Another NeoVibe Deug, sorry all

[sjaltenb]

No sound, No light (unless I touch the soldering iron to the lamp driver emitter, then the lamp works as it should...and controls fluctuate speed and brightness) This is the strangest part to me!

All Qs are correct in voltage, except those that are affected by C12 (which is in the mail)

EXCEPT Q11 and Q12, which are carrying 23V on the collector and varrying voltages on the E,C. Varry between 8-17, very fast.

I have hit every pad a few times with no luck, and i keep checking for bridges, but will keep checking. Any ideas??

Driver voltages:
23.37
6-8
6-7

THANKS!

[R.G.]

No sound, No light (unless I touch the soldering iron to the lamp driver emitter, then the lamp works as it should...and controls fluctuate speed and brightness) This is the strangest part to me!

Not strange at all. It probably means that your probably-grounded soldering iron tip is grounding the emitter of the lamp driver, which is otherwise ungrounded.

Use your ohmmeter to measure the resistance between lamp driver emitter and ground with the power to the circuit off. I think you'll find it's high resistance.

[sjaltenb]

Yessir...2.2Mohm

All values of those resistors are correct. Trimpot makes no difference...hmmmmmmm

[R.G.]

Yessir...2.2Mohm

All values of those resistors are correct. Trimpot makes no difference...hmmmmmmm

2.2M to ground when it's supposed to be a couple of hundred ohms...

Here's a couple of hints:

The measured resistance from component lead to component lead that goes through a solder joint, through PCB trace copper, through the second solder joint and finally to the second lead will measure as a short circuit if the leads, solder joints, and trace are correctly connected. If it measures significantly different from a short circuit, something is wrong with that current path. Measuring from lead to lead, not solder joint to solder joint checks out the solder joints too.

[bt2513]

I agree with R.G.  It sounds like a cold solder joint.  Maybe start with the components that connect to ground and work your way towards the lamp driver.  I guess just test each trace to ground for continuity...

[sjaltenb]

 

So sorry....I double checked the resistors and I had made an error. Next purchase...desk lamp. Anway, a quick tuning of the trimpot and voila!

Thanks for helping me debug anyway. I'll try to be more sure next time! Now, of course, I am lacking a single resistor (i had misplaced the correct value in another slot) so once again, I am a single resistor away (68ohm) from a working univibe!