Bitmain Antminer S19J Pro
Bitmain Antminer S19J pro series has been a workhorse in the crypto mining industry for years. However, as these machines age, certain common faults begin to appear. If you are running older models, specifically the s19j pro, you have likely encountered a board that refuses to hash despite the ASIC chips appearing fine.
This is often due to a known weak point on older hashboard designs: the MOSFET circuit. If your board is down, there is a very good chance you are dealing with the infamous s19j pro MOSFET issue.
The good news is that this is usually a straightforward, inexpensive repair. In this guide, we will explain why this happens, how to diagnose it in under ten seconds, and the two ways to fix it.
Why Do Some S19s Have MOSFETs?
It is interesting to note the design evolution of Bitmain hardware. While older S19 series models utilized these MOSFET chips on their hashboards as power switches, Bitmain largely phased them out in newer model designs.
It is widely assumed in the repair community that this shift occurred because a significant percentage of older hashboard failures were directly related to this single component failing. By removing it in later iterations, they improved overall long-term reliability.
The Economics of Repair
Because the s19j pro is now a bit older, repair costs need to make sense relative to the machine’s value. A MOSFET issue is generally not difficult to repair, meaning it shouldn’t be an expensive service.
For technicians, it’s important to price this repair fairly. For customers, if a repair shop quotes a high price just for this specific fix, it might actually be more economical to simply buy a used, good-condition hashboard instead of paying for the repair.
Diagnosing the s19j pro MOSFET issue in 10 Seconds
How do you know if your expensive ASIC chips are dead, or if it’s just a $2 MOSFET stopping the show? You can find out very quickly.
As shown in the image below, the square box indicates where the MOSFET is usually located on the hashboard layout.
The diagnostic test is simple:
- Connect the hashboard to your tester.
- Power it on.
- Carefully use metal tweezers to briefly bridge (connect) the input line to the output line across the MOSFET pads.
The Result: If your tester suddenly initializes and successfully detects all the ASIC chips while you are bridging the connection, congratulations! Your ASIC chips are fine; you have confirmed a standard s19j pro MOSFET issue. The MOSFET is simply failing to “open the gate” and allow power through to the chips.
Two Ways to Fix It
Once you have confirmed the problem, you have two paths for repair.
Method 1: The Professional Replacement (Recommended) The best and most professional way to repair this is to replace the faulty component. A new MOSFET chip is incredibly cheap—usually costing between $1 and $2. Simply remove the old component and solder on a new one (or use a dedicated MOSFET repair kit). This returns the board to its original factory specification.
Method 2: The Bridge Bypass (The “Quick Fix”) If you do not have spare MOSFET chips on hand and need the miner running immediately, there is an alternative method. Many repair shops simply create a solder bridge across the pads, permanently bypassing the MOSFET’s switching functionality entirely.
While this “quick and dirty” method gets the Antminer hashboard working again instantly, it is not the recommended professional method, as you are removing a component originally designed to manage power flow. However, in a pinch, it is a widely used technique to get back online fast.