St251n 20603
About the St251n 20603 PCB
St251n 20603 is an open source PCB design by schlae, published on GitHub. It is a 4-layer board measuring 137.4 × 199.1 mm, with 277 components from 133 distinct parts.
Other key parts include the 8051, 74LS573, 74LS14, CDM6264 and AIC-010L. By type, the board carries 99 resistors, 90 capacitors, 20 ICs, 18 transistors, 10 inductors and 6 connectors.
From the project
Repair info and schematics for mostly older MFM hard drives
This site contains extensive information about the control boards used in some 1980s hard drives made by Seagate.
Full schematics and even KiCad layouts are available for a number of different boards. My hope is that this will
1. Aid anyone attempting to repair one of these drives. Loading the schematic and layout in KiCad will let you click on a part on the layout and highlight it in schematic. 2. Inform anyone studying the history of small hard drives. For example, this information shows how Seagate integrated various functions into custom chips.
Main components on the St251n 20603
St251n 20603 bill of materials (BOM)
277 components, 133 distinct parts.
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | 8051 | PLCC-44 | U1 |
| 1 | 74LS573 | SOP127P1065X265-20_SHRINK | U2 |
| 1 | 74LS14 | SOP127P620X175-14_SHRINK | U3 |
| 1 | CDM6264 | SOP127P1270X305-28_SHRINK | U4 |
| 1 | AIC-010L | PLCC-44 | U5 |
| 1 | ~ | PLCC-44 | U6 |
| 1 | SRAM_6116 | SOP127P1250X255-24 | U7 |
| 1 | 11747-501 | SOP127P1250X255-24 | U8 |
| 1 | AIC-270L | PLCC-28 | U9 |
| 1 | DP8462 | PLCC-28 | U10 |
| 1 | 11734-501 | PLCC-44_16.6x16.6mm_P1.27mm | U11 |
| 1 | 74LS155 | SOP127P620X175-16_SHRINK | U13 |
| 3 | 74LS174 | SOP127P620X175-16_SHRINK | U21, U22, U23 |
| 1 | 74LS257 | SOP127P620X175-16_SHRINK | U24 |
| 1 | 74LS00 | SOP127P620X175-14_SHRINK | U27 |
| 1 | 74LS196 | SOP127P620X175-14_SHRINK | U28 |
| 1 | 74LS123 | SOP127P620X175-16_SHRINK | U29 |
| 1 | 74F08 | SOP127P620X175-14_SHRINK | U30 |
| 6 | ? | SOT95P230X117-3 | Q1, Q8, Q9, Q10, Q11, Q12 |
| 1 | 2SD1760 | TO-252-2 | Q2 |
Show 113 more
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 3 | IRFD110 | DIP-4_W7.62mm | Q3, Q4, Q5 |
| 5 | BC846 | SOT95P230X117-3 | Q6, Q7, Q15, Q16, Q18 |
| 1 | BC846A | SOT95P230X117-3 | Q13 |
| 1 | "1A" | SOT95P230X117-3 | Q14 |
| 1 | 2N3906 | SOT95P230X117-3 | Q17 |
| 1 | 10MHz | Crystal_SMD_HC49-SD | Y1 |
| 1 | 15MHz | Crystal_SMD_HC49-SD | Y2 |
| 1 | ID | PinHeader_2x04_P2.54mm_Vertical | J2 |
| 1 | POWER | Samtec_HPM-04-01-x-S_Straight_1x04_Pitch5.08mm | J3 |
| 1 | SPINDLE | PinHeader_2x07_P2.54mm_Vertical | J4 |
| 1 | STEPPER | PinHeader_2x05_P2.54mm_Vertical | J5 |
| 1 | HEADS | PinHeader_2x12_P2.54mm_Vertical | J6 |
| 1 | SCSI | PinHeader_2x25_P2.54mm_Horizontal | J8 |
| 1 | 11738-502 | MOT_DRIVE_SMT | 4H1 |
| 1 | SSI296 10206-501 | PLCC-44_16.6x16.6mm_P1.27mm | 6A1 |
