St251 20938
About the St251 20938 PCB
St251 20938 is an open source PCB design by schlae, published on GitHub. It is a 2-layer board measuring 136.8 × 199.1 mm, with 225 components from 118 distinct parts.
By type, the board carries 83 resistors, 74 capacitors, 10 inductors, 7 connectors, 7 test points and 5 transistors.
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.
St251 20938 bill of materials (BOM)
225 components, 118 distinct parts.
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | BC859 | SOT95P230X117-3 | Q1 |
| 1 | 2SD1760 | TO-252-2 | Q2 |
| 3 | IRFD110 | DIP-4_W7.62mm | Q3, Q4, Q5 |
| 1 | Crystal_Small | Crystal_SMD_HC49-SD | Y1 |
| 1 | Crystal_Small | Crystal_HC49-U_Vertical | Y2 |
| 1 | control | EDGE_34_100 | J1 |
| 1 | data | EDGE_20_100 | 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 | CONFIG | PinHeader_2x08_P2.54mm_Vertical | J7 |
| 1 | 74LS14 | SOP127P620X175-14 | 1D1 |
| 1 | 7406 | SOP127P620X175-14 | 1E1 |
| 2 | 74LS74 | SOP127P620X175-14 | 1F1, 2F1 |
| 1 | 11647-502 | PLCC-44_16.6x16.6mm_P1.27mm | 2B1 |
| 1 | 74F138 | SOP127P620X175-16 | 2D1 |
| 1 | 74F10 | SOP127P620X175-14 | 2E1 |
| 1 | R6518 | PLCC-44_16.6x16.6mm_P1.27mm | 3A1 |
| 1 | 27C32 | DIP254P1524X635-24 | 4A1 |
Show 98 more
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | 11791 | MOT_DRIVE | 4H1 |
| 1 | SSI296 10206-501 | PLCC-44_16.6x16.6mm_P1.27mm | 6A1 |
| 1 | 74LS373 | SOP127P1065X265-20 | 6B1 |
| 1 | 74LS273 | SOP127P1065X265-20 | 6C1 |
| 1 | 11782-501 | 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 | 10F1, 10H1, 11F1 |
| 1 | 10189-521 | SOIC-20W_7.5x12.8mm_P1.27mm | 11E1 |
| 4 | BL9 | D_SMA | CR1, CR5, CR6, CR8 |
| 1 | 1N4002 | D_DO-35_SOD27_P10.16mm_Horizontal | CR2 |
| 1 | BZX84C5V1 | SOT-23 | CR4 |
| 1 | P6KE13 | D_DO-15_P15.24mm_Horizontal | CR7 |
| 1 | LED_Small_Filled | PinHeader_1x02_P2.54mm_Vertical | DS1 |
| 1 | Conn_01x03 | PinHeader_1x03_P2.54mm_Vertical | JP1 |
| 1 | Jumper_2_Open | PinHeader_1x02_P2.54mm_Vertical | JP2 |
| 1 | Jumper_2_Open | R_1206_3216Metric | JP4 |
| 1 | 0 | R_1206_3216Metric | JP10 |
| 1 | DNI | R_1206_3216Metric | JP11 |
| 1 | 10uH | L_1206_3216Metric | Langle1 |
| 4 | 1/2 STEP | TestPoint_THTPad_2.0x2.0mm_Drill1.0mm | TP1, TP2, TP3, TP4 |
| 2 | 1/2 STEP | TestPoint_THTPad_1.0x1.0mm_Drill0.5mm | TP5, TP6 |
| 1 | Jumper_2_Bridged | SolderJumper-2_P1.3mm_Bridged_Pad1.0x1.5mm | TP8 |
| 1 | BAS16W | SOT-323_SC-70 | D1 |
| 2 | 22uH | L_Axial_L13.0mm_D4.5mm_P15.24mm_Horizontal_Fastron_HCCC | L1, L2 |
| 2 | 2.2uH | L_1206_3216Metric | L4, L5 |
| 3 | 10uH | L_1206_3216Metric | L6, L7, L11 |
| 1 | 2.7uH | L_1206_3216Metric | L8 |
| 2 | 39uH | L_1206_3216Metric | L9, L10 |
| 26 | 0.1uF | C_1206_3216Metric | C1, C2, C9, C16, C28, C30, C32, C33 +18 |
| 7 | 0.01uF | C_0805_2012Metric | C3, C8, C22, C24, C35, C36, C37 |
| 4 | 100pF | C_0805_2012Metric | C4, C13, C21, C41 |
| 1 | 0.068uF | C_1210_3225Metric | C5 |
| 3 | 18nF | C_0805_2012Metric | C6, C57, C58 |
| 1 | 0.012uF | C_1206_3216Metric | C7 |
| 2 | 22pF | C_0805_2012Metric | C10, C67 |
| 3 | 0.1uF | C_1210_3225Metric | C11, C12, C60 |
| 1 | 330pF | C_0805_2012Metric | C14 |
| 2 | 0.015uF | C_0805_2012Metric | C15, C71 |
