Problem with power section. Reading 60v on multimeter.

Discuss x0x construction and related issues

Moderators: altitude, adafruit_support_bill, adafruit, phono, hamburgers

Please be positive and constructive with your questions and comments.
User avatar
dcandusso
 
Posts: 9
Joined: Wed Sep 17, 2008 2:48 am

Problem with power section. Reading 60v on multimeter.

Post by dcandusso »

Hi, I am getting 60v at J4 at both pin 1 and pin 3.
All testing worked as per instructions in the power section except for the last step. Any clues?
Thanks in advance.

User avatar
mmm
 
Posts: 517
Joined: Tue Apr 24, 2012 1:51 am

Re: Problem with power section. Reading 60v on multimeter.

Post by mmm »

60V would probably kill the opamp; I'm also not quite sure how such a high voltage would be generated anyway. What do you measure between pin 4 and pin 8 of the opamp?

User avatar
dcandusso
 
Posts: 9
Joined: Wed Sep 17, 2008 2:48 am

Re: Problem with power section. Reading 60v on multimeter.

Post by dcandusso »

Thanks for your reply. I am getting 64v between pin 4 and 8.

User avatar
mmm
 
Posts: 517
Joined: Tue Apr 24, 2012 1:51 am

Re: Problem with power section. Reading 60v on multimeter.

Post by mmm »

That's actually the op amp supply voltage and of course way too high. The AN6562 is rated up to 30V when run from a single supply. 64V as a supply voltage would probably kill it.
What kind of power supply are you using?

User avatar
dcandusso
 
Posts: 9
Joined: Wed Sep 17, 2008 2:48 am

Re: Problem with power section. Reading 60v on multimeter.

Post by dcandusso »

I am running the one that shipped with the kit. The only thing is I am in Australia 240V. The power supply output correctly as I checked it with a multimeter. All other voltages match as per instruction steps.

User avatar
mmm
 
Posts: 517
Joined: Tue Apr 24, 2012 1:51 am

Re: Problem with power section. Reading 60v on multimeter.

Post by mmm »

It's a bit hard to believe that all other voltages should check out ok. Is the power supply auto-switching so that it automatically adjusts to different line voltages? If that was a 110V supply operating under 240V the voltage would be plausible.

User avatar
dcandusso
 
Posts: 9
Joined: Wed Sep 17, 2008 2:48 am

Re: Problem with power section. Reading 60v on multimeter.

Post by dcandusso »

Just checked power supply and it is 230v-50Hz - 9v output.
Also, when i check J4, both pin 1 and pin 3 show 60v.

BTW - I really appreciate your help!

User avatar
mmm
 
Posts: 517
Joined: Tue Apr 24, 2012 1:51 am

Re: Problem with power section. Reading 60v on multimeter.

Post by mmm »

dcandusso wrote:Just checked power supply and it is 230v-50Hz - 9v output.
Also, when i check J4, both pin 1 and pin 3 show 60v.
The power supply seems to be the correct one (if the output is also AC, not DC).

We probably need to work forward from that supply into the actual supply circuit on the IOboard.

Please measure the output of the wall wart supply; make sure that you multimeter is set to "AC" here.

Then measure the voltage at the 7805 regulator (IC20). This is of course DC, please set the multimeter accordingly. Attach the negative probe to the metal tab of IC20 and then measure the voltage on the two outer legs.

User avatar
dcandusso
 
Posts: 9
Joined: Wed Sep 17, 2008 2:48 am

Re: Problem with power section. Reading 60v on multimeter.

Post by dcandusso »

Hello, The regulator is measuring 31v and 10v on the two outer legs.

User avatar
mmm
 
Posts: 517
Joined: Tue Apr 24, 2012 1:51 am

Re: Problem with power section. Reading 60v on multimeter.

Post by mmm »

Please measure the output of the wall wart supply, too. Make sure the multimeter is set to AC.

Can you test the multimeter against a known voltage - for a example against a 9V battery?

User avatar
dcandusso
 
Posts: 9
Joined: Wed Sep 17, 2008 2:48 am

Re: Problem with power section. Reading 60v on multimeter.

Post by dcandusso »

The supplied wall unit is reading 10.9 Vac on the multimeter.
I tested another wall unit with a 4.5Vdc rating and it had 4.7 V measured.

User avatar
mmm
 
Posts: 517
Joined: Tue Apr 24, 2012 1:51 am

Re: Problem with power section. Reading 60v on multimeter.

Post by mmm »

Can you post a picture of the IOboard (both top and bottom)? I'm a bit at a loss so far since IC20 should theoretically be capable of taking +31V and then still regulating it down to 5V. However it would get very hot.
At the moment I suspect a problem in the "voltage doubler" section of the power supply.

User avatar
dcandusso
 
Posts: 9
Joined: Wed Sep 17, 2008 2:48 am

Re: Problem with power section. Reading 60v on multimeter.

Post by dcandusso »

Hi MMM,

Here is a link to the images. https://www.dropbox.com/sh/sgjwmeavxegl ... nUTxa?dl=0

Also, just to let you know, when I first started the build, I placed an incorrect capacitor into C1. I noticed this the first time I put power into the I/O as smoke started to appear from C1. I replaced C1 with the correct capacitor, however could this have potentially ruined another part?

User avatar
mmm
 
Posts: 517
Joined: Tue Apr 24, 2012 1:51 am

Re: Problem with power section. Reading 60v on multimeter.

Post by mmm »

Just to make sure: IC21 and IC22 are correct? If they are then we can continue further.

C1 shouldn't blow under normal circumstances at all (unless you fitted an electrolytic cap instead of it and the wrong way).

I guess at this point we need to take out as many active components out of the equation as possible. As I said, we should work from the wall wart into the circuit. Please remove R1 and R2, this will disable the whole circuit around IC23. Then measure the voltage (DC) between and the R1 solder pad closest to C5 and the middle solder pad for J4.

There's always the possibility of a copper bridge on the PCB or some kind of inadvertent solder bridge. That's very hard to see on the pictures, though.

User avatar
dcandusso
 
Posts: 9
Joined: Wed Sep 17, 2008 2:48 am

Re: Problem with power section. Reading 60v on multimeter.

Post by dcandusso »

I have checked IC21 and IC22 and both appear to be correct. Voltage measured between and the R1 solder pad closest to C5 and the middle solder pad for J4 = 68.6 V(ac). No DC voltage.

Locked
Please be positive and constructive with your questions and comments.

Return to “Making x0x”