6v & 90v DC Power supply

[Michael A. Terrell]

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

Stay away from early jukeboxes and old NCR cassh registers, too!

--
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 James,

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

Thanks! That is one big organ. The 20HP blower motor alone speaks
volumes. I wish we had one of these somewhere in California.

Regards, Joerg

 

[James F. Mayer]

Hello James,


Thanks! That is one big organ.

It is built into the whole building.


The 20HP blower motor alone speaks

volumes. I wish we had one of these somewhere in California.

It was in the Paramont Theater in Oakland California back in 1932.

 

[Rich Grise]

It is built into the whole building.

The 20HP blower motor alone speaks

It was in the Paramont Theater in Oakland California back in 1932.

"Installed in 1931 at a price of $20,000 this Mighty Wurlitzer enjoyed
only a brief period of glory before the theatre closed in 1932. By the
late 1950's, the organ was sold and placed in storage."
-- http://www.roaring20spizza.com/history.htm

But, wasn't $20K in 1931 dollars equivalent to about two mil nowadays?
=:-O

Thanks,
Rich

 

[Bart Rowlett]

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.

Probably the easiest is to obtain one of the original power supplies.

Most installations using the RT-70 were in conjunction with an RT-66/RT-67
or RT-68 and an audio distribution amplifier. A separate vibrator power
supply was supplied those cases where the RT-70 was used 'stand alone'.
One approach to homebrewing a vehicular power supply is to mimic the
original vibrator supply. Provide the heater supply through dropping
resistors and emulate the vibrator supply by building an inverter using a
pair of switching transistors and a junk 60 Hz power transformer.
Regulation isn't necessary if you get the right transformer. The only
thing the least bit tricky with this approach is properly snubbing the
primary leakage inductance to prevent destroying the switching transistors.

Probably the most compact approach is to build a flyback supply with both
a six and 90 volt output. Regulate the 6 volt output and let the 90 volt
output track. The advantage of the flyback supply is that it can be
designed to operate over a wide range of input voltages while maintaining
a regulated output. In addition, the overall size will be much smaller due
to the high switching frequencies (300 kHz typical) used by modern flyback
controller chips.

 

[Ken Taylor]

Probably the easiest is to obtain one of the original power supplies.

Most installations using the RT-70 were in conjunction with an RT-66/RT-67
or RT-68 and an audio distribution amplifier. A separate vibrator power
supply was supplied those cases where the RT-70 was used 'stand alone'.
One approach to homebrewing a vehicular power supply is to mimic the
original vibrator supply. Provide the heater supply through dropping
resistors and emulate the vibrator supply by building an inverter using a
pair of switching transistors and a junk 60 Hz power transformer.
Regulation isn't necessary if you get the right transformer. The only
thing the least bit tricky with this approach is properly snubbing the
primary leakage inductance to prevent destroying the switching transistors.

Probably the most compact approach is to build a flyback supply with both
a six and 90 volt output. Regulate the 6 volt output and let the 90 volt
output track. The advantage of the flyback supply is that it can be
designed to operate over a wide range of input voltages while maintaining
a regulated output. In addition, the overall size will be much smaller due
to the high switching frequencies (300 kHz typical) used by modern flyback
controller chips.

Here's a reference to 'Silicon Chip' magazine, who ran some articles about
these devices.
http://www.siliconchip.com.au/cms/A_30674/article.html

I recall seeing a commercial unit which was a semiconductor equivalent of
the vibrator, two AC132 transistors (IIRC) as a multivibrator running into a
transformer. The article above gives enough hints to be useful though.

Here's some other useful links:
http://www.radios.freeserve.co.uk/vibrators/vib.htm

Woops, here we go, found the one I was after:
http://www.vmarsmanuals.co.uk/newsletter_articles/vibrator.pdf
Circuit for the solid-state vibrator.

Cheers.

Ken

 

[John Fields]

I heard a decently accurate electronic piano sound long before I heard
anything remotely resembling the timber of a B3.

 

[clifto]

Not that I would be one to pass up a good straight line, but just in case...

Main Entry: tim·bre
Variant: also tim·ber /'tam-b&r, 'tim-; 'tam(br&)/
Function: noun
: the quality given to a sound by its overtones: as
a : the resonance by which the ear recognizes and identifies a voiced
speech sound
b : the quality of tone distinctive of a particular singing voice or
musical instrument
?tim·bral /'tam-br&l, 'tim-/ adjective

Source: Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc.

 

[Christopher Bucca]

I assume that you do not have the companion AM-65 audio amplifier?
Shame, because internal to that unit is a power supply (don't remember the
numbers now) that allowed you to operate the AM-65/RT-70 combo from 6, 12 or
24 volts depending on the power supply used. The usually supplied unit used
24 volts (Korean War American military standard elec system). If you can't
get the 12 volt version, modification instructions can be found in a 73
Magazine article called
"New Orders for the R-108" which was a companion receiver for the big
brother of the RT-70, the RT-68. R-108 used the same series of plug in
internal power supplies that the AM-65 did.
There was also a magazine article in the now defunct as well Ham Radio
mag titled "Get on Six Meters-The Easy Way". It dealt with a manpack 6
channel radio of Canadian ancestry that also needed 90 Volts. I have the
entire run of that magazine from 1969 to 1990 on cd. If I can figure out how
to extract the stuff off the disk, I'll email it to you. Now, the fee for
such information.....
You will regale me with tales of operation and modification of
aforementioned Olive Drab garbed electronic equipment!!! I'll email you
later from my own account so that you will get my real email address, or you
can use the arrl reflector. 73

Chris
[email protected]