On 4/14/2009 4:58 AM Eeyore spake thus:
Aha! So much for relying on Wikipedia as a reliable source of information.
-- Save the Planet Kill Yourself - motto of the Church of Euthanasia (http://www.churchofeuthanasia.org/)
On Mon, 13 Apr 2009 23:36:55 +0100, "Dave Plowman (News)" put finger to keyboard and composed:
Maybe these two examples (Method 1 and Method 2, also reproduced at the epanorama site) explain it better:
The same DC current flows from hot to ground, and cold to ground. Therefore the current flowing between hot and cold is zero.
- Franc Zabkar
-- Please remove one \'i\' from my address when replying by email.
It's fine. But the Wiki piece gives a good description for those who don't need to know how to do it.
--
*Real women don\'t have hot flashes, they have power surges.
Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
On 4/11/2009 1:48 PM Franc Zabkar spake thus:
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.)
-- Save the Planet Kill Yourself - motto of the Church of Euthanasia (http://www.churchofeuthanasia.org/)
Go and take a look. I am a registered contributor.
Graham
Correct. Hence minimising any noise contribution from the phantom PSU. Having said which they are usually very well regulated anyway.
Graham
On 4/15/2009 8:11 AM Eeyore spake thus:
Yes, I see you seem to be the entity known as "Pasoundman" there. And looking through your "contributions", I can see you tried to muck up the article on total harmonic distortion, resulting in a page that would have completely baffled anyone going there looking for information on the subject:
However, that edit, which the subsequent editor termed "vandalism", was quickly reverted (in less than an hour), and your content is gone to this day:
-- Save the Planet Kill Yourself - motto of the Church of Euthanasia (http://www.churchofeuthanasia.org/)
On Tue, 14 Apr 2009 16:08:57 -0700, David Nebenzahl put finger to keyboard and composed:
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.
- Franc Zabkar
-- Please remove one \'i\' from my address when replying by email.
On 4/15/2009 1:26 PM Franc Zabkar spake thus:
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.
Can you tell me where (grid coordinates) D301 is? I can't find it at all.
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?
-- Save the Planet Kill Yourself - motto of the Church of Euthanasia (http://www.churchofeuthanasia.org/)
On Wed, 15 Apr 2009 14:47:38 -0700, David Nebenzahl put finger to keyboard and composed:
AFAICT, there is only one zener. It regulates the power for both channels.
D301 is adjacent to C305, at coordinates E15. Right above all three components is a label, "D301 HZ3ALL".
I'm looking at page 19 of the service manual.
- Franc Zabkar
-- Please remove one \'i\' from my address when replying by email.
On 4/15/2009 3:00 PM Franc Zabkar spake thus:
Ack! No wonder: I was looking at the manual supplement, which omits the zener. Like I said, a dumb mistake. Thanks!
-- Save the Planet Kill Yourself - motto of the Church of Euthanasia (http://www.churchofeuthanasia.org/)
On Wed, 15 Apr 2009 15:16:48 -0700, David Nebenzahl put finger to keyboard and composed:
As you say, the zener has been deleted from the parts list in the supplement, yet pin 20 of the IC is still sitting at 2.6V. Maybe the potential divider inside the IC sets the voltage.
- Franc Zabkar
-- Please remove one \'i\' from my address when replying by email.
I guess you never saw any of the battery powered tube hearing aids? They used less power than a mic preamp, due to their directly heated filaments.
-- You can\'t have a sense of humor, if you have no sense!
I'm no expert on valves, but perhaps a type suitable for a low fi device like a hearing aid might be somewhat lacking in a mic? Good noise performance is difficult to achieve with valve mics - which may not be a consideration if used as a close vocal mic etc - but can well be for classical stuff.
--
*There are two sides to every divorce: Yours and shit head\'s*
Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
Stick your head back up your ass, with your arrogance. You aren't the only one to ever work in a recording, or broadcast studio. As far as costs on fiber, I'm on the other side of the world, and it wouldn't help you. Find a local supplier and see what you need. No matter what I post, you will find fault with it simply to be an ass.
I want no favors from you nor do I really give a damn, now that I no longer design studios or communication systems. The only reason I was reading this newsgroup was to help where I could, but the group had turned into a bunch of know it all hacks. At one time it was a good place to share information, and people wanted to help. Well, enjoy the shit hole you've turned it into.
-- You can\'t have a sense of humor, if you have no sense!
I actually pulled apart a tube hearing aid as a kid. The whole hearing aid was around the size of a packet of cigarettes, & the tubes were maybe half the size of a cigarette. I have no idea whether or not they did anything unusual to heat the filaments.
--
W
. | ,. w , "Some people are alive only because
\\|/ \\|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------
Directly heated filaments don't have a separate cathode, and require a lot less current to operate. That hearing aid would be worth a lot of money to a collector these days.
Motorola built portable two way radios with direct heated filament tubes to extend battery life, plus the fact that they heat n a fraction of as second, you can shut down the entire transmit section while monitoring the base station. The US military was still using them for the MPs into the '70s because they were rugged, and heavy. They would survive if the MP had to subdue someone, and it hid the ground.
-- You can\'t have a sense of humor, if you have no sense!
It's long gone, I'm afraid.
That's pretty impressive for a gizmo with tubes in it. ;^)
--
W
. | ,. w , "Some people are alive only because
\\|/ \\|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------
I figured that. They were rare when they were new, and very few survived when the early solid state versions hit the market.
The tubes had a small spring that shock mounted them into their inline sockets, and the tubes were similar to those developed for early missile guidance systems. The ones used in a missile were soldered in, while the portable radios used special sockets. I still had a couple sets of the sub miniature tubes from damaged radios I junked for the potted IF filters.
Some radios even survived being used as a replacement for their nightstick when it was taken by a suspect. Those rounded steel cases leave nasty bruises. :)
-- You can\'t have a sense of humor, if you have no sense!
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