short question about 78S05

Status
Not open for further replies.
Jump to Latest
Miniwatt

Miniwatt

Member
Joined 2004
#1
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.:xeye:

Could it be I got the wrong part?
 
#2
yes-it sould be bad chip,or you zapped it somehow ;

this pinout?
 

Attachments

  • pinout.gif
    pinout.gif
    9.8 KB · Views: 145
#3
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..
 
#4
Miniwatt said:
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..
Click to expand...


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?

:clown:


is it necesary that I say.....been there.......etc.......
 
#5
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
 
#6
rja said:
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
Click to expand...


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😀 )
 
#10
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
 
Status
Not open for further replies.
Top Bottom