Originally Posted by prjoe

Hi all,
Does anyone know if it's normal operation on these units while wired in series to have voltage fluctuation? When the cases are not touching, the voltage is steady, but when they touch, the voltage starts to fluctuate rapidly. With the units separated I get 12.6V / 25.2V stable accordingly.
Is this something to worry about? Please let me know if something doesn't look right.
I fear connecting my PL8 and burning it.
Thanks in advanced for any input you can provide.

This is how it's wired now.
Attachment 5086024

The cases touching shouldn't make a difference because the cases are supposed to be connected to the AC ground, and each AC ground should be common with the main AC ground.

Originally Posted by prjoe

Hi all,
Does anyone know if it's normal operation on these units while wired in series to have voltage fluctuation? When the cases are not touching, the voltage is steady, but when they touch, the voltage starts to fluctuate rapidly. With the units separated I get 12.6V / 25.2V stable accordingly.
Is this something to worry about? Please let me know if something doesn't look right.
I fear connecting my PL8 and burning it.
Thanks in advanced for any input you can provide.

This is how it's wired now.
Attachment 5086024

Looks like the ribbon cable is wired incorrectly. Pin 8 on the ribbon cable is voltage adjust, which is close enough to ground to power up the PS, but it's not the correct place to tie PsKill (5) and PsOn (4). You should tie 1-2-3-4-5 all to DC ground. Leave 8 open unlesss you want to raise the output voltage. Look back at post 551 for more details on adjusting the output voltage.

Originally Posted by Dusey52

Looks like the ribbon cable is wired incorrectly. Pin 8 on the ribbon cable is voltage adjust, which is close enough to ground to power up the PS, but it's not the correct place to tie PsKill (5) and PsOn (4). You should tie 1-2-3-4-5 all to DC ground. Leave 8 open unlesss you want to raise the output voltage. Look back at post 551 for more details on adjusting the output voltage.

Thanks for your feedback Dusey52,

I tried your suggestion and changed the wiring leaving #8 open as I don't want to adjust voltage. Close but not quite there. Still getting voltage fluctuation on the 24V side y get from 24.3 up to 24.7v, on the 12v side however, I'm getting 12.4 to 12.5v.
As soon as I separate them, voltages become steady (12.5 - 24.8). This is frustrating.

Again, I appreciate your input.

See if this helps prjoe.

For each individual power supply and ribbon cable also connect the Voltage Adjust #8(+12V Return Sense) and Current Share #9 to DC ground.
Then connect the PSUs together in series.

xandrios, do you know what header pins 7 (ribbon 6) & 12 (ribbon 7) are?

It looks to me like pin 7 (ribbon 6) is the - return sense.

Originally Posted by xandrios

See if this helps prjoe.

For each individual power supply and ribbon cable also connect the Voltage Adjust #8(+12V Return Sense) and Current Share #9 to DC ground.
Then connect the PSUs together in series.

Hi xandrios,

Thanks for your reply.
Tried what you suggested and I keep having the same issue.
So far I've tried the following ribbon wire combinations:
1/2/3 to grnd 4/5/8 shorted
1/2/3 to grnd 4/5 shorted
1/2/3/4/5 to grnd
1/2/3/4/5/8/9 to grnd

Re-did all 10gauge wires and crimpings
Floated one unit with 3 fiber washers between case and board, cut GRND jumpers.
I'm beginning to think one of my units is hosed.
But the strange thing is if I test each one individually, they behave as expected. It's hard to believe this has not happened to someone before.
Some pics of the suspects:

At least one of the big heat sinks is live AC. I hope you aren't running them with the case off (like in the pictures).

Also, as I posted earlier, it shouldn't make any difference if the cases touch, because both cases should be grounded to the same AC ground.

typeRA is right, the cases should both be grounded through the A/C plugs so they should already be 'shorted together'. If you have a meter, you might verify ground continuity (or check to see if there's any voltage between the cases). There should be zero ohms and zero volts. You also could try taking the tape off of the spare wires and make sure none of them are shorting together.

In one of your previous posts you mentioned using three fiber washers on the two mounting screws, shouldn't that be four (1 each top & bottom for the two screws)?

Originally Posted by Dusey52

typeRA is right, the cases should both be grounded through the A/C plugs so they should already be 'shorted together'. If you have a meter, you might verify ground continuity (or check to see if there's any voltage between the cases). There should be zero ohms and zero volts. You also could try taking the tape off of the spare wires and make sure none of them are shorting together.

In one of you previous posts you mentioned using three fiber washers on the two mounting screws, shouldn't that be four (1 each top & bottom for the two screws)?

Continuity checked ok, (no beeps) and zero volts between the cases. I used 3 washers on each screw, one between the screw and the board, and 2 between board and case. Also the jumpers are snipped for redundancy.
One other thing is that I bought these units as a lot of 2. But the part numbers are different. The grounded unit is PN 321632-501 and the isolated unit for 24V is PN 321632-001. Might it be they don't play nice together?

