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JVC KM-F250: Difference between revisions

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Fix Y/C I/O entries: consolidate to two entries per connector (S-VHS and U-VCR modes), add REF SC output, fix description text (via update-page on MediaWiki MCP Server)
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|description=The JVC KM-F250 is a professional rack-mountable frame synchronizer with integrated full-frame time base correction, originally marketed by JVC's Professional Products division. Though officially designated a "frame synchronizer," the unit performs full-frame TBC processing conforming to CCIR Recommendation 601 at 13.5 MHz, 8-bit 4:2:2 sampling, effectively making it a multi-purpose TBC suitable for professional video production and archival workflows.
|description=The JVC KM-F250 is a professional rack-mountable frame synchronizer with integrated full-frame time base correction, originally marketed by JVC's Professional Products division. Though officially designated a "frame synchronizer," the unit performs full-frame TBC processing conforming to CCIR Recommendation 601 at 13.5 MHz, 8-bit 4:2:2 sampling, effectively making it a multi-purpose TBC suitable for professional video production and archival workflows.


The KM-F250 accepts composite (VBS), Y/C separate, and analog component (Y/R-Y/B-Y) video inputs. A loopthrough reference sync (black burst/genlock) input is provided for synchronizing output timing to external equipment, along with a dedicated DOC (dropout compensator) RF carrier input for use with VTRs that provide an RF output. The unit provides two composite video outputs, component outputs, Y/C separate outputs, and three sync reference outputs (ADV SYNC for VTR servo lock, REF SYNC composite sync, and REF BB black burst).
The KM-F250 accepts composite (VBS), Y/C separate, and analog component (Y/R-Y/B-Y) video inputs. A loopthrough reference sync (black burst/genlock) input is provided for synchronizing output timing to external equipment, along with a dedicated DOC (dropout compensator) RF carrier input for use with VTRs that provide an RF output. The unit provides two composite video outputs, component outputs, Y/C separate outputs, and four sync reference outputs (ADV SYNC for VTR servo lock, REF SYNC composite sync, REF SC color subcarrier, and REF BB black burst).


The unit includes comprehensive proc amp controls behind the front panel: video (Y) level, chroma level, U-V balance, and setup level — each with a variable/unity switch allowing ±3 dB adjustment (±10% for setup). An H position control allows output horizontal timing adjustment within ±7 µsec, and a Y/C timing control adjusts chroma-to-luminance phase within ±1 µsec. A chroma advance switch advances the chroma output by 1H with respect to luminance when enabled. All front-panel controls can be disabled via a LOCAL/REMOTE switch when using the optional RM-P250 remote control unit.
The unit includes comprehensive proc amp controls behind the front panel: video (Y) level, chroma level, U-V balance, and setup level — each with a variable/unity switch allowing ±3 dB adjustment (±10% for setup). An H position control allows output horizontal timing adjustment within ±7 µsec, and a Y/C timing control adjusts chroma-to-luminance phase within ±1 µsec. A chroma advance switch advances the chroma output by 1H with respect to luminance when enabled. All front-panel controls can be disabled via a LOCAL/REMOTE switch when using the optional RM-P250 remote control unit.
