TP2 at 7V

[homefire]

Actually this is a good thing for me. I have two PCB waiting to have something done with them. Your the Teacher! I'm leaning all the Pit Fall and crap that can go wrong. LOL Thank You Sir.

[Tibuck19]

YEAAA! Next !

loll beside having the ability of confusing everyone, I think for a newbie I ve done rather well hahaha besides you would get lonely if I didn t have so many questions .

[homefire]

YEAAA! Next !

[Tibuck19]

Let's take these one at a time:
Firstly, If you're getting +7V on TP2 with reference to TP10, then U3 (78L05) is kaput. Either that, or there's a short somewhere that's putting 7V onto the 5V line. You can easily check that (as mentioned before) by snipping off the output pin on U3.
Secondly, I think you're getting confused about U1 (79L05) because the pinout is different between U1 and U3. On U1 the middle pin is not the common, it's the input voltage.
Refer to Step 1 in the Build Document, where it says "Measure the voltage at U8 pin 4 (see Fig. 2)" to check the -5V supply.

Correct ashomefire also pointed out , lucky I had on last spare and it solved the problem ,Thanks again George, Sorry for all the confusion I will better explain on the next MD loll

[Tibuck19]

on 79L05 which is located on U1 I get 12V on the input and 7V on the common using middle pin as gound /// 12 - 7 = 5 GOOD

Measuring 78L05 which is located on U3 i'm getting 7V output and 9V on the input using middle pin as ground/// 9 - 7 = 2 Toast Your getting 2 Volts to much thru the Regulator. Replace it.

That Solved it , and the depth has increased , Thank you too all of you that I have confused Problem Solved, ON to the next one hahahaha. Thanks Homefire and George.

[Qiaozhi]

OK! Sorry if I got you all confused, I am getting 7V on TP2 When I measure with TP10, on 79L05 which is located on U1 I get 12V on the input and 7V on the common using middle pin as gound, Measuring 78L05 which is located on U3 i'm getting 7V output and 9V on the input using middle pin as ground . I am using a multimeter and not the oscop for these readings.

Let's take these one at a time:
Firstly, If you're getting +7V on TP2 with reference to TP10, then U3 (78L05) is kaput. Either that, or there's a short somewhere that's putting 7V onto the 5V line. You can easily check that (as mentioned before) by snipping off the output pin on U3.
Secondly, I think you're getting confused about U1 (79L05) because the pinout is different between U1 and U3. On U1 the middle pin is not the common, it's the input voltage.
Refer to Step 1 in the Build Document, where it says "Measure the voltage at U8 pin 4 (see Fig. 2)" to check the -5V supply.

[homefire]

on 79L05 which is located on U1 I get 12V on the input and 7V on the common using middle pin as gound /// 12 - 7 = 5 GOOD

Measuring 78L05 which is located on U3 i'm getting 7V output and 9V on the input using middle pin as ground/// 9 - 7 = 2 Toast Your getting 2 Volts to much thru the Regulator. Replace it.

[Tibuck19]

OK ... now I'm totally confused, and probably so is everyone else.

Please can you re-state the current situation with the power supply voltages. Which ones are correct, and which ones are wrong?
What do you mean by "78l05 AKA U3 is at 7 and 9 V"?

OK! Sorry if I got you all confused, I am getting 7V on TP2 When I measure with TP10, on 79L05 which is located on U1 I get 12V on the input and 7V on the common using middle pin as gound, Measuring 78L05 which is located on U3 i'm getting 7V output and 9V on the input using middle pin as ground . I am using a multimeter and not the oscop for these readings.

[homefire]

Dang. Measure the Voltage across the Regulators. . In/Out.. You should see Your supply voltage Minus the rated voltage. Anything less would indicate Shorted Regulator. Any thing more indicates Bad Regulator or Resistance on the control pin.

[Qiaozhi]

George im sorry I looked at the wrong one the 78l05 AKA U3 is at 7 and 9 V and I keep saying the 78l05 when I mean the 79l05 ,Gesss am I ever going to get it right for pete-sake loll , As I mention before I already replaced the 79l05 U1 not the 78l05

OK ... now I'm totally confused, and probably so is everyone else.

Please can you re-state the current situation with the power supply voltages. Which ones are correct, and which ones are wrong?
What do you mean by "78l05 AKA U3 is at 7 and 9 V"?

[Tibuck19]

In that case, it looks like the 78L05 must be faulty ... OR, there's a short somewhere that's putting 7V on the output pin. I would try disconnecting the 78L05 output pin (just snip it off with some side cutters) and measure the voltage between TP10 and the dangling output wire of the 78L05. I suspect you'll find it's +5V. If not, it's faulty. Then measure the voltage between TP10 and the pad where the wire was originally connected. Is it +7V?

George im sorry I looked at the wrong one the 78l05 AKA U3 is at 7 and 9 V and I keep saying the 78l05 when I mean the 79l05 ,Gesss am I ever going to get it right for pete-sake loll , As I mention before I already replaced the 79l05 U1 not the 78l05

[Qiaozhi]

George, the exact same voltage get from TP10 the output pin is at 12V using the input as -0V and the common pin is at 7V . this might be normal loll but when i have the probs on TP3 and try putting thr ground lead on TP10 I get a tiny spark, It has to be something Silly

In that case, it looks like the 78L05 must be faulty ... OR, there's a short somewhere that's putting 7V on the output pin. I would try disconnecting the 78L05 output pin (just snip it off with some side cutters) and measure the voltage between TP10 and the dangling output wire of the 78L05. I suspect you'll find it's +5V. If not, it's faulty. Then measure the voltage between TP10 and the pad where the wire was originally connected. Is it +7V?

[Tibuck19]

What are the voltages on the 78L05 outer pins with reference to the middle (0V) pin?
I know they should be the same as when you measured them with reference to TP10, but just humor me.

George, the exact same voltage get from TP10 the output pin is at 12V using the input as -0V and the common pin is at 7V . this might be normal loll but when i have the probs on TP3 and try putting thr ground lead on TP10 I get a tiny spark, It has to be something Silly

[Qiaozhi]

I'm looking for the problem and going around the hole board and those two resistors are the only two that are off specs and even after testing a new resistor (47K which is the closes I have) and replacing it , it still drops down to 22K, the 78l05 is in the correct way unless its a slik screening error which is next to impossible.

What are the voltages on the 78L05 outer pins with reference to the middle (0V) pin?
I know they should be the same as when you measured them with reference to TP10, but just humor me.

[Tibuck19]

Why would R21 and R22 effect +5v supply? Maybe a stupid question, what voltage would you read if the 78L05 was connected reversed?

I'm looking for the problem and going around the hole board and those two resistors are the only two that are off specs and even after testing a new resistor (47K which is the closes I have) and replacing it , it still drops down to 22K, the 78l05 is in the correct way unless its a slik screening error which is next to impossible.