HP Color LaserJet 2550 Printer
Middle Frame Assembly Diagram

Registration sensor board - RG5-6967 Drawer connector - WT2-5737 Entrance guide - RF5-4065 Transfer inlet guide assembly - RB3-1088 Resistor - RH5-3115 Compression spring - RB3-0015 Spring - RB3-1092 Spring - 1091 Bushing - RB3-1094 Transfer roller assembly - RF5-4067 Torsion spring - RB2-9999 Cable clamp - WT2-5700 High voltage cable assembly - RG5-7130 M3 truss-head phillips screw - XA9-0890 M3 truss-head phillips screw - XA9-0890 Mount, antenna contact - RB2-9851 Mount, terminal - RB2-9850 Tension spring - RS6-2766 Sensor PC board - WG8-5382 Cable assembly - RG5-7128 Paper feed belt - RB3-0063 Paper feed belt - RB3-0063 Pulley roller - RB3-0067 Pulley roller - RB3-0067 Sensor flag roller - RB2-7195 Sensor assembly mounting holder - RB2-9924 Sensor arm and flag - RB2-9925 Contact plate - RB3-0066 Contact plate - RB3-0065 Gear cover - RB3-0052 Cable assembly - RG5-7122 Registration shutter assembly - RG5-6940 Grounding cable - RG5-7123 Registration roller assembly - RG5-6939 M4 pan-head phillips screw - XA9-1262 M4 pan-head phillips screw - XA9-1262 M4 pan-head phillips screw - XA9-1262 M4 pan-head phillips screw - XA9-1262 M4 pan-head phillips screw - XA9-1262 M4 pan-head phillips screw - XA9-1262 M4 pan-head phillips screw - XA9-1262 M4 pan-head phillips screw - XA9-1262 M4 pan-head phillips screw - XA9-1262 M4 pan-head phillips screw - XA9-1262 30 tooth gear - RS7-0428 Connector assembly - RH2-5519 Transfer side plate - RB3-0057 Transfer side plate - RB3-0057 Insulating sheet - RB3-1110 Bushing - RS5-1637 Spring - RB3-0048 Spring - RB3-0047 Spring - RB3-0046 Spring - RB3-0044 Spring - RB3-0043 Spring - RB3-0042 22 tooth gear - RB3-0022 Spring - RB3-0016 Spring - RB3-0045 Idle gear shaft - RB3-0060 Belt roller - RB3-0012 Feed drive shaft - RB3-0011 Feed plate - RB3-0010 Rubber foot - RB3-0286 Rubber foot - RB2-6297 Rubber foot - RB2-6297 Paper feed belt - RB3-0063 Paper feed belt - RB3-0063 Pulley roller - RB3-0061 Pulley roller - RB3-0061 Feed guide drive belt - RB1-8668 Ground plate - RB3-0009
REF PART # DESCRIPTION
1 RB1-8668 Feed guide drive belt - Small belt approximately 5/16 inch wide with 'A' shaped ribs on it - Between the feed drive roller and the small center roller - Driven via the transfer roller gear train
2 RB3-0061 Pulley roller (accommodates three feed belts) - Small black roller approximately 3.49cm (1-3/4 inches) long with three ball type pulleys - Mounts just behind the transfer roller in the middle frame assembly (two used)
3 RB3-0063 Paper feed belt - Small black rubber belt approximately 1/8 inch wide with little 'A' shaped ribs on it - Goes between the feed drive roller and the pulley rollers (eight used)
4 RB2-6297 Rubber foot - Square self-adhesive rubber foot - Attaches to the rear of the middle frame assembly (two used)
5 RB3-0286 Contact plate - Runs between the shaft on the registration roller and the metal entrance guide assembly
6 RB3-0009 Static eliminator ground plate - Right angled metal piece with small teeth on top edge - Mounts from underneath on the middle frame assembly just behind the pulley rollers
7 RB3-0011 Feed drive shaft - Long shaft with eight feed belt ball type pulleys and one ribbed feed guide drive belt pulley - Mounts behind the transfer roller on the middle frame assembly
8 RB3-0012 Belt roller - Small oval shaped roller approximately 1-3/4 inches long - Mounts toward the center of the metal feed plate on the middle frame assembly
9 RB3-0060 Idler gear shaft - Short metal rod - Shaft for the transfer and feed drive idler roller - Mounts on the left side of the middle frame assembly
10 RB3-0045 Electrical contact spring - Rear electrical contact spring - Provides high voltage to the toner cartridge via a cable assembly and connection through the carousel plate assembly - Connects to the high voltage board
11 RB3-0016 Electrical contact spring - Spring steel wire with compression springs formed on both ends - One end provides upward pressure on the right bushing for the transfer roller - Connects to high voltage board
12 RB3-0022 22 tooth gear (Black plastic) - Small gear with diagonally cut teeth - Idler gear between the transfer roller assembly and the feed drive shaft - Mounts on the left side of the middle frame assembly
13 RB3-0042 Electrical contact spring - Mounts on the middle frame assembly behind the transfer roller - Of the four similar springs, this one is next to the one on the far left - Connects to high voltage board
14 RB3-0043 Electrical contact spring - Mounts on the middle frame assembly behind the transfer roller - Of the four similar springs, this one is on the far right - Connects to high voltage board
15 RB3-0044 Electrical contact spring - (Front) Provides high voltage to the toner cartridge via a cable assembly and connection through the carousel plate assembly - Connects to the high voltage board
16 RB3-0046 Electrical contact spring - Mounts on the middle frame assembly behind the transfer roller - Of the four similar springs, this one is just to the left of the one on the far right - Connects to high voltage board
17 RB3-0047 Electrical contact spring - Mounts on the underside of the middle frame assembly - Connects to high voltage board
