Recap guide

Recap the Kaypro II

Same story as the Osborne: the rice-paper RFI caps in the power supply are the ones that blow.

Open the interactive checklist Tick off each capacitor as you replace it. It saves in your browser.

Worth a recap. Reports say it is a common and useful fix on this machine.

Which board do I have?

Boards changed during production. These notes come from the linked sources, and many are only partly documented, so check the board in front of you.

Kaypro II main board 81-110-A (Medium confidence). How to tell: Early board, serial 4037 in one repair log. Capacitors: Only four electrolytics: C19, C20 and C69 at 47uF 10V and C4 4.7uF 35V. Capacitor list differs from other revisions: not known. Source
Kaypro II main board 81-110-B1 (Low confidence). How to tell: Later board, #36311 in the same log. Capacitors: Cap list not given. Capacitor list differs from other revisions: not known. Source
Kaypro II supplies (Low confidence). How to tell: The early machine had a California DC supply, another page shows an Astec AA12450. Capacitors: No cap lists. Capacitor list differs from other revisions: not known. Source

Where to start

Clues from write-ups and forum threads, not a diagnosis. Low confidence means one thread or one repair; high means several write-ups agree.

Blown RFI caps (Medium confidence). One repair after smoke from a Kaypro II found the RFI suppressor caps had failed (4.7 nF per the spec, plus one 0.22 uF) and shows what replaced them. Source
Power supply electrolytics (Medium confidence). Another repair replaced four electrolytics, lists their values, and notes which ceramics were left alone. Source

Tips, tales and maybes

Found in write-ups and forum threads. These are other people's reports, not tested by us. Check part references and values against your own board.

Story: RFI cap pop and smoke (Medium confidence). A Kaypro II popped and smoked when an RFI suppressor blackened. The author replaced three 4.7nF caps with spare 10nF ones after forum friends said they would do, and noted a larger 0.22uF cap would likely go next. Source
Story: Kaypro II low +12V and four caps replaced (Medium confidence). A Kaypro II repair log replaced C19, C20 and C69 (47uF 10V) and C4 (4.7uF 35V), and found the supply gave +10.5V when at least +11.5V was needed. The output voltages were adjustable on the California DC supply. Other faults were chips and corrupt ROMs. Source
Tip: Two supply makers: Astec and California DC (Medium confidence). A write-up says Kaypros used either an Astec supply (white PCB) or a California DC one (blue PCB) and that many Kaypros, like Apple IIs, have supply caps that pop and smoke as paper insulation fails. Identify which supply you have before ordering parts. Source
Story: Kaypro 4 intermittent power and dimming (Low confidence). A Kaypro 4 thread with drives not getting 5V and the display dimming drew advice to start with the electrolytics, inspect high-current solder joints with magnification, and replace supply parts one at a time. One owner recommended recapping all boards. Source

Before you start

Boards changed during production. Check your board number against the guides before you order parts.
A mains power supply can hold a dangerous charge. If you are not trained to work on one, have a professional do it.

Guides we used

This page and the interactive bench are built from these. They have the photos and the full detail, so please read them and support their authors.

Smoke from a Kaypro II. The fault and the fix (Write-up) by Terry Stewart (Classic Computers NZ). Has a capacitor list. Identifies the failing RFI caps and what replaced them
Kaypro II repair (Write-up) by Thomas Brase (retrocmp.de). Has a capacitor list. Replaced four electrolytics with values and listed the ceramics left alone
Kaypro II (List) by oldcrap.org. Cap list exists only as an image on the page
Tech Flashback: Reviving the Kaypro 4 (Write-up) by Gough Lui. Mentions the PSU cap issue only in passing

The capacitor list

We have not checked a capacitor list for this machine yet, so none is shown. Follow the guide above for your board, then add the capacitors in the interactive checklist and it builds a shopping list for you.

Skip the sourcing

Ready-made kit: Amazon · eBay
Already recapped: Amazon · eBay

While you are in there

Need the machine itself?: Amazon · eBay
A box of spare capacitors: Amazon · eBay

Affiliate links. As an Amazon Associate I earn from qualifying purchases. These links only search by name. Disclosure

Steps, tools and safety

The steps, the tools in top, middle and budget picks, and the safety list are the same for every machine, so they live on one page: How to recap, step by step.

Values are shown as published in the guides above, and boards changed during production. Check the board in front of you. A recap involves hot tools and, on some machines, dangerous voltages. You do it at your own risk.