Antminer T21 Hashboard Repair Guide
Complete T21 hashboard repair — BM1368 chip diagnostics, voltage domain testing, and component replacement for the budget S21 variant.
Overview
The Antminer T21 is the cost-effective variant of the S21, delivering 190 TH/s using the same BM1368 ASIC chip (5nm). Each hashboard contains approximately 108 BM1368 chips organized into ~12 voltage domains. The T21 uses lower-bin BM1368 chips compared to the S21, resulting in slightly lower hashrate but otherwise identical architecture.
Because the T21 shares the BM1368 chip with the S21, the repair procedures are nearly identical. The key differences are the chip count per board and the chip binning (performance grade). If you are familiar with S21 repair, T21 repair will be straightforward.
This guide assumes familiarity with the S21 Hashboard Repair Guide. Where procedures are identical, we reference the S21 guide to avoid duplication. This guide focuses on T21-specific differences and considerations.
Safety: Disconnect power, wait 60 seconds, and wear an ESD wrist strap. The T21 PSU delivers 12V at up to 300A.
T21 vs S21 Comparison
| Parameter | T21 | S21 |
|---|---|---|
| ASIC Chip | BM1368 (same) | BM1368 (same) |
| Chips per Board | ~108 | ~129 |
| Voltage Domains | ~12 | ~12 |
| Chips per Domain | ~9 | ~10–11 |
| Core Voltage | 0.30V | 0.30V |
| Hashrate per Board | ~63 TH/s | ~67 TH/s |
| Total Hashrate | ~190 TH/s | ~200 TH/s |
| Total Power | ~3610W | ~3500W |
| Chip Binning | Lower bin | Higher bin |
| Repair Procedure | Identical | Identical |
Hashboard Specifications
| Parameter | Value |
|---|---|
| ASIC Chip | BM1368 (5nm SHA-256) |
| Package | BGA |
| Chips per Board | ~108 |
| Voltage Domains | ~12 |
| Core Voltage (VDD) | 0.30V ±0.02V |
| I/O Voltage | 1.8V |
| Input Voltage | 12V DC |
| Power per Board | ~1203W |
| PSU | APW17 |
Required Tools
Same as S21 — see S21 Required Tools.
Repair Procedure
Step 1: Visual Inspection
Same procedure as S21. Inspect for burnt components, cracked joints, corrosion, shifted chips, and connector damage. The T21 PCB layout is very similar to the S21 but with fewer chip positions populated.
T21-specific notes:
- Some chip positions on the PCB may be unpopulated (empty pads) — this is normal for the T21 and does not indicate missing chips
- The empty pads correspond to where the S21 has additional chips in its higher-count configuration
Step 2: Voltage Domain Testing
Identical procedure to S21. Each domain targets 0.30V ±0.02V.
The T21 has ~9 chips per domain instead of the S21's 10–11. This means:
- Domain resistance will be slightly higher (fewer parallel chip resistances)
- Expected resistance range: 3–12Ω per domain
- A domain with fewer chips (due to the empty positions) is normal
Refer to S21 Step 2: Voltage Domain Testing for detailed measurement procedures.
Step 3: Signal Chain Testing
Binary search method through 108 chips — probe at chip #54 (midpoint). The chain protocol (CLK, CI, RI, RST, BO) and voltage levels (1.8V) are identical to the S21.
~7 steps to isolate the exact faulty chip in the 108-chip chain.
Step 4: Component-Level Diagnosis
Identical to S21:
- Chip testing: Diode mode, 0.3–0.6V = healthy, near 0V = shorted
- Buck converter testing: 12V input, switching signals, inductor, capacitors
- Temperature sensors: I2C bus check, pull-up resistors
See S21 Step 4 for detailed procedures.
Step 5: BM1368 Chip Replacement
Identical BGA rework procedure to S21:
- Flux → preheat 150°C → hot air 350–380°C → remove chip
- Clean pads → apply flux → place new chip → reflow
- Cool → clean → inspect
See S21 Step 5 for the complete BGA rework procedure.
BM1368 replacement chips are interchangeable between T21 and S21. However, T21 boards use lower-bin chips. You can use any BM1368 — it will be configured at the T21's operating frequency regardless of binning.
Step 6: Verification
- Domain resistance check
- Powered voltage test — all domains at 0.28–0.32V
- Full mining test:
- All ~108 chips detected
- Hashrate ~63 TH/s per board (~190 TH/s total)
- Temperature readings normal
- 24-hour burn-in
ssh root@<miner-ip>
cat /tmp/freq.txt # ~108 chips per board
cat /tmp/temp.txt
dmesg | grep chainCommon Failure Patterns
Same as S21 — see S21 Common Failure Patterns. The most common T21-specific note is that lower-bin chips may be slightly more susceptible to voltage stress, so overvoltage from a failed regulator is particularly damaging.
Troubleshooting FAQ
Can I use T21 hashboards in an S21 or vice versa?
No. Despite using the same chip, the boards have different chip counts and different firmware expectations. The control board firmware is model-specific.
Are T21 repair parts the same as S21?
Yes for BM1368 chips, buck converter components, capacitors, and other discrete parts. The PCBs themselves are different.
Why does my T21 have higher power consumption per TH than the S21?
The T21 uses lower-bin BM1368 chips that are less efficient than the S21's higher-bin chips. This is why the T21 draws 3610W for 190 TH/s (19.0 J/TH) while the S21 draws 3500W for 200 TH/s (17.5 J/TH).
Is T21 repair economically worthwhile?
At 190 TH/s, the T21 is a very capable miner. Repair economics are similar to the S21 — single-chip replacements are always worthwhile, and even multi-chip repairs are usually cost-effective compared to board replacement.
Related Guides
- Antminer S21 Hashboard Repair — same chip, shared repair procedures
- BM1368 ASIC Chip Reference
- Soldering Techniques
- Multimeter Testing Guide
Antminer S21 Thermal Maintenance Guide
Complete guide to S21 thermal paste replacement, heatsink cleaning, fan maintenance, and cooling optimization for peak performance.
Antminer S19 Pro Hashboard Repair Guide
Step-by-step S19 Pro hashboard repair — BM1398 chip testing, 38 voltage domain diagnostics, PIC troubleshooting, and chip replacement.