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The KM-F250 was produced in several regional variants with significant differences in Y/C signal handling:
The KM-F250 was produced in several regional variants with significant differences in Y/C signal handling:
* '''KM-F250U''' — NTSC variant for the US market (120V, 60Hz). Y/C uses separate BNC connectors for luminance and chrominance. Supports Y/C at 3.58 MHz (S-VHS NTSC) and 688 kHz (U-matic DUB).<ref name="bcs-listing">[https://www.broadcaststore.com/store/model_detail.cfm?id=7814 BroadcastStore.com — "JVC KM-F250U TBC &/or Frame Synchronizer"] — US broadcast equipment dealer listing confirming KM-F250U model designation.</ref><ref name="reddit-kmf250u">[https://www.reddit.com/r/VIDEOENGINEERING/comments/1erdlcu/my_jvc_kmf250_frame_synchronizertime_base/ Reddit r/VIDEOENGINEERING — "My JVC KM-F250 Frame Synchronizer/Time Base Corrector"] — Owner photos of a KM-F250U unit showing front panel, rear I/O, and internal components.</ref>
* '''KM-F250U''' — NTSC variant for the US market (120V, 60Hz). Y/C uses a [[Hirose 7-pin DUB]] connector supporting both S-VHS (3.58 MHz) and U-matic DUB (688 kHz) modes, selectable via internal switches behind the front panel.<ref name="bcs-listing">[https://www.broadcaststore.com/store/model_detail.cfm?id=7814 BroadcastStore.com — "JVC KM-F250U TBC &/or Frame Synchronizer"] — US broadcast equipment dealer listing confirming KM-F250U model designation.</ref><ref name="reddit-kmf250u">[https://www.reddit.com/r/VIDEOENGINEERING/comments/1erdlcu/my_jvc_kmf250_frame_synchronizertime_base/ Reddit r/VIDEOENGINEERING — "My JVC KM-F250 Frame Synchronizer/Time Base Corrector"] — Owner photos of a KM-F250U unit showing front panel, rear I/O, and internal components.</ref>
* '''KM-F250E''' — European PAL variant (100–240V, 50/60Hz). Y/C uses a 7-pin DIN connector (with included 7P-to-BNC adapter cable). Supports Y/C 443 at 4.43 MHz (PAL S-VHS), Y/C 924 at 924 kHz (hi-band U-VCR), and Y/C 629 at 629 kHz (VHS). Output Y/C format is selectable via a rear-panel switch (443/924/629), while input Y/C format is set via an internal select pin.<ref name="service-manual">[[:Document:JVC KM-F250E Service Manual]] — JVC service manual No. 6455 for the KM-F250E. Contains circuit descriptions, adjustment procedures, exploded views, parts lists, and schematic diagrams.</ref>
* '''KM-F250E''' — European PAL variant (100–240V, 50/60Hz). Y/C uses a 7-pin DIN connector (with included 7P-to-BNC adapter cable). Supports Y/C 443 at 4.43 MHz (PAL S-VHS), Y/C 924 at 924 kHz (hi-band U-VCR), and Y/C 629 at 629 kHz (VHS). Output Y/C format is selectable via a rear-panel switch (443/924/629), while input Y/C format is set via an internal select pin.<ref name="service-manual">[[:Document:JVC KM-F250E Service Manual]] — JVC service manual No. 6455 for the KM-F250E. Contains circuit descriptions, adjustment procedures, exploded views, parts lists, and schematic diagrams.</ref>
* '''KM-F250EG''' — European PAL variant (230V, 50Hz)
* '''KM-F250EG''' — European PAL variant (230V, 50Hz)
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|weight=6.9 kg
|weight=6.9 kg
|av_system=NTSC, NTSC 4.43, PAL
|av_system=NTSC, NTSC 4.43, PAL
|frequency=50Hz, 60Hz
|frequency=50Hz,60Hz
|power_avg=40
|power_avg=40
}}
}}
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}}
}}
{{AV input
{{AV input
|label=Y/C In (Y)
|label=Y/C In (S-VHS)
|signal=S-Video (Y/C)
|signal=S-Video (Y/C)
|connector=BNC
|connector=Hirose 7-pin DUB
|count=1
|audio=None
|location=rear
|notes=Luminance (Y) input, 1.0 Vp-p, 75 ohms. On NTSC models, shared BNC between S-VHS (3.58 MHz) and U-matic DUB (688 kHz) Y/C modes. On PAL models (E/EG), Y/C uses a 7-pin DIN connector instead of separate BNCs.
