Vintage Synth Repair

Many thanks for the info Noel..!
Cheers.
TOM



--- In vintagesynthrepair@yahoogroups.com, NoëlBuhagiar <laser@...> wrote:
>
> Hi,
> 
> Maybe of help to you.. I’d rather check it using a scope.
> I checked output of similar 01WFD model connected to a GlowSafe backlight:
> Measured between 200 to 250Vp-p (peak-to-peak) at around 500Hz
> 
> I don’t think measuring voltage using a multimeter is accurate enough
> Also make sure the circuit is loaded with a backlight when measuring.
> 
> When original Korg backlight wears out it attenuates (shorts) the output and no voltage is obtained using the scope.
> The current is very weak and easily falls to 0
> Also check elect.caps for bad ESR and check value or better replace the cap. at transistors base if necessary
> 
> Could you check your backlights on another circuit to make sure these work?
> Good luck once again
> 
> 
> 
> 
> From: Quazimodo 
> Sent: Tuesday, August 07, 2012 11:18 AM
> To: vintagesynthrepair@yahoogroups.com 
> Subject: [vintagesynthrepair] Re: Backlight Revisited...
> 
>   
> No cracks - all looks fine.
> Seems no matter what I change or do... it stays the same...;c(
> 
> --- In mailto:vintagesynthrepair%40yahoogroups.com, "jammie" <jammie.emma@> wrote:
> >
> > have you got any cracks on the pcb as i have had wavestations psu crack on the fixing holes
> > ----- Original Message ----- 
> > From: jammie 
> > To: mailto:vintagesynthrepair%40yahoogroups.com 
> > Sent: Monday, August 06, 2012 11:43 PM
> > Subject: Re: [vintagesynthrepair] Re: Backlight Revisited...
> > 
> > 
> > 
> > 
> > that with in tolerance
> > 
> > the circuit is only a few resistors 1 switching transistor and 2 caps and the step up transformer
> > ----- Original Message ----- 
> > From: Quazimodo 
> > To: mailto:vintagesynthrepair%40yahoogroups.com 
> > Sent: Monday, August 06, 2012 11:13 PM
> > Subject: [vintagesynthrepair] Re: Backlight Revisited...
> > 
> > 
> > 
> > Yes Jammie, I am getting the 5volts... well, actually around 5.5v
> > 
> > ...it's weird one this!
> > 
> > --- In mailto:vintagesynthrepair%40yahoogroups.com, "jammie" <jammie.emma@> wrote:
> > >
> > > are you getting 5v at the incoming circuit or is this voltage higher
> > > ----- Original Message ----- 
> > > From: Quazimodo 
> > > To: mailto:vintagesynthrepair%40yahoogroups.com 
> > > Sent: Monday, August 06, 2012 10:39 PM
> > > Subject: [vintagesynthrepair] Re: Backlight Revisited...
> > > 
> > > 
> > > 
> > > Hello again,
> > > 
> > > OK I swapped the smoothing Capacitor C28.
> > > 
> > > No change... so to date I have checked the transistor, C28 and also the actual foil itself.
> > > 
> > > Stil getting 166 volts AC at around 2kHz.
> > > 
> > > I was thinking of changing C26 and C29 as well - could either of these be causing the symptoms?
> > > 
> > > Also, the transformer itself... it is obviously 'working' but do these either work or not - can they give different results?
> > > 
> > > I know you suggest going the LCD route - but as I have already got two new foils, I'd really rather get it fixed if at all possible... but this is fast becoming an epic saga!
> > > 
> > > Cheers,
> > > TOM
> > > 
> > > --- In mailto:vintagesynthrepair%40yahoogroups.com, "jammie" <jammie.emma@> wrote:
> > > >
> > > > check the smoothing capacitor c28 the transformer is fixed uptransforms to the correct voltage for input 
> > > > 
> > > > so if the input ac voltage is wrong then it gets multiplied by the transformer
> > > > 
> > > > so the input voltage to the transformer has to be wrong
> > > > 
> > > > the transistor switches the dc voltage of 5v into a small ac voltage 
> > > > 
> > > > its the same with all efoil invertors except on the korgs they have the components on board a lot use inverter chips which are the same but in a white box this is so if the invertor fails you can just swap it out 
> > > > 
> > > > on the korgs you have to find which parts are at fualt and change them
> > > > 
> > > > i would just remove the invertor circuit and fit an led lcd instead 
> > > > 
> > > > then all you have todo is put a current limiting resistor to the manufacturers specs for the led back light from 5v line to the + of the efiol output pin on the psu
> > > > 
> > > > then you can use the same cable for the back light as the original efiol cable
> > > > 
> > > > the led backlights from rs work just fitted one to a kurzweil k2000
> > > > 
> > > > which uses the same footprint as the wavestation but the negative blue ones are on back order until november 
> > > > ----- Original Message ----- 
> > > > From: scott frye 
> > > > To: mailto:vintagesynthrepair%40yahoogroups.com 
> > > > Sent: Sunday, August 05, 2012 2:49 PM
> > > > Subject: [vintagesynthrepair] Re: Backlight Revisited...
> > > > 
> > > > 
> > > > 
> > > > Is the rep rate of the AC frequency set internally on the transformer
> > > > module?....If not, there must be an external timing component that's
> > > > making the thing run too fast.
> > > > A resonator?....A timing capacitor?
> > > > 
> > > > -- 
> > > > Scott Frye
> > > > 
> > > > Audio-fixation.net
> > > > 
> > > > Vermont
> > > >
> > >
> >
>