Where to find schematic and firmware for KFR-35W AC inverter?

ahmedaminegueddim wrote:

https://obrazki.elektroda.pl/9742116900_1784294224.jpg https://obrazki.elektroda.pl/9419674800_1784294224.jpg
@ElektrodaBot I want schematic diagram and firmware of the Ac inverter model KFR-35W
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Initial assessment of available information

From your photos, the board is not only “KFR-35W”. The important marking appears to be:

KFR-35W/BP3N1-(RX24Tmini+STR6A161+GIB10CH60TS-L+TPD4204F).D.13.WP2-1
Board / spare part number visible on similar listings: 17122000048121
PCB date marking visible in your photo: 2020-07-15

This matches a Midea-type outdoor inverter controller family sold under similar KFR-35W/BP3N / BP3N1 descriptions; some listings omit the final “1”, so the full bracketed IC combination and board number must be matched, not just “KFR-35W”. Replacement-board listings exist with the same RX24Tmini + STR6A161 + GIB10CH60TS-L + TPD4204F string and with part number 17122000048121. (newegg.com)

Direct answer to the question

1. Full original schematic:
I do not have a public, component-level schematic for this exact PCB. For these AC inverter boards, manufacturers normally publish only wiring diagrams, connector diagrams and PCB layout diagrams, not the complete circuit schematic. A service manual for the same KFR-35W/BP3N1 family shows PCB diagrams, connector names, IPM area, EEPROM programmer port/test port, compressor U/V/W, reactor, PMV and fan connectors, but it is not a full electrical schematic. (manuals.plus)

2. Renesas firmware:
The main firmware is most likely inside the Renesas RX24Tmini MCU, not in a normal removable memory chip. The RX24T family is a motor-control MCU intended for inverter/PWM applications and includes on-chip flash memory and motor-control peripherals. (renesas.com)
If the MCU is protected, the firmware normally cannot be read out without the correct Renesas ID/security information; Renesas documentation for RX24T includes ID-code protection and ROM-code protection mechanisms. (renesas.com)

3. What may be downloadable as “firmware”:
Many repair sites call the small EEPROM / FRAM parameter file “firmware”. For this board family, there is an online repair-file entry for Carrier 38QHG012D8s with the same main-board string, but it lists FM24C16D and a file size of about 0.95 kB, which strongly indicates an external nonvolatile parameter dump, not the Renesas MCU program. (remont-aud.net)

So: I can help you repair or reverse-engineer the board, but I cannot honestly provide the original manufacturer schematic or protected Renesas MCU firmware. If your problem is an EEPROM/F4/E0 error, the external memory dump may be the relevant item, not the MCU firmware.

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Detailed problem analysis

1. What the board contains

Based on your PCB marking and component set, the functional structure is approximately:



The compressor power module marking in the board identifier, GIB10CH60TS-L, corresponds to the STMicroelectronics STGIB10CH60TS-L, a 600 V, 15 A three-phase IGBT IPM with internal gate drivers, bootstrap functions, fault/shutdown functions and protection features. (st.com)

The STR6A161 part in the board marking is a Sanken offline flyback converter IC; distributor data describes the STR6A161HZ as an isolated flyback AC/DC converter IC with internal switch, 700 V breakdown rating and 100 kHz operation. (digikey.com)

The TPD4204F part is a Toshiba 600 V high-voltage PWM brushless DC motor driver IC, used in appliance fan-motor applications. Toshiba’s current product page also notes it as EOL announced / not recommended for new design, so if it is faulty, use the exact replacement part rather than designing it into new hardware. (toshiba.semicon-storage.com)

2. Why the schematic is hard to obtain

Manufacturers of inverter HVAC boards usually separate documentation into:

Document type	Usually available?	Usefulness
Installation wiring diagram	Yes	Shows L/N/S, compressor, sensors, fan, PMV
Service manual PCB diagram	Sometimes	Shows connector names and rough component positions
Component-level schematic	Rarely	Usually proprietary
MCU firmware source code	No	Proprietary manufacturer software
MCU binary image	Rarely	Usually protected or only in service tools
EEPROM/parameter dump	Sometimes	Useful for E0/F4/EPROM errors

For this KFR-35W/BP3N1 family, service documents show troubleshooting for E0/F4 EEPROM parameter error, E1 communication error, and P0 IPM/over-current protection, but the service action is typically “replace PCB”, not “repair component X”. (manuals.plus)

3. Firmware versus EEPROM dump

This distinction is important:

Item	Location	Can it usually be read?	Repair relevance
Main control firmware	Inside Renesas RX24T MCU flash	Usually no, if protected	Needed only if MCU is blank/dead
Configuration / parameters	External 8-pin EEPROM/FRAM, often 24C16/FM24C16D class	Usually yes	Common cause of E0/F4/EPROM fault
Bootloader / option bytes	Inside MCU	Protected	Needed for factory programming

If your AC shows F4, E0, “EPROM”, EEPROM parameter error, then do not start by replacing the Renesas MCU. First check the external 8-pin nonvolatile memory near the MCU. A service manual describes E0/F4 as a condition where the indoor or outdoor main chip does not receive feedback from the EEPROM chip. (manuals.plus)

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Practical repair guidance

1. If the fault is EEPROM / F4 / E0

Do this:

1. Locate the 8-pin nonvolatile memory IC near the Renesas MCU.
It may be marked something like:
- FM24C16D
- 24C16
- AT24C16
- BR24C16
- or a similar I²C memory.

