K5synth

The LM386 doesn't produce any noise. Even if you unplug the signal there 
will still be some. Sctually the problem is a noisy ground. It's sharing 
the same ground for all the board(s).

nelsonj_sce@... a écrit:

> 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.
>
>
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-- 
antdes45@...