Duocast turns into a random step sequencer on 27v???

[AaronW]

Curious if anyone has any thoughts on where to start looking at in the circuit for this issue. On 9v, everything is fine. Switch to 27v, play a note and it sounds like you’re playing through a glitchy random arpeggiator.

Any ideas what could cause this? Or where to start looking?

Thanks!

 

[zgrav]

are all the caps rated for at least 35V? have you measured the output from your charge pump to see if you are getting 27v when you switch it in?

 

[AaronW]

are all the caps rated for at least 35V? have you measured the output from your charge pump to see if you are getting 27v when you switch it in?

Measuring off of D4 I’m getting 26.7v, and yes I used 50v caps.

 

[zgrav]

check the voltages at each pin of the transistors in both the 9v and the 27 v settings. consider posting a close-up picture of each side of the pcb and see if you can get some help spotting the problem.

 

[AaronW]

So had to change the battery in my multimeter, and either it was off or I did something, I’m only getting 17.5v when in 27v mode.

9v - BC549C CBE - 6.53/2.5/2.43 PNP - 2.86/6.53/6.78
27v - BC549C CBE - 17.45/6.93/7.33 PNP 9.38/17.50/17.80

 

[AaronW]

check the voltages at each pin of the transistors in both the 9v and the 27 v settings. consider posting a close-up picture of each side of the pcb and see if you can get some help spotting the problem.

Above are the photos, just checked all solder joints, part values and locations. Really at a loss as to what it could be? Is there a way to test if the chip is bad? Or is it most likely somewhere else in the circuit?

 

[zgrav]

check your resistor values against the parts list to make sure they are all correct. is the transistor in a socket? make sure the transistor leads are making a good connection to your socket. make sure you do not have any shorts from the solder points touching each other. from the pictures it looks like some of them are very close together. check your voltage on the charge pump IC to see what you get on each of the pins.

 

[AaronW]

check your resistor values against the parts list to make sure they are all correct. is the transistor in a socket? make sure the transistor leads are making a good connection to your socket. make sure you do not have any shorts from the solder points touching each other. from the pictures it looks like some of them are very close together. check your voltage on the charge pump IC to see what you get on each of the pins.

Transistors are soldered. I’ve double checked values. There are no solder joints touching. I’ll measure the charge pump IC pins next.