Editing Super Nintendo Troubleshooting Guide

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[[File:Super Famicom (photo).jpg|thumb|300px|Super Famicom. The Super NES shares its board family.]]
This guide covers fault-finding on the '''Super Nintendo Entertainment System''' and its Japanese equivalent the Super Famicom. Its figures come from Nintendo's own service literature for the machine — the Playtronic ''Manual Técnico do Super NES'' and the Japanese Famicom / Super Famicom / Game Boy service manual, both hosted on this wiki.<ref name="playtronic">Nintendo / Playtronic, ''Manual Técnico do Super NES'', Rev.&nbsp;01/94, hosted at [[Nintendo Super NES Technical Manual (Playtronic, Rev. 01-94)]]. Console theory of operation (pp.&nbsp;2-1 to 2-2): the AC adapter supplies 10&nbsp;V DC unregulated; the on-board supply section comprises a noise filter, reverse-current protection, the power switch, a spike suppressor, a ripple filter and the regulator, and produces a regulated Vcc of 5&nbsp;V and an unregulated Vs of 7&nbsp;V used by the audio amplifier; the controller input section uses diode and capacitor arrays for surge protection and pull-up resistors, and the CPU samples the controllers about every 17&nbsp;ms; the system timing section feeds a 21&nbsp;MHz master clock to the CPU, PPU1, PPU2 and connector P1, and the CPU divides it by 6, 8 and 12 to give 3.58, 2.68 and 1.79&nbsp;MHz, with DMA always at 2.68&nbsp;MHz; the RESET section uses a 4&nbsp;MHz oscillator, a 74HCU04 hex inverter, the CIC and the reset switch, and applies CIC reset to PPU2 first, then PPU1, then the CPU. Parts list: F1 a 1.5&nbsp;A SSTR axial fuse, U12 a 7805, X1 a 21.453666&nbsp;MHz (PAL-M) crystal, X2 a 4&nbsp;MHz ceramic oscillator, and a 24.57&nbsp;MHz ceramic oscillator. Adjustment and fault-finding: TC1 set to 21.453666&nbsp;MHz; the 4&nbsp;MHz CIC clock acceptable between 3.8 and 4.2&nbsp;MHz. Disassembly: switch the console on with the AC adapter disconnected to discharge C67 before opening it. GPM section (pp.&nbsp;3-1 ff.): the ground-plane mainboard removed the lower RF shield, shortened the PCB, deleted C67 and the 4&nbsp;MHz oscillator, built the sound module circuit onto the mainboard, made TC1 a through-hole part, and removed the cartridge lock bar from the upper housing in favour of a warning label. IC handling notes (p.&nbsp;8-2): do not measure ICs with a multimeter or signal tracer.</ref><ref name="famsm">Nintendo, ''ファミコン・スーパーファミコン・ゲームボーイ サービスマニュアル'' (Famicom / Super Famicom / Game Boy Service Manual), issued 7 August 1992, hosted at [[Nintendo Famicom Service Manual]]. HVC section, pp.&nbsp;2–10: AC adapter rated DC&nbsp;10&nbsp;V with a normal no-load output of DC&nbsp;13.5&nbsp;±&nbsp;1.5&nbsp;V; HVC power-circuit block diagram showing a 7805 with 13–14&nbsp;V in and 5&nbsp;V out, drawn in both the standard and the VCCI variant; RF switch terminal carrying DC&nbsp;5&nbsp;V in game mode; the three solder points that need reinforcing around the DC jack; "before you decide it is a fault" table, p.&nbsp;3; controller fault symptoms and the plug-in controller connectors, p.&nbsp;4; exploded parts diagrams, pp.&nbsp;7–9; Famicom repair price list, p.&nbsp;10 (60-pin card connector, 15-pin D-sub jack, crystal, RF modulator unit, DC jack, 7805 three-terminal regulator, fuse listed for VCCI boards only, electret microphone, CMOS 4021 and 4069 in the controllers). SHVC section, pp.&nbsp;11–15: power-switch harness polarity; SHVC power circuit, 7805 with 13–14&nbsp;V in and 5&nbsp;V out; Super Famicom repair price list (1.5&nbsp;A SSTR axial fuse, 7805, 62-pin card connector in upper and lower halves, sound module).</ref> Where a figure is not in one of those, it is not given here.

For preventive care, the connector work and the GPM board changes see [[Super Famicom Maintenance Guide]]; for capacitor values by board revision see [[Super Famicom Capacitor Replacement Guide]].

''Super Famicom Box, the Satellaview and the unreleased CD add-ons are not covered.''

