Precision 7920 Tower BIOS Recovery

When performing BIOS recovery, be sure remove all external USB devices except for wired mouse and keyboard.  While holding CTRL + ESC keys, introducing power to the workstation (connecting power cord) should trigger the BIOS recovery process (menu displays on monitor).  Many attempts may be needed until you get the right timings (let go of the keys when the keyboard light lights up).

The recovery image USB is non-bootable, FAT32 formatted and use small capacity of 32GB or less.  Temporarily remove the system boot drive may help in some cases.

Yeah I've being trying it with everything removed that I can so the only USB connections are the keyboard, mouse and disk I'm hoping it updates off, and I've even removed all internal disks now too. I've been holding onto CTRL-ESC for 5-10 mins though.. so maybe thats where I've been going wrong. 

What I've noticed is that in the first attempt after the CMOS battery removal and CMOS jumper short, the display is just black, the blinking white cursor never happens. Its just every attempt after that that the white cursor happens until I remove the CMOS battery again.  

Hi

Hope this helps, although I note you have already covered most (if not all) of the parts...

The /writehdrfile can also be -writehdrfile and is part of the BIOS executable.

NB: By unplugging the Storage device as @Chino de Oro suggests does negate the need to remove the bitlocker system, if you can do the conversion on the actual USB.

@anne_droid​ 

So when I try /writehdrfile with the 2.46 version I downloaded (and checked the SHA to make sure its valid), it gives an error that its an unrecognized command line option, and to use /? to show command help. When I do that it shows the various options available such as /s to suppress the user interface, /f to override soft dependency errors etc. The only option that seems even remotely like creating a hdr or rcv file is the option /BIOSMeasurement which it says "Dump PCR0 measurement to a file", but BIOS Measurement doesn't sound anything related to BIOS recovery. 

Am I missing something very obvious here? Do I need to go to a much older BIOS version to get this functionality, and if so any idea on which version might be a good one to use?

Hi

Sorry.

You are correct, in that.......

• Not All BIOS Updates Support /writehdrfile:
  Some Dell BIOS executables may not recognize this option and will return an error like "Invalid command line" or "Unrecognized command line option" if unsupported.

@anne_droid​ 

So is there any way to produce the .rcv file for the 7920, or is the only method to rename the downloaded BIOS exe to that? 

I have not found anyway to produce an RCV file for the 7920, 

• Rename the downloaded .exe BIOS file to BIOS_IMG.rcv;

is the perceived wisdom, but I cannot check it's validity.

Sorry.

Yes, you can rename the BIOS.exe file to BIOS_IMG.rcv to perform BIOS recovery.

https://www.dell.com/support/contents/en-us/videos/videoplayer/how-to-recover-from-booting-issues-using-the-bios-recovery-tool/6079779755001

@Chino de Oro​ 

You mention above to remove all external USB other than keyboard & mouse. I've removed all storage devices from the system, other than 3 USB devices I've connected at the front, back top and back bottom, to try and increase the odds of one of them being detected. There's nothing USB related other than that other than the keyboard and mouse as mentioned, and the network has been removed so it doesn't have that option either. Do you see any issue with this?

Also.. when I boot it, the caps lock comes on for about 5 seconds, then turns off, and then comes back on again when the Dell logo comes on screen. Which turn on am I supposed to be releasing Ctrl-Esc on? I'm presuming the first one, although I've tried both without success so far. But I'd like to clarify this so its one less thing to wonder if I'm doing wrong. 

The mentioning of removing all external USB devices was for recovery preparation and was referring to USB devices that could have been use such as external drives, headset, game gears type of devices.  The only USB devices being for recovery process are mouse, keyboard and recovery image USB drive. 

About recovery process, it should start with system powered off and power cord removed.  The main action of process is pressing and holding both of Ctrl + Esc key and introducing power to the system by plugging in the power cord.  That should trigger the BIOS recovery process.  For visualization, the timing to release the Ctrl + Esc keys when you see the keyboard light lights up.  In your case was the Cap lock key light.

If the recovery menu did not display, restart the process again until you get the right timing of triggering the process.  Once the menu is displayed, it would be obvious to follow the screen and select recovery.  It's just another way of perform flashing the BIOS to correct the assumed corrupted one, using the BIOS image from USB.

@Chino de Oro​ 

OK, thats pretty clear. The one remaining question I have is.. since I bought the system, once I plug in the power cord, the system does a semi power-up of sorts without the power button being pressed, nothing appears on screen and then after 20-30 seconds powers itself off automatically. I assume pressing Ctrl+ESC during this period is immaterial (even though I do it anyway), and it is only after the subsequent power on via pressing the power button that the recovery menu will appear? 

