6v & 90v DC Power supply

[Rich Grise, but drunk]

People like the old Hammond organs like the B3 because the can't go
out of tune. The mechanical tone generator makes sure of that. They
only sound like a skating rink in, get this, A SKATING RINK!

Well, being the insufferabley pedantic researcher that I am, I came
up with a page:
http://en.wikipedia.org/wiki/Hammond_organ

that about a third of the way down, says:
"... Accurate imitation of the Hammond sound with simple electronic
circuitry was difficult, because the subtly-changing phase relationships
between tonewheels could not be easily replicated...."

OK, fair enough.

I guess a piano is even harder - they don't even reproduce well from a
live recording!

Cheers!
Rich

 

[Joerg]

Hello Rich,

that about a third of the way down, says:
"... Accurate imitation of the Hammond sound with simple electronic
circuitry was difficult, because the subtly-changing phase relationships
between tonewheels could not be easily replicated...."

OK, fair enough.

Even with complicated electronics it wasn't. IIRC it was Suzuki-Hammond
which came out with the XK2 and then the XK3. Those are pretty elaborate
synthesizer organs. But according to the experts it just ain't the same.

Regards, Joerg

 

[w_tom]

Buy a DC-DC converter that includes other protection
features (ie overvoltage and overcurrent protection) and
outputs known parameters (ie ripple voltage). I doubt you
will find a single DC-DC converter for both voltages. But a
small converter for each voltage should work. Many sources
including this one that just arrived on my desk -
www.astrodyne.com .

BTW, power from automotive systems should also worry about
load dump. Technically load dump can be a transient as much
as 270 volts on a 12 volt system. In reality, such events may
only be 50 volts or less. Transients that would not damage
other automotive electronics already designed for this rare
and so destructive event.

That is a problem with some regulators such as 78xx series.
Maximum voltage is typically not sufficient for automotive
purposes - would require additional protection.

 

[Rich Grise]

Hello Rich,


Even with complicated electronics it wasn't. IIRC it was Suzuki-Hammond
which came out with the XK2 and then the XK3. Those are pretty elaborate
synthesizer organs. But according to the experts it just ain't the same.

It seems like, no matter how closely you try to mimic the waveform of a
real instrument, there's always something that says, "This is electronic."
Or, maybe more accurately, "This is not real." ;-)

Cheers!
Rich

 

[Rich Grise]

On Wed, 28 Dec 2005 02:20:02 -0500, w_tom wrote:

.

BTW, power from automotive systems should also worry about
load dump. Technically load dump can be a transient as much
as 270 volts on a 12 volt system. In reality, such events may
only be 50 volts or less. Transients that would not damage
other automotive electronics already designed for this rare
and so destructive event.

That is a problem with some regulators such as 78xx series.
Maximum voltage is typically not sufficient for automotive
purposes - would require additional protection.

This is what transzorbs
http://www.vishay.com/docs/88301/15ke.pdf
and hash chokes are for.

I'm not affiliated with Vishay, formerly General Semiconductor,
just a satisfied customer. I've used them to protect circuits
against the transients caused by a 5 KV arc in an ion gun.

Cheers!
Rich

 

[James F. Mayer]

Hello again James,
I just came across this site while looking
for something else.

http://web.telia.com/~u85920178/use/tubepsu.htm
Look at the the 6V AC from 12 V DC. Nifty!

Here is another
http://www.i4at.org/lib2/inverter.htm
You want DC out so you will have to fit a bridge rectifier
and filter capacitors to the output of the transformer
just like Harry Lythall's circuit above.

Regards,
John Crighton
Sydney

I'm going to build a modified Lythall but I need to determine what the
wattage of the 330 Ohm resisters would be. I'm thinking they should be
fairly high.

 

[w_tom]

Actually SGS Thompson that specifically makes protectors for
automobiles and load dump (do what 'too small' transzorb would
also do) acknowledge in their app notes that:

" ... there are several existing products products able to
clamp this overvoltage at the board level, for example the
LDP24 or RBO series. The protection at the alternator level
is a quite new concept and all the technical problems do not
seem to be completely solved."

