Author Topic: 78l05  (Read 574 times)

brujo

78l05
« on: September 18, 2021, 01:44:28 PM »
Hi there, I build this crap-fi delay (pt2399) but I'm getting only 1,5v on 78l05 output,any suggestions?



antonis

Re: 78l05
« Reply #1 on: September 18, 2021, 02:36:03 PM »
Flip 78l05 180o..
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

brujo

Re: 78l05
« Reply #2 on: September 18, 2021, 02:42:02 PM »
I will try It,thank you
Cheeers

The delay Is After a ne555 oscillator,and they share 9v . Let's are

Yazoo

Re: 78l05
« Reply #3 on: September 18, 2021, 06:08:59 PM »
Sorry to be a contrarian, but the orientation for the 78l05 shown on the layout is correct. If it was a full 7805, not the TO92 version used here, you would have to rotate it.

Rob Strand

Re: 78l05
« Reply #4 on: September 18, 2021, 07:32:49 PM »
You could measure the current going into the board.  (To measure current you need to wire the meter in series with the power.  Once you make the measurement set the meter and probe positions back to volts straight away.)
 
« Last Edit: September 18, 2021, 07:36:32 PM by Rob Strand »
Plopping around the pot since an early age.

ElectricDruid

Re: 78l05
« Reply #5 on: September 18, 2021, 07:41:23 PM »
Sorry to be a contrarian, but the orientation for the 78l05 shown on the layout is correct.

No-one said the layout was wrong, only that if you're getting 1.2V out of it, putting it in the other way around is a likely solution since it's probably back-to-front.

I've made this stupid mistake enough times to know by now, but it still happens.;)

If the PT2399 is socketed, you could test it with the chip taken out. It's good practice to check power voltages first before putting chips in, in general. Another potential cause is something dragging the output down, like a bad 2399, or a short.

HTH

antonis

Re: 78l05
« Reply #6 on: September 19, 2021, 06:27:57 AM »
Another potential cause is something dragging the output down, like a short..

Actually a "short" in the form of 32/10 voltage divider.. :icon_wink:
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

brujo

Re: 78l05
« Reply #7 on: September 19, 2021, 08:58:58 AM »
Here


duck_arse

Re: 78l05
« Reply #8 on: September 19, 2021, 10:52:53 AM »
what voltage do you have on pin 2 of PT?
"I'm your vehicle, baby", but go easy on the clutch.

"You've got a suss sus sus sus sus sus sus suspect device."

Rob Strand

Re: 78l05
« Reply #9 on: September 19, 2021, 06:26:25 PM »
Quote
what voltage do you have on pin 2 of PT?
It's a marker pen dot over a PCB hole identifying a PCB cuts.   Looks a bit odd in the pic I think it's light blue.
So no pin 2 Ref cap.
« Last Edit: September 19, 2021, 06:28:25 PM by Rob Strand »
Plopping around the pot since an early age.

brujo

Re: 78l05
« Reply #10 on: September 22, 2021, 11:38:37 AM »
it was a bad 78l05,probably connected with reversed polarity?!
this is voltages on pt2399
1=5v
2=2.5v
3=0v
4=0v
5=3.45v
6=2.5v
7=0.65v
8=0.65
9=2.5v
10=2.5v
11=2.5v
12=2.5v
13=1.3v
14=2.8v
15=2.5v
16=2.5v