Very hot 7805 on MidiBoxSEQ

[Guest kostix]

Hello everybody !

Is it normal for the 7805 to get as hot as if i would touch it i would seriously burn myself, with a midiboxseq,  2 lcds 40x2, and all the other functions, leds etc being on ?

I'm wondering if i have something wrong somewhere,

I check the current flowing thru the entire circuit, but my multimeter wont let me measure currents higher than 200mA, and it goes above the 200mA.

i'm using a 1A 9v AC transformer

The front panel is ready, out of 3mm white plywood, lookin pretty neat! So now only this little issue and i'm off to make the case :)

any ideas?

thanks in advance

[pay_c]

Within a Seq this is normal.

You have to think of following: The whole circuit (without LEDs and backlighting) uses up app. 50 to 100 mA, but the LEDs are using about 100 mA and the backlight about 100-300 mA each. So you´re coming beyond the 500 mA like nothing. 500mA x 4 Volt downgrading the 9 Volt = 2 Watts pure heat.

Just *DO* use a heatsink on the 7805, then everythings OK.

Greetz.

[Guest kostix]

hey again

I appreciate this soon reply

Heatsink it is then :)

one more thing,

i wonder if its normal that the rectifier diode bridge also gets very hot

i believe i am using 1A rated one

should i get a higher amperage one ?

KostiX

[pay_c]

You can leave those ones in there (also it´s not to normal that theyre getting hot). Normally they´re rated with a pretty good safety (if 1 Amp is stated, they take 1,5).

If they fry anyhow sometime, you can still change them.  ;D ;)

Anyhow, the best is a ready bridge recitifier (the round ones). They take up a lot (!). Never burnt one up to now (and thats some wonder with all those shorts I built)...