| 1 | 1uF/35 | CP_EIA-3528-12_Kemet-T | C17 |
| 1 | 39nF | C_1206_3216Metric | C18 |
| 1 | 1000pF | C_1206_3216Metric | C19 |
| 1 | 150pF | C_0805_2012Metric | C20 |
| 1 | 68pF | C_0805_2012Metric | C23 |
| 4 | 47pF | C_0805_2012Metric | C25, C26, C34, C38 |
| 5 | 22uF 25V | CP_EIA-7343-31_Kemet-D | C27, C44, C51, C64, C65 |
| 1 | 4.7uF 35V | CP_EIA-6032-20_AVX-F | C29 |
| 1 | 15pF | C_0805_2012Metric | C31 |
| 1 | 10uF 25V | CP_EIA-7343-31_Kemet-D | C39 |
| 1 | 6.8uF 25V | CP_EIA-7343-31_Kemet-D | C43 |
| 3 | 0.1uF | CP_EIA-3216-10_Kemet-I | C46, C47, C48 |
| 2 | 10uF | CP_EIA-7343-31_Kemet-D | C59, C69 |
| 1 | 1uF 35V | CP_EIA-3528-12_Kemet-T | C63 |
| 3 | 1.62K | R_1206_3216Metric | R1, R31, R57 |
| 2 | 5.1 | R_1206_3216Metric | R1B1, R9 |
| 1 | 2.43K | R_1206_3216Metric | R2 |
| 1 | 64.9 | R_1206_3216Metric | R3 |
| 2 | 100 1% | R_1206_3216Metric | R4, R25 |
| 3 | 20K | R_1206_3216Metric | R5, R40, R60 |
| 1 | 330 | R_1210_3225Metric | R6 |
| 1 | 220 | R_1210_3225Metric | R7 |
| 1 | 47.5 1% | R_1206_3216Metric | R8 |
| 10 | 3K | R_1206_3216Metric | R10, R12, R13, R19, R35, R44, R58, R59 +2 |
| 3 | 100 | R_1206_3216Metric | R11, R41, R63 |
| 12 | 1K | R_1206_3216Metric | R14, R15, R16, R17, R18, R20, R36, R37 +4 |
| 1 | 511 1% | R_1206_3216Metric | R21 |
| 2 | 162 | R_1206_3216Metric | R22, R23 |
| 1 | 357 | R_1206_3216Metric | R24 |
| 2 | 499 1% | R_1206_3216Metric | R26, R27 |
| 1 | 10 1% | R_1206_3216Metric | R28 |
| 1 | 1.82K 1% | R_1206_3216Metric | R29 |
| 1 | 2.61K | R_1206_3216Metric | R30 |
| 1 | 14.7K 1% | R_1206_3216Metric | R32 |
| 1 | 0 | R_1206_3216Metric | R33 |
| 1 | 8.87K | R_1206_3216Metric | R33B1 |
| 1 | 2K | R_1206_3216Metric | R34 |
| 5 | 10K | R_1206_3216Metric | R42, R45, R52, R53, R66 |
| 3 | 5.1 | R_1210_3225Metric | R43, R47, R48 |
| 1 | 1.3K | R_1206_3216Metric | R46 |
| 1 | 820K | R_1206_3216Metric | R49 |
| 1 | 15K 1% | R_1206_3216Metric | R50 |
| 1 | 17.4K | R_1206_3216Metric | R51 |
| 1 | 10K 1% | R_1206_3216Metric | R55 |
| 1 | 100K | R_1206_3216Metric | R56 |
| 1 | 1.3K 1% | R_1206_3216Metric | R61 |
| 1 | 47.5K | R_1206_3216Metric | R64 |
| 1 | 1M | R_1206_3216Metric | R65 |
| 5 | 5.1 | R_2512_6332Metric_Pad1.40x3.35mm_HandSolder | R67, R67B1, R68, R68B1, R81 |
| 1 | 475 | R_1206_3216Metric | R69 |
| 1 | 22.1 | R_1206_3216Metric | R72 |
| 1 | 51 | R_1206_3216Metric | R78 |
| 1 | 3.01K | R_1206_3216Metric | R79 |
| 1 | 26.1K | R_1206_3216Metric | R80 |
| 1 | DNI | R_1206_3216Metric | R82 |
| 1 | 750 1% | R_1206_3216Metric | R87 |
| 1 | 220/330 | R_Array_SIP10 | RN1 |
St251 20938 design files
The KiCad project lives in the schlae/HardDriveInfo repository on GitHub; these links point at the commit this page was built from.
St251 20938: common questions
How big is the St251 20938 PCB?
The St251 20938 measures 136.8 × 199.1 mm, has 2 copper layers and is 1.6 mm thick.
How many components are on the St251 20938?
225 components, from 118 distinct parts. The full bill of materials is listed on this page.
Where can I download the St251 20938 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 St251 20938 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.