== Discharge C67 before you open it ==

Nintendo's '''first''' disassembly instruction is not about screws:

: Before disassembling, switch the console's power supply ON with the AC adapter disconnected, in order to discharge capacitor C67. This capacitor is known to discharge during maintenance, causing damage to components.<ref name="playtronic" />

C67 is the reservoir on the DC input and it holds its charge after the adapter is out. Flicking the power switch with nothing plugged in empties it through the console's own load. On a GPM board there is no C67 — Nintendo deleted it in that revision — but the step costs nothing and you do not always know which board you have until it is open.<ref name="playtronic" />

== Power ==

'''The NTSC and Japanese consoles take 10 V DC at 850 mA, centre negative.''' Centre negative means the '''centre pin is 0 V and the outer sleeve is positive'''. PAL consoles take '''9 V AC''' and rectify it on the board. The two are not interchangeable in either direction.<ref name="fullsnes">Martin Korth, ''fullsnes'' — SNES hardware specifications — https://problemkaputt.de/fullsnes.htm , section "SNES Power Supply". NTSC and Japanese consoles take 10&nbsp;V DC at 850&nbsp;mA through a series diode, so the internal unregulated rail sits near 9&nbsp;V; PAL consoles take 9&nbsp;V AC and rectify it on board. A 7805 produces the only logic rail, +5&nbsp;V, and the CPU, PPU and APU run solely from it; the unregulated rail feeds only the audio amplifier, and the console runs without it but silently. Also the source for the anti-eject lever fitted to the power switch of earlier consoles.</ref>

The supply is unregulated. The Famicom-family HVC-002 adapter, which the Super Famicom also uses, is specified by Nintendo to read '''DC 13.5 ± 1.5 V off-load''', and Nintendo's power-circuit block diagram labels the 7805's input arm '''13–14 V'''.<ref name="famsm" /> '''A high off-load reading is normal and is not a reason to replace the adapter.'''

{| class="wikitable styled-table" style="width:95%;"
|+'''Power test points'''
! Where !! Expected !! Note
|-
| Adapter, '''no load''' || 12.0–15.0 V DC || Nintendo's figure is 13.5&nbsp;±&nbsp;1.5&nbsp;V<ref name="famsm" />
|-
| Plug polarity || Centre '''0 V''', sleeve '''positive''' || A centre-positive supply of the right voltage will destroy the console
|-
| '''F1''' || Continuity || A '''1.5 A''' SSTR axial fuse. Both Nintendo parts lists carry it<ref name="playtronic" /><ref name="famsm" />
|-
| '''U12''' (7805) input || 13–14 V off-load, sagging under load || U12 is the regulator on SHVC-CPU boards; on 1CHIP and SNN boards the same part is at '''U9'''<ref name="playtronic" />
|-
| U12 output — '''Vcc''' || 5.0 V DC || '''The only regulated rail in the machine.''' The CPU, PPU1, PPU2 and APU all run from it and nothing else<ref name="playtronic" /><ref name="fullsnes" />
|-
| '''Vs''' — unregulated || ~7 V by Nintendo's figure; near 9 V by measurement || Feeds '''only''' the audio amplifier. The console runs without it, silently<ref name="playtronic" /><ref name="fullsnes" />
|}

'''There is no +12 V rail and no 3.3 V rail in a Super Nintendo.''' If you are probing for one, stop. "IC601" is not a designator on any of these boards either — the regulator is U12, or U9 on the later single-chip boards.

== Clocks and reset ==

Nintendo's own description of the timing section: a '''21 MHz''' master clock goes to the CPU, to PPU1 and PPU2 and to connector P1. The CPU divides it by '''6, 8 and 12''' to give '''3.58, 2.68 and 1.79 MHz'''; the CPU core runs at 3.58 MHz, address-mapped transfers at 2.68 MHz, and DMA always at 2.68 MHz regardless of address.<ref name="playtronic" />

The exact master frequency '''depends on the region''' and the wrong figure will send you chasing a fault that is not there:

{| class="wikitable styled-table" style="width:80%;"
|+'''Master clock by region'''
! Region !! Frequency
|-
| NTSC (North America, Japan) || 21.47727 MHz
|-
| PAL (Europe, Australia) || 21.281370 MHz
|-
| '''PAL-M''' (Brazil, Playtronic) || '''21.453666 MHz'''
|}

Nintendo's Brazilian manual specifies the TC1 adjustment at '''21.453666 MHz''' because it is a PAL-M manual.<ref name="playtronic" /> '''Do not apply that figure to an NTSC or European machine.'''

The reset section is a '''4 MHz oscillator (X2)''', a '''74HCU04''' hex inverter, the CIC and the reset switch. Nintendo gives the acceptable 4 MHz range as '''3.8 to 4.2 MHz'''. The CIC's reset is applied to '''PPU2 first''', which introduces a delay, then passed to PPU1 and only then to the CPU — both PPUs must be running before the CPU is released.<ref name="playtronic" />

That ordering is diagnostically useful: '''a fault that holds PPU2 in reset stops the whole machine''', and looks identical to a dead CPU.

