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 Post subject: Majestic Super-B Current Supply Schematic
PostPosted: Oct Sun 14, 2018 6:46 am 
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Location: Camino, California
Am working on one of these, and I know they've been documented here fairly well, but I've redrawn the schematic, with slightly more clarity, for those who may be working on one.
The lower schematic shows numerals which correspond to the parts layout drawings featured on Page 741 of the Rider's combined vols. 1-3 under "Eliminators".

This shows the Standard and Super variants, which feature two variable compression resistors and the toggle switch between the two knobs.

http://www.martinihenry.com/temp/Majestic%20Super%20B%20Current%20Supply.pdf

http://www.martinihenry.com/temp/Rider%20p_%20741

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 Post subject: Re: Majestic Super-B Current Supply Schematic
PostPosted: Oct Mon 15, 2018 6:14 pm 
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Thanks, I will need this one day.

Jeff

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 Post subject: Re: Majestic Super-B Current Supply Schematic
PostPosted: Oct Mon 15, 2018 8:10 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: S. Dartmouth MA 02748-1225 USA
My first estate clean out included six of these Majestic B's. Other brands are the Kokomo, Exide, Acme, most using the BH rectifier that are getting had to find that still work. I recall "trying" to create a simple solid state replacement. Since I did not want to get into the tar box, the silicon rectifier delivered enough current to take out one of the chokes. So, I fell back on BH's I had... Getting replacement for the carbon pile rheostats is another issue. Some of these rheostats where built with drawn brass housings of the wrong brass alloy the would split open spilling out all the graphite... Often the supplies are found in a rusted condition, have spent their life next to the lead/acid 6 volt "A" battery...

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 Post subject: Re: Majestic Super-B Current Supply Schematic
PostPosted: Oct Tue 16, 2018 9:31 pm 
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Chas wrote:
Often the supplies are found in a rusted condition, have spent their life next to the lead/acid 6 volt "A" battery...



And NEVER with their tops around. In fact, I've never seen one in person, only in photos!

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 Post subject: Re: Majestic Super-B Current Supply Schematic
PostPosted: Oct Tue 16, 2018 9:34 pm 
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Would you all agree that the .1 uf cap coming off one side of the main and forming the ground, would best be replaced by an actual connection to ground via a 3-wire cord?

Maybe the addition of a RFI suppressor safety cap across the line on the input side would be prudent, too?

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 Post subject: Re: Majestic Super-B Current Supply Schematic
PostPosted: Oct Tue 16, 2018 10:00 pm 
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N6MKC wrote:
Would you all agree that the .1 uf cap coming off one side of the main and forming the ground, would best be replaced by an actual connection to ground via a 3-wire cord?
Maybe the addition of a RFI suppressor safety cap across the line on the input side would be prudent, too?
No, Only improvement would be to use safety type cap and reduce to .005mf.

The Majestic was intended to be used in all 20's battery radios. Some of these radios have common grounds to the filament connected to the B-. Using a 3-wire cord will bring the home ground system into the radio for an antenna effect along with the noise.
The OEM bi-polar plug is used to be able to choose with side of line gets coupled to reduce hum... I would suggest an ELMENCO fused plug, 1 amp fuses for fire protection, the plug is reversible.

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 Post subject: Re: Majestic Super-B Current Supply Schematic
PostPosted: Oct Tue 16, 2018 11:44 pm 
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Okay, didn't consider that. Thanks for the tips!

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 Post subject: Re: Majestic Super-B Current Supply Schematic
PostPosted: Oct Wed 17, 2018 12:28 am 
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If, diodes are used to sub for the BH, consider using an old tube base, include at least a 100 ohm 5 watt resistor in series with the paired cathodes.

It is possible the diodes could create a switching buzz. If that happens use a .001/1kv general purpose disc ceramic cap across each diode. As said, the whole works will fit into a tube base. Be sure to use a 4-pin base that has the alignment pin as the pins are not polarized on the socket, just the sleeve.

Please do not attempt to take apart the carbon compression rheostats or squirt any "cleaner" into them. If the rheostats seem erratic, remove them, back-off the knob but do not remove. Carefully tap the body of the rheostat on the bench rotate position and tap a few more times. That should loosen up the carbon and redistribute. Re-install, it should be fine...
A cracked brass shell can be carefully patched to keep the carbon in or replace the rheostat...

They are full of crumbling rubber covered stranded wire, that will have to go...

The Majestic power supply is often overlooked as it does not have an "A" supply.

For years I have used these with a charger/"B" supply relay and a storage battery to run my display radios. The transfer relay has a coil that goes in series with the "A" supply, normal contacts power the trickle charger. When the radio is turned on the current transfers the relay and the charging stops and the "B" eliminator goes on...

YMMV

Chas

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 Post subject: Re: Majestic Super-B Current Supply Schematic
PostPosted: Sep Tue 24, 2019 2:11 am 
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Would it be a good idea to remove the (2) 0.1uF capacitors across the HV secondary winding if 1N4007 diodes were used to replace the Raytheon BH tube? I suppose a series dropping resistor would be needed with silicon rectifier replacements. What would be a good value to use?
WB6FBF


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 Post subject: Re: Majestic Super-B Current Supply Schematic
PostPosted: Sep Tue 24, 2019 3:51 am 
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Rod Clay, Would it be a good idea to remove the (2) 0.1uF capacitors across the HV secondary winding if 1N4007 diodes were used to replace the Raytheon BH tube?

I would not remove the caps, there is a possibility of switching noise from the diodes. The BH did make noise that is why the caps.

I suppose a series dropping resistor would be needed with silicon rectifier replacements. What would be a good value to use?

Start with 100 ohms, load the AMP B+ with enough resistance to draw say 60ma. The resultant voltage should not be more than 135, add that to the 100 ohms.

WB6FBF

Chas

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 Post subject: Re: Majestic Super-B Current Supply Schematic
PostPosted: Nov Tue 19, 2019 1:31 am 
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1. What voltage ratings are recommended for the 0.1uF caps? I have a Raytheon BH tube (used) coming in the next few days. One of the later production UX based short shell types. It has a nice clear bulb. I hope that is a good sign and it is good. If not I will try for a (hopefully) NOS BH tube next time.
2. What is the maximum value of the voltage control primary rheostat as used on the "Master" and "Special Master" Models? I have a B Battery Eliminator that uses a "V.C." rheostat on the primary winding (mine uses a 400 Ohm wire wound type rheostat).
3. What is the largest value input filter cap recommended with BH tubes? The supply I am currently working on has just a single section filter but does use a large filter choke. One of the filter caps (Stromberg Carlson) is a metal cased 5UF (no voltage rating) and is in fairly good shape for its age (90+ years). The other one is a paper cased unit (same physical size) and is unmarked. I am guessing it was 5-6 uF and it is in poor condition now. I didn't make any notes on which one was the input cap so I am not sure what value to use.
73, Rod WB6FBF


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