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Loewe TVs Q2500 VGA Module

Recreation of VGA module PCB for Loewe TVs with Q2500M chassis.

Project based on work done by Oelii from circuit-board.de/forum

Schematic recreated from the scratch in KiCad. PCB based on Oelii's layout and verified with Desing/Electrical Rules Checker tools.
Components footprints replaced with KiCad standard ones.

Chassis compatibility

Unverified, obtained from post by djcalle on circuit-board.de/forum:

  • Q23, Q24, Q25 can accept VGA cards.
  • Q25 and Q24 use the same VGA card (only 2 differences: cable length and 150R termination on RGB lines.)
  • Q25 seems to be inconsistent with VGA card compatibility.
  • Q24 seems consistent with vga card compatibility.
  • Q23 uses its own different card.

Original schematic from Loewe Q2500-M chassis service manual pcb_top

Recreated schematic and PCB scheme pcb_top pcb_bottom pcb_dimensions

Bill of materials

Reference Value Footprint Qty
C811,C817,C826,C828,C829 100n 0805 5
C813,C814,C821,C827 10p 0805 4
C816 10u 0805 1
C818 22n 0805 1
C822 100p 0805 1
L816,L826 1210(3225) 4.7uH 2
R814,R819,R821,R823,R828,R829 100R 0805 6
R817 10k 0805 1
R818 1k 0805 1
R827 47k 0805 1
R836,R837,R838 150R 0805 3
I811 74HCT86 SO-14 1
W801 VGA DSUB-15
Edge pin offset 8.35mm
Mounting holes offset 10.89mm		 1
W831 JST XH 2.54 12 Pin 1

Order boards from manufacturer

Send "gerbers" folder content packed to zip archive.

Build Notes

L816 and L826 SMD 1210(3225) inductors value are unknown; 4.7uH in Q2300 VGA module schematic; can be replaced with 0R resistor.

W831 connector originally is Molex 22-23-2121. Probably can be replaced with XH 2.54 12 pin connectors / cables, note pins step 2.5/254 mm. Pay attention on cable connectors type: same direction or reverse direction. Most cable are up to 30 cm, sometimes 50 cm. Measure what you need before ordering.

Double-check ground and VCC connection on VGA module PCB and TV chassis before soldering 12-pin W831 connector and power on.

Install

Q2400 chassis: Q2400 Module connection diagram

Q2500 chassis: Q2500 Module connection diagram

Required TV and adapter board modifications

Mods information provided by @neonname.

Combined VGA adapter board output and TV input termination/load resistance for RGB lines should be ~75 Ohm.

Q2400

TV Signal Board schematic: Q2400 Signal Board schematic Q2400 signal board already have 75 Ohm termination resistors on RGB lines.
150 Ohm RGB termination resistors on adapter board should be removed.

Q2500-B

TV Signal Board schematic: Q2500-B Signal Board schematic PCB components side: Q2500-B Signal Board PCB PCB solder side: Q2500-B Signal Board PCB PCB missing W1011 VGA connector and RGB input resistors, RGB input connected to ground with 0R load resistors.
Suggested changes, needs to check on real board:

  • Replaсe R2641, R2643, R2646 (0R) with 27R, add missing R1016, R1017, R1018 47R resistors (like Q2500-M) (probably incorrect termination)
  • Or replaсe R2641, R2643, R2646 (0R) with 150R; add missing R1016, R1017, R1018 (0R) (like Q2500-H). Note: R2512, R2513, R2514.

Q2500-H

TV Signal Board schematic: Q2500-H Signal Board schematic PCB components side: Q2500-H Signal Board PCB PCB solder side: Q2500-H Signal Board PCB Recommended changes:

  • Replaсe R2641, R2643, R2646 (68R) with 150R; R1016, R1017, R1018 (10R) with 0R; R2512, R2513, R2514 (0R) with 47R; remove C1016, C1017, C1018.

Q2500-M

TV Signal Board schematic: Q2500-M Signal Board schematic PCB components side: Q2500-M Signal Board PCB PCB solder side: Q2500-M Signal Board PCB Suggested changes, needs to check on real board:

  • Replaсe R2641, R2643, R2646 (47R) with 150R; R1016, R1017, R1018 (27R) with 0R; remove C1016, C1017, C1018. Note: R2512, R2513, R2514.