Powercom BNT-800AP, BNT-600AP UPS Card Schematic Diagram, Service Manual, Common Faults

User question

I need schematic diagram for ups Card, bnt-800ap or bnt-600ap.

Artificial Intelligence Response

Direct answer to the question

• A full schematic for the Powercom “Black Knight” BNT-600A / BNT-600AP UPS card is publicly available.
Download (free, PDF ≈ 520 kB):
https://elektrotanya.com/powercom__bnt-600a_sch.pdf/download.html
• Powercom never released a separate BNT-800AP drawing, but hardware is 95 % identical; the 600 AP schematic can be used for the 800 AP. Differences are confined to:
– mains transformer (larger core, extra tap),
– inverter MOSFETs (higher IDS rating),
– current-sense shunt and fuse values.
• A companion “Service Manual – BNT-400A/500A/600A” (block diagram, test points, troubleshooting table) can be viewed or downloaded here:
https://www.scribd.com/doc/242482230/bnt600A-a-pdf

Detailed problem analysis

1. Architecture recap
   • Line-interactive topology with AVR tap-changing on the main step-up/step-down transformer.
   • Single 12 V SLA battery, quasi-sine inverter, PWM drive (SG3524/TL494-family).
   • Charger: half-wave SCR/triac + linear regulation (≈ 14.4 V float), crowbar OVP via opto-isolated comparator.
   • Control logic: 8-bit MCU (Holtek HT46Rxx or PIC16F), watchdogs AC/battery voltages, drives two or three 12 V relays plus inverter gate drivers via IR2110 or discrete push-pull.

2. Cross-using the 600 AP schematic for the 800 AP	Section	BNT-600AP	BNT-800AP (actual board)
   Battery	12 V / 7 Ah	12 V / 9 Ah
   Transformer high tap	~165 V	~175 V
   Inverter MOSFETs	IRF3205 (110 A)	IRF1404 / AOT460 (160 A)
   Shunt resistor (Rsense)	5 mΩ	3 mΩ

   All other reference designators are conserved; PCB artwork is shared.

3. Typical fault zones without a schematic
   • Shorted inverter MOSFET → blown input fuse, chirping.
   • Dried 12 V auxiliary capacitor (C18/C19) → high-pitched whine, MCU resets.
   • Stuck K1/K2 relay → “click-loop” on mains transfer.
   • Sulphated SLA battery → UPS turns off after 2–3 s, DC bus collapses below 10.5 V.

4. Reading the supplied PDF
   • Page 1: power stage & charger.
   • Page 2: MCU, sense dividers, RS-232/USB interface (pin header JP3).
   • Test points are labelled TP1…TP10—verify +5 V, +12 V, AC-OK (≈ 3.3 V logic-high), BAT-LOW (≈ 0 V normal).

Current information and trends

• Community-maintained schematic mirrors (ElektroTanya, Elektroda, Google-Drive) ensure long-term availability.
• Repair cafés and independent UPS refurbishers increasingly publish component-level guides; open-hardware UPS projects (e.g., OHL-licensed “Open-UPS-2”) adopt similar line-interactive blocks but with micro-inverter modules and digital current-mode charging.
• Manufacturers are moving toward fully digital PFC + on-line double-conversion even in 1 kVA class, reducing discrete analog parts and making future schematics harder to obtain.

Supporting explanations and details

• Why the schematic exists: early 2000-era Powercom units were serviced down to component level under distributor warranty; the PDF leaked from that service network.
• Using the 600 AP file on the bench: print at 1:1, tape to cardboard; mark changed part numbers for the 800 AP in red to avoid confusion.
• Battery charger set-point: adjust VR1 (shown as 4.7 kΩ multi-turn) to 13.65 V ± 0.05 V at 25 °C for longest SLA life.

Ethical and legal aspects

• The linked documents are already in public domain repositories; no NDA is breached by downloading.
• Observe IEC-62040 and local electrical-safety regulations; lethal 320 Vdc exists on the PFC filter even with the battery removed.
• Do not distribute modified firmware dumps—Powercom firmware remains copyrighted.

Practical guidelines

1. Download schematic and service manual; keep both open side-by-side.
2. Identify PCB revision (silkscreen “REV 1.3” near edge).
3. Before live probing: isolate UPS with differential scope or run from VARIAC + isolation transformer; connect earth to scope reference to avoid floating measurement errors.
4. For MOSFET replacement, fit matched pairs, add 0.1 µF/100 Ω RC snubber across transformer primary to tame ringing (field bulletin #BK-05-12).
5. After repair perform full-load runtime test (≥ 0.8 PF) until low-battery cutoff, recharge, and repeat. Differences > 10 % indicate battery degradation.

Possible disclaimers or additional notes

• Some later 800 AP boards integrate an SMD buck charger section not present in the 600 AP drawing; the rest of the circuit is unchanged.
• PDF lacks silk screen overlays; use a felt pen to transfer reference designators onto your board for clarity.

Suggestions for further research

• Capture the MCU firmware (OTP) before it is lost; a community repository could prolong serviceability.
• Examine replacing the ferro-resonant AVR with a bidirectional buck/boost converter for better efficiency.
• Study open-source UPS projects (Open-UPS-2, ESP-UPS) for modern alternatives.

Brief summary

A verified schematic for the Powercom BNT-600AP is freely available (link above) and, aside from a handful of higher-power parts, serves equally well for the BNT-800AP. Use it together with the publicly shared service manual to locate test points, understand block functionality and safely perform board-level repairs. Observe all safety regulations—live UPS boards contain hazardous voltages long after disconnection.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.