Hot Tubes' cd4049ube getting hot

[anotherjim]

On things getting warmer..
Bear in mind that the power dissipation is watts = amps x volts.
In general, increasing volts will cause amps to increase too.
So double volts = double amps.
So, if 1v x 1A = 1W
Then 2v x 2A = 4W
So double volts actually means QUADRUPLED power dissipation.
That isn't just a bit warmer, is it?

[bool]

WRT hot lytics: recently I masured a small class-a headphone amp after half-hour warmup (with quick case top removal); 54C at heatsink; a 15mm-near lytic measured 48C at the vent...

[swever]

My cd4049ube voltages:

Pin1: 8.11
Pin2: 0
Pin3: 8.11
Pin4: 2.77
Pin5: 2.77
Pin6: 2.77
Pin7: 2.77
Pin8: 0
Pin9: 8.11
Pin10: 0
Pin11: 2.77
Pin12: 3.00
Pin13: 0.00
Pin14: 2.77
Pin15: 3.00
Pin16: 0.00

[swever]

1- Have you tested the chips in a breadboard? The board without the chips? Are all inverters in a chip working correctly? Sometimes digital logic burns in a conducting state, so that may explain the high current draw (and temperature). Could be an inverter that is not used in the effect.

2 - Or you may have a solder bridge somewhere, engaging one of the unused inverters.

3 - Unlikely: Interference forcing one or more inverters to be constantly switching.

1 - I've used the chips from this batch in onther stuff and they all worked fine and stayed cool. I've tried three or four different ones and they all get hot in this board.

2 - I end up with this as the reason for something not working right way too often, so I can't be sure it's not this time.  However, I've tested everything for shorts and breaks a few times now and did not find anything yet.

3 - Is there a way to verify it's not that without a scope?

[marcelomd]

Hmmm... Can't think of anything besides a scope =\

This is really unlikely, but is quick to check with a scope. I suggested in case you had one on hand.

Last time I saw something like that happen, the root cause was the layout being too sensitive, and the failure was triggered by fluorescent lights nearby.

Maybe try with a battery, better power filtering, or take it outside =)