}}
{{AV input
|label=Y/C In (S-chroma)
|signal=S-Video (Y/C)
|connector=BNC
|count=1
|count=1
|audio=None
|audio=None
|location=rear
|location=rear
|notes=S-VHS chrominance input. NTSC models: 3.58 MHz, 0.286 Vp-p (burst level), 75 ohms. PAL models (E/EG): 4.43 MHz, 0.3 Vp-p (burst level), 75 ohms. On PAL models this signal is carried via the 7-pin DIN Y/C connector rather than a separate BNC.
|notes=S-VHS Y/C input mode, selected via Y/C INPUT switch behind front panel. Y = 1.0 Vp-p with sync, C = 0.286 Vp-p (burst level) at 3.58 MHz, 75 ohms. Connect to 7-pin Y/C output of S-VHS VTR.
}}
}}
{{AV input
{{AV input
|label=Y/C DUB INPUT
|label=Y/C In (U-VCR)
|signal=Y/C DUB color-under
|signal=Y/C DUB color-under
|connector=Hirose 7-pin DUB
|connector=Hirose 7-pin DUB
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|audio=None
|audio=None
|location=rear
|location=rear
|notes=U-matic/VHS chrominance input. NTSC models: 688 kHz (U-matic DUB), 0.50 Vp-p, 75 ohms. PAL models (E/EG): switchable between 924 kHz (hi-band U-VCR, C = 1.0 Vp-p VBS) and 629 kHz (VHS, C = 1.0 Vp-p VBS) via internal select pin. On PAL models this signal is carried via the 7-pin DUB Y/C connector.
|notes=U-matic DUB input mode, selected via Y/C INPUT switch behind front panel. Y = 1.0 Vp-p with sync, C = 0.50 Vp-p at 688 kHz, 75 ohms. Connect to DUB output of 3/4" U-format VCR.
}}
}}
{{AV input
{{AV input
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|signal=Component (YPbPr)
|signal=Component (YPbPr)
|connector=BNC
|connector=BNC
|count=1
|count=3
|audio=None
|audio=None
|location=rear
|location=rear
|notes=Analog component Y/R-Y/B-Y input. Y: 0.7V video + 0.3V sync (1.0 Vp-p total), 75 ohms; R-Y and B-Y: 0.7 Vp-p at 100% colour bars (0.525 Vp-p at 75%), 75 ohms.
|notes=Analog component Y/R-Y/B-Y input via three BNC connectors. Y: 0.7V video + 0.3V sync (1.0 Vp-p total), 75 ohms; R-Y and B-Y: 0.7 Vp-p at 100% colour bars (0.486 Vp-p at 75%), 75 ohms.
}}
}}
{{AV input
{{AV input
|label=Reference Sync
|label=GENLOCK
|signal=Composite (CVBS)
|signal=Composite (CVBS)
|connector=BNC
|connector=BNC
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|audio=None
|audio=None
|location=rear
|location=rear
|notes=Black burst (0.45 Vp-p) or composite video (1.0 Vp-p) reference input. Two BNC connectors — one serves as loopthrough output. Unused connector should be terminated with 75-ohm plug (included).
|notes=Black burst (0.45 Vp-p) or composite video (1.0 Vp-p) reference input. Two BNC connectors configured as loopthrough. Unused connector should be terminated with 75-ohm plug (included).
}}
}}
{{AV input
{{AV input
|label=DOC RF In
|label=DOC
|signal=RF
|signal=RF
|connector=BNC
|connector=BNC
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|count=2
|count=2
|location=rear
|location=rear
|notes=Composite video (VBS) output, 1.0 Vp-p, 75 ohms. Two independent BNC outputs (COMP VIDEO -1 and -2), active simultaneously in Operate mode.
|notes=Composite video (VBS) output, 1.0 Vp-p, 75 ohms. Two independent BNC outputs, active simultaneously in Operate mode.