| 1 | 10210-501 | SOP127P1065X265-20 | 7C1 |
| 1 | 11743-501 | SOP127P1070X255-28 | 7E1 |
| 1 | 10223-502 | SOP127P1065X265-16 | 7F1 |
| 1 | 11744-502 | SOIC-24W_7.5x15.4mm_P1.27mm | 8F1 |
| 1 | 10188-501 | SOIC-20W_7.5x12.8mm_P1.27mm | 10E1 |
| 3 | 11721-501 | SOP127P1065X265-20_SHRINK | 10F1, 10H1, 11F1 |
| 1 | 10189-502 | SOIC-20W_7.5x12.8mm_P1.27mm | 11E1 |
| 2 | ? | D_DO-35_SOD27_P10.16mm_Horizontal | CR1, CR6 |
| 1 | BZX84C5V1 | SOT-23 | CR4 |
| 1 | BL9 | D_DO-15_P15.24mm_Horizontal | CR5 |
| 1 | P6KE13 | D_DO-15_P15.24mm_Horizontal | CR7 |
| 2 | Jumper_2_Bridged | PinHeader_1x02_P2.54mm_Vertical | JP1, JP2 |
| 1 | 10uH | L_1206_3216Metric | Langle1 |
| 6 | 1/2 STEP | TestPoint_THTPad_1.5x1.5mm_Drill0.7mm | TP1, TP2, TP3, TP4, TP5, TP6 |
| 4 | 1/2 STEP | TestPoint_THTPad_D2.5mm_Drill1.2mm | TPE1, TPE2, TPE3, TPE4 |
| 1 | DNI | SOT-23-3 | D1 |
| 1 | ? | D_DO-41_SOD81_P12.70mm_Horizontal | D2 |
| 1 | RED | PinHeader_1x02_P2.54mm_Vertical | D11 |
| 2 | 22uH | L_Axial_L13.0mm_D4.5mm_P15.24mm_Horizontal_Fastron_HCCC | L1, L2 |
| 1 | 10uH | L_1206_3216Metric | L3 |
| 2 | 1.5uH | L_1206_3216Metric | L4, L5 |
| 2 | 4.7uH | L_1206_3216Metric | L6, L7 |
| 1 | 3.9uH | L_1206_3216Metric | L8 |
| 1 | 33uH | L_1206_3216Metric | L9 |
| 1 | 22uH | L_1206_3216Metric | L10 |
| 39 | 0.1uF | C_1206_3216Metric | C1, C2, C6, C9, C15, C16, C19, C22 +31 |
| 4 | 0.01uF | C_0805_2012Metric | C3, C35, C36, C37 |
| 1 | 1uF 35V | C_1210_3225Metric | C4 |
| 1 | 0.068uF | C_1210_3225Metric | C5 |
| 1 | 0.033uF | C_1206_3216Metric | C7 |
| 7 | ? | C_0805_2012Metric | C8, C29, C42, C49, C54, C69, C90 |
| 1 | 22pF | C_0805_2012Metric | C10 |
| 3 | 0.1uF | C_1210_3225Metric | C11, C12, C50 |
| 1 | 120pF | C_0805_2012Metric | C13 |
| 1 | 330pF | C_0805_2012Metric | C14 |
| 2 | 1uF 35V | CP_EIA-7343-31_Kemet-D | C17, C31 |
| 1 | 39nF | C_1206_3216Metric | C18 |
| 1 | 220pF | C_0805_2012Metric | C20 |
| 2 | 100pF | C_0805_2012Metric | C21, C41 |
| 1 | 39pF | C_1206_3216Metric | C23 |
| 4 | 47pF | C_0805_2012Metric | C25, C26, C34, C38 |
| 5 | 22uF 20V | CP_EIA-7343-31_Kemet-D | C27, C40, C44, C64, C65 |
| 1 | 0.47uF | C_1812_4532Metric | C32 |
| 2 | ? | C_1210_3225Metric | C39, C59 |
| 1 | 10uF 25V | CP_EIA-7343-31_Kemet-D | C43 |
| 1 | 27pF | C_0805_2012Metric | C45 |
| 3 | 0.1uF | CP_EIA-3216-10_Kemet-I | C46, C47, C48 |
| 1 | 1.5uF 35V | CP_EIA-7343-31_Kemet-D | C61 |
| 1 | 1uF 35V | CP_EIA-3216-10_Kemet-I | C62 |
| 1 | 1uF 35V | CP_EIA-3528-12_Kemet-T | C63 |
| 1 | 39pF | C_0805_2012Metric | C67 |
| 2 | ? | C_1206_3216Metric | C72, C91 |
| 1 | DNI | C_0805_2012Metric | C76 |
| 1 | 1.1K | R_1206_3216Metric | R1 |
| 2 | 10 | R_1206_3216Metric | R1B1, R28 |
| 1 | 2.21K | R_1206_3216Metric | R2 |
| 1 | 59.0 | R_1206_3216Metric | R3 |
| 6 | 10K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R4, R86, R88, R89, R90, R94 |
