Tempo Knob weirdness

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cleaninglady
 
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Joined: Thu Jun 14, 2012 6:33 am

Tempo Knob weirdness

Post by cleaninglady »

I have a xox on the bench with a weird Tempo Knob.

It's not increasing Tempo when wound clockwise or with the Tap tempo function using the switch in that pot.

If the pot is wound anti clockwise the Tempo decreases though.

Do you have any advice on where i should look to fix this.

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cleaninglady
 
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Re: Tempo Knob weirdness

Post by cleaninglady »

Just bumpng this post. I'm still in need of some help on this

I read in another thread that maybe i should have a look at Q25.

Another thing i thought of was maybe the Crystal Resonator was kaput.

I put it on the 'scope and (with logo facing me) i measured the outside legs with the xoxbox in Keyboard mode.

Left leg , i got : Fluctuating 6-12 MHz , Fluctuating 500 - 700 mV Vpp , Fluctuating 350 - 500mV Vmin
Right leg , i got : Solid 4.7MHz , 500mV Vpp , 300mV Vmin

Are these normal readings for the Crystal Resonator ?

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antto
 
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Re: Tempo Knob weirdness

Post by antto »

Q25 is in the analog section, the vco.. so it has pretty much nothing to do with the tempo, which is generated entirely by the firmware with timers

check the voltages on pins 38 and 39 on the cpu, one at a time
when you turn the encoder slowly, the voltage on those pins should alternate between low and high
i suspect that in your case maybe one of the two is sitting either high or low and not changing at all

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cleaninglady
 
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Re: Tempo Knob weirdness

Post by cleaninglady »

Thanks for the reply antto !

I checked both Pins 38 and 39 with the DMM , they both change when the encoder is turned slowly but the changes are more intermittent in the clockwise direction.

I'm only getting 4.79 volts at Pins 38 and 39. Shouldn't it be bang on 5V ?

Luap
 
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Re: Tempo Knob weirdness

Post by Luap »

Bad encoders are not uncommon.

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cleaninglady
 
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Re: Tempo Knob weirdness

Post by cleaninglady »

Bad encoders are not uncommon.
So i have heard. I can purchase one off Willxyx.
I suppose while i'm at it, i should pick up a 16 MHz Crystal Resonator...if i end up needing one.

Would like to sort out why this is happening first.

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