Input from another engineer on a
good approach is welcomed...
.
My Experiment: I will
observe the voltage ripple on an oscilloscope using a 473 ohm 50 Watt
load resistor in place of the 106 speaker. The before measurement will
be like a stock 106 and after is with the multiple 100uf filter
capacitors applied as seen in the graphic below.
Hello Seoul,
So. Korea. I am happy someone on planet earth finds my current project
interesting. I had to order another transformer through Amazon which has
isolation 115vac to 115vac for $20, the original one I bought ($45)
doubled the voltage but ended up not being isolated primary to secondary,
dangerous! Still need a few weeks to iron out the details. Thank you for
visiting.
Post to my
Google
Group
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The Uncle mentioned using a capacitor
across the field coil terminals mounted after the old disk rectifier
full wave bridge. A good
value to try is an electrolytic
220uf @ 250 volts. Observe the proper capacitor polarity across the two
bottom screws on the two rectifiers. I expand with a similar approach but using an
isolated external add-on power supply.
|
The
finished enclosed size is 9" x 4" x 4"
|
|
R1 & R2 will be
finalized for value after practical hands on experimenting based upon an
isolated 115 vac RMS. |
|
After relentlessly
searching all sources, finding the only "available parts"
guided the design |
| I will list all the parts
and their source if anyone shows interest.. Mouser &
Amazon |
| Finding a cost effective
transformer was difficult. The total parts including a 35-watt transformer is around $100 |
| With no-load, LED
On indicates a dc shock hazard at Term-2, the charge bled off of C1 & C2
& C3 LED is off. R3 is backup! |
| C1 & C2 & C3 might be
reduced or doubled up on, something construction and bench testing would verify. |
| Photo
taken by Jason of Theremin World. Sparks Museum in Bellingham,
Washington has an old 106 power supply sitting on top of a RCA
106.Loudspeaker. The tapestry cabinet behind the RCA Theremin. The 106
Speaker has a AC & DC model. |
Post any input or questions
at Theremin
World I am oldtemecula or post to my Google
Group
|
RCA's that use the 105 speaker with
a dynamic coil, use the field coil as part of the power supply filtering which needs more explanation than I will give.
Find
Info Here
Playing a tube/valve theremin it might be
wise to plug all your power cords into a ground
fault interrupter for safety. Read
me
|
Radiola 106 Speaker
Specs |
| From Original
Label = |
105/125vac Cycles =
25/60hz Watts = 22w 22w/115v = 191
ma |
| From RCA
Schematic = |
Field Coil = 80 volts @ 170
ma Field Coil dc resistance measured = 473 ohms |
Click on any photo to see a larger version
Unplug
everything from power, wait 5 minutes before touching any connections!
| Take the Hum Free dc
power supply output leads and connect to the two screw terminals in the
center of each rectifier (looks
like big coil in graphic) indicated below as 110
Volts A.C. The direction of
hook-up does not matter, only in this situation.
|
|
There is a
voltage drop across the rectifier, check
for 80 volts dc across the bottom two screws on the rectifiers.
|
| It might be better to bypass the two
rectifiers by removing the brown wires
on the bottom screws. Use these wires tied to the Hum Free wires
from Term-2 for a direct connection to the field coil. Then check for 80
volts at term-2. The Hum Free power supply output can be shorted briefly
without damage. Things will spark and warm up. * The isolation
transformer is designed to shut down temporarily if overheated. * |
|
This above
connection explanations need
validation
|
 |
The
RCA LOUDSPEAKER 106 has a DC model, which is similar to the AC
model.
Before
making internal connections unplug the Power Supply from power, wait 5 minutes
so
energy stored in the capacitors has a chance to discharge!
This
is an experimental design in development, build and use at your
own risk.
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