Sinclair ZX Spectrum Capacitor Replacement Guide - Revision history

Josh at 09:43, 12 May 2025

2025-05-12T09:43:31Z

← Older revision		Revision as of 10:43, 12 May 2025
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	* [[Sinclair ZX Spectrum Power Supply Repair]]		* [[Sinclair ZX Spectrum Power Supply Repair]]
	* [[Sinclair ZX Spectrum Composite Video Mod]]		* [[Sinclair ZX Spectrum Composite Video Mod]]
			[[Category:Sinclair Computers]]
	[[Category:Sinclair ~~ZX Spectrum~~]]
	[[Category:Capacitor Replacement Guides]]		[[Category:Capacitor Replacement Guides]]

Josh at 09:42, 12 May 2025

2025-05-12T09:42:57Z

← Older revision		Revision as of 10:42, 12 May 2025
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	~~<templatestyles src="Template:StyledTable/styles~~.~~css" />~~		Replacing the electrolytic capacitors (“recapping”) in your Sinclair ZX Spectrum is a crucial maintenance step to ensure long-term reliability, stable video output, and protection against power-related failures. Aging capacitors are a common cause of instability, random resets, video artifacts, and audio noise.

	'''Replacing the electrolytic capacitors (“recapping”) in your Sinclair ZX Spectrum is a crucial maintenance step to ensure long-term reliability, stable video output, and protection against power-related failures. Aging capacitors are a common cause of instability, random resets, video artifacts, and audio noise.'''		== Visual Inspection & Failure Signs ==

	== 🔍 Visual Inspection & Failure Signs ==
	* '''Bulging or leaning capacitors''' – especially the large power filter (C9 on Issue 2/3 boards).		* '''Bulging or leaning capacitors''' – especially the large power filter (C9 on Issue 2/3 boards).
	* '''Leaking electrolyte''' – brown or green crust at the base of a capacitor.		* '''Leaking electrolyte''' – brown or green crust at the base of a capacitor.
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	If '''any''' capacitor shows signs of failure, it is strongly recommended to replace '''all''' electrolytics on the board.		If '''any''' capacitor shows signs of failure, it is strongly recommended to replace '''all''' electrolytics on the board.

	== 📋 ZX Spectrum Capacitor Lists ==		== ZX Spectrum Capacitor Lists ==
	The original ZX Spectrum was produced in several board revisions (Issue 1–6A). Capacitor values are generally consistent, but always verify against your board’s silkscreen.		The original ZX Spectrum was produced in several board revisions (Issue 1–6A). Capacitor values are generally consistent, but always verify against your board’s silkscreen.

	=== 🖥️ ZX Spectrum 16K/48K (Issue 2, 3, 4, 4A, 5, 6A) ===		=== ZX Spectrum 16K/48K (Issue 2, 3, 4, 4A, 5, 6A) ===
	{\| class="wikitable styled-table" style="width:100%; text-align:center;"		{\| class="wikitable styled-table" style="width:100%; text-align:center;"
	\|+'''ZX Spectrum Mainboard Electrolytic Capacitors'''		\|+'''ZX Spectrum Mainboard Electrolytic Capacitors'''
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	''Some early Issue 1 boards have minor differences; always check your board.''		''Some early Issue 1 boards have minor differences; always check your board.''

	=== 💾 ZX Spectrum+ and 128K Models ===		=== ZX Spectrum+ and 128K Models ===
	The ZX Spectrum+ uses the same mainboard as late 48K models, with identical capacitor values. The 128K “Toastrack” and +2 add a few extra capacitors for the sound circuit, DC-DC converter, and RAM.		The ZX Spectrum+ uses the same mainboard as late 48K models, with identical capacitor values. The 128K “Toastrack” and +2 add a few extra capacitors for the sound circuit, DC-DC converter, and RAM.

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	''The +2A/+3 models use a different PCB and power supply; consult their specific service manuals for capacitor lists.''		''The +2A/+3 models use a different PCB and power supply; consult their specific service manuals for capacitor lists.''

	== 🛠️ Recapping Procedure ==		== Recapping Procedure ==
	# '''Disassemble''' – Remove case screws, carefully separate keyboard membrane from mainboard.		# '''Disassemble''' – Remove case screws, carefully separate keyboard membrane from mainboard.
	# '''Label keyboard and speaker leads.'''		# '''Label keyboard and speaker leads.'''
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	# '''Reassemble and test''' – Power up with a known-good supply.		# '''Reassemble and test''' – Power up with a known-good supply.

