luxman A-383 part 2

Today i made quite some progress with debugging my luxman A-383 amp.At this moment there seem to be 3 main problems:

  • Two fuses blow as soon as record selection circuitry is attached
  • The input / record selection is f*cked up
  • Somewhere the left channel is chopped off

The input and record selection is build up around two analog switch arrays (TC9163AN) which must have had quite a blast (did i already mention the amp broke because of a _very_ faulty input device?). Replacing both chips solved problem 1. Still the input / record select remains faulty. The right channel is omni-present (comes thru regardles of which input connected to or which input selected) while the left channel does not come thru at all.The TC9163AN uses a 14 bit pattern for switch selection. This pattern is clocked into its shift register. There are 6 data lines going to the input board: DATA, CLK, STIN, STRC, RCT1 and RCT2 (these lines come from a obscurely large Luxman chip on the front panel). At this moment only the DATA, CLK and STIN lines are important (STIN and

tone test

STRC work as a kind of chip select). Using the logic analyzer shows that the DATA line is doing what it is supposed to, but… there are _no_ clock pulses! Those pulses are needed to shift the data bits into the register. This could explain why there is no reaction when pressing the buttons. Unfortunately the big luxman chip is as a big black box and is not described in the service manual. Tomorrow i’ll write a little gpio driver and use a gumstix to generate appropriate clock and data signals. If we can get the right behavior we nailed down the problem. Only thing left is a solution.
Until then i bypass the input by directly wiring the CD input to find out where problem 3 occurs.

After some effort i succeeded to access the tone board (a lot of screws and cable ties), the second step after the input board). Using a little pd program (right laptop in top image) to generate two test signals (10KHz and 1KHz semi square waves for right and left respectively) i can now trace down the signals using the 2 channel scope (can’t do without this bitscope thingy already). As it is already quite late i only checked to see if it survives the tone board, which it does (left laptop in top image).

So far for now


3 Responses to “luxman A-383 part 2”

  1. Jason Yates Says:

    I recently had lightning run in on my Luxman A-383 amp. All the components were powered through a surge protector (and run through a switch that was turned off), but the amp still seemed to take the brunt of the jolt.
    I’m not adept at Hi-Fi, so my amp is in the shop. The dude there is having problems locating parts, but I’m not sure exactly what he’s looking for. It’d be super-cool if you might share a few pages of the service manual. Any suggestions about finding parts?

  2. I got the service manual and some parts from Sven Eiman:

  3. jason yates Says:

    Hey Simon,
    I’m still working on our A-383 and keeping our fingers corssed. We’ve replaced the IC-901 and got power back. Now we’re looking to replace a fried panel input board. Would you happen to have a part number for this part?

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