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DIY Stompboxes => Building your own stompbox => Topic started by: brujo on September 18, 2021, 01:44:28 PM

Title: 78l05
Post by: brujo 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?

(https://i.postimg.cc/Z0L74x3d/Screenshot-2021-09-17-15-36-12-25.jpg) (https://postimg.cc/Z0L74x3d)
Title: Re: 78l05
Post by: antonis on September 18, 2021, 02:36:03 PM
Flip 78l05 180o..
Title: Re: 78l05
Post by: brujo 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
Title: Re: 78l05
Post by: Yazoo 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.
Title: Re: 78l05
Post by: Rob Strand 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.)
 
Title: Re: 78l05
Post by: ElectricDruid 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
Title: Re: 78l05
Post by: antonis 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:
Title: Re: 78l05
Post by: brujo on September 19, 2021, 08:58:58 AM
Here
(https://i.postimg.cc/phxtRxkw/IMG20210919145714.jpg) (https://postimg.cc/phxtRxkw)
Title: Re: 78l05
Post by: duck_arse on September 19, 2021, 10:52:53 AM
what voltage do you have on pin 2 of PT?
Title: Re: 78l05
Post by: Rob Strand 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.
Title: Re: 78l05
Post by: brujo 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