Mitsubishi ML-F80 Capacitor Replacement Guide

ML-F80 main board. The video and RF board, with most of the larger electrolytics, is at the top left

Mitsubishi's service information for the Mitsubishi ML-F80 has not been found online, so no list of capacitor values is available. A published photograph of the main board shows where the electrolytic capacitors are. Record the values from your own board before ordering parts.

What the photograph shows

The photograph of an ML-F80 main board, marked J0510425K, shows these electrolytic capacitors:

Electrolytic capacitors visible in the photograph

Board	Position	Where
Main	C6	Beside the video socket
Main	Unmarked	Lying flat between R7 and Q1, near the sound socket
Main	C9, C10	Beside the LED connector CON-LED
Main	Unmarked	Lying flat by R13, right of the printer connector
Main	C11	Beside the oscillator
Main	C120	Beside IC10B, among the video RAMs
Main	C126	Beside IC5D, among the DRAMs
Main	C153	Beside the AY-3-8910A
Main	C8	Bottom right corner
Main, left edge	Two by C4	Next to the zener diode ZD1
Video and RF (55-4007D)	About eight	Round the LVA510 and 74LS04

Positions C127, C128 and C129 are marked on the board but were empty on the photographed machine.

Which to replace first

Advice on the MSX Resource Center forum is to replace the main supply's capacitors whatever their condition, to judge the audio and video capacitors by the picture and sound, and to leave the small decoupling capacitors unless they show a fault. The supply's reservoir capacitors are not in the published photograph; find them on your own machine beside the transformer and rectifier. Then:

1. The capacitors on the video and RF board and beside the video and sound sockets, if the picture or sound is poor.
2. The remaining main board capacitors, if one shows leakage or bulging.

See Capacitor Failure Symptoms for what a failed capacitor looks like.

Recording your board

1. Unplug the computer. The power cord, switch and transformer carry mains voltage.
2. Open the case, photographing each screw and connector as you go; see the Mitsubishi ML-F80 General Maintenance guide.
3. Photograph each board from above, then each electrolytic close up so the printing on its sleeve can be read.
4. Write down each capacitor's designator, capacitance, voltage, diameter, height and the side its stripe faces.
5. Order replacements with the same capacitance, at least the same voltage, and a size that fits.

Record of your ML-F80's capacitors

Board	Ref	Value	Voltage	Diameter × height	Notes
Supply
Main	C6
Main	C8
Main	C9
Main	C10
Main	C11
Main	C120
Main	C126
Main	C153
Video and RF

Replacing them

1. Replace one capacitor at a time, with the stripe on the same side as the original.
2. Unplug the leads between the video and RF board and the main board by their connector bodies before lifting either board.
3. Clean off any electrolyte and look at the tracks under the capacitors for corrosion.
4. Work on an earthed mat; the main board carries a "STATIC PREVENT DISCHARGE" marking.

Checks after the work

Switch on and measure at a cartridge slot against pin 41: +5 V on pins 45 and 47, +12 V on pin 48, −12 V on pin 50. Measure −5 V at pin 1 of one of the D416C-2 video RAMs, against pin 16. Check the picture on composite (or RGB on a French machine) and the sound. Remaining faults are covered in the Mitsubishi ML-F80 Troubleshooting Guide.

Related pages

• Mitsubishi ML-F80
• Mitsubishi ML-F80 General Maintenance
• Mitsubishi ML-F80 Troubleshooting Guide
• Capacitor Failure Symptoms