22 (C132) and how pin 22 of IC201 goes to the mike's power circuit.

AFAICT, there is only one zener. It regulates the power for both
channels.

Can you tell me where (grid coordinates) D301 is? I can't find it at all.

D301 is adjacent to C305, at coordinates E15. Right above all three
components is a label, "D301 HZ3ALL".

I'm viewing the schematics in the service manual and its supplement that
you gave us a link to. Am I missing something really obvious here? Or do
you have another diagram?

I'm looking at page 19 of the service manual.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
.

Relevant Pages

  • Re: Dell
    ... put finger to keyboard and composed: ... Got Got some power circuitry with a beeper. ... 110 Twinalert PC Power and Cooling Systems. ...
    (sci.electronics.repair)
  • Re: Adapting a microphone to remote phantom power
    ... put finger to keyboard and composed: ... I was looking at the manual supplement, ... the zener has been deleted from the parts list in the ...
    (sci.electronics.repair)
  • Re: Viewsonic schematics VX910
    ... finger to keyboard and composed: ... What is the rating of the monitor's power ... How much power does the backlight require? ...
    (sci.electronics.repair)
  • Re: laptop motherboard power remain on
    ... put finger to keyboard and composed: ... I read the same value of a v+ power input. ... That's an RS232 interface chip. ...
    (sci.electronics.repair)
  • Re: Very hot hot zener diode in NAD T762
    ... put finger to keyboard and composed: ... some of these diodes do run hot. ... Why not replace the single 5V1 zener with two series 2V7 zeners? ...
    (sci.electronics.repair)