This would explain why an 'up to 270 volt' transient is not
routinely observed. Still, automotive electronics typically
should withstand about 50 volts ballpark without damage.
Transzorb could be but one part of that protection system. Or
a DC to DC converter that specifically has such protection
could be obtained. A weakness of Transzorbs are their low
power abilities. The advantage - those avalanche diodes can
handle so much more power than conventional zeners. My first
design that used Transzorb was maybe 20 years ago. GS was
selling Transzorbs even long before then.

Load dump does not occur frequently. But that one time can
be so destructive. Best to consider load dump when attaching
any electronics to automotive power because even trivial
protection does so much.

 

[gb]

I need to generate 6v DC and 90v DC from a 12v DC automotive
electrical system to power an RT-70A/GRC surplus military radio. I need
about 250 mA at +6 volts and about 75 mA at +90 volts. I was thinking
about using the guts from an old battery back up but it would be a bit of
a kluge. Are there any 90 volt regulators in the 78xx series? How do I
get the voltage up to where I can get something that I can get the 90
volts from. Getting the 6 volts doesn't seem to be a problem. A 7806 off
the battery should work for that unless any of you can see a problem doing
that. Maybe the common common would be a problem. Right now I'm running
it off of an HP6299A and an HP6236B with commons jumpered. I'd like to be
able to go portable with it.

You will find a number of solutions (e.g. battery radios) in the Usenet
group: rec.antiques.radio_phono

gb

 

[Joerg]

Hello Rich,

It seems like, no matter how closely you try to mimic the waveform of a
real instrument,...

I have a feeling that this is exactly the problem. Engineers try to
mimic the output waveform instead of looking how the real instrument is
built. If they did that, they'd try to emulate all the individual parts
and pieces.

Regards, Joerg

 

[clifto]

"... Accurate imitation of the Hammond sound with simple electronic
circuitry was difficult, because the subtly-changing phase relationships
between tonewheels could not be easily replicated...."

OK, fair enough.

I guess a piano is even harder - they don't even reproduce well from a
live recording!

I heard a decently accurate electronic piano sound long before I heard
anything remotely resembling the timber of a B3. Still haven't heard
anything that sounds exactly like a B3 (other than an A100 or another
B3).

 

[Rich Grise]

Hello Rich,


I have a feeling that this is exactly the problem. Engineers try to
mimic the output waveform instead of looking how the real instrument is
built. If they did that, they'd try to emulate all the individual parts
and pieces.

Regards, Joerg

Yabbut, how many gyrators and phase shifters and stuff does it take to
model, for example, a bowed string? ;-)

Thanks!
Rich

 

[Spehro Pefhany]

Yabbut, how many gyrators and phase shifters and stuff does it take to
model, for example, a bowed string? ;-)

Thanks!
Rich

Whatever it is, if it has to come out of speakers it isn't going to
sound quite right.


Best regards,
Spehro Pefhany

 

[Joerg]

Hello Spehro,

Whatever it is, if it has to come out of speakers it isn't going to
sound quite right.

In case of a Hammond organ it might since it has a speaker. Of course,
it's a tube amp but that is a whole other matter which alone could make
this thread balloon.

It'll take a lot of gyrators and filters but considering that one can
buy a 400MHz DSP for less than a crate of beer these days it should be
feasible. In case of our piano the DSP still couldn't win. The piano
doesn't need power. Not even light since it has its own candles.

Regards, Joerg

 

[nothermark]

Hello Jim,


But then be prepared for some major restoration. The bearings of a lot
of these are nearly shot, mostly from sitting in an attic for decades.
It's like old pond pumps. They run fine for a few weeks and then the
racket increases, some weird noises appear, things get hot and they
seize up.

I restored an old Hammond organ. These generate the tones in a similar
manner. A motor (plus a start motor) and over a hundred pickup coils on
the long secondary shaft. 20 hours of hard work got it going again but
we have accepted the fact that some of the bearings are pretty much over
the hill. So it needs 2-3 starts to coax it to run without that mild
screeching in the background. Getting spare parts from a company that
went out of business 30 years ago just isn't going to happen.

