Vintage Synth Repair

Thanks very much for your help.

I first used the coil in my JX8P to fix that bad MKS-70. So now the 
MKS-70 is working fine and I'm in the process of making the bad coil 
work. 

I check it out yesterday. It was too bad as in addition to the 
original problem it has, two legs broke as I took it out of the 
circuit. It is no surprise that some of the lead didn't show any 
resistance/continuinity between them.

I tried to resolder the microscopic wires to the legs but many broke 
out, so what I did I removed the coil's cover, so I can have access 
to the coil leads, then I extended them by soldering new wires to the 
leads and then back to the legs. 

What I found is that the coil going from leg 8 to 9 (the ones which 
connects to the two diodes) is probably dead. So I used a wire taken 
from an old PC speaker and recoiled, measuring about 3ohms, like it 
should - from what I know. Then soldered the leads to legs 8 and 9.

I haven't put it back into the circuit yet, will do later today.

;)





--- In vintagesynthrepair@...m, "John Brewer" <john@...> 
wrote:
>
> Hi,
> Ok, so the voltage to the display circuit is correct so you need 
not worry
> any further about the 11 volts as this is not an issue as far as 
the display
> is concerned. It will be interesting to know in what way the coil 
failed.
> Can you let us know what you find wrong with it.
> You will remember you measured 11 volts AC coming from the 
transformer and
> going into the ~ ~ of the rectifier D4.   D4 changes this AC into 
DC which
> then charges the capacitor and smoothes the DC voltage.  If this 
capacitor
> was not loaded by the rest of the circuit, the DC would measure at 
about 17
> volts.  However, the capacitor is loaded by other parts of the 
organ so the
> voltage is lower.  You have measured 11 volts DC which is 
reasonable.
> Unless there are any other issues with the instrument then all is 
well.
> Best regards,
> John.
> ----- Original Message -----
> From: "gil_we" <gil_we@...>
> To: <vintagesynthrepair@yahoogroups.com>
> Sent: Monday, September 04, 2006 7:55 PM
> Subject: [vintagesynthrepair] Re: What causes bad unregulated 
voltage on the
> power supply ?
> 
> 
> > Thanks,
> >
> > The voltage feeding the transistors is 5v indeed.
> > The display works ok so far (I'm also working on fixing the bad 
coil
> > as well... to fit it back into my JX8P).
> >
> > So what you're saying is that there is a mistake in the
> > schematics ?... Where does the 11v going into D4 is origin from ?
> > Is that the transformer ?...
> >
> >
> >
>