How to connect 40 leds to 40V AC supply?

[FE3T]

I have 2 pcs Technics SE-A900 power amps
(Looks almost like this:



The meters on the frontpanel are bacligthed with 10 ligth bulbs wich are very expensive, AND it seems like they dont last to long either.

So i consider too replace the whole shabang with high output leds.

But i need to know how to hook up enough leds to get a decent backligth.

If someone could take the time too show me a drawing of how 30 or 40 leds can be hooked up to the existing supply (38-40 volts AC) i would be really happy

[morpheus82]

hmm...i don't know if you will have the same vintage effect...otherwise...
if you think to use white leds, you need 3,5vdc for each, and rectifying 40vac you can obtain about 55v,so 16leds in series; you can place in parallel 4 led strings(or more...) and the job is done!
i've done it rectifying 220vac and works but i added an lm317 in current limiter configuration at 30mA: a lot of light!!if you want you can do it but take into account the voltage drop across the regulator, you will have about 52 volts...or less...

[cpemma]

Originally posted by FE3T
If someone could take the time too show me a drawing of how 30 or 40 leds can be hooked up to the existing supply (38-40 volts AC) i would be really happy

First job is to put a bridge rectifier on the AC supply, otherwise you'll see flicker as each LED will be running on half-wave rectified power (they're light-emitting diodes) and you'd need to take steps to block or bypass the negative-going part of the sine wave or the LEDs would die - unlike a regular silicon diode, they'll only stand around 5V max reverse voltage.

Smoothing is optional. With the full-wave rectified sine wave I don't think you'll see flicker, but if you do decide to smooth, the 38-40V AC will rise to about 52-55V DC so use that in calculations rather than the RMS 38-40 figure.

Then trot along to linear's site and use the Wizard, it will design the most efficient system for you.

[megajocke]

Why not use the DC supply that's already in the amp instead of adding another recitfier and smoothing?