Regards, Joerg

what kind of bearings? - ball bearings are like tubes - thay have
numbers and substitutes. Bronze bearings are routinely made by
machinists. Babbit is hardest as it is poured in place but you might
be better off replacing them with something else like bronze. Bearing
technology is not all that complicated if you poke into the right
group of folks.

 

[Spehro Pefhany]

Hello Spehro,

In case of a Hammond organ it might since it has a speaker. Of course,
it's a tube amp but that is a whole other matter which alone could make
this thread balloon.

Don't some of them have rotating speakers?

It'll take a lot of gyrators and filters but considering that one can
buy a 400MHz DSP for less than a crate of beer these days it should be
feasible. In case of our piano the DSP still couldn't win. The piano
doesn't need power. Not even light since it has its own candles.

Regards, Joerg

Sure, but can you flip a switch and be playing the flute or er-hu?


Best regards,
Spehro Pefhany

 

[Michael A. Terrell]

Don't some of them have rotating speakers?

That is a "Leslie" speaker. I have to service the one at my church.
The bearings are shot.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Joerg]

Hello Spehro,

Don't some of them have rotating speakers?

That was an accessory item, a Leslie speaker. A huge cabinet with a
rotating speaker on slide contacts, motors, gears. We don't have one and
we wouldn't know where to put it anyway. The amp under the organ is only
20W AFAIK with a huge speaker. That's real watts, not PMPS or whatever
kids call "power" these days. Meaning it can make the sound of a large
pipe organ and not lose steam after holding the bass chord for more than
a hundred milliseconds.

Sure, but can you flip a switch and be playing the flute or er-hu?

Actually you could. Ours doesn't have the flute presets but drawbars.
With these you can set the ratio of all the harmonics and the manual
shows the settings for a lot of common instruments. Some sound real,
some don't. But we also have a small environmentally friendly (zero
electric power, made from wood) flute. Not that I can play it but my
wife can.

Regards, Joerg

 

[Joerg]

Hello Michael,

That is a "Leslie" speaker. I have to service the one at my church.
The bearings are shot.

If you get stuck or need a rare part talk to Bob:
http://www.tonewheel.com/services.htm

That's where I got my Hammond oil. Very friendly and helpful. His dog
was very friendly as well, he greeted me first.

Regards, Joerg

 

[James F. Mayer]

Hello Spehro,


That was an accessory item, a Leslie speaker. A huge cabinet with a
rotating speaker on slide contacts, motors, gears. We don't have one and
we wouldn't know where to put it anyway. The amp under the organ is only
20W AFAIK with a huge speaker. That's real watts, not PMPS or whatever
kids call "power" these days. Meaning it can make the sound of a large
pipe organ and not lose steam after holding the bass chord for more than a
hundred milliseconds.


Actually you could. Ours doesn't have the flute presets but drawbars. With
these you can set the ratio of all the harmonics and the manual shows the
settings for a lot of common instruments. Some sound real, some don't. But
we also have a small environmentally friendly (zero electric power, made
from wood) flute. Not that I can play it but my wife can.

Regards, Joerg

The Wurlitzer down at Roaring 20s Pizza and Pipes
http://www.roaring20spizza.com/ actually plays instruments like horns and
drums.

 

[Joerg]

what kind of bearings? - ball bearings are like tubes - thay have
numbers and substitutes. Bronze bearings are routinely made by
machinists. Babbit is hardest as it is poured in place but you might
be better off replacing them with something else like bronze. Bearing
technology is not all that complicated if you poke into the right
group of folks.

More like bronze bearings. But it ain't that easy. When you take it
apart you end up with hundreds of pieces. It is the most complicated
concoction of moving mechanical parts I ever encountered. The photo at
near bottom show just a small part of it:
http://www.myplanet.net/x77dude/photos.html

Regards, Joerg