Vintage Synth Repair

hi folks, i have a midiboard here that im fixing up. i had to put some new slider pots in, and the ones that actually fit perfectly are ones w/ LED's in them. so i've got them all wired up w/ a 10k resistor upstream of each LED's anode leg, and i ran a connecting harness to the +5V voltage regulator, but now im a little scared to connect it, cause i dont know if the current draw might be an issue. see, i can't find the service manual or schematics, so i dont know what the PSU is rated for. its a pretty big machine, w/ a +12/-12/+5 PSU, and the LED's appear to draw about 13mA per LED and there are 7 of them. how can i figure out if this is safe on the PSU with no service manual? thanks for the help, rj

--- In vintagesynthrepair@yahoogroups.com, "r_j_d_2.phila" <r_j_d_2.phila@...> wrote:
>
> hi folks, i have a midiboard here that im fixing up. i had to put some new slider pots in, and the ones that actually fit perfectly are ones w/ LED's in them. so i've got them all wired up w/ a 10k resistor upstream of each LED's anode leg, and i ran a connecting harness to the +5V voltage regulator, but now im a little scared to connect it, cause i dont know if the current draw might be an issue. see, i can't find the service manual or schematics, so i dont know what the PSU is rated for. its a pretty big machine, w/ a +12/-12/+5 PSU, and the LED's appear to draw about 13mA per LED and there are 7 of them. how can i figure out if this is safe on the PSU with no service manual? thanks for the help, rj
>

When asking a question like this, it's probably a good idea to state the model of the device in question; in this case the Kurzweil.  In any case, I would venture to guess that you're probably safe with the extra load here, since it's under or close to 1/10th of an amp.

Of course, if you're really in doubt, just don't connect the LED's!

John

At 3:33 Uhr +0000 27.03.2010, kindabizzy2 wrote:
> When asking a question like this, it's probably a good idea to state the
>model
> of the device in question; in this case the Kurzweil.

He actually did that - it's the Kurzweil Midiboard. A masterkeyboard
roughly the same vintage as the famed K250.

> In any case, I would venture to guess that you're probably safe with the
>extra
> load here, since it's under or close to 1/10th of an amp.

Indeed. Practically all power supplies are designed with a certain margin.
Compared to the amount drawn by typical 80's logic chips the additional
draw from the LED's is probably like a drop in the ocean.

great-thanks guys! 

--- In vintagesynthrepair@yahoogroups.com, Malte Rogacki <gacki@...> wrote:

>
> At 3:33 Uhr +0000 27.03.2010, kindabizzy2 wrote:
> > When asking a question like this, it's probably a good idea to state the
> >model
> > of the device in question; in this case the Kurzweil.
> 
> He actually did that - it's the Kurzweil Midiboard. A masterkeyboard
> roughly the same vintage as the famed K250.
> 
> > In any case, I would venture to guess that you're probably safe with the
> >extra
> > load here, since it's under or close to 1/10th of an amp.
> 
> Indeed. Practically all power supplies are designed with a certain margin.
> Compared to the amount drawn by typical 80's logic chips the additional
> draw from the LED's is probably like a drop in the ocean.
>