Dell psu conversion help

[kdog]

Hi all
I'm hoping someone can help with the pinout details on these psu's I scored for dirt cheap.
I have a pair of each shown. One is a 750w dell F750e-S0 (smaller one) and the other is a dell 870w A870P-00 (square one). I'm intending to mod and series one pair for a 24v output bench too power supply. I'm fine with the float mod req for one as the outputs are not isolated, but first I need to turn them on!
They seem to work cause the status LED shows OK
Before anyone gets too keen... yes I've searched the net. RC groups, tech sites, here and youtube.
I can find endless info about hp's and other models of dell's but frustratingly not these. Almost all other models have a L-R transposition of the power terminals and the pins. At first I thought the pins would still be the same maybe opposing, but noooooo...
I've had a quick probe and determined that the pins are different to the aforementioned similar models.
Before I blow them trying to figure it out, does anyone know? Or can anyone give me a tip on figuring out how to determine the pins. I can use online info a a guide for some pins eg. If it shows 3.3v I know what it is but most won't be that easy.
I'm new to these so any help would be greatly appreciated
Thanks
K

 

[kdog]

I know that on the a870p I have to short two pins to ground. They're the pskill and pson ( or whatever the names are). If I start shorting random pins to grnd am I going to damage something or are they fairly fail safe? I really don't want to kill it before I even get it going!
Likewise on the f750e I think I have to jumper two pins with a 500-1k resistor. Again am I going to damage anything if I try every combo possible to find it?
Any wisdom appreciated!
K

 

[kdog]

WIN!
I've turned the both of the A870P psu's on...yeha! Just when I'd resigned myself to having more crap that was going to end up lying around... I followed a net trail that lead me to the Russian electrotransport forum. Can't read Russian to save myself but they had pics of the same dell psu as mine, and a single word followed by many !!!!s which I assumed was power!!!!
Thanks to the RC groups thread for leading me there.
Check the pic for the diagram. If anyone wants details I can post more about it.
Screen shot of the RC site with the interpretation ( but no mention of model no.)

 

[Hillhater]

Well done !! :lol:
That is the true spirit of DIY "suck it and see" testing.... you deserve a degree in internet research !

 

[kdog]

See if I can replicate the good fortune for the next pair.
Pretty stoked to be having. 1700w charger for $10au. 8)

 

[Hillhater]

Pretty stoked to be having. 1700w charger for $10au. 8)

Careful... you have a 1700W POWER SUPPLY,..its not a charger !,,no CC/CV profile control

 

[kdog]

Err yeh right you are HH! Slip of the tongue there. It is powering an adaptto system so that'll take care of the charging end of business... But I have another question now.
I have decoupled secondary (12v) ground from the primary (240v)ground on the second unit. This is to isolate it when in use in a series config with the first.
I haven't finished testin it out yet, in fact since the mod I've only just plugged it in (powered) but haven't turned the psu 'on'
So far so good, no pops and LED is happy green.
The case is isolated from DC output, but remains connected to mains earth. However ( when just plugged in) im getting aprox 54vAC on both pos and neg output terminals to case.
I've limited understanding on this but is this bc there is no reference to ground and the output V floats up.
Should I power the PSU up?
Will it survive
If it does- will it matter for the final DC voltage.
I don't want 54ac 'ripple' on a 24vdc supply!
Any thoughts appreciated.
K

 

[kdog]

So I shorted the output neg to the case and only 3mA flowed to bring the AC back to zero... So I'm happier that there is no power in it, but stil not sure if its going to end up in the final output and/or matter.
I've a friend with a oscilloscope so I might try scoping it.
Any thought appreciated.

 

[kdog]

Well I just series them up and it seems fine. Got a 24v 1700w power supply now-sweet. The 54v AC Voltage seems to disappear with a load ( I think). Only tested at 100w (halogens)
I did get a fault light appear on one test- not sure why, they both turned themselves off. No harm done, might have been me half flicking the switch on or something like that.

 

[kdog]

MORE SUCCESS!

Ive just succeeded in turning on the dell f750-s0. No direct info on the web but I followed instructions on rc groups to narrow down pins.
Ground pins 13& 14 ( I used 300ohm R). When you look at the bottom side they're first and second from the left...that was it! Takes about 1 sec to turn on.
Pretty happy cause I scoured the internet for months to find a direct answer, there wasn't one.


Edit: at first I thought it was just pin 14 but my finger was grounding 13- so do both. No sure of orders etc.