Wavefront travel case Theremin Repair
 

Hi,

I've been given a wavefront travel case Theremin to repair.... seems the
power supply is dead, it has a 3 pin DIN connector alas I am not 100% sure
as to what the voltages should be on these pins? Is there anyone out there
who knows? I tried e-mailing the company however haven't received a reply.

So far the voltages measured on the pins on the din connector are -12, 0
and -0.71V - I guess the latter pin should be +12v. The power supply that
came with the unit is an adapted computer psu with output voltages of +/-12v
and +5v - but only 3 outputs are used. Looking at the resistor to the 'on'
LED (220 ohms) I am now 90% sure that there should be +12V and not +5V on
this line. I just want to be 100% sure if possible. The transformer is one
of those impossible to open things (sealed - cant see any screws) and as its
not mine, I'm not overly keen to take a hacksaw to it.

Anyway, hope someone out there knows, tho I guess its a long shot ;) so
thanks in advance for your help.

Colin

Colin,
While I'm hardly a Theremin expert, here are a few ideas...

An LED powered from 12V thru 220 Ohms is going to draw about 47 milliamps which is pretty high. I think 220 Ohms is more
typical for an LED that's run on 5 volts.

If you're sure it's *either* +5 or +12 (and not some other voltage), there's probably no harm in hooking to +5 and giving it
a try. Most circuits will be okay if powered from a significantly lower voltage than they were designed for - they won't
work, but won't be damaged either.

If the power supply is the kind used inside a PC, the wire colors are pretty standardized. Black is 0V, yellow is +12, and
red is +5.

Eric Law
Wilmington, MA

"Colin Swift" wrote in message ...
Hi,

I've been given a wavefront travel case Theremin to repair.... seems the
power supply is dead, it has a 3 pin DIN connector alas I am not 100% sure
as to what the voltages should be on these pins? Is there anyone out there
who knows? I tried e-mailing the company however haven't received a reply.

So far the voltages measured on the pins on the din connector are -12, 0
and -0.71V - I guess the latter pin should be +12v. The power supply that
came with the unit is an adapted computer psu with output voltages of +/-12v
and +5v - but only 3 outputs are used. Looking at the resistor to the 'on'
LED (220 ohms) I am now 90% sure that there should be +12V and not +5V on
this line. I just want to be 100% sure if possible. The transformer is one
of those impossible to open things (sealed - cant see any screws) and as its
not mine, I'm not overly keen to take a hacksaw to it.

Anyway, hope someone out there knows, tho I guess its a long shot ;) so
thanks in advance for your help.

Colin

"Colin Swift" ) writes:
Hi,

I've been given a wavefront travel case Theremin to repair.... seems the
power supply is dead, it has a 3 pin DIN connector alas I am not 100% sure
as to what the voltages should be on these pins? Is there anyone out there
who knows? I tried e-mailing the company however haven't received a reply.

So far the voltages measured on the pins on the din connector are -12, 0
and -0.71V - I guess the latter pin should be +12v. The power supply that
came with the unit is an adapted computer psu with output voltages of +/-12v
and +5v - but only 3 outputs are used. Looking at the resistor to the 'on'
LED (220 ohms) I am now 90% sure that there should be +12V and not +5V on
this line. I just want to be 100% sure if possible. The transformer is one
of those impossible to open things (sealed - cant see any screws) and as its
not mine, I'm not overly keen to take a hacksaw to it.

You do realize that those computer power supplies expect a decent load on
the output(s)? If they aren't loaded properly, you won't see the voltages
it is supposed to supply.

Before assuming the power supply is bad, you'd better make sure it is properly
loaded.

And if the power supply is bad, it's likely simplest to replace the whole
thing. It surely can't be "adapted" very much.

If the power supply is bad, you can't really assume anything. If you think
it's adapted, then you really need to know what voltages it was supposed
to put out.

Micahel

Anyway, hope someone out there knows, tho I guess its a long shot ;) so
thanks in advance for your help.

Colin

"Michael Black" wrote in message
...

"Colin Swift" ) writes:
Hi,

I've been given a wavefront travel case Theremin to repair.... seems
the
power supply is dead, it has a 3 pin DIN connector alas I am not 100%
sure
as to what the voltages should be on these pins? Is there anyone out
there
who knows? I tried e-mailing the company however haven't received a
reply.

So far the voltages measured on the pins on the din connector are -12, 0
and -0.71V - I guess the latter pin should be +12v. The power supply
that
came with the unit is an adapted computer psu with output voltages of
+/-12v
and +5v - but only 3 outputs are used. Looking at the resistor to the
'on'
LED (220 ohms) I am now 90% sure that there should be +12V and not +5V
on
this line. I just want to be 100% sure if possible.