	== ⚙️ Post-Recap Voltage / Ripple Checks ==		== Post-Recap Voltage / Ripple Checks ==
	{\| class="wikitable styled-table" style="width:80%; text-align:center;"		{\| class="wikitable styled-table" style="width:80%; text-align:center;"
	\|+'''Expected Rails – BASIC prompt, no peripherals'''		\|+'''Expected Rails – BASIC prompt, no peripherals'''
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	''Excessive ripple can cause video instability or RAM errors.''		''Excessive ripple can cause video instability or RAM errors.''

	== 🧰 Recommended Tools & Parts ==		== Recommended Tools & Parts ==
	* 40–60 W temperature-controlled soldering iron (fine tip)		* 40–60 W temperature-controlled soldering iron (fine tip)
	* Solder wick and/or desoldering pump		* Solder wick and/or desoldering pump
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	* Kapton tape (to insulate capacitors near the modulator or case)		* Kapton tape (to insulate capacitors near the modulator or case)

	== 💡 Extra Tips ==		== Extra Tips ==
	* '''Check your power supply first!''' A faulty PSU can damage new capacitors and ICs.		* '''Check your power supply first!''' A faulty PSU can damage new capacitors and ICs.
	* '''Replace all electrolytics at once''' – partial recaps are not recommended.		* '''Replace all electrolytics at once''' – partial recaps are not recommended.
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	* If you have video mods (composite, S-Video), ensure you use quality capacitors in the video path (C1, C3, C6, C27).		* If you have video mods (composite, S-Video), ensure you use quality capacitors in the video path (C1, C3, C6, C27).

	== 🔗 Related Pages ==		== Related Pages ==
	* [[Sinclair ZX Spectrum Troubleshooting Guide]]		* [[Sinclair ZX Spectrum Troubleshooting Guide]]
	* [[Sinclair ZX Spectrum Power Supply Repair]]		* [[Sinclair ZX Spectrum Power Supply Repair]]
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	[[Category:Sinclair ZX Spectrum]]		[[Category:Sinclair ZX Spectrum]]
	~~[[Category:Sinclair Maintenance Guides]]~~
	[[Category:Capacitor Replacement Guides]]		[[Category:Capacitor Replacement Guides]]

Josh: Automated update by bot

2025-05-04T11:42:08Z

Automated update by bot

New page

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'''Replacing the electrolytic capacitors (“recapping”) in your Sinclair ZX Spectrum is a crucial maintenance step to ensure long-term reliability, stable video output, and protection against power-related failures. Aging capacitors are a common cause of instability, random resets, video artifacts, and audio noise.'''

== 🔍 Visual Inspection & Failure Signs ==
* '''Bulging or leaning capacitors''' – especially the large power filter (C9 on Issue 2/3 boards).
* '''Leaking electrolyte''' – brown or green crust at the base of a capacitor.
* '''Corrosion or PCB staining''' – green residue or darkened areas around caps.
* '''Video or audio glitches''' – rolling picture, loss of sync, or buzzing audio may indicate dried-out decoupling capacitors.
* '''Intermittent resets or boot failures''' – often caused by high-ESR or failed timing capacitors.

If '''any''' capacitor shows signs of failure, it is strongly recommended to replace '''all''' electrolytics on the board.

== 📋 ZX Spectrum Capacitor Lists ==
The original ZX Spectrum was produced in several board revisions (Issue 1–6A). Capacitor values are generally consistent, but always verify against your board’s silkscreen.

