6v & 90v DC Power supply

[James F. Mayer]

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.

 

[Joerg]

Hello James,

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. ...

You can build a step-up or flyback with the LM3478. Tough to solder
though, it's a TSSOP package. Don't know what current you need but just
pick a suitable FET.

For 6V I'd use a buck regulator instead of wasting 50% of the energy in
a series regulator.

Regards, Joerg

 

[Bill Turner]

ORIGINAL MESSAGE:

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.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I'd use one of those small inexpensive inverters which put out 120vac
and then use a conventional transformer/rectifier system. You can pick
up the inverter at any truck stop.

73, Bill W6WRT

 

[Highland Ham]

I'd use one of those small inexpensive inverters which put out 120vac

and then use a conventional transformer/rectifier system. You can pick
up the inverter at any truck stop.

============================
Those 'inexpensive inverters' might need some attention in respect of
the 'hash' they create , possibly causing interference in the receiver.

Frank

 

[Fred Bloggs]

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. ]

90V @70ma is only 6.3W and a step-up of no more than 90/12=7.5. This
would be something like a 24VAC center-tapped transformer turned
backwards with a multivibrator drive of the secondary at 50-60Hz and the
usual primary is rectified and capacitor filtered to produce the 90V.
Since the reflected current is only about 1/2A, you can then feedback
the rectified HV to drive an error amp that regulates the center tap
down to 9V or so.

 

[John Crighton]

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 James,
Speaking as a cheapskate ham/hobbyist, how
about salvaging parts from a computer power supply.
Find a dud power supply for free at computer
shops/dumpsters/rubbish tips/roadside etc.
Salvage the TL494 integrated circuit that can
be found in many computer power supplies.

You could build a 90 Volt power supply as
Ray Robinson has down here
http://www.shlrc.mq.edu.au/~robinson/Information/Inverter_4W.html

Here is a link to the TL494 Data sheet
http://focus.ti.com/lit/ds/symlink/tl494.pdf

This link tells you how to use the TL494 IC
http://focus.ti.com/lit/an/slva001d/slva001d.pdf

Use another TL494 in a buck converter for your
12 Volts to 6Volts power supply module.
Look at the bottom of this page for more info.
http://focus.ti.com/docs/prod/folders/print/tl494.html
Your 7806 is probably a better idea, saves a lot
of messing about.
Or
you could use the guts of a mobile phone
car charger. The charger that fits into the
cigarette lighter in a motor car.
You can find them in pawn shops for a dollar
or two. Dud ones even cheaper. Usually
just a broken connection from rough handling.
http://www.onsemi.com/pub/Collateral/MC34063A-D.PDF
Look at page 7 Figure 10 Step down converter.

In the few car phone chargers that I opened,
the IC was a MC34063 and the schematic was
very similar to that shown in figure 10
Just change R1 or R2 slightly so that you
get 6 Volts out.
You may have to check/change the value of
resistor Rsc to be closer to that shown in figure 10
You might even get away with not changing the
inductor. Try it and see if the original inductor
works well enough for you.

A ton of reading, bits and pieces for free
or dirt cheap.
What a great hobby, this is James, eh!

Regards,
John Crighton
Sydney

 

[John Crighton]

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

 

[Bill Turner]

ORIGINAL MESSAGE:

Those 'inexpensive inverters' might need some attention in respect of
the 'hash' they create , possibly causing interference in the receiver.

Frank

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

True for any kind of inverter.

73, Bill W6WRT

 

[Bill Turner]

ORIGINAL MESSAGE:

Hello James,
Speaking as a cheapskate ham/hobbyist, how
about salvaging parts from a computer power supply.
Find a dud power supply for free at computer
shops/dumpsters/rubbish tips/roadside etc.
Salvage the TL494 integrated circuit that can
be found in many computer power supplies.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Excellent info, John. Thanks!!

73, Bill W6WRT

 

[RST Engineering]

Do it the way the original radio did it -- dynamotor. You can still find
them in the back room at a lot of military surplus electronics junk stores.

Jim

 

[Joerg]

Hello Jim,

Do it the way the original radio did it -- dynamotor. You can still find
them in the back room at a lot of military surplus electronics junk stores.

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

 

[David Harmon]

On Tue, 27 Dec 2005 05:58:18 GMT in sci.electronics.design,
[email protected] (John Crighton) wrote,

This link tells you how to use the TL494 IC
http://focus.ti.com/lit/an/slva001d/slva001d.pdf

So why is the guy from TI showing NTE transistors for the power
switching? Nothing in the TIP line good enough?

 

[Rich Grise]

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.

So, put the cam thingie on some sort of spindle, with some kind of
depth gauge thingie, (maybe a slide pot and a stick), and map the
disks, and just make the same waveform from ROM?

Good Luck!
Rich

 

[Joerg]

Hello Rich,

So, put the cam thingie on some sort of spindle, with some kind of
depth gauge thingie, (maybe a slide pot and a stick), and map the
disks, and just make the same waveform from ROM?

That has been tried many times. Several rather expensive electronic
organs have come out claiming to emulate a Hammond. So far the real
enthusiasts do anything to get their hands on the real thing, knowing
that there will come a day when the last one croaks. IIRC it was Paul
Shaffer (the guy who makes the music at david Letterman's show) who
spent the equivalent of a luxury car to have one restored.

Regards, Joerg

 

[James F. Mayer]

On Tue, 27 Dec 2005 05:58:18 GMT in sci.electronics.design,
[email protected] (John Crighton) wrote,

So why is the guy from TI showing NTE transistors for the power
switching? Nothing in the TIP line good enough?

Probably good enough for his measly 32 volts. I need to modify that
circuit to work on outputs of 90 volts and 6 volts.

 

[Rich Grise, but drunk]

Hello Rich,


That has been tried many times. Several rather expensive electronic
organs have come out claiming to emulate a Hammond. So far the real
enthusiasts do anything to get their hands on the real thing, knowing
that there will come a day when the last one croaks. IIRC it was Paul
Shaffer (the guy who makes the music at david Letterman's show) who
spent the equivalent of a luxury car to have one restored.

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

cheers!
Rich

 

[Joerg]

Hello Rich,

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

Ok, I am not much of an expert on instruments or music in general. But a
Hammond organ can fill a living room with a sound that, with the eyes
closed, you'd think you are sitting in a cathedral. And lots of rock
bands wouldn't use anything else. That is why a lot of Hammonds have
been "sawed in halves" so they can be transported to the next gig. You
could even buy split versions built into professional transport cases.

Regards, Joerg

 

[Michael A. Terrell]

Hello Rich,

Ok, I am not much of an expert on instruments or music in general. But a
Hammond organ can fill a living room with a sound that, with the eyes
closed, you'd think you are sitting in a cathedral. And lots of rock
bands wouldn't use anything else. That is why a lot of Hammonds have
been "sawed in halves" so they can be transported to the next gig. You
could even buy split versions built into professional transport cases.

Regards, Joerg

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.

--
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

 

[Michael A. Terrell]

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

cheers!
Rich

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!

--
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 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