Ionizer2 - Q3 question

[Oh_Discordia!]

Q1 and Q2 are MPSA18's and I socketed Q3 as I dont have the 2n2907A that it calls for. no matter what I've tried subbing in (BC179, 2N4125, 2N5401 only because they're on hand) I can get it to sound ok, but only with the oscillation all the way down. If i move it pretty much at all - squeal city.

Are there certain values for the MPSA18's that i should have looked for? is it possible that my hfe on Q1 and Q2 are too high?

Thanks

 

[BuddytheReow]

That's exactly what the oscillation control does even with the 2n2907. I view it as a noise generator: fun to play with but not to play through.

 

[Oh_Discordia!]

That's exactly what the oscillation control does even with the 2n2907. I view it as a noise generator: fun to play with but not to play through.

Really? I mean I can’t move it 5 degrees before it squeals to a degree that I couldn’t play through if I tried. Or totally glitches out and I get no signal. There’s like no useable range even as a noise generator

 

[BuddytheReow]

When I played around with mine the "squeals" go away when I play but come back when no notes are played. Does the pitch change as you turn it?

 

[Oh_Discordia!]

When I played around with mine the "squeals" go away when I play but come back when no notes are played. Does the pitch change as you turn it?

mine's the same for that first 5 degrees. i can play through the squeal.....but turn it any further and i cant.

 

[BuddytheReow]

The board is pretty small, but take a look at all your solder joints and reflow the suspects. You've got a cold joint somewhere

 

[Oh_Discordia!]

The board is pretty small, but take a look at all your solder joints and reflow the suspects. You've got a cold joint somewhere

will do. fingers crossed thats it. appreciate it!