Hold the Ctrl + Esc keys while introducing power to your system by plugging in the power cord.  Do not press the power button.  

Since you had noticed that the LED lighted up whenever you plugged in power cord, that was the moment the system did a quick check and found the command for BIOS recovery from keyboard, it should trigger the process and displays on the monitor screen.

Unfortunately you lot are barking up the wrong tree, this exe file file and renaming to .hdr will never work. I had two bricked dell T7820 (shares the same bios as the T7920, correct me if I am wrong). I went down the rabbit hole and the only way to get the system back is flashing the bios yourself using a programmer. quick write-up of my journey on the way to recovering my systems.

✅ Dell T7820 BIOS Recovery Summary


(W25Q256JVFQ, CH341A Programmer, No .HDR Available)

If your Dell Precision T7820 is bricked due to a BIOS update failure (no POST, black screen, fan spin only), here’s what actually works — since no forums gave a full working answer when I searched.

❌ .HDR File Not Present — USB Recovery Won’t Work

Dell BIOS .exe files sometimes contain a hidden .hdr file used for recovery via USB, but:

This means:

• USB BIOS recovery won’t work
• BIOS Recovery Mode (blinking amber/white power LED) is not enough to restore it
• You must flash the BIOS chip manually

✅ The Only Working Fix: Manual Flash via CH341A Programmer

🧠 What You’ll Need:

1. CH341A programmer
   • ⚠️ Default "black/gold" models output 5V data lines, which can damage 3.3V flash chips.
   • ✅ Recommended: Use a CH341A v1.7, which supports 1.8V / 2.5V / 3.3V / 5V logic levels natively — no modding required.
2. 16-pin SOIC clip
   • The BIOS chip is in a 16-pin WSON/SOP package — not an 8-pin SOIC.
3. Proper wiring (see below)
4. Software: NeoProgrammer (or ASProgrammer)
5. A known-good .bin BIOS file (32MB, dumped or sourced)

📌 BIOS Chip Information

• Model: Winbond W25Q256JVFQ
• Capacity: 256 Mbit (32MB)
• Voltage: 2.7V – 3.6V → requires 3.3V
• Package: SOP-16 (Wide SOIC / WSON-16 format)
• Protocol: SPI NOR Flash

📸 Correct Pinout (Pin 1 Top-Right, Standard Orientation)
TOP VIEW (Clip on chip, notch/dot is on top-right → ●)

_________________________
|                      ●             ← Pin 1 (marked on chip)
| 8 7 6 5 4 3 2 1               | ← Top row of clip
| 9 10 11 12 13 14 15 16 | ← Bottom row of clip
|_________________________|

✅ Active Pins to Use:
Pin # Name Use
1 HOLD# Pull high (to VCC)
2 VCC 3.3V power
7 CS# Chip Select
8 DO MISO (data out)
9 WP# Pull high (to VCC)
10 GND Ground
15 DI MOSI (data in)
16 CLK Clock

Only these 8 pins are required. The others are not connected (NC).

✅ These are the only 8 active pins. The others are NC (Not Connected).
✅ Use a multimeter in continuity mode to test and label each SOIC clip wire before wiring to your CH341A.

🛠️ Step-by-Step Process

1. Connect your 16-pin SOIC clip, using only the 8 pins above
2. Supply 3.3V via CH341A or external adapter (1.8V will not work)
3. Set the software to chip: W25Q256FV (fallback for JV)
4. Read the chip and save a full dump (32MB) as a backup
5. Flash your known-good .bin BIOS file
6. Disconnect, reassemble, and power on — you should see POST

🧪 Important Lessons Learned

• ❌ Do not use 1.8V — this chip is 3.3V only
• ❌ An unmodded CH341A can damage the chip due to 5V data lines
• ✅ CH341A v1.7 is safer — fully supports 1.8V, 2.5V, 3.3V, and 5V
• ❌ .HDR extraction tools will not help — it’s not present in the Dell BIOS file
• ✅ A 16-pin SOIC clip is required — not 8-pin
• ✅ Only 8 of the 16 pins on the BIOS chip are used — wire them correctly!

🧰 Tools I Used:

• CH341A programmer (v1.7 — highly recommended)
• 16-pin SOIC clip (wired manually to 8 pins)
• NeoProgrammer v2.1
• 32MB .bin BIOS file (from known-good system or Dell extraction)
• Multimeter (for voltage and continuity testing)

If you're stuck with a bricked Dell T7820 and getting no help from forums or Dell, this is the method that actually works. Happy to answer questions or share wiring diagrams — I made every mistake along the way so you don't have to.

Good luck, and I hope this post saves someone a few days of trial and error. 💻🛠️