| 1 | 2K | R_1206_3216Metric | R5 |
| 7 | 10K | R_1206_3216Metric | R6, R7, R46, R52, R53, R66, R104 |
| 1 | 59.0 1% | R_1206_3216Metric | R8 |
| 1 | 5.1 | R_1206_3216Metric | R9 |
| 4 | 10 | R_1210_3225Metric | R10, R13, R19, R33 |
| 1 | 162 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R11 |
| 16 | 1K | R_1206_3216Metric | R14, R15, R16, R17, R18, R20, R34, R36 +8 |
| 3 | 499 1% | R_1206_3216Metric | R21, R26, R27 |
| 2 | 88.7 | R_1206_3216Metric | R22, R23 |
| 1 | 1.33K | R_1206_3216Metric | R24 |
| 1 | 100 1% | R_1206_3216Metric | R25 |
| 1 | 2.61K | R_1206_3216Metric | R30 |
| 1 | 1.00K | R_1206_3216Metric | R31 |
| 1 | 10.0K 1% | R_1206_3216Metric | R32 |
| 1 | 10.0K | R_1206_3216Metric | R33B1 |
| 2 | 3.01K | R_1206_3216Metric | R35, R79 |
| 1 | 100K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R40 |
| 11 | ? | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R41, R43, R44, R45, R47, R48, R59, R70 +3 |
| 1 | 4.75K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R42 |
| 2 | 825K | R_1206_3216Metric | R49, R65 |
| 1 | 14.7K 1% | R_1206_3216Metric | R50 |
| 1 | 14.0K | R_1206_3216Metric | R51 |
| 1 | 10K 1% | R_1206_3216Metric | R55 |
| 1 | 100K | R_1206_3216Metric | R56 |
| 1 | 1.62K | R_1206_3216Metric | R57 |
| 1 | ? | R_Axial_DIN0204_L3.6mm_D1.6mm_P7.62mm_Horizontal | R58 |
| 1 | 20K | R_1206_3216Metric | R60 |
| 1 | 1.0K 1% | R_1206_3216Metric | R61 |
| 1 | 6.2K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R64 |
| 5 | 5.1 | R_2512_6332Metric_Pad1.40x3.35mm_HandSolder | R67, R67B1, R68, R68B1, R81 |
| 1 | 499 | R_1206_3216Metric | R69 |
| 1 | ? | R_1210_3225Metric | R72 |
| 1 | 1.0K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R75 |
| 4 | 1K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R76, R91, R92, R93 |
| 1 | ? | R_1206_3216Metric | R77 |
| 1 | 825 | R_1206_3216Metric | R78 |
| 1 | 162 | R_1206_3216Metric | R84 |
| 1 | 5.62K 1% | R_1206_3216Metric | R87 |
| 1 | 3.85K | R_1206_3216Metric | R99 |
| 3 | TERM | R_Array_SIP8 | RN1, RN2, RN3 |
St251n 20603 design files
The KiCad project lives in the schlae/HardDriveInfo repository on GitHub; these links point at the commit this page was built from.
St251n 20603: common questions
How big is the St251n 20603 PCB?
The St251n 20603 measures 137.4 × 199.1 mm, has 4 copper layers and is 1.6 mm thick.
How many components are on the St251n 20603?
277 components, from 133 distinct parts. The full bill of materials is listed on this page.
Where can I download the St251n 20603 design files?
From the schlae/HardDriveInfo repository on GitHub, which has the KiCad layout and the schematic; the links under Design files point to each one.
Can I use the St251n 20603 design in my own project?
The repository has no license, so all rights stay with schlae. Use it as a reference, and ask the author before reusing the design.