}}
}}
{{AV output
{{AV output
|label=Y/C Out (Y)
|label=Y/C Out (S-VHS)
|output_type=Video
|output_type=Video
|signal=S-Video (Y/C)
|signal=S-Video (Y/C)
|connector=BNC
|connector=Hirose 7-pin DUB
|count=1
|location=rear
|notes=Luminance (Y) output, 75 ohms. NTSC models: 1.0 Vp-p, shared BNC between S-VHS and U-matic DUB modes. PAL models (E/EG): 0.7V video + 0.3V sync (443 mode) or 0.35V + 0.15V sync (924/629 modes), via 7-pin DIN connector.
}}
{{AV output
|label=Y/C Out (S-chroma)
|output_type=Video
|signal=S-Video (Y/C)
|connector=BNC
|count=1
|count=1
|location=rear
|location=rear
|notes=S-VHS chrominance output. NTSC models: 3.58 MHz, 0.286 Vp-p (burst level), 75 ohms. PAL models (E/EG): 4.43 MHz, 0.3 Vp-p (burst level), 75 ohms, via 7-pin DIN connector. Output format selectable via Y/C OUTPUT switch.
|notes=S-VHS Y/C output mode, selected via Y/C OUTPUT switch behind front panel. Y = 1.0 Vp-p with sync, C = 0.286 Vp-p (burst level) at 3.58 MHz, 75 ohms. Connect to 7-pin Y/C input of S-VHS VTR.
}}
}}
{{AV output
{{AV output
|label=Y/C DUB OUTPUT
|label=Y/C Out (U-VCR)
|output_type=Video
|output_type=Video
|signal=Y/C DUB color-under
|signal=Y/C DUB color-under
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|count=1
|count=1
|location=rear
|location=rear
|notes=U-matic/VHS chrominance output. NTSC models: 688 kHz, 0.85 Vp-p, 390 ohms. PAL models (E/EG): switchable between 924 kHz (0.5 Vp-p, 75 ohms) and 629 kHz (0.5 Vp-p, 75 ohms) via Y/C OUTPUT switch, via 7-pin DUB connector.
|notes=U-matic DUB output mode, selected via Y/C OUTPUT switch behind front panel. Y = 1.0 Vp-p with sync, C = 0.85 Vp-p at 688 kHz, 390 ohms. Connect to DUB input of 3/4" U-format VCR.
}}
}}
{{AV output
{{AV output
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|signal=Component (YPbPr)
|signal=Component (YPbPr)
|connector=BNC
|connector=BNC
|count=1
|count=3
|location=rear
|location=rear
|notes=Analog component Y/R-Y/B-Y output. Y: 1.0 Vp-p (with sync), 75 ohms; R-Y/B-Y: 0.7 Vp-p (100% colour bars), 0.525 Vp-p (75%), 75 ohms.
|notes=Analog component Y/R-Y/B-Y output via three BNC connectors. Y: 1.0 Vp-p (with sync), 75 ohms; R-Y/B-Y: 0.7 Vp-p (100% colour bars), 0.486 Vp-p (75%), 75 ohms.
}}
}}
{{AV output
{{AV output
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|location=rear
|location=rear
|notes=Reference composite sync output from internal SSG, 4 Vp-p, 75 ohms. For genlocking downstream equipment to the KM-F250's timing reference.
|notes=Reference composite sync output from internal SSG, 4 Vp-p, 75 ohms. For genlocking downstream equipment to the KM-F250's timing reference.
}}
{{AV output
|label=REF SC
|output_type=Video
|signal=Composite (CVBS)
|connector=BNC
|count=1
|location=rear
|notes=Reference color subcarrier output from internal SSG, 1 Vp-p, 75 ohms. For genlocking downstream equipment. Note: Do not connect to VTR SC input terminal; this output is not for feeding subcarrier back to VTRs.