Thanks

Originally Posted by typeRA

At least one one the big heat sinks is live AC. I hope you aren't running them with the case off (like in the pictures).

Also, as I posted earlier, it shouldn't make any difference if the cases touch, because both cases should be grounded to the same AC ground.

Thanks for the concern, I'm running them without the case because I'm making so many changes to the ribbon taking all suggestions and it's a pain to be taking the cover on and off after every try. I always make sure nothing is in contact before I plug the units, and I only test the probes at the binding posts.

Thanks for your suggestions.

Originally Posted by typeRA

At least one one the big heat sinks is live AC...

Yep, I can attest to the accuracy of the above statement. Don't ask me how

Edit:
In case anyone wants to know, it's the larger one, the one nearest the AC mains input.

Originally Posted by prjoe

Continuity checked ok, (no beeps) and zero volts between the cases. I used 3 washers on each screw, one between the screw and the board, and 2 between board and case. Also the jumpers are snipped for redundancy.
One other thing is that I bought these units as a lot of 2. But the part numbers are different. The grounded unit is PN 321632-501 and the isolated unit for 24V is PN 321632-001. Might it be they don't play nice together?

Thanks

I have the same two part numbers, 321632-501 & 321632-001. They work together just fine. The only difference is I isolated the -501 and left the -001 stock.

As far as continuity goes, I have ground continuity from the case to the A/C ground lug on both power supplies. So, when they're plugged into an A/C power source, there's ground continuity from case to case via the A/C line. Electrically, the cases are connected just as if they were physicaly tied together with a ground strap. If you do not have ground continuity between cases, your assertion that one of them is bad may be spot on.

There's a lot of great information on the preceding pages but the 'unknown' pins always bugged me so here's an update to what the various pins do, enjoy.


PIN .......... Ribbon Wire ....... Description
. 1 ............ N/A ...................... +5VSB
. 2 ............ N/A ...................... +5VSB
. 3 ............ N/A ...................... +5VSB
. 4 ............ 3 .......................... Fan speed, ground for minimum speed. (For variable speed use ~4.6v to Vcc.)
. 5 ............ N/A ...................... -12V
. 6 ............ 5 .......................... PsKill, ground this and PsOn to turn on the PS.
. 7 ............ 6 .......................... +S (positive sense)
. 8 ............ N/A ...................... DC ground
. 9 ............ 8 .......................... -S (negative sense)
10 ............ 4 .......................... PsOn, ground this and PsKill to turn on the PS.
11 ............ 9 .......................... Current Share
12 ............ 7 .......................... Power OK/Fault (OK = 3.8V, Fault = 0V).
N/A .......... 1 .......................... Ground from the output board back to the main board (needs to be tied to DC ground).
N/A .......... 2 .......................... Ground from the output board back to the main board (needs to be tied to DC ground).
N/A ........ 10 .......................... Ground from the output board back to the main board (not needed).

OK, so what's the deal with pins 7 & 9, pin 9 is voltage adjust, right? Well, yes and no. High end power supplies regulate voltage at the load (as opposed to at the PS). They accomplish this by monitoring the voltage at the load using two small sense wires (+S & -S). The voltage at the load is feed back to the voltage regulator so the regulator can compensate for any line loss caused by large currents flowing through the primary output wires. If the sense pins are connected as originally intended, +S to the positive output line and -S to the negative output line, the PS will run at its rated output of 12.15V at the point where +S & -S are connected. If they're left open, you'll get about 12.5V. Now since these 'sense' pins give us access to the voltage regulator circuit, we have direct control over the regulator (within limits). To raise the output voltage you pull -S up or pull +S down (or both) using an appropriate resistor. A simple way to accomplish this is to connect a resistor between +S & -S. They're actually already tied together via a resistor internally, we're just adding a parallel resistor to lower the value.

Here's a few examples of connecting +S to -S via a resistor and the resulting output voltage:

1.8K ......... 13.8V
2.1K ......... 13.6V
2.3K ......... 13.5V
2.7K ......... 13.35V
3.3K ......... 13.2V
3.9K ......... 13.1V
4.7K ......... 13.0V
10K .......... 12.7V

Note: The closer to OVP (~13.8V) you get, the more likely you are to have issues with the PS shutting down unexpectedly and/or not being able to deliver full current.

Thanks, Dusey.
That's one of the most useful posts I have seen.

Please put a link to that post in the sticky thread here

http://www.rcgroups.com/forums/showthread.php?t=1292514

John

Hey Dusey52.

Just caught your question from post #560.

I stated that ribbon wire #8 was the +12V Sense Return(also called -Ve Sense or Vs-) to keep in sync with the logic of PSU manufacturers.

The "Return" part just means the return for the +12v.

So that would make it the sense line for Ground(-Ve).

This can be see in a pinout for the 1300W DL580 G3 PSU.

If you didn't want to run the small sense wires to the load then voltage compensation can also be maintained

by sending a portion of the Current Share signal to the negative sense line.

The Current Share output voltage increases with load.

In general the Sense lines are internally connected as described in the second image.