I recently restored a gorgeous Luxman M-4000A power amplifier and this stunning matching Luxman C-5000A preamplifier.

You can read about my M-4000A restoration here. This post looks at the C-5000A, a rare and beautifully built preamplifier, from the somewhat enigmatic manufacturer, Luxman.

Service Data

The Luxman C-5000A is so rare that, despite searches and contact with the Luxman Yahoo group and the Luxman Vintage Audio website, no service manuals are available for the ‘A’ series models. There is service data available for the M-4000 and C-5000, but these are quite different so that data is not much help.

The only thing anyone found was a sketchy hand-drawn M-4000A schematic. Unfortunately, no information identifying the functions or settings of the various trimmers in either unit was ever located. This meant I had to proceed blindly with the Luxman C-5000A.

Someone had worked on both pieces previously, replacing various parts and creating the problem of not being sure the new parts were of the same spec as the originals. Experience tells me that in many cases they are not. Without factory service data, one can never really be sure. The other issue is that, without factory service data, setting the equipment up correctly after working on it can be difficult.

Modularity

The C-5000A is built in a way that most modern gear is not. The preamp is completely modular, with a chassis, in which the various modules reside, as plug-in cards. This approach is more akin to that found in test and measurement gear and is only rarely found in consumer audio equipment.

Accuphase is one other such manufacturer which has always used this form of modular construction. This form of construction makes servicing and repairs both easy and hard – easy because the boards just unplug from the backplane inside the chassis; and bad because you need extender cards to allow you to make measurements and adjustments.

Restoration

This particular C-5000A was much like the M-4000A in that it was dirty, had poor-quality replacement capacitors in places and needed some TLC. The following images document my service and restoration of this lovely old piece of equipment. You can of course find more about the C-5000A at The Vintage Knob.

Cleaning

Refurbishment

Adjustment

This part was hardest because of the lack of any schematics and service data. Experience helps here though and with enough time spent measuring, adjusting, thinking and measuring, I was able to reverse-engineer most of the critical adjustments in this preamp.

It’s not that hard to do, but you have to have a sound grasp of the general adjustments audio amplifiers and preamplifiers need. There are power supply voltages, biasing and DC symmetry and these make up the bulk of the adjustment process here, and elsewhere.

Results

With all the cleaning, attention to card edge connectors, careful adjustment and those god-awful Suntan and other ridiculous capacitors removed and everything replaced with premium parts, this Luxman C-5000A has a new lease on life.

Her owner was very pleased of course and really, what a great result. The Luxman C-5000A preamp is a serious unit, make no mistake. Transformers in the phono preamp tell you just how serious, try to find a transformer-based phono preamp today and check out how expensive they are and you’ll have a better understanding of why equipment like this simply must be saved.

If this is your type of thing, by all means, grab a Luxman C-5000A if you can find one. Just be prepared to take her to someone good for the inevitable service and overhaul work needed at this age.