K5synth

Here is the latest, it is good news.

Today I got my parts for DigiKey.  As below I replaced my backlight
with a blue backlight from nightlaunch.  It worked with my stock K5
inverter.  However, my stock inverter was very flakey, even after I
did the resolder job so I decided to replace the stock inverter with
the DigiKey part.  (Digikey part #289-1032-ND).  The good news is that
inverter works (even though it is only about 95V @ about 550Hz).  It
is a slightly different color than before, but it still looks great. 
Also- THERE IS VIRTUALLY NO HUM!  

The only warning is the Digikey part is not the exact same size as the
original inverter - it is a bit smaller in footprint and a lot
shorter.  The stock inverter has only three connections (in - out -
ground) and the new inverter has a fourth pin for mounting.  Because
the part is smaller, I used the original hole for the "out", but I had
to wire up jumpers to the "ground" and the "in" - not a big deal but
it is some extra work  - and you don't want to see pictures of my ugly
job.  :).  But so far so good.

Also, I did the 147K resistor hack and it seems to have gone well.  My
K5 is a louder, but the headphones have even more noise now.  I have
been looking things over and I think the headphone noise is because
they use a cheap LM386 op-amp and a bad overall design for the
headphone amp.  I am trying to see if I can replace this with a better
op-amp, otherwise I think the only good solution is to just bypass
their circuit completely and make a better headphone amp and wire it
up to the K5.

Anyway, again the good news is that for less than $30 delivered you
can get nightlaunch backlight and a Digikey inverter and have a new
backlight that does not hum!  :)   

Now for the headphone amp...








--- In k5synth@yahoogroups.com, "nelsonj_sce" <nelsonj_sce@y...> wrote:
> Update:
> Well today I ordered a new inverter from www.DigiKey.com.  I found an
> inverter that looks like it will do the job - for those interested
it is:
> 
> Digikey part #	289-1032-ND  and it only cost $11.90 - not bad.
> 
> I am not sure if it will fit exactly in the same slots as the original
> inverter so it might require some additional wiring.
> 
> Anyway, I had my K5 open to look at the power supply to plan the new
> inverter install when my K5 started "humming", and guess what, I now
> have a beautiful blue backlight.  It looks great, a very cool blue. 
> So it appears my inverter was not bad, but it just has bad solder
> joints.  It is working for now but tomorrow I will likely take out the
> board and redo all the solder joints.  
> 
> Just some additional info I learned in researching backlights and
> inverters.  The "brightness" of the backlight is a function of the
> voltage and frequency applied to the backlight.  It appears one has a
> lot of flexibility in selecting the inverter output voltage and freq.
> For example, nightlauch says you can "test" the backlight by plugging
> it directly in to a wall socket (120V AC @ 60 Hz here in the US)!  The
> higher the voltage and freq the brighter the backlight.   However, the
> backlight will "burn out" quicker the higher the freq.  So there is a
> trade off, high freq = bright but shorter life.  
> 
> Right now my stock inverter is putting out about 102V @ 380 Hz.  I
> think the inverter I ordered will put out about 95V @ 540 Hz and
> should work with a 3 - 6 V DC input.
> 
> Next step, 147k resistors (also ordered from Digikey today).  
> 
> 
> 
> --- In k5synth@yahoogroups.com, "nelsonj_sce" <nelsonj_sce@y...> wrote:
> > Well I replaced my backlight with one I ordered from
> www.nightlaunch.com.
> > 
> > It took less than two weeks from when I ordered and the parts look
> good.  
> > 
> > Good news/bad news though on my backlight.  
> > 
> > The good news:  I had no problems removing the LCD, taking out the old
> > backlight and sliding in the new backlight.  The new light has some
> > wires and a plastic "tab" that kind of gets in the way, so I soldered
> > the backlight wires to where the wires connect to the LCD board. 
> > Hint:You have to cut the new backlight to size, so make the backlight
> > a little longer (say 1/4 inch) than the original to make things
easier.
> > 
> > Bad news: My backlight does not work but I think my inverter is the
> > problem.  I am only getting about 1/2 Volt at the output of my
> > inverter, and I am supposed to get 120V @400Hz if I understand the
> > part correctly.  I tested my inverter before I did the backlight
> > install and saw it had low voltage, but I was hoping that my existing
> > "dead" backlight was causing the problem (i.e. it was shorted.) I
> > guess not because even with the new backlight I get very low voltage.
> > 
> > Anyway, it looks like I need to get an inverter.  I can get an
> > inverter from nightlaunch for $17.99+s/h but it needs 9V DC.  I
> > understand the inverter in the K5 uses 5V DC. 
> >  
> > Q1: Does the K5 inverter use 5V DC?
> > Q2: If I measure the voltage on the two wires to the left of the
> > inverter, should I get 120V if everything is working? (My Fluke says
> > it is good <=1kHz)
> > Q2: Does anyone know where to get a compatible K5 inverter and how
> > much it will cost?
> > 
> > Thanks again for all the help.  This group is great.