}}
}}
{{AV output
{{AV output
Line 194: Line 185:
| Y (luminance) || 1.0 Vp-p (with sync) || 0.7V + 0.3V sync (Y/C 443) or 0.35V + 0.15V sync (Y/C 924/629) || 75 Ω
| Y (luminance) || 1.0 Vp-p (with sync) || 0.7V + 0.3V sync (Y/C 443) or 0.35V + 0.15V sync (Y/C 924/629) || 75 Ω
|-
|-
| S-chroma || 3.58 MHz, 0.286 Vp-p (burst) || 4.43 MHz, 0.3 Vp-p (burst) || 75 Ω
| C (S-VHS, 3.58 MHz) || 0.286 Vp-p (burst) || 4.43 MHz, 0.3 Vp-p (burst) || 75 Ω
|-
|-
| U-chroma (U-matic DUB) || 688 kHz, 0.50 Vp-p || 924 kHz, 1.0 Vp-p (VBS) || 75 Ω
| C (U-VCR, 688 kHz) || 0.50 Vp-p || 924 kHz, 1.0 Vp-p (VBS) || 75 Ω
|-
|-
| C (VHS) || — || 629 kHz, 1.0 Vp-p (VBS) || 75 Ω
| C (VHS) || — || 629 kHz, 1.0 Vp-p (VBS) || 75 Ω
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| Component Y || 0.7V + 0.3V sync || 0.7V + 0.3V sync || 75 Ω
| Component Y || 0.7V + 0.3V sync || 0.7V + 0.3V sync || 75 Ω
|-
|-
| Component R-Y || 0.7 Vp-p (100%) / 0.525 Vp-p (75%) || 0.7 Vp-p (100%) / 0.525 Vp-p (75%) || 75 Ω
| Component R-Y || 0.7 Vp-p (100%) / 0.486 Vp-p (75%) || 0.7 Vp-p (100%) / 0.486 Vp-p (75%) || 75 Ω
|-
|-
| Component B-Y || 0.7 Vp-p (100%) / 0.525 Vp-p (75%) || 0.7 Vp-p (100%) / 0.525 Vp-p (75%) || 75 Ω
| Component B-Y || 0.7 Vp-p (100%) / 0.486 Vp-p (75%) || 0.7 Vp-p (100%) / 0.486 Vp-p (75%) || 75 Ω
|-
|-
| Reference sync || Black burst 0.45 Vp-p or composite 1.0 Vp-p || Black burst 0.45 Vp-p or PAL-B composite 1.0 Vp-p || 75 Ω (loopthrough)
| Reference sync || Black burst 0.45 Vp-p or composite 1.0 Vp-p || Black burst 0.45 Vp-p or PAL-B composite 1.0 Vp-p || 75 Ω (loopthrough)
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| Y (luminance) || 1.0 Vp-p (with sync) || 0.7V + 0.3V sync (443) or 0.35V + 0.15V sync (924/629) || 75 Ω
| Y (luminance) || 1.0 Vp-p (with sync) || 0.7V + 0.3V sync (443) or 0.35V + 0.15V sync (924/629) || 75 Ω
|-
|-
| S-chroma || 3.58 MHz, 0.286 Vp-p (burst) || 4.43 MHz, 0.3 Vp-p (burst) || 75 Ω
| C (S-VHS, 3.58 MHz) || 0.286 Vp-p (burst) || 4.43 MHz, 0.3 Vp-p (burst) || 75 Ω
|-
|-
| U-chroma (U-matic DUB) || 688 kHz, 0.85 Vp-p || 924 kHz, 0.5 Vp-p || NTSC: 390 Ω / PAL: 75 Ω
| C (U-VCR, 688 kHz) || 0.85 Vp-p || 924 kHz, 0.5 Vp-p || NTSC: 390 Ω / PAL: 75 Ω
|-
|-
| C (VHS) || — || 629 kHz, 0.5 Vp-p || 75 Ω
| C (VHS) || — || 629 kHz, 0.5 Vp-p || 75 Ω
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| Component Y || 1.0 Vp-p (with sync) || 0.7V + 0.3V sync || 75 Ω
| Component Y || 1.0 Vp-p (with sync) || 0.7V + 0.3V sync || 75 Ω
|-
|-
| Component R-Y/B-Y || 0.7 Vp-p (100%) / 0.525 Vp-p (75%) || 0.7 Vp-p (100%) / 0.525 Vp-p (75%) || 75 Ω
