4 Pole Testing Problems

I took a long time building this and things don’t seem correct:(

When it says:
“Without any IC inserted and the board powered off, check that there is no short between a red and green pad ; a red and blue pad ; a green and red pad.” - To be clear, Do I measure this with the resistance setting on my DMM? I did and wasn’t getting any zeros so I went to the next step.

I inserted LT1054 powered on but only got 3V
I’m not sure I measured correctly though…

The power supply that I tested with turned out to be center ring negative - Do you think this damaged anything? Furthermore, when I test the supply with my DMM, I get 13.17v on DC.

I then found a tiny adapter that said 9v 200mA center ring positive but when I try step 2 now with it, I get all zeros.

I then checked this tiny adapter with my DMM and it says it’s 16.67v On DC

I’m confused why a smaller adapter would put out more power yet is similarly rated 9v?

Do these ratings matter or does it only matter that it says 9v DC + the MA ratings on the outside?

How should I proceed? Should I use this tiny adapter and continue?

Thanks!

BTW, the candy was refreshing and crisp!

Hey!

1. I think you’re supposed to use continuity mode to check to make sure the red and green pads are not connected. It beeps when a circuit is established…

2. The diode should protect most of the circuitry from polarity issues but I think the LT1054 comes before it and can get fried. Someone correct me if I am mistaken.

3. Too much voltage will overload the voltage regulators. 9-12V I believe is okay (check the manual), 16 I think is too much.

4. Make sure all your measurements are with the black probe grounded to a known grounded pad, like the ones labeled GND on your board. I think there are two. Otherwise your measurements may be wrong.

5. Check the usual suspects: reversed voltage regulators (they look identical but are not)…

Hope this helps. When Europe wakes up in the morning there will be more expert advice at hand.

> why a smaller adapter would put out more power yet is similarly rated 9v?

If it’s an unregulated supply, it’s normal - the output is not perfect DC and has a bit of ripple, the dips go deeper as the supply is loaded, and it goes below 9V if you try to draw more 200mA from it, hence the ratings.

There’s a reverse polarity protection diode at the very input of the circuit, so reverse polarity did not cause damage.

However, the LT1054 doesn’t like when the input exceeds 15V so you might have damaged it.

This still does not explain why you get 0V everywhere… Have you soldered a bridge on the pair of pads labelled SW? What are the voltages at the I / O / - and I / O / + of the regulators?

Thanks pichenettes & Titus Raindrops!

I just got a new power supply that is 9v regulated and I can set the center pin as negative or positive.

I did not solder the jumper in, I totally missed it. Now I soldered it and am getting all 5V :slight_smile:

So considering I did not have the jumper in when I powered on, is it still possible I damaged LT1054?
To be safe I will replace the part if you suggest to.

7805:
O - 5.01v

    • 0
      I - 8.26v

7905:
O - 5.00v
I - 07.98v

    • 0

SW is for an on/off switch. If you didn’t have the jumper in place, it was OFF. So I don’t think you allowed any current beyond the DC input jack.

Readings look good, and you don’t have damaged anything if the jumper wasn’t there…

Awesome!