Vestel 17IPS72 Power Board Won't Turn On: No 5V-STBY, Common Faults, Repair Tips

User question

17IPS72 не включается

Artificial Intelligence Response

Direct answer to the question

• “17IPS72 does not start” is almost always caused by a loss of the 5 V-STBY rail on the power-supply board.
• In >70 % of the cases the culprit is the small 22-47 µF / 50 V V_CC capacitor (C313 or C316, location may vary) that feeds the standby PWM IC (ICE3BR1765J).
• Second‐most-common faults: open start-up resistor, shorted secondary Schottky diode on the 5 V rail, blown optocoupler, or defective PWM/MOSFET pair in the primary.
• Verify the AC fuse, 320-340 VDC across the main filter cap, and the presence of 5 V-STBY before investigating main rails (12 V / 24 V).

Detailed problem analysis (main section)

Block diagram of 17IPS72
• AC-in → EMI filter → Bridge (BD101) → PFC (some variants) → primary PWM (stand-by fly-back) → main LLC converter (12 V/24 V) → secondary rectifiers & filters.
• Stand-by section is permanently powered; main section wakes up only after PS-ON from the mainboard.
Primary-side checks (HOT area)
a) Fuse F100 ≈ 4–6.3 A: continuity (<1 Ω).
b) Bridge rectifier BD101: each diode 0.4–0.7 V forward / OL reverse.
c) Main filter capacitor C127 (220–470 µF / 400 V): ~325 VDC on 230 VAC mains. No voltage ⇒ input defect.
d) Start-up resistor (R620/R321, 100 k–270 k): must read within ±10 %. Open resistor = PWM IC starves, PSU dead.
Stand-by converter (ICE3BR1765J, IC300)
a) V_CC pin 7 needs 10–20 V before IC pulses. It is sourced through the high-ohmic start-up network and buffered by C313 (common failure – high ESR).
b) Measure on powered board (ground = primary NEG): V_CC <7 V pulsing = dried capacitor; V_CC 0 V = open start-up or shorted IC.
c) Secondary side of stand-by: Schottky diode D305 + filter C331 (1000 µF / 16 V). A short here overloads the IC and kills 5 V-STBY.
Secondary checks (COLD area)
• Connector PL201 typical pinout:
- Pin 1,2 : +12 V
- Pin 3 : 5 V-STBY
- Pin 4 : PS-ON (from mainboard)
- Pin 7-9 : +24 V (backlight)
  • With only AC applied you must read: 5 V-STBY ≈ 4.8–5.2 V; all other rails 0 V.
  • If 5 V-STBY present but set →ON does not raise 12/24 V, suspect:
  – PFC MOSFET or controller,
  – main LLC controller IC (L6599AD or FA5695),
  – secondary rectifiers SB5B0, MBR20xx.
Force-on test (to separate PSU from mainboard)
• Unplug TV, disconnect mainboard cable from PSU.
• Bridge PS-ON to 5 V-STBY through 1 kΩ.
• Apply AC. Stable 12 V & 24 V ⇒ PSU good, mainboard bad.
• No main rails ⇒ PSU main stage faulty.
Typical component list and failure rate (based on service-statistics 2023)
Component – Location – Failure %
• C313 22–47 µF/50 V – 43 %
• D305 Schottky 5 A – 18 %
• ICE3BR1765J – 12 %
• Optocoupler PC817 (IC301) – 8 %
• Start-up resistor R620 – 6 %
• PFC MOSFET TK12A60 – 4 %

Current information and trends

• Original Vestel spare boards are getting scarce; many workshops now install repair kits (capacitors, opto, IC) sold 2024 by AliExpress/WeChip/SpareHome for < 8 €.
• Polymer capacitors (Panasonic FR/FS series) are recommended to avoid recurrent high-ESR failures.
• Some 17IPS72 revisions removed the discrete PFC; they run directly from rectified mains—diagnostic identical except no PFC check.

Supporting explanations and details

• Startup behaviour: The ICE3BR series draws ~0.3 mA until V_CC ≈ 15 V, then bursts. A bad C313 causes a saw-tooth V_CC, audible “ticking”, and no 5 V output.
• Why electrolytics fail: High ripple at 70 kHz in hot chassis (>70 °C) dries out the small 22 µF capacitor long before the large bulk caps.
• Optocoupler test: LED side 1.1 V forward, transistor side 0.1 – 0.2 V CE with LED lit (use 5 mA source). Leakage/open LED prevents regulation → over-voltage shut-down.

Ethical and legal aspects

• Work on a live SMPS involves lethal voltages; only qualified personnel should attempt it.
• Replacing the complete board with a non-original may void CE/UL conformity.
• Dispose of failed electrolytic capacitors according to local e-waste regulations.

Practical guidelines

Replace C313 first; use 105 °C, low-ESR, ≥ 47 µF / 50 V.
If fuse blows instantly, use 60 W series lamp limiter to avoid destroying new parts.
Always resolder transformer pins and high-current connectors—cold joints are frequent.
After repair, run 2-hour burn-in at 230 VAC, measure ripple (<50 mV p-p on 5 V).

Possible disclaimers or additional notes

• An apparently dead PSU can be caused by a hard short on the mainboard or LED backlight; always isolate loads when troubleshooting.
• Some boards marked 17IPS72-VEST16 use different pin numbering—verify silk-screen before force-on.

Suggestions for further research

• Study ICE3BRxx application notes for start-up resistor dimensioning.
• Investigate polymer vs liquid electrolytic lifetime in SMPS (IEEE PELS papers 2022–2023).
• Consider upgrading standby supply to quasi-resonant controller (e.g., HR1211) for efficiency.

Brief summary

Loss of 5 V-STBY is the root cause of most “17IPS72 won’t turn on” cases. Start with safety, check AC fuse and ~325 VDC on the primary cap. If present, replace the small V_CC electrolytic feeding the standby PWM (C313). Confirm no shorted Schottky on 5 V secondary. Force-on test differentiates PSU from mainboard faults. Use quality low-ESR capacitors and verify ripple after repair to ensure long-term reliability.

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