Hello Michael,

They have a Hammond B3 at my church, with the Leslie speaker. There
is another model Hammond in storage that needs a lot of work. Someone
had it on their screened in porch and the finish is ruined, but it still
plays.


Just make sure that the oiling intervals are religiously kept. If the
other one still plays be grateful for that. If it's the same model or
nearly the same keep it. Even if the finish is beyond repair some day
you might be really thankful to be able to scavenge its tone generator
once the TG on the other Hammond goes.

A bad finish is often easy to fix compared to taking the whole machinery
apart. Ours has a superb finish condition but it had been run dry for
more than a decade before it was given to us. So the TG is quite worn :-(

Actually it was so bad that when I was done it gulped almost two cans of
Hammond oil.

Some words of caution: The rectifier tube of the amp in the bottom is
located pretty close to the back and it gets freaking hot. I would take
care that the organ is never placed against a curtain or other flammable
material and that nobody stores any stuff behind it. The power cord on
ours almost crumbled in my hands and when attemting to swap it I
discovered that this instrument did not have a single fuse. So I made a
nice box with fuse and IEC connector.

Regards, Joerg

http://www.analogconsultants.com

On Wed, 28 Dec 2005 01:34:30 +0000, Michael A. Terrell wrote:
"Rich Grise, but drunk" wrote:

Well, tastes vary, but really! Who wants a music box that makes it
sound like you're at a skating rink? ;-P

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

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

http://www.analogconsultants.com

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.

"James F. Mayer" wrote:
Probably good enough for his measly 32 volts. I need to
modify that circuit to work on outputs of 90 volts and 6 volts.

On Wed, 28 Dec 2005 02:42:58 +0000, Joerg wrote:

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.


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

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

On Wed, 28 Dec 2005 02:20:02 -0500, w_tom top-posted:
....
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" wrote:
Probably good enough for his measly 32 volts. I need to
modify that circuit to work on outputs of 90 volts and 6 volts.

"John Crighton" wrote in message
...
On Tue, 27 Dec 2005 02:02:15 GMT, "James F. Mayer"
wrote:

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.


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.

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.

Rich Grise wrote:
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. :-)

"James F. Mayer" wrote in message
nk.net...
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

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

http://www.analogconsultants.com