Kyocera has been on my radar for a few years now, but it’s never really been of a ton of interest to me. Fast forward to a few months ago, a close friend picked up an A-910 local to him very cheaply. Seeing how well built the 910 was through his photos, the 910 moved up on my list. Well, after a couple of weeks, an A-910 was listed about 20 minutes from me for a price I couldn’t refuse. It’s crazy, as Kyocera’s 910 series is extremely rare in the US.
The 910 is of the best constructed amplifiers I’ve personally had through my hands, and that’s not a small feat.
The entire bottom portion of the chassis is made of a special ceramic composite material which was said to reduce resonance and vibration from transferring into the 910. It adds a ton of weight and makes the 910 a very heavy integrated amplifier.
Externally, every piece of the 910 is made of metal. Everything from the knobs to the accents. It’s astonishing. Even the front feet are made from solid aluminum, and are adjustable.
I removed the bottom panel and snapped some photos of the power supply and Sanken outputs. I’ve yet to see photos of the power supply section of the 910 on the internet, so these may be a first. Overall, it is cleanly laid out and the wiring is neat. The boards in the 910 are covered with the typical 70’s/80’s corrosive glue, so that will have to be dealt with.
As you can see, this amplifier was designed with elegance in mind. It was not just an integrated amplifier shoved into a generic chassis and pushed out the door - It was much more than that. Kyoto Ceramics, known as Kyocera, used their ceramics engineering pedigree to their benefit to create a chassis that was as effective at mitigating resonance issues as it was beautiful to look at.
The above image is a high res scan I took from one of Kyocera's pieces of advertising literature for the A-910. Upon first look, even the average person should be able to easily appreciate the design effort and approach taken when engineering this gorgeous amplifier.
Preface:
I've had some spare time this past week, so I decided to start working on the A-910. This is going to be a thorough restoration where no stone will go unturned.
There are no other posts online about the A-910 in terms of servicing, so I plan on posting the restoration process in detail. Please bare with me as I am a full time student, and also working to make ends meet. This will likely be a very slow process, as I will be working on this unit in my free time; usually during the weekends. I am also a very meticulous worker, so I will be spending a lot of time doing some things that other people may overlook. I am doing this as a labor of love, as this is my personal unit. I haven't entirely decided whether or not I will be keeping the A-910 though. I have wanted one for my collection for the past couple of years, but being in the situation I am in now, I am not sure if I can justify yet another amplifier in the collection. I may have to thin the herd in other areas though, as I really like this amplifier.
Overview of work to be done:
The Kyocera A-910 will require a fairly straightforward, yet comprehensive restoration. It suffers from many of the same issues that similar amplifiers of this era do. Issues like bad soldering and corrosive glue are here in spades. Old capacitors, dirty switches and potentiometers, carbonized relay contacts, crusty adjustment trimmers, messy wave soldering flux residue... You get the idea. All of these issues need to be addressed to assure the stable working condition of this amplifier for the next few decades. Like I said before... comprehensive.
A small rant about the misnomer of a "restoration":
One of my biggest pet peeves in the audio world is the common practice of dramatizing work done to audio gear. This is usually done to artificially and disingenuously drive the price of gear on the second hand market up. Many people believe that a "restoration" only includes spraying deoxit into the UI potentiometers, cleaning the faceplate, blowing dust bunnies out of said piece of equipment, and less frequently, a basic recap. This is very far from the truth, and usually puts honest technicians like myself in a bad spot when confronted about why it takes as long as it does for a thorough restoration. Audio gear of this age suffers from much more than the typical bad capacitors, and usually requires specialized service to guarantee the stability of the unit overtime. Again, the term comprehensive servicing comes into play again. Remember this.
What I believe a "restoration" is:
In my eyes, a restoration is where a piece of equipment is brought back to factory specifications and working condition both inside and out. This is accomplished by addressing every issue both known and observed. Things such as removing corrosive glue, reflowing and defluxing circuit boards, replacing capacitors and known problematic signal transistors and regulators, addressing heat related issues such as PCB and trace damage, remounting outputs and drivers on new thermal interfaces, and even a thorough cleaning. There are more steps to take than this, especially depending on what it is to be worked on, but you get the idea. There is much more to a "restoration" than what most eBay sellers would leave you to believe.
Back to the topic at hand... The A-910.
This past weekend I started work on the 910. I decided to attack one part of the amplifier at a time. I do this to make it easier to isolate possible issues that could be created by working on the amplifier. The saying "Show me where you were and I'll show you where the issue is" is very true. It's always best to work in small steps and avoid working on everything at once.
The A-910 takes up about as much bench real estate as I can offer. It is 17"x6"x17" and weighs an impressive 50 pounds. Much of the 910's weight comes from the massive transformer, and the ceramic composite base. To ease in moving large equipment around on my bench, I use a small platform with caster wheels mounted to it. It makes it much easier to rotate equipment without having to strain and risk damage.
As you can see in the following photos, the A-910 seems to be a relatively straightforward design. Power supply smack in the center, main amplifiers on either side, preamp section toward the back, and interface circuitry to the front. The amplifier cards are mounted directly to the heatsinks, which are then mounted to the CCR base with four screws. All of the wiring is attached to the corresponding PCBs with screw terminals and header plugs. No annoying wire wraps anywhere to be seen. This makes disassembly and reassembly relatively easy. I take photos of the wiring before removal so I have a reference as to how to reattach them when the time comes.
Power supply section:
Getting to work on the A-910, I decided to start with the bottom power supply board. This board is mounted to the bottom side of the CCR chassis, and supplies power to various parts of the amplifier. There are many wires leading to and from this board, so noting where each wire goes upon removal of the board is of utmost importance. All of the wires are attached either by header plug, or by screw terminal. Kyocera added a nice touch by soldering the very tip of each wire leading to the screw terminals, mitigating the risk of having wires fray and short on one another.
Upon removal of the power supply board, I spotted a few issues right off the bat. One of the issues immediately apparent was the use of corrosive glue which was used to hold down a large capacitor on the board. The glue had creeped to a nearby jumper and had started corroding it. I removed the capacitor, cleaned the glue residue, and replaced the jumper with a new one. Luckily, this was the only area on the power supply board which had corrosive glue used on it. Unfortunately for many other areas in the amplifier, this is common. Removing corrosive glue and repairing damage it causes is easily one of the most time consuming processes there is to do when servicing equipment like this. Many times the glue will cause irreversible damage to components like semiconductors. This leads to the mandatory removal and replacement of said components to avoid issues down the line.