Operator Reviews & Case Reports
What Operators Say
The field assessment on our eight Antminer S19 units found two intake filters completely clogged with construction dust from a nearby renovation. Hash rate had dropped 12% over three weeks and we blamed the pool. Replacing filters and cleaning heat sinks brought output back within 48 hours. The report included part numbers from a supplier in Dongdaemun.
— Tae-woo Kim, 8-unit operation, Mapo-gu
We hired Apphemlockcore before buying six used Whatsminers from a broker in Incheon. Their pre-purchase audit flagged one unit with a failing fan bearing that would have cost us a board within a month. Negotiated ₩400,000 off the lot price based on their report. The scheduling took longer than expected—about ten days to get on-site—but the work itself was thorough.
— Sarah O’Brien, small farm operator, Incheon
Maintenance planning session was useful for building our quarterly calendar. Marcus asked detailed questions about our ventilation setup that our previous consultant skipped. Only reservation: the session ran 20 minutes over the booked 90 minutes, which was fine for us but worth noting if you have a tight schedule.
— Hyun-woo Lee, co-location tenant, Suwon
Hash rate audit confirmed our suspicion that one rack was on a degraded circuit. Voltage sag was pulling two units below 0.05 TH/s effective output. Electrician fixed the line the following week. Remote audit was cheaper than a full visit and gave us enough evidence to push the building manager.
— Anika Patel, 14-unit setup, Gangnam
Case Report: Yongin Farm Thermal Recovery
Client: Private operator, 12 SHA-256 units (mixed Antminer S19 and S19 Pro)
Challenge: Summer temperatures in an uninsulated warehouse pushed board temperatures above 85°C on four units. Pool reject rate climbed to 4.2% over two weeks.
Our work: On-site field assessment with infrared thermal mapping across all racks. Identified inadequate exhaust ducting and three seized fan motors on the south-facing rack.
Outcome: Client installed inline exhaust booster fans (₩180,000 total parts cost) and replaced three fans (₩45,000 each). Reject rate returned to 0.3% within five days. Estimated board replacement cost avoided: approximately ₩2,400,000.
Timeline: Assessment on a Tuesday, report delivered Friday, client completed repairs the following Monday.
Case Report: Pre-Acquisition Audit, Incheon Broker Lot
Client: First-time operator purchasing six used units
Challenge: No local standard for evaluating second-hand SHA-256 hardware before purchase.
Our work: Pre-acquisition field assessment at broker warehouse. Benchmarked each unit for 24 hours, inspected fans, boards, and PSU connectors.
Outcome: Five units passed with minor filter replacement needed. One unit flagged for fan bearing failure and undervolting instability. Client purchased five units, negotiated separate price on the sixth after repair.
Timeline: Inquiry to report in six business days.