St225 20427
About the St225 20427 PCB
St225 20427 is an open source PCB design by schlae, published on GitHub. It is a 2-layer board measuring 136.8 × 199.1 mm, with 212 components from 110 distinct parts.
Other key parts include the 8051, 74LS373, CDM6264, AIC-010L and AIC-300L. By type, the board carries 94 resistors, 54 capacitors, 33 ICs, 8 transistors, 8 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 St225 20427
St225 20427 bill of materials (BOM)
212 components, 110 distinct parts.
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | 8051 | PLCC-44 | U1 |
| 3 | 74LS373 | SOP127P1065X265-20_SHRINK | U2, U4, U19 |
| 1 | CDM6264 | SOP127P1270X305-28_SHRINK | U3 |
| 1 | AIC-010L | PLCC-44 | U5 |
| 1 | AIC-300L | PLCC-44 | U6 |
| 1 | SRAM_6116 | SOP127P1250X255-24 | U7 |
| 1 | AIC-250L | PLCC-28 | U8 |
| 1 | DP8455 | PLCC-20 | U9 |
| 1 | MC3479 | PLCC-20 | U10 |
| 2 | 74LS240 | SOP127P1065X265-20_SHRINK | U11, U12 |
| 1 | 74F08 | SOP127P620X175-14_SHRINK | U13 |
| 1 | 74LS14 | SOP127P620X175-14_SHRINK | U14 |
| 4 | 74F38 | SOP127P620X175-14_SHRINK | U15, U16, U17, U18 |
| 1 | 7406 | SOP127P620X175-14_SHRINK | U20 |
| 1 | 11647-501 | PLCC-44 | U21 |
| 1 | SSI257_2 | SOP127P1065X265-20_SHRINK | U22 |
| 1 | 74LS196 | SOP127P620X175-14_SHRINK | U23 |
| 2 | 74F74 | SOP127P620X175-14_SHRINK | U24, U30 |
| 1 | 74F04 | SOP127P620X175-14_SHRINK | U25 |
| 1 | 74LS00 | SOP127P620X175-14_SHRINK | U26 |
Show 90 more
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | 75448 | SOP127P620X175-8_SHRINK | U27 |
| 1 | 11695-502 | SOP127P1065X265-16_SHRINK | U28 |
| 1 | 74LS123 | SOP127P620X175-16_SHRINK | U29 |
| 1 | 74F109 | SOP127P620X175-16_SHRINK | U31 |
| 1 | 11642-501 | SOP127P620X175-16_SHRINK | U32 |
| 1 | SSI280.2 | PLCC-28 | U33 |
| 3 | BD436 | TO-126-3_Horizontal_TabDown | Q1, Q3, Q5 |
| 2 | 2N6039 | TO-126-3_Horizontal_TabDown | Q2, Q4 |
| 3 | DNI | SOT-23 | Q6, Q7, Q10 |
| 1 | 20MHz | Oscillator_DIP-14 | X1 |
| 1 | HEADS | PinHeader_2x08_P2.54mm_Vertical | J1 |
| 1 | POWER | Samtec_HPM-04-01-x-S_Straight_1x04_Pitch5.08mm | J3 |
| 1 | SPINDLE | PinHeader_1x07_P2.54mm_Vertical | J4 |
| 1 | STEPPER | PinHeader_1x05_P2.54mm_Vertical | J6 |
| 1 | SCSI | PinHeader_2x25_P2.54mm_Horizontal | J8 |
| 1 | SCSI ID | PinHeader_2x03_P2.54mm_Vertical | J9 |
| 3 | 1N5818 | D_DO-35_SOD27_P10.16mm_Horizontal | CR1, CR2, CR3 |
| 3 | ? | JMP2 | JP1, JP2, JP3 |
| 1 | RED | PinHeader_1x02_P2.54mm_Vertical | D1 |
| 1 | 1N4148 | SOT-23 | D2 |
| 2 | 2.7uH | L_1206_3216Metric_Pad1.22x1.90mm_HandSolder | L1, L2 |
| 2 | 12uH | L_1206_3216Metric_Pad1.22x1.90mm_HandSolder | L3, L4 |
| 1 | 3.9uH | L_1206_3216Metric_Pad1.22x1.90mm_HandSolder | L5 |
| 1 | 10uH | L_1206_3216Metric_Pad1.22x1.90mm_HandSolder | L6 |
| 2 | 22uH | L_Axial_L13.0mm_D4.5mm_P15.24mm_Horizontal_Fastron_HCCC | L7, L8 |
| 25 | 0.1uF | C_1206_3216Metric_Pad1.33x1.80mm_HandSolder | C1, C8, C17, C22, C25, C27, C28, C29 +17 |
| 1 | 0.01uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C2 |
| 1 | 100pF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C3 |
| 4 | 0.1uF | C_1210_3225Metric_Pad1.33x2.70mm_HandSolder | C4, C5, C10, C13 |
| 2 | 22pF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C6, C15 |
| 1 | 330pF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C7 |
| 1 | 270pF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C9 |
| 3 | 1uF 20V | CP_EIA-3528-21_Kemet-B_Pad1.50x2.35mm_HandSolder | C11, C12, C50 |
| 2 | 47pF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C14, C55 |
| 1 | 10uF 35V | CP_EIA-7132-20_AVX-U | C18 |
| 1 | 0.012uF | C_1210_3225Metric_Pad1.33x2.70mm_HandSolder | C19 |
| 1 | 0.47uF | C_1812_4532Metric_Pad1.57x3.40mm_HandSolder | C20 |
| 1 | DNI | C_1812_4532Metric_Pad1.57x3.40mm_HandSolder | C21 |
| 1 | 22pF | C_0805_2012Metric | C23 |
| 1 | 100uF | C_Axial_L12.0mm_D6.5mm_P20.00mm_Horizontal | C24 |
| 1 | 10uF 35V | CP_EIA-7132-20_AVX-U_Pad2.72x3.50mm_HandSolder | C26 |
| 1 | 100pF | C_0805_2012Metric | C36 |
