WS 26 How to change the Capacitor of a SEIKO 5M42* Kinetic
*and 5M22, 5M23, 5M43 etc.


I have seen a couple of online watch parts sites that sell these kits 30235MZ online. Also I have seen Ebay auctions offering these spares. It seemed that in the past, obtaining these was difficult. Thanks to the internet, it is not anymore.
In the mean time I have replaced 3 more capacitors on Seikos from my private collection and my observation is, that the factory charge of the TC920S Li-Ion keeps the watches powered for months! At the time of writing (12th January 2007) my 3 Seikos had been running for over 4 months and now I think they might as well run for 2 years, just like on a regular watch battery. The capacitor TC920S seems to be just like a rechargeable Li-Ion battery. I never expected to get that much output from the factory charged replacement capacitors.

Reto Castellazzi, January 2007 last edited
(May 2006, repair work and photos)

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I was too optimistic, this Bergeon opener did NOT open that 10 year old SEIKO :)

OVERVIEW of all TOOLS used

STEP 1: OPEN THE CASE BACK. See STEP 9 for a picture

Here is the cut open spare 30235MZ bag with its content next to the open watch

Another look at the new parts. The new capacitor's top is golden as are the contacts

STEP 2: OPEN THE ROTOR SCREW and remove the rotor and the rotor wheel below the rotor (staged photo!)

Here are all the parts, old parts left and top, new parts on the right

STEP 3: OPEN THE TWO SCREWS of the capacitor plate and lift off the capacitor insulation (orange)

Here is a look at the empty space giving view to the underside of the calendar mechanism and day wheel

The view of the new and old capacitor as seen when looking at the movement

The old capacitor: SII SL920 by Seiko Instruments.

The new capacitor: maxell TC920S Li-ion



I tried to use the old capacitor plate but then found, the new one did not only look better, but also fitted better!

STEP 6: REPLACE THE ROTOR WHEEL. Make sure that it engages with the small wheel (round inset) of the winding mechanism


STEP 8: TIGHTEN THE ROTOR SCREW. I made a small service mark. From the "chewed" screw slots I could tell that this capacitor had been replaced before

STEP 9: CLOSE THE CASE BACK. I used the Bergeon 5700Z case opener since the case back was hard to open

A look at the case back. Somewhat confusing production date for me. 1988 according to the serial number. Watch was purchased in 1996

The only explanation I have right now is, that the case backs might have been swapped during the first service

HAPPY END! It seems that the TC920S Li-Ion are like a rechargeable battery.

Expect ca. 7 months from the factory charged batteries/capacitors