18 RB3-0048 Electrical contact spring - Mounts on the middle frame assembly behind the transfer roller - Of the four similar springs, this one is on the far left - Connects to the high voltage board
19 RS5-1637 Bushing (black plastic) - Mounts on the right end of the registration roller assembly
20 RB3-1110 Insulating sheet (Transparent plastic) - For the power supply base assembly - Mounts to the underside of the middle frame assembly
21 RB3-0057 Transfer slide plate - Small 'U' shaped metal insert plates - Mount in the bushing wells for the transfer roller on the middle frame assembly (two used)
22 RH2-5519 Connector assembly - For optional paper tray - Mounts to the bottom right side of the middle frame assembly
23 RS7-0428 30 tooth gear (White plastic) - Mounts on the end of the registration roller drive shaft
24 XA9-1262 M4 pan-head Phillips screw with self-tapping threads - 10mm long - Used primarily to secure metal parts to the internal plastic frames
25 RG5-6939 Registration roller assembly - Includes the roller, bushings, mounting plate, paper sensor, and the sensor flag - Mounts from the bottom toward the front center of the middle frame assembly
26 RG5-7123 Grounding cable assembly - Connects from the optional tray connector housing to the metal right side frame assembly
27 RG5-6940 Registration shutter assembly - Includes the metal roller, mounting frame, grounding springs, and the dual coupling gear - Mounts over the registration roller at the front of the middle frame assembly
28 RG5-7122 Cable assembly - 'Y' type cable (three connectors) - The 14-pin connector splits into an 8-pin connector and a 6-pin connector
29 RB3-0052 Gear Cover (Small Black plastic cover) - Covers the left end of the feed drive shaft - Mounts towards the left side of the middle frame assembly
30 RB3-0065 Contact plate - copper clad metal spring - Holds the left end of the small 500 Meg-ohm resistor
31 RB3-0066 Contact plate - copper clad metal spring - Holds the right end of the small 500 Meg-ohm resistor - Mounts on the left side of the middle frame below the entrance guide assembly
32 RB2-9925 Sensor arm and flag - Activates the photo sensor (Does NOT include the roller)
33 RB2-9924 Sensor assembly mounting holder - Holds the leading edge paper sensor (PS720) for the fusing assembly - Mounts on the underside left on the middle frame assembly
34 RB2-7195 Sensor flag roller (small White plastic roller) - Mounts in the sensor arm flag for the leading edge paper sensor for the fusing assembly (PS720)
35 RB3-0067 Pulley roller (accommodates one feed belt) - Small black roller approximately 1.59cm (5/8 inch) long with one ball type pulley - Mounts just behind the transfer roller in the middle frame assembly (two used)
36 RG5-7128 Cable assembly (four 3-pin connectors) - Connects between the DC controller board (J107 and J138) and the leading edge paper sensor for the fusing assembly (J720) and the registration sensor (J711)
37 WG8-5382 Sensor PC board - Small board with flag activated photo sensor - (PS718) Paper sensor for the multipurpose tray - Mounts in the lower right of the front frame assembly
38 RS6-2766 Tension spring - Provides a small amount of return tension for the sensor flag arm on the leading edge sensor for the fusing assembly (PS720)
39 XA9-0890 M3 truss-head Phillips screw with machine threads - 6mm long - Primarily used to secure metal to metal parts
40 RG5-7130 High voltage cable assembly - Connects between the high voltage board spring contacts (on the middle frame assembly) and the cables for the toner cartridge carousel left plate assembly (J511 and J512)
41 WT2-5700 Cable clamp - White plastic clamp with mounting pin - Mounts on the upper right side of the front frame assembly and the lower left side of the middle frame assembly (two used)
42 RB2-9999 Torsion spring - Secures the belt roller (for the feed drive shaft) in the top of the middle frame assembly
43 RF5-4067 Transfer roller assembly - Long black foam type roller - Transfers static charge to paper - Mounts towards the front and on top of the middle frame assembly
44 RB3-1094 Bushing assembly (Black plastic bushing with small guide roller on top) - Holds the right end of the transfer roller assembly in the middle frame assembly
45 RB3-0015 Compression spring - Provides upward pressure for the left transfer roller bushing
46 RH5-3115 Resistor - 500 Mega Ohm, 300mW - Mounts on the left side of the middle frame below the entrance guide assembly - Held in place with two small contact plates
47 RB3-1088 Transfer inlet guide assembly - Angled metal guide between the registration roller and the transfer roller - Mounts to the middle frame assembly
48 RF5-4065 Entrance guide assembly - Mounts in front of the transfer roller assembly (behind the transfer inlet guide)
49 WT2-5737 Drawer connector - Connector located on bottom of tray assembly frame on right side, which connects tray assemblies to each other - One mounts on the left side of the middle frame and two on the base assembly pan (three used)
50 RG5-6967 Registration sensor PC Board - Small board with flag activated photo sensor - (PS711) Mounts in the registration assembly on the underside of the middle frame