Help me fix my SH-101

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snod_donkey
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Help me fix my SH-101

Post by snod_donkey » Sat May 14, 2011 8:04 pm

Looking for some help from an SH-101 expert...

Just picked the unit up today in a non working state and not sure what part of the circuit is at fault.
Powers up, lights do what they should and all looks to be working ok but no sound output at all from vco or noise

I have narrowed it down to the VCA section not being triggered by the internal gate signal. If i put 5 volts on the external gate input the vca starts working ok.... the socket is ok as i have checked with a meter

So what i want to know as i cant work it out from the circuit is what generated the gate signal ?? Just hope its not the cpu gone down :(

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Solderman
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Re: Help me fix my SH-101

Post by Solderman » Sat May 14, 2011 8:37 pm

Gate triggered from the keyboard comes from pin 38 of the CPU, through an inverter, and out to the "gate out" jack, next to the "gate in" (switched)input jack, before splitting to auto-portamento, VCA control switch and the envelope input.

Insert 5V at the Gate input and set the envelope trigger switch to Gate+Trig, with portamento set to On. Switch keys, and if the keyboard retriggers the VCA, it could just be the Gate In switched jack has lost continuity from the Gate Out jack. If it doesn't, and Trig works using an external CV that changes voltage, with portamento On, then something very well could be wrong with the keyboard itself. Check the two terminals on the keyboard for a secure connection, and maybe also check continuity for each wire on the terminals. The CPU should be fine if the LED's are behaving normally.
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snod_donkey
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Re: Help me fix my SH-101

Post by snod_donkey » Sat May 14, 2011 8:49 pm

Solderman wrote:Gate triggered from the keyboard comes from pin 38 of the CPU, through an inverter, and out to the "gate out" jack, next to the "gate in" (switched)input jack, before splitting to auto-portamento, VCA control switch and the envelope input.
Insert 5V at the Gate input and set the envelope trigger switch to Gate+Trig, with portamento set to On. Switch keys, and if the keyboard retriggers the VCA, it could just be the Gate In switched jack has lost continuity from the Gate Out jack. If it doesn't, and Trig works using an external CV that changes voltage, with portamento On, then something very well could be wrong with the keyboard itself. The CPU should be fine if the LED's are behaving normally.

thanks for that... just so happens i was testing pin 38 as you was replying. already checked the sockets and all ok there. Not the keyboard either as it does not work with the sequencer either when you hit play. The 101 always has some sort of pattern stored even if your not able to do it from the keyboard... This narrows it down to the cpu gate output on pin 38 of the cpu. I will check with a scope or logic probe tomorrow and see what going on there ;)

Thanks

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