Stim or MS 2.2 voltage problem

[trakkies]

Right. Trying to remember if you've checked D15 - the zener diode - for a short?

Next thing to try is to remove L1 and L2 in turn carefully as they have to be re-fitted. Measure after removing each one. This is to isolate which of the 5v feeds has the short. This checks Vsyn and Vref for the short. If neither it must be Vcc. Hopefull.

Don't lose heart. Fault finding is simply a case of going through all the possible causes one by one and eliminating them. And you'll learn about things as you go. I'm assuming you're looking at the schematic and seeing what each component mentioned is and does?

[magflip]

I've tested D15. It's OK.
I removed L1 and L2 to tests, but I don't know how measure them. I think I haven't tools to this (only a DVM, without inductance function). There is a simple way to test L1 and L2?

I analyzed the schem of v2.2 and I realized the inductors L1 and L2 comes after LM2937. If LM2937 doesn't send 5v by pin3, how the problem could be in another components? The problem wouldn't be in components/rail before the LM2937?
By the way, when I replaced C15 and C16, I replaced the LM2937 by LM7805, because I didn't find original component for sale in my region. Anyway, after replaced, in the tests, LM7805 resulted same of LM2937.

[trakkies]

Removing L1 and L2 is simply to find out if the short on the 5 volt rail goes - ie you now have 12v on pin 1 of U5, and 5v on pin 3.

[magflip]

I'd some measurements 'on their own'.
With stim plugged and powered, black lead of DVM on non-banded D13 and another lead in banded side, DVM show 9.13v.
On v2.2, a rail between banded of D13 and pin1 of U5 and (+) of C15 had a hole. Using black lead of DVM in pin2 of U5 and another lead on this hole, I shouldn't have same voltage (9.13v)?

Without L1 and L2:
- pin1 of U5 + 32 of dip40 = 0v
- pin3 of U5 + 32 of dip40 = 0v

A doubt: to the tests without L1 and L2, I had to connect (jumper) the holes of inductors?

[trakkies]

Banded side of D13 should be connected to Pin1 of U5 by a track on the PCB. U5 is the 5 volt regulator. Pin3 should show 5v. Pin 1 should be approx the voltage of your power supply.

By removing L1 and L2 you've proved the short isn't after either of those 5v rails (Vsyc and Vref). So they can be replaced.

By elimination, it looks like the short is on the Vcc rail.

Next thing I'd look at is U6, as it appears to be the only thing directly connected to Vcc, if you've removed U1.

One other thing - can you measure how much current MS is drawing from your power supply?

[magflip]

trakkies,
the test I did yesterday when I measured the voltage on the track between the non patterned side of the D13 and the pin1 of the U5, was not about 9.13v.
The problem could not be there?

Anyway, how can I test the U6? And, how can I measure how much current MS is drawing from my power supply?

[trakkies]

You said in an earlier post that you had approx 9v on the input to D13 (Pin2 on the schematic) and approx 0v on the output of it.

Now:-
"the test I did yesterday when I measured the voltage on the track between the non patterned side of the D13 and the pin1 of the U5, was not about 9.13v."

Those readings don't agree, as the output of D13 is connected to PIn1 on U5.

Can you take a good picture of the PCB showing U5 and post here?

[magflip]

When I tested the D13, I put the black lead of DVM in and non banded side and the other lead in side stamped, resulting in 9.13v.
When I tested the trail that connects the banded side of D13 and the pin1 of the U5, I put the black lead of the DVM in the pin2 of U5(GND) and the other lead on the trail. The measurement can not be made this way?
If I can not, I suppose I'll have to do a course in electronics before continuing the adventure with MS. LOL

I have attached photos of the U5 as requested.

C360_2014-10-20-18-48-31-688.jpg

C360_2014-10-20-18-48-58-741.jpg

C360_2014-10-20-18-49-24-032.jpg

[trakkies]

Normal way to measure voltages is with the black lead of the DVM connected to ground.

[magflip]

How can I test the U6? And, how can I measure how much current MS is drawing from my power supply?

[magflip]

Finally I think I have identified the problem, but please do not laugh if I'm talking nonsense.
I connected my MS in stim and fed with 12v.
I measured the D13 putting the two ends of the DVM at their ends and found 8.95v. I measured the D13 again placing one end of the DVM in non printed side and the other test lead on pin 19 of DIP40, having obtained 9.43v
On the trail that connects the printed side of the D13 to C15 and U5, I put one lead of the DVM, and the other lead I put back on the 19 pin DIP40. Result: 0.40v.
Then I ask: this last measurement (at the track), should not have given the same 8.95v (or at least approximately so) when measuring the D13 in your extremities?
After that, I replaced the D13 component thinking he might be short. I did the measurements again and got the same results.

As I understand it, the stamped side of the D13 are coming out just 0.40v. That's right, or is this the problem? If this is the problem, how do I fix it since it seems that the problem is not in the component itself?

[Matt Cramer]

Try desoldering the D19 diode and see if that gets you the 5 volt reading back.

[magflip]

I remove the D19 and the results I got the measurements were the same.