JX-8P reloaded (2)

Before going into work with JX I cleaned the keyboard in the last few days. The keys were sticky and smeary from nicotine and dirt, so I put them all into denture cleaner over night and on the next day brushed them with dish liquid.

A small plastic strip on the bottom side of the keyboard must be removed to get the keys out. It puzzles me that Roland glued the strip instead of choosing a solution that would be faster to recover at service. One also has to manually (un-)clip 61 springs with a pliers, one for each key. Compared to the Yamaha keyboard on the Korg 01/W this is cumbersome.

Having the best opportunity, I checked the aftertouch sensor for proper operation. As you may read on analog.no or synthzone.com, early JXs may suffer from oxidation on the metal films of the sensor. With not having the sound engine operational yet, I measured the resistance changing on pressure and, to my feeling, didn’t find any anormalities (equally somewhere below 20kΩ along the sensor).

6 Responses to “JX-8P reloaded (2)”

  1. Sergio sagt:

    Hey, have you got a copy of the service manual of Roland JX-8P? I need to make some fix in one of them, and I have no information yet.
    I’ll be very happy if I could get one.
    Thanks for your time.

    • Hajo sagt:

      Hi Sergio,
      scanning schematics is an imposition. It’s not that I wouldn’t like to help you but after all there’s still this copyright thing left, so please pardon me for not being able to help you.

      King regards,

  2. Frank sagt:

    As I am looking for someone that has a dis-assembled JX-8P such as yourself I need to ask of you a big question.
    I have recently purchased a JX that is not fully functional.
    It appears that on my mainboard there is a missing transistor at location Q4. If there ever was a transistor in this location that is.
    The bg thing I wish to ask of you is if you would retrieve the specification and values printed upon this transistor, for it would be greatly appreciated in helping me to get my synth functioning.
    The location Q4 is easily found near the bottom of the main board near the printing of the word „BOARD“.
    If you are willing to help me out with this problem I wish to thank you greatly.
    Thanks – Frank.

    • Hajo sagt:

      Hi Frank,
      the types of transistors Q4 and Q5 have changed during production. The first layout is with R28 and R30 populated as 56 Ohms / 0.5 W resistors and with Q4=2SD571L and Q5=2SB605L. The revised layout is with R28 and R30 not populated and Q4 as 2SD313 or 2SD880 and Q5 as 2SB507 or 2SB834. My JX-8P comes with Q4=2SD313 and Q5=2SB507.

      Hope this helps,

  3. Jeff sagt:

    Hi, I recently got a jx-8p from a friend, and it won’t turn on. He treated it nicely, but hadn’t played it in years. Any idea what might cause such a problem, and how costly the repair might be? I am reluctant to spend $80 for a diagnosis and estimate, as that may put any repair outside my budget. The power cord seems to be fine (I used an ordinary outlet tester). If I wear headphones, I can detect a barely audible „pop“ when I flip the switch, but nothing else. Nothing lights up, and it doesn’t produce sound.

    Any advice would be greatly appreciated. Thanks.

    • Hajo sagt:

      Hi Jeff,

      start with the power supply unit and check if the ±15V and ±5V voltages are O.K. There is a fair chance that just IC2 has died; this is a linear voltage regulator which will cost you less than one dollar. Better ask a technician for help unless you are confident about how to do this safely and accurately.