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Simon's flea market find #178967 06/18/08 12:37 PM
Joined: Aug 2001
Posts: 7,520
pauluk Offline OP
From SimonUK:

Thought this might be suitable for the nostalgia pics. See if anyone can I.D. it.

Got some time to myself a week ago Sunday and went to Ayr market (the local flea market). I returned home with the little gem in the attached pics much to my wifes delight. The guy only wanted £1 for it (nearly $2).

As you can see there are three commutators low tension at one end with high tension next to it and mid tension at the other end. Applying 12vdc to the L.T. brushes gives 360vdc at the mid and well over 600vdc at H.T. My 1kv dvm decided it didn't want to work on the 1000v range and all my others are 600vdc max. As you can see from the tag its a TYPE H.164, there are the remnants of some sort of stamp in the centre of the tag, there's another round stamp on the back RLP 272. The field windings are shunt connected to the LT commutator but going by the length of the leads I reckon there might have been some sort of field regulator used in its original configuration. I'm guessing it was mechanically driven to provide power for the vacuum tubes in some sort of portable radio application.

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Re: Simon's flea market find [Re: pauluk] #178980 06/19/08 04:26 AM
Joined: Jul 2005
Posts: 223
aussie240 Offline
This device goes under different names; "dynamotor", "genemotor" or just plain "rotary converter". These were very common in military gear, and this example looks of the WW2 era. They were particularly common in aircraft and other mobile applications to provide the high tension for vacuum tube equipment from a low voltage DC supply; typically 12V(road vehicle) or 28V(aircraft) This one would be from a radio transceiver. The lower voltage output is for the receiver and audio stages while the higher voltage powers the transmitter output valve.
Rotary converters like this have also been made to produce AC output with slip rings substituted for the brushes on the output winding. These were used where the output had to be a sine wave or of high power, as vibrator or early transistor inverters give out a square wave of limited power. These days even ordinary bipolar transistors are becoming obsolete for voltage conversion, with more efficient MOSFET's taking their place.

Re: Simon's flea market find [Re: aussie240] #178981 06/19/08 12:08 PM
Joined: Sep 2001
Posts: 806
NJwirenut Offline
The stub shaft and mounting flange were probably used to attach a blower wheel to cool the equipment.

Re: Simon's flea market find [Re: NJwirenut] #179012 06/21/08 06:31 AM
Joined: Aug 2001
Posts: 7,520
pauluk Offline OP
I'd agree, it certainly looks like the type of dynamotor which was used extensively at one time to power valve/tube equipment in mobile applications.

Whether the HT voltages you obtained would be those which were originally specified for this unit is hard to say though. 600V D.C. wouldn't be at all unreasonable for high-power transmitter finals, but 360V sounds a little on the high side if it was for feeding the general receiver and signal stages. If used for R/T, it might have been used for supplying power to the modulator, which on an A.M. transmitter needs a substantial amount of power (about 50% of the power needed to generate the R.F. carrier). The other stages would then be run via decoupled reduced voltages, as in line-powered equipment.

Re: Simon's flea market find [Re: pauluk] #179025 06/21/08 06:34 PM
Joined: Oct 2004
Posts: 50
SimonUK Offline
The voltage was higher than 600V D.C. It was out of range on my multimeter. My 1000V meter didn't want to play when I tested it. I'm pretty certain there was an AVR used to regulate the voltage as one of the field wires is way longer than the other. It'll make an interesting wee display at the next vintage rally I attend with my old generators and stationary engines.

Here's a link to my youtube channel where I'm starting to put some videos of my stuff.

Re: Simon's flea market find [Re: SimonUK] #179033 06/22/08 07:23 AM
Joined: Jul 2005
Posts: 223
aussie240 Offline
There is the possibility of the motor portion being for 6V and not 12, especially if it was for a car radiotelephone. Some Genemotors were meant to be used with a carbon pile regulator. I have one such item in my collection. It's meant for a 24 (28V) supply with carbon pile regulator which drops the supply to 18V for which the input is designed. A carbon pile regulator is an electromechanical voltage regulator that works on the principle of carbon discs being pressed together at a greater or lesser pressure to control the resistance. What forces the discs together is a spring with a solenoid to offset the spring pressure. Increase the solenoid voltage and carbon pile resistance goes up.
So, the carbon pile is in series with the genemotor input with the solenoid across the genemotor input. If supply voltage rises, which it will when the output load is small, then more current into solenoid, carbon pile resistance increases and genemotor input drops. Simple and effective enough for the circuitry it powers. Voltages of 300 and 600 are certainly not unsual either. I use 24v or 18v genemotors on 12V and get a proportionally lower output which is more convenient for typical valve receiving applications.
There is indeed a blower attached to many units, and sometimes a channel switching mechanism in aircraft transceivers also coupled to the drive shaft.


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