Power wierdness

[MikeH]

Ok- I have a preamp circuit board I pulled from an old amp, that requires 35v to run.  So I rigged up this based on a frequency central design.  I just reduced the number of diodes so I only get 35v:



I soldered up the pcb and rigged it up on my bread board, I get 35v out with 12v in.  Perfect.

So, I hook it up in the enclosure, with the other board, and an LED, filtering cap on the DC jack (1000uf) and I turn it on, and the LED blinks on and off, about every second, and I'm not getting 35v.  Thats weird... so I remove the circuit portion, so all I have is the charge circuit, filtering cap, a switch, and the LED, like this:



... and it still blinks on and off.  And I'm getting around 11v, not 35v.  Am I missing something here?

[theehman]

Possibly the preamp is pulling more current than the power supply can deliver?

[MikeH]

That's what I thought at first, but it still did the same thing after I disconnected the preamp.  Also, I'm using a 1000ma wall wart, so...

[frequencycentral]

Mike don't you need a resistor in series with that LED?

BTW, R.G. is the man to thank for the design: http://www.geofex.com/circuits/+9_to_33.htm

[MikeH]

I left the resistor out of my doodle, but yeah, I've got one in there.

[mth5044]

Isn't 1000u a bit big?

[MikeH]

Isn't 1000u a bit big?

Yeah, it's all I had on hand at the moment.


Anyway - I figured it out.  I thought I had enough clearance around my traces to screw mount the pcb, but part of it was shorted out.  Weird result though.