The inline LED resistor is 220 ohm, LED's dropping voltage is about 1.2 V.
With 5 V that is about 17 mA, for 12 V that would be about 50 mA and
that amount of current would kill most LED's rather sooner than later.
Bottom line... that 'on line' should be + 5 Volts.

Ok...so lets get this one straight....you accepted someone's Theremin to
repair...with absolutely no idea how to repair it?. After your done
thoroughly killing it to the point of no return, send it off to me.

--
Kim..."A Man Of True Frankenstinean Proportions"
"Colin Swift" wrote in message
...
Hi,

I've been given a wavefront travel case Theremin to repair.... seems the
power supply is dead, it has a 3 pin DIN connector alas I am not 100% sure
as to what the voltages should be on these pins? Is there anyone out there
who knows? I tried e-mailing the company however haven't received a reply.

So far the voltages measured on the pins on the din connector are -12, 0
and -0.71V - I guess the latter pin should be +12v. The power supply that
came with the unit is an adapted computer psu with output voltages of
+/-12v
and +5v - but only 3 outputs are used. Looking at the resistor to the 'on'
LED (220 ohms) I am now 90% sure that there should be +12V and not +5V on
this line. I just want to be 100% sure if possible. The transformer is one
of those impossible to open things (sealed - cant see any screws) and as
its
not mine, I'm not overly keen to take a hacksaw to it.

Anyway, hope someone out there knows, tho I guess its a long shot ;) so
thanks in advance for your help.

Colin

Colin Swift wrote:
Hi,

I've been given a wavefront travel case Theremin to repair.... seems the
power supply is dead, it has a 3 pin DIN connector alas I am not 100% sure
as to what the voltages should be on these pins? Is there anyone out there
who knows? I tried e-mailing the company however haven't received a reply.

So far the voltages measured on the pins on the din connector are -12, 0
and -0.71V - I guess the latter pin should be +12v. The power supply that
came with the unit is an adapted computer psu with output voltages of +/-12v
and +5v - but only 3 outputs are used. Looking at the resistor to the 'on'
LED (220 ohms) I am now 90% sure that there should be +12V and not +5V on
this line. I just want to be 100% sure if possible. The transformer is one
of those impossible to open things (sealed - cant see any screws) and as its
not mine, I'm not overly keen to take a hacksaw to it.

Anyway, hope someone out there knows, tho I guess its a long shot ;) so
thanks in advance for your help.

Colin


----------------------------

I dunno, but if you ever get it fixed, please feel free to yell "Beam Me
Up, Scotty!!"

'motsco'

"motsco_ _" "motsco_ wrote in message
...

I dunno, but if you ever get it fixed, please feel free to yell "Beam Me
Up, Scotty!!"

What does that have to do with a Theremin?

N

I've been given a wavefront travel case Theremin to repair.... seems the
power supply is dead, it has a 3 pin DIN connector alas I am not 100% sure
as to what the voltages should be on these pins? Is there anyone out there
who knows? I tried e-mailing the company however haven't received a reply.

Hi,

Have got the Theremin working, tho I'm still unsure as to the correct
operational voltage. I used a 7 volt battery on the non-working +V line and
lo and behold the thing lights up and plays just fine. as folks have pointed
out, the LED resistor points to the +V line being 5 volts. The LED is
actually a panel mount LED unit which has written on the side 5V, 20MA -
though this still means the resistor is a bit low for 12V, also a bit high
for a 5V supply. There is an IC which is fed off the two supply lines which
( LM13600, according to the data sheets) requires +/- 15volts.

I guess the main thing is its working and building a PSU for it will be no
problem.

Thanks for your help.

Colin

"NSM" bravely wrote to "All" (01 Mar 05 06:31:46)
--- on the heady topic of " Wavefront travel case Theremin Repair"

NS From: "NSM"
NS Xref: aeinews sci.electronics.repair:42073


NS "motsco_ _" "motsco_ wrote in message
NS ...

I dunno, but if you ever get it fixed, please feel free to yell "Beam Me
Up, Scotty!!"

NS What does that have to do with a Theremin?

Sargent had a theremin in the original Star Trek TV show theme music.
BTW the Beach Boys' "Good Vibrations" used one too.

A*s*i*m*o*v

.... Guitar smashing doesn't bother me. Some "need" smashing. -Chet Atkins

I've been given a wavefront travel case Theremin to repair.... seems the
power supply is dead, it has a 3 pin DIN connector alas I am not 100% sure
as to what the voltages should be on these pins? Is there anyone out there
who knows? I tried e-mailing the company however haven't received a reply.

You might ask on Levnet, I don't own that type, but I'd be VERY surprised if
one of us dosen't have the info you seek.


So far the voltages measured on the pins on the din connector are -12, 0
and -0.71V - I guess the latter pin should be +12v.

Almost certainly.


FWIW, how did you come by it?