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Sinclair ZX Spectrum Troubleshooting Guide
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== RAM Failures == === Lower RAM (16K/48K: 4116) === * Each chip = 1 bit; all 8 must work for 16K operation. * Needs +5 V, +12 V, and -5 V. * Failure symptoms: black screen, coloured stripes, random resets, or garbage display. * One chip hotter than others often indicates failure. === Upper RAM (48K: 4532/4164) === * Adds 32K for 48K total. * Failure symptoms: boots as 16K, random crashes, corrupted graphics, or βRβ errors on startup. * Can be removed for 16K-only operation. === 128K/+2/+3 RAM (41464/4464) === * 8 Γ 41464 (128K) or 8 Γ 4464 (256K). * Failure: random crashes, corrupted display, βRAMTOPβ errors, or beeper noise. === Diagnosis / Fix === * Swap suspected chip, or socket & replace. * If still faulty after RAM swap, check multiplexers (74LS157/74LS32). * Test for correct voltages at each RAM chip.
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