There is a guide HERE <ADMIN NOTE: Broken link has been removed from this post by Dell> on how to remove your power supply to the 780mt, DT is HERE. <ADMIN NOTE: Broken link has been removed from this post by Dell>

Hi there,

The following Dell power supply part numbers are compatible with the Optiplex 780MT and 780DT:

Optiplex 780MT: 18N8R, FR607
Optiplex 780DT:  FR597, N249M, T164M

I hope that helps! 

Does this mean a P192M is not compatible? Or is there a long list of compatible power supplies? My question really stems from I mated this PS with a C27VV motherboard and I get the 1-3-2 beep codes with 1, 3 diagnostics lights when I plug in the supply. I have reseated and swapped the ram several times and still get the beeps. I have removed the battery for several minutes. I can find nothing on what to try next so I'm reaching out.

Does this mean a P192M is not compatible? Or is there a long list of compatible power supplies? My question really stems from I mated this PS with a C27VV motherboard and I get the 1-3-2 beep codes with 1, 3 diagnostics lights when I plug in the supply. I have reseated and swapped the ram several times and still get the beeps. I have removed the battery for several minutes. I can find nothing on what to try next so I'm reaching out.

The 1,3 diagnostic lights is to do with your memory, see HERE. <ADMIN NOTE: Broken link has been removed from this post by Dell> Have you tried taking them out, and reseating them making sure the gold areas are free from dirt. Also putting them back one at a time to find if any are faulty.

Yes I have, several times. Swaping them around. Even trying just one at a time in the slot 1 position.

I did try a different CPU on the board and was able to get it to not immediately beep code, but at that point I did not have any drives connected or the heat sink on so I couldn't do anything other than shut it off. Once the heat sink was back in place I got the beep codes again. Taking the heat sink off and reseating the CPU several times did not stop the beep codes again.

Hi there,

P192M doesn't appear to be a valid substitute part for the Optiplex 780 DT or MT according to the information I have. Is this a part that you have replaced yourself or was it shipped with your system? I just want to double-check what the situation is with the power supply.

Can you try each individual stick of memory in the rest of the memory slots? It may be the case that slot 1 is faulty. Also, have you added any third-party memory to the system? If so, can you give me the specification of the memory or a link to the vendor where you purchased the memory?

John C,

Actually I had gone to the Dell support website and looked up replacement parts for the 780MT and a referbished P192M was the only PS listed for sale. I did an online search on the part number and the listings I saw also listed it as 780MT compatible. So I purchased one figuring it was compatible. But now you have me wondering.

Fred

To answer your other question John, the memory I have is Kingston KTD-XPS730AS/2G. And yes I tried 1 stick at a time in various locations.

Actually I had gone to the Dell support website and looked up replacement parts for the 780MT and a referbished P192M was the only PS listed for sale...

Regarding the above, do you have the link that you visited handy? I'd just like to check that out for you.

Also, from the memory that you mentioned, that does appear to be third-party memory. Do you have the memory that was originally in the system? If so, what happens if you install that in the system? Do you still get the same issue or does the system POST and boot okay?

If you don't have the memory that was originally in the system, do you have any other DDR3 1066MHz memory sticks available to try?

Here is the listing from the Dell website about the PS I originally asked about. I had to grab the search engine cache as the PS sold so the page is now gone.

webcache.googleusercontent.com/search

Refurbished: 305-Watt Power Supply for Dell OptiPlex 580/ 760/ 780/ 960 Desktop System  

A Power Supply is a direct replacement for the original part, which supplies power to other component in your Dell™ system. This product has been designed to convert general-purpose alternating current electric ... Full Description

Starting Price  $84.99

Usually Ships: Within 24 Hours  

--------------------------------------------------------------------------------

Manufacturer Part# : P192M | Dell Part# : P192M

No, I do not have the original factory Memory. I first tried 4 sticks of this Crucial memory, swapping them every way possible.

www.newegg.com/.../Product.aspx

Then I read on-line that this model Dell only works with certain memory stick controller chips. So I went to the Kingston website and ordered what they claimed was compatible which is different from their mainstream DDR3 sticks.

Now I am also wondering if the Dell 780 doesn't recognise Single Rank memory sticks.

Hi there,

I would say that as the part did come from Dell that it is compatible. From a technical support point of view, we would not send out this power supply for any Optiplex 780 as we didn't ship out any Optiplex 780 with this power supply, according to the information I have.

Regarding the memory, it may be the case that the motherboard is faulty. The problem we have is that you don't have the original Dell memory to test in this system. The system should be able to take Single and Dual Rank memory sticks without problem but when it comes to third-party memory, we can never guarantee complete compatibility.

If possible, I'd like to get the system down to its most basic components, just to try and get an indication of any problems. If you could remove the following, it would be a great help:

** Please remove the power cord from the back of the system before doing this. **

1) Power and data cables from the optical and hard drives.
2) Any internal speakers.
3) Any PCI/PCI-Express video cards.
4) All memory from the system.

Switch the system back on and make a note of what the diagnostic LEDs show at that point. After this, add each individual component back, one by one. What we're looking for is something out of the ordinary so please make a note of what the diagnostic LEDs show after adding in each component. 

Please let me know how you get on.

Hi John,

All the trials I have been doing so far with swapping out memory and PS units has been done with only the PSU, Motherboard, CPU, CPU fan, front panel connector, and the various memory sticks.

I unplugged the HDD and optical drives when I first encountered a problem posting and have no cards in the PCI/PCI-E slots. I had the same idea to get to the most basic configuration to try and get it to post. I have not tried it with no memory instaled.

I also finally came to the same conclusion that it must be something in the Motherboard as at this point it is the only common part as I have swapped out everything including the CPU just in case. My new motherboard is due to arrive Saturday.

Thanks,

Fred