=== 🖥️ ZX Spectrum 16K/48K (Issue 2, 3, 4, 4A, 5, 6A) ===
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''ZX Spectrum Mainboard Electrolytic Capacitors'''
! Ref !! Capacitance !! Voltage !! Purpose / Rail
|-
| C1 || 1 µF || 63 V || Composite video coupling
|-
| C2 || 22 µF || 16 V || 5 V decoupling (ULA)
|-
| C3 || 1 µF || 63 V || EAR/MIC input coupling
|-
| C5 || 22 µF || 16 V || 5 V decoupling (CPU)
|-
| C6 || 1 µF || 63 V || EAR/MIC output coupling
|-
| C7 || 22 µF || 16 V || 5 V decoupling (RAM)
|-
| C8 || 22 µF || 16 V || 5 V decoupling (RAM)
|-
| C9 || 1000 µF || 16 V || Main 5 V power filter
|-
| C10 || 22 µF || 16 V || 5 V decoupling (ROM)
|-
| C11 || 22 µF || 16 V || 5 V decoupling (logic)
|-
| C12 || 22 µF || 16 V || 5 V decoupling (logic)
|-
| C27 || 1 µF || 63 V || MIC output coupling
|}

''Some early Issue 1 boards have minor differences; always check your board.''

=== 💾 ZX Spectrum+ and 128K Models ===
The ZX Spectrum+ uses the same mainboard as late 48K models, with identical capacitor values. The 128K “Toastrack” and +2 add a few extra capacitors for the sound circuit, DC-DC converter, and RAM.

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''ZX Spectrum 128K/+2 Additional Electrolytic Capacitors'''
! Ref !! Capacitance !! Voltage !! Purpose
|-
| C46 || 470 µF || 16 V || DC-DC converter smoothing
|-
| C47 || 100 µF || 16 V || +12 V RAM supply
|-
| C48 || 22 µF || 16 V || +12 V RAM supply
|-
| C49 || 10 µF || 16 V || +12 V RAM supply
|-
| C50 || 1 µF || 63 V || Audio coupling
|-
| C51 || 1 µF || 63 V || Audio coupling
|-
| C52 || 1 µF || 63 V || Audio coupling
|}

''The +2A/+3 models use a different PCB and power supply; consult their specific service manuals for capacitor lists.''

== 🛠️ Recapping Procedure ==
# '''Disassemble''' – Remove case screws, carefully separate keyboard membrane from mainboard.
# '''Label keyboard and speaker leads.'''
# '''Desolder capacitors''' – Use solder wick or a pump; avoid lifting PCB pads.
# '''Install new capacitors''' – Match '''polarity''' (long lead = +), and lead spacing (2.5 mm or 5 mm).
# '''Keep capacitor height ≤ 13 mm''' to clear the case.
# '''Clean flux residue''' with IPA and inspect for solder bridges.
# '''Reassemble and test''' – Power up with a known-good supply.

== ⚙️ Post-Recap Voltage / Ripple Checks ==
{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''Expected Rails – BASIC prompt, no peripherals'''
! Test Point !! Voltage (DC) !! Max Ripple (p-p)
|-
| Main 5 V (IC pin 14/28) || 4.90 – 5.10 V || < 50 mV
|-
| +12 V (128K RAM, if present) || 11.5 – 12.5 V || < 100 mV
|-
| -5 V (128K RAM, if present) || -4.5 – -5.5 V || < 100 mV
|}

''Excessive ripple can cause video instability or RAM errors.''

== 🧰 Recommended Tools & Parts ==
* 40–60 W temperature-controlled soldering iron (fine tip)
* Solder wick and/or desoldering pump
* Leaded 63/37 or quality lead-free solder
* '''105 °C, low-ESR''' radial electrolytic capacitors (Nichicon, Panasonic, Rubycon)
* Isopropyl alcohol (IPA) and antistatic brush
* Kapton tape (to insulate capacitors near the modulator or case)

== 💡 Extra Tips ==
* '''Check your power supply first!''' A faulty PSU can damage new capacitors and ICs.
* '''Replace all electrolytics at once''' – partial recaps are not recommended.
* '''Observe polarity!''' Electrolytic capacitors are polarized; incorrect fitting can cause failure.
* '''Keep leads short''' and capacitors close to the PCB for best fit.
* '''Clean up any electrolyte residue''' from old leaking capacitors to prevent corrosion.
* If you have video mods (composite, S-Video), ensure you use quality capacitors in the video path (C1, C3, C6, C27).

== 🔗 Related Pages ==
* [[Sinclair ZX Spectrum Troubleshooting Guide]]
* [[Sinclair ZX Spectrum Power Supply Repair]]
* [[Sinclair ZX Spectrum Composite Video Mod]]

[[Category:Sinclair ZX Spectrum]]
[[Category:Sinclair Maintenance Guides]]
[[Category:Capacitor Replacement Guides]]