Keep frying trem LED

[tubesornothing]

Hey all, I have a few amps with LED in the cathode.  On one particular amp, I keep frying the LED.  Trem continues to work though.  The LED usually give out one last blurp when I switch on the trem, so I am figuring a spike.

Here is the schemo - any suggestions?

thanks

[Tiny_Daddy]

Try adding some resistance, maybe a couple of hundred ohms in series with the LED.

[sluckey]

That LED is drawn backwards. Do you really have the LED cathode tied to the tube cathode?

[Merlin]

Assuming you have the LED in the right way round, move the 0.1u cap so that it connects to ground instead of to the LED.

[tubesornothing]

Sluckey - I always get diodes backwards.  Conventional notation versus electron flow messes with my old head.

Merlin - I thought that bypass cap might be the culprit. a little surge of 400V at power up would surely screw up the diode!


Thanks guys.

[HotBluePlates]

I always get diodes backwards.  Conventional notation versus electron flow messes with my old head.

The key is remembering the diode symbol is an arrow and a minus sign. The minus sign goes to the more negative side for forward biasing. Or, you could say the arrow points in the direction of conventional current flow.

What gets people confused is they think about the rectifier in the high-voltage power supply, with the minus towards the B+. That's because you want the diode to conduct when the transformer voltage is more positive than the filter cap voltage.