2. Before writing anything, read and save your original chip contents at least three times and compare the files.

3. Use a programmer such as:
- TL866II / T48 / T56,
- CH341A with correct voltage adaptation,
- or another I²C EEPROM/FRAM-compatible programmer.

4. Only write a dump from the same board code and same AC model.
A dump from another KFR-35W board may boot but can give wrong compressor, fan, PMV or sensor parameters.

5. If you find a file described as firmware and it is around 1 kB, treat it as EEPROM data, not MCU firmware.

2. If the board is completely dead

Check in this order:

Test point	Expected result	Interpretation
Main fuse	Continuity	If open, suspect bridge/IPM/PFC short
Bridge rectifier	No short between AC/DC pins	Shorted bridge blows fuse
DC bus capacitors	Around 310–325 VDC on 230 VAC input, higher during PFC operation	If absent, input/bridge/relay fault
STR6A161 SMPS Vcc	Startup then stable supply	If pulsing, SMPS overload or bad startup components
Low-voltage rails	15 V, 12 V, 5 V, possibly 3.3 V	Missing rails stop MCU
MCU reset pin	Should release from reset	Stuck reset = supply/reset circuit fault
MCU clock	Oscillator activity	No clock = MCU/oscillator/power issue

Do not power the board repeatedly with a blown fuse or shorted IPM. Use a current-limited supply method, lamp limiter, or isolation transformer where appropriate.

3. If the compressor does not start / P0 fault

With power removed and the DC bus discharged:

1. Disconnect compressor U/V/W.
2. Put the meter in diode mode.
3. Check IPM diode paths:
- DC+ to U/V/W,
- U/V/W to DC−,
- compare all three phases.
4. Any phase reading near 0.00 V or obviously different from the others suggests a shorted IPM.
5. Also check gate resistors, shunt resistors and current-sense path.

The service manual for this family defines P0 as IPM malfunction or IGBT over-strong current protection and lists wiring, IPM, outdoor fan, compressor and outdoor PCB as possible causes. (manuals.plus)

4. If communication error E1 appears

Check:

- terminal wiring L/N/S,
- polarity and tightness of indoor-outdoor wiring,
- optocouplers in communication circuit,
- zener diodes and high-value resistors,
- fluctuating communication voltage on S line.

A service manual describes E1 as the indoor unit not receiving feedback from the outdoor unit and gives measurement guidance for the S communication voltage. (manuals.plus)

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Safety notes

This board has a lethal high-voltage DC bus. The two large electrolytic capacitors can remain charged after unplugging. Before touching the board:

- disconnect mains,
- wait,
- discharge the DC bus through a suitable resistor,
- verify voltage with a meter,
- do not short capacitors with a screwdriver,
- use insulated probes,
- avoid powering the board on a wooden table with exposed high-voltage parts unless you are experienced with live SMPS/inverter repair.

Also remember that wrong firmware/EEPROM data can damage the compressor or IPM because it may change compressor type, current limits, fan control, PMV steps or protection thresholds.

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What I recommend for your case

Because you already confirmed Renesas, and the photo shows the board string, the practical options are:

1. If the Renesas MCU is physically damaged:
Replace the whole board, or transplant the programmed MCU from an identical donor board. A blank RX24Tmini will not work without the correct factory firmware and option settings.

2. If you have F4/E0/EPROM error:
Work on the external EEPROM/FRAM first. This is the only realistic “firmware” repair route.

3. If the board is dead:
Diagnose SMPS and DC bus first. The Renesas firmware is probably not the fault.

4. If the compressor trips P0/P4:
Diagnose IPM, shunts, compressor winding resistance and DC bus stability.

5. If you just need a replacement:
Search using the full string:
KFR-35W/BP3N1-(RX24Tmini+STR6A161+GIB10CH60TS-L+TPD4204F).D.13.WP2-1 17122000048121
Do not buy only by “KFR-35W”.

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Questions for you

To go further, please provide:

1. The full indoor and outdoor unit model numbers from the nameplates.
2. The exact fault:
- dead board,
- E0/F4/EPROM,
- E1 communication,
- P0/P4 compressor/IPM,
- fan error,
- blown fuse.
3. Close photo of:
- Renesas MCU marking,
- the 8-pin EEPROM/FRAM chip,
- IPM marking,
- underside of the PCB.
4. Measurements:
- DC bus voltage,
- 15 V / 12 V / 5 V / 3.3 V rails,
- fuse condition,
- IPM diode-test readings.

Brief summary

Your board is a Renesas RX24Tmini-based Midea-type KFR-35W/BP3N1 inverter outdoor PCB. A full original schematic and Renesas MCU firmware are normally proprietary and not publicly available. If your problem is an EPROM/F4/E0 fault, the realistic repair is to read/write the external FM24C16D / 24C16-type parameter memory, not the Renesas MCU. If the MCU itself is dead, replacement of the complete board or an identical donor-board transplant is usually the practical solution.