I'm having problems. Booo!

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DiscoVolante
 
Posts: 23
Joined: Tue Nov 01, 2005 4:45 pm

I'm having problems. Booo!

Post by DiscoVolante »

Okay, I just finished assembling my x0x kit, and it's not working properly. When I'm listening in random mode through the headphone out jack I can only hear very quiet notes (as in, I have to strain to hear anything). As I was listening, I touched the board and accidentally discovered that when I put my fingers over the solder joints of Q1-4 I can hear everything just fine, at normal volume (my methods are very scientific, I know).

A couple of other quirks that may or may not be related: my LEDs don't light up, except for right when I plug the x0x in. Also, when I unplug the x0x with headphones on, I hear one perfect note at normal volume through my headphones. Even when I'm not touching Q1-4.

I've looked all over the board for bridges, but I haven't found any. I've re-soldered a bunch of the joints in the VCA area around Q1-4 just for good measure. That's about where my BANNED troubleshooting skills end. Also, my multimeter's obscure battery is dead.

Guest
 

Post by Guest »

Sounds like you have an "open" (cold solder joint), not a "close" (solder bridge). Make sure that when you solder a joint, the solder is melting because both the pad and the lead are hot, not just because the iron tip is hot.

Get a new multimeter if your battery is dead and obscure. Even a cheap one will allow you to test continuity.

DiscoVolante
 
Posts: 23
Joined: Tue Nov 01, 2005 4:45 pm

Post by DiscoVolante »

Thanks for the response.
I've made a discovery. I can hear accented notes just fine, but the un-accented notes can only be heard if I put my finger on those transistors. Also, my LEDs work after all - just not in random mode, which I guess is normal.

This leads me to suspect that the problem is in the VCA. I'm very new to all of this though, so I'm not sure. Any thoughts?

What's the best way to check continuity so I can zero in on the problem area? I'm getting a new multimeter tomorrow.

Jonnay
 
Posts: 142
Joined: Thu Jun 02, 2005 12:28 pm

Post by Jonnay »

Sounds like a problem in the VCA envelope to be specific. (well, really, there isn't tha much else to the VCA circuit except the 6110, but I digress...)

Double check the orientation of D35 and D36. Also make sure that Q31 and Q32 are oriented properly, and you have the right transistor in the right spot. (one is a 733 PNP, the other is a 536 NPN)

I think you should see a positive voltage between D35 and ground when a note is struck.

DiscoVolante
 
Posts: 23
Joined: Tue Nov 01, 2005 4:45 pm

Post by DiscoVolante »

Ohh, I think I see the problem! One of those diodes is in backwards. You, sir, are my saviour.

I'll fix it in the morning.

DiscoVolante
 
Posts: 23
Joined: Tue Nov 01, 2005 4:45 pm

Post by DiscoVolante »

Well, that was the problem. One of those diodes was in backwards. I fixed that and everything was fine. Now x0x164 is all done. Wooo hoo!

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