short question about 78S05

[Miniwatt]

I finished the PS for my tube preamp, the filament supply has a 78S05. What I bought says 'L78S05CV'

It doesn't work, when I measure after the regulator I get 0 volts. Rectifying etc all works fine, I get about 10 volts. I triple-checked the circuit, and everything's wired like it should be.

Could it be I got the wrong part?

[Zen Mod]

yes-it sould be bad chip,or you zapped it somehow ;

this pinout?

[Miniwatt]

Thanks Zen Mod, yeah, that's it. Are those things sensitive to static or something? I got it in a paper baggy together with some resistors, plugs and other small things, could that be the cause?

I got everything finished, that was the last part missing, had to go to the shop for it, and it looks like I can go one more time... Argh..

[Zen Mod]

Originally posted by Miniwatt
Thanks Zen Mod, yeah, that's it. Are those things sensitive to static or something? I got it in a paper baggy together with some resistors, plugs and other small things, could that be the cause?

I got everything finished, that was the last part missing, had to go to the shop for it, and it looks like I can go one more time... Argh..

I know that waiting for part (one bloody part ) can be frustrating.........but look at that in this manner- just imagine that this poor chip is STK.........fake or not, but certainly non-functional ;
then imagine that you rose 65 Euros for that dreky STK ,and warranty is ....zilch...........

ya happpppppppy now?




is it necesary that I say.....been there.......etc.......

[rja]

7805 is easy to work with, so if it isn't working in your circuit, try it out of the circuit. Connect it to the 12v and ground supplies through a molex connector inside your PC, without any additional components - if you don't measure 4.95v to 5.05v through pin 3, then you have a bad part.

If you do get 5v, then your circuit needs looking at.

--Rich

[Miniwatt]

Originally posted by rja
7805 is easy to work with, so if it isn't working in your circuit, try it out of the circuit. Connect it to the 12v and ground supplies through a molex connector inside your PC, without any additional components - if you don't measure 4.95v to 5.05v through pin 3, then you have a bad part.

If you do get 5v, then your circuit needs looking at.

--Rich

Hmm, nice tip. Don't feel like getting my pc out of the closet, I take it I can use any 12 v supply? (I'm thinking of that electric train transformer lying here somewhere )

[rja]

Yup. PC is good though, because the 12v and gnd are next to each other, and the 78xx should plug straight in.

But yeah, any DC PSU giving more than 8v should allow the 7805 to function correctly.

--Rich

[DigitalJunkie]

Yea,that should work fine too.
I usually use the same trick for testing regulators.

[Miniwatt]

On 14 volts I get around 4 V on the output..

[rja]

Then I'd say it's faulty. Make sure it isn't overtheating - unlikely if you've just plugged it in to measure output voltage...

Sounds like you have a bad one. When you get a replacement, test it outside of the circuit initially to ensure you know you're starting with a working device.

--Rich