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:
Regards, Joerg
Stay away from early jukeboxes and old NCR cassh registers, too! :-)
Hello James,
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
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.
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.
electrical
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the
voltage
transistors.
HP6299A
Here's a reference to 'Silicon Chip' magazine, who ran some articles about these devices.
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:
Woops, here we go, found the one I was after:
Cheers.
Ken
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.
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. 73Chris snipped-for-privacy@arrl.net
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