| 1 | 1uF 20V | CP_EIA-6032-15_Kemet-U | C39 |
| 2 | ? | C_1206_3216Metric_Pad1.33x1.80mm_HandSolder | C44, C48 |
| 1 | 0.12uF | C_1206_3216Metric_Pad1.33x1.80mm_HandSolder | C51 |
| 2 | 0.012uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C52, C53 |
| 2 | 162 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R1, R2 |
| 1 | 357 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R3 |
| 1 | 39 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R4 |
| 1 | 2.4K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R5 |
| 5 | 100 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R6, R26, R53, R72, R89 |
| 1 | 54.9 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R7 |
| 1 | 2.8K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R8 |
| 1 | 698 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R9 |
| 3 | 330 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R10, R20, R28 |
| 1 | 1.36K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R11 |
| 16 | 11 | R_1210_3225Metric_Pad1.30x2.65mm_HandSolder | R12, R21, R32, R39, R40, R41, R42, R43 +8 |
| 1 | 560 | R_1210_3225Metric_Pad1.30x2.65mm_HandSolder | R13 |
| 4 | DNI | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R14, R55, R56, R63 |
| 1 | 10 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R15 |
| 5 | 1K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R16, R24, R73, R78, R90 |
| 1 | 22.1K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R17 |
| 1 | 56 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R18 |
| 1 | 10K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R19 |
| 4 | 100 | R_1210_3225Metric | R22, R29, R65, R66 |
| 1 | 750 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R23 |
| 3 | 2K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R25, R30, R58 |
| 1 | 0.39 | R_Axial_DIN0309_L9.0mm_D3.2mm_P20.32mm_Horizontal | R27 |
| 4 | 3.3K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R31, R59, R74, R76 |
| 4 | 120 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R33, R34, R35, R57 |
| 1 | 16K | R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | R36 |
| 4 | 810 | R_1210_3225Metric_Pad1.30x2.65mm_HandSolder | R37, R38, R49, R62 |
| 1 | 5.1 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R44 |
| 1 | 510 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R46 |
| 1 | 51 | R_1206_3216Metric | R54 |
| 1 | 62K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R60 |
| 3 | 6.2K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R64, R67, R68 |
| 3 | 51 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R69, R70, R71 |
| 1 | 22 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R75 |
| 1 | 1.8K? | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R79 |
| 1 | 47 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R80 |
| 1 | 150 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R81 |
| 1 | 4.75K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R82 |
| 2 | 680 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R83, R84 |
| 1 | 511 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R85 |
| 1 | ? | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R86 |
| 1 | 4.32K | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R87 |
| 1 | 221 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R88 |
| 1 | 470 | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R91 |
| 3 | TERM | R_Array_SIP8 | RN1, RN2, RN3 |
St225 20427 design files
The KiCad project lives in the schlae/HardDriveInfo repository on GitHub; these links point at the commit this page was built from.
St225 20427: common questions
How big is the St225 20427 PCB?
The St225 20427 measures 136.8 × 199.1 mm, has 2 copper layers and is 1.6 mm thick.
How many components are on the St225 20427?
212 components, from 110 distinct parts. The full bill of materials is listed on this page.
Where can I download the St225 20427 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 St225 20427 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.
