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[jamiewoody]

i took my concertmate 500 (sk1) apart for the first time. i did not touch the circuit board.

i had an external power supply, which i set to the desired voltage. DC 7.5 volts. it is a varriable voltage adapter, and i am certain, as i checked before and after, the setting was correct.

when i plugged it in, i got a hum, and the keyboard ceased to work.

i put it back together, batteries in place. it still does not work, and i get the hum.

is there anything i can do? has anybody ran into anything similar to this?

if you can help, please do! thanks.

[Circuitbenders]

i assume it doesn't work with batteries either? ARe you sure you had the correct polarity power supply and that it was DC rather than AC.

I'm guessing you might have fried something in the power area of the board. Possibly the polarity protection diode or some other diode around the power input has gone short or completely fried for some reason. See if anything is getting hot when you plug the power in.

Do SK1's have voltage regulators? I don't have one here to actually take a look at.

[jamiewoody]

my homer simpson "DOH!" moment...

thanks for the input, i'll do just what you said and go from there.

i'll poke around with my multimeter and see what i can find. i needed an excuse to practice using that anyway...

so, check for heated components,of course, the first rule of troubleshooting is PRAY,, the second rule, is look for obvious visual tip offs, blisters/burns on components.

any other advice?

________________________

on the power supply, it was a variable voltage supply, designed for consumer electronics. i had the voltage set at 7.5. i am not sure about the polarity.

on batteries/power in general, i find that casio is a pain in the bum! i mean, instead of the battery compartment being a box, it is encased by the top and bottom of the box, so it is near impossible to keep batteries from jumping loose!

is there a practical suggestion for powering projects like this?

[C M O S]

Hi, i don't know if you got the sk1 working or not but if you need a service manual for this try this link:-
http://www.electro-music.com/forum/topic-11486.html
They have a manual ready for download and this may help in the repair process

[jamiewoody]

thank you so much, cmos!!! downloading it as i speak!

i sort of put the concertmate 500 on the backburner to work on a couple of other synths.

i thought of trying something a friend who went to electronics school suggested: take soldering iron and heat up each solder point on pc board to see if there was a cold solder joint, or  slag.

i'll read this manual from cover to cover! 

[C M O S]

 No Problem, hope it helps. A high quality scanned archive...i think you would agree!!

[jamiewoody]

YUP! i haven't had the opportunity to check it out with the manual as of yet. but, it seems like pretty simple logic to follow.