On a GPM board the 4 MHz oscillator was removed along with C67, and Nintendo's manual states the timing and reset sections differ there.<ref name="playtronic" />

== Nintendo's order of suspicion ==

Where Nintendo's fault tree names a component, it names these:<ref name="playtronic" />

* '''F1''', the 1.5 A fuse — dead console.
* '''U12''', the 7805 — dead console, or a 5 V rail that is low or absent.
* '''X1''', the 21 MHz oscillator — no picture, or a picture that cannot be brought into adjustment at TC1.
* '''X2''', the 4 MHz oscillator — the CIC cannot run, so the console will not start.

If TC1 cannot be adjusted or the adjustment will not hold, Nintendo's replacement sequence starts with the oscillator at X1.<ref name="playtronic" />

== Symptom table ==

{| class="wikitable styled-table" style="width:100%;"
! Symptom !! Work through, in order
|-
| '''Completely dead — no LED'''
| Adapter off-load reading and polarity → DC jack and its solder joints → power switch → '''F1''' continuity → '''U12''' input and output.
|-
| '''LED on, black screen, no sound'''
| Clean the 62-pin connector and the cartridge edge, and retest with a second cartridge. Then 5 V at the CPU and both PPUs → 21 MHz at X1 → 4 MHz at X2, within 3.8–4.2 MHz → reset released. Remember the reset order: PPU2, then PPU1, then CPU.
|-
| '''Picture, no sound'''
| The audio amplifier runs from the '''unregulated''' rail, not the 5 V rail. Check that rail before suspecting the sound module. A console with a healthy 5 V rail and a dead unregulated rail plays silently but otherwise normally.<ref name="playtronic" /><ref name="fullsnes" />
|-
| '''Wrong or missing colours'''
| Nintendo prints a dedicated colour-fault tree; it is reproduced on [[Super Famicom Maintenance Guide]]. Check the AV lead and the television first.
|-
| '''Picture cannot be tuned, or drifts'''
| TC1, against the '''region-correct''' master frequency. If it will not hold, X1.<ref name="playtronic" />
|-
| '''Corrupted sprites or backgrounds, Mode 7 wrong'''
| VRAM, then PPU1 and PPU2. A PPU that fails only on Mode 7 effects is a documented pattern, so test a Mode 7 title before clearing the PPUs.
|-
| '''Freezes, or works only with the cartridge pressed'''
| The 62-pin connector. Nintendo supplies it as two service parts, an upper and a lower half, so a damaged one can be replaced.<ref name="famsm" />
|-
| '''Power cuts out when a cartridge is removed'''
| Not a fault on earlier consoles. The power switch carries an '''anti-eject lever''' that rides in a notch in the cartridge; on cartridges with a diagonal notch it switches the console off as the cartridge comes out.<ref name="fullsnes" /> Nintendo deleted the lock bar on GPM machines and replaced it with a warning label.<ref name="playtronic" />
|}

== Probing, safely ==

* '''Do not measure ICs with a multimeter or a signal tracer.''' Nintendo's own handling notes say plainly that the test voltage a meter applies will damage the device, and that if you must measure an IC's resistance you should use the lowest range and accept the risk.<ref name="playtronic" /><ref name="famsm" />
* '''The power switch harness is polarised.''' Nintendo marks + and − on the switch body and specifies the red lead to + and the black to −. Reversing it is a self-inflicted fault created during reassembly.<ref name="famsm" />
* '''The front unit's FFC goes in one way round.''' The unprinted side is the contact face; the blue-printed side is not. Fitting it reversed gives dead controller ports on a console that is otherwise fine.<ref name="famsm" />
* The console opens with '''six''' security screws in the lower case, taking a 4.5&nbsp;mm Gamebit driver. The sound module, where fitted, comes off with two screws and lifts vertically.<ref name="playtronic" />

== Thermal checks ==

After a minute or two, a device markedly hotter than its neighbours is usually shorted internally. Freeze spray is the complementary test. The 7805 is meant to run hot — it is dropping 8 V or so at whatever the console draws, and that is where the heat goes.

== Related pages ==
* [[Super Nintendo Entertainment System]]
* [[Super Famicom Maintenance Guide]]
* [[Super Famicom Capacitor Replacement Guide]]
* [[Nintendo Super NES Technical Manual (Playtronic, Rev. 01-94)]]
* [[Nintendo Famicom Service Manual]]
* [[SNES Schematic]]
* [[Recommended Tools]]

== References ==
<references />

[[Category:Nintendo]]
[[Category:Troubleshooting Guides]]