Along with a listing of current Service Centres for North America and Europe, this section consists of of technically-oriented projects and articles. Hardware Fault Diagnosis & Repair guide by Martin Straw [21010093+], a former Chroma tech from the UK, should get you or your tech off to a good start with Chroma repairs.
For the technically capable, there are several do-it-yourself projects that will enhance or help repair your Chroma. Sandro Sfregola  and David Clarke [21030085++] detail the Chroma Expansion Board, a hardware upgrade in the form of a small circuit board that can be mounted on top of the existing computer board inside the Chroma.
David has also contributed an article on building new voice boards; and Sandro details how to swap the power supply. David's one-off ChromaKnob describes a "more intuitive and more easily used programming interface" custom hardware add-on for the Chroma, which consists of an add-on unit with knobs for each program parameter. And David Wilson of the New England Synthesizer Museum contributes the schematics for a voice board test controller. Mark David [21030170+] offers documentation to an abortive software editor project for Windows.
David Clarke is the major contributor here, with a number of interesting topics covered. His Voice Board Revisions: The Changing Face of Chroma Dual Channel Voice Boards reviews in detail several generations of voice boards, including a series that he produced himself. How the Chroma Tunes Itself offers insight into several "tuning quirks." The Chroma Pressure Sensor & Interface covers the (rare, though well-integrated) pressure sensor option, reviewing the parts involved and the technical details of its operation, along with a Q&A. Keyboard Velocity Curves examines the differences between keyboard responsiveness in three different firmware revisions. And EPROM Code contains downloads of EPROM code in binary format, and disassembled Chroma source.
There's an excerpt available of Chroma-related information from Hal Chamberlin's 1985 book, Musical Applications of Microprocessors, which provides a technical overview. Chroma to Chroma Interface Lead provides a wiring diagram for the parallel RS232 cable. Fender's Triad Interface, from Polyphony magazine in 1983, is an overview of a computer interface designed by CBS/Fender. Gene Stopp's The ARP/Rhodes Chroma VCO is a discussion of Chroma waveforms.
Posts of note to the mailing list:
- Rolling your own SPSU aux board, Mark Smith [2103-PT-002], March 2008
- CC board acid damage repair info, Brian Marshall , March 2007
- Martin Straw's power supply update procedures, Tom Moravansky , September 2006
- Stack Switch Repair, Tom Moravansky, August 2006
- Info on Chroma Cassette Cable, including wiring information, David Clarke [21030085++], January 2001
Off Site Articles
Randel Osborne 
Randel has three brief photo essays of repairs he has done to his Chroma. The first, "Rhodes Chroma 1," covers a number of installations and replacements, including a power supply, auxiliary board, and CPU Plus. The second article, "Rhodes Chroma 2," shows replacement of the capacitors and op-amps on the voice cards. The third, "Rhodes Chroma 3," documents the replacement of op amps on the Channel Mother Board and EQ Board. Finally, "Chroma Enabler" details the design and implementation of a large, 97-knob physical controller for the CC+ equipped Chroma.