| Component R-Y/B-Y || 0.7 Vp-p (100%) / 0.486 Vp-p (75%) || 0.7 Vp-p (100%) / 0.486 Vp-p (75%) || 75 Ω
|-
| ADV SYNC || 4 Vp-p (advanced 8H) || 4 Vp-p (advanced 8H) || 75 Ω
|-
|-
| ADV SYNC || — || 4 Vp-p (advanced 8H) || 75 Ω
| REF SYNC || 4 Vp-p || 4 Vp-p || 75 Ω
|-
|-
| REF SYNC || — || 4 Vp-p || 75 Ω
| REF SC || 1 Vp-p || 1 Vp-p || 75 Ω
|-
|-
| REF BB || — || 0.45 Vp-p || 75 Ω
| REF BB || 0.45 Vp-p || 0.45 Vp-p || 75 Ω
|}
|}


''Note: On NTSC models, Y/C signals use separate BNC connectors for luminance and chrominance. On PAL models (E/EG), Y/C input and output use a combined 7-pin DIN connector with an included 7P-to-BNC adapter cable. The Y/C input format on PAL models is set via an internal select pin (Y/C 443, Y/C 924, or Y/C 629); the output format is selectable via the Y/C OUTPUT switch behind the front panel.''
''Note: On NTSC models (KM-F250U), Y/C input and output use a single [[Hirose 7-pin DUB]] connector supporting both S-VHS (3.58 MHz) and U-matic DUB (688 kHz) modes. The Y/C INPUT and Y/C OUTPUT switches behind the front panel select between S-VHS and U-VCR modes. On PAL models (E/EG), Y/C input and output use a 7-pin DIN connector with an included 7P-to-BNC adapter cable; the input format is set via an internal select pin (Y/C 443, Y/C 924, or Y/C 629), while the output format is selectable via the Y/C OUTPUT switch.''


== Performance Specifications ==
== Performance Specifications ==


The following performance measurements are from the KM-F250E service manual.<ref name="service-manual" />
The following performance measurements are from the KM-F250U user manual<ref name="manual-specs" /> and KM-F250E service manual.<ref name="service-manual" />


{| class="wikitable"
{| class="wikitable"
! Parameter !! Composite !! Component !! Y/C Separate
! Parameter !! Composite !! Component !! Y/C Separate
|-
|-
| S/N ratio || colspan="3" | 57 dB (p-p/RMS, 100 kHz – 5 MHz)
| S/N ratio || colspan="3" | 58 dB or more
|-
|-
| Residual jitter || ±15 nsec || ±15 nsec || Luminance ±15 nsec, hue ±3°
| Residual jitter || ±15 nsec || ±15 nsec || Luminance ±15 nsec, hue ±2°
|-
|-
| K Factor (2T Pulse) || 3% || 1% || 1%
| K Factor (2T Pulse) || 3% || 1% || 1%
|-
|-
| Frequency response || 3.2 MHz, ±0.5 dB || Y: 5.2 MHz, ±0.5 dB; R-Y/B-Y: 2.2 MHz, ±0.5 dB || Y: 5.2 MHz, ±0.5 dB; C: 500 kHz, ±3 dB
| Frequency response || 4 MHz, ±0.5 dB || Y: 5.5 MHz, ±0.5 dB; R-Y/B-Y: 2.5 MHz, ±0.5 dB || Y: 5.5 MHz, ±0.5 dB; C: 500 kHz, −3 dB
|}
|}


Ambient operating temperature: −5 to 40°C (23 to 104°F).
Ambient operating temperature: 5 to 40°C (41 to 104°F).


== Known Issues ==
== Known Issues ==
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