Problem with Lambda Dual PSU

[tdstotler]

Hello everyone,

Got a quick question.. I've got a few Lambda LCD A 22
Dual regulated power supplies. I am trying to
Use them for some projects that need Dual polarity
18 volt.. I have the negative output of the top
supply connected to the positive supply of
The bottom supply to act as the common ,
Then I take the positive from the top and the
Negative from the bottom. I have done this on
My bench lambda power supplies and it works
Perfectly, when I try this on any of these units I cannot
Get the common to act as a zero reference ,
If I measure either positive or negative I  getting
36 volts ????
I've attached a picture of the hookups, not sure
What I am doing wrong here, any advice would be
Appreciated.
Todd

http://m1048.photobucket.com/albumview/albums/tdstotler/Mobile%20Uploads/IMG_4442.jpg.html?o=0&newest=1

 

[Biasrocks]

Sounds like not referencing ground with one side of the multimeter and your getting the +/- voltages together.

Regards,
Mark

 

[tdstotler]

I turned on my dual lab Lambda PSU which is hooked up for Dual Polarity and checked that with the same multimeter and
I was getting 18 V postive and Negative, but when I check the one I am trying to use it gives me the 36....
So I didnt think it was the Multi Meter not measuring properly...

 

[Biasrocks]

Can you post a closeup photo of the connector strips?

Regards,
Mark

 

[tdstotler]

http://m1048.photobucket.com/albumview/albums/tdstotler/Mobile%20Uploads/IMG_4467-1.png.html?o=0

 

[Biasrocks]

http://m1048.photobucket.com/albumview/albums/tdstotler/Mobile%20Uploads/IMG_4467-1.png.html?o=0

It looks like the side you're measuring doesn't have an AC connector or a Ground connection, unless the two sides are somehow attached at those connections I don't see how it could work properly. Do you have ground continuity between Pin 5 & 13? Do you have AC on 9-10?

Here's how I read the terminals.

1-2, 9-10 AC IN
3,11    SENSE (-)
4,12    DC (-)
5,13    DC GROUND
6,14    DC (+)
7,15    SENSE (+)
8,16    PO (Power Off??)

How does the other side measure?

Regards,
Mark

 

[tdstotler]

Ahhh and there is my mistake, I don't have AC
On pins 9 and 10.. I only had AC on the bottom
Connectors, my thought was they were connected
In the power supply. I should just be able to  jumper
The AC from the bottom connectors to
The top 9 and 10 AC correct?

 

[tdstotler]

Ok On all these power supplies pin 9 and 10
Have a jumper cable on them???
If this is a AC input this would have to be removed
Or else I'm going to short the AC input ..,

 

[tdstotler]

On closer inspection on the psu, on the terminal
Strip of 9 and 10 that is jumpered on all
These units I have, it clearly shows a line
Connecting 9 and 10 if you look closely
at the photo you can see it..
I'm not too sure 9 and 10 are AC inputs now after
Seeing that, I can't find any info about these
Units online anywhere..

 

[Biasrocks]

That could be me mistake, chances are there's only one AC input for both outputs.

I can see the ground connection on Pin 5 but I don't see anything on Pin 13.

So, can you verify that you have a proper ground connection back to the AC ground on Pins 5 and 13.

You should also measure DCV from Pin 5/13 (assuming they are in fact grounded) to Pin 12 for (-) and 5/13 to Pin 14 for (+).

Regards,
Mark

 

[tdstotler]

Ok.. Measured continuity from pin 5 which
Has the AC ground attached back to
Pin 13 ( the top ground) and they do show
Continuity.  I measured DC again using the
Top negative connected to the bottom positive
As the common and I am still getting
36 volts.. I have my Lambda Lab supply set
Up right in front of me which is hooked up the same
Exact way ( neg to positive for common, in a dual
Polarity) and I am getting the proper positive and
Negative 18 volts , so it's not the multimeter.
Not sure why the common is not
(zeroing) out on these units ????

 

[tdstotler]

I thought it might have something to do
With the voltage sense pins but my lambda bench
Lab power supply is hooked up
In the same exact manner with both voltage sense
Pins attached to there respective positive or
Negative pins..

 

[tdstotler]

I do believe pins 5 and 13 are AC ground,
If these units are like my other lambda psu's but
Then again I may be wrong...

 

[Biasrocks]

Ok.. Measured continuity from pin 5 which
Has the AC ground attached back to
Pin 13 ( the top ground) and they do show
Continuity.  I measured DC again using the
Top negative connected to the bottom positive
As the common and I am still getting
36 volts..

As I would expect.

Measuring between DC common (Pin 13) and Top Negative, should be -18v. Pin 13 and Top Positive should be +18v.

Regards,
Mark

 

[tdstotler]

Ok maybe I'm confused here but this is
How I am reading the terminals :

Pins 5 and 13 are AC ground

Top pin 14 is the top negative which is connected
To the bottom pin 6 which is the bottom
Positive , this should create the 0 volt reference
Ground for dual polarity..
Then pin 12 on the top is the positive 18
And pin 4 on the bottom is the negative
Polarity..

I have my lambda lab bench psu hooked up
In this same manner and it reads perfectly
18 volts plus or minus using the common
Ref ..

For some reason connecting the top neg to
The bottom positive on these units are not
Creating a zero reference common for dual
Polarity.. Maybe there is something with the
Design of these supplies that prevent that.
Just sucks because I have several
Of these that I wanted to use in a dual polarity
Power supply..

 

[Biasrocks]

Ok maybe I'm confused here but this is
How I am reading the terminals :

Pins 5 and 13 are AC ground

Top pin 14 is the top negative which is connected
To the bottom pin 6 which is the bottom
Positive , this should create the 0 volt reference
Ground for dual polarity..
Then pin 12 on the top is the positive 18
And pin 4 on the bottom is the negative
Polarity..

I have my lambda lab bench psu hooked up
In this same manner and it reads perfectly
18 volts plus or minus using the common
Ref ..

For some reason connecting the top neg to
The bottom positive on these units are not
Creating a zero reference common for dual
Polarity..

Right.

Try measuring as I suggested and report back.

Regards,
Mark