Determining how to fix the 100 watt suitcase unit

[binggibbs]

Can someone tell me how the tone of each key is generated and delivered to the pre-amp.  i am working on a unit and none of the keys put out any sound.  I looking at the input to the preamp with an O scope and there is nothing coming from the keyboard.  I assume that I should see some audio somewhere...

[Mark II]

Hi Bing.
Check the grey RCA cable coming from the harp. Jiggle and twist it a bit.
kind regards

Mark II

[sean]

You very likely have three dead pickups... or more.

The pickup rail is wired in groups of (three pickups in parallel) in series with (three pickups in parallel) in series with (three pickups in parallel) in series with ....

So if any of the (three pickups in parallel) groups contain three dead pickups, then the whole harp is an open circuit, and makes no sound.

This series-parallel wiring is implemented like this:


Here is an alternative drawing:

Ignore my "Okay to split here" arrows!


Anyway, if you don't get any signal when you put your oscilloscope leads on the RCA jack that is at the left rear of the harp, you could easily test each individual pickup with your scope.

Or, you could use my old-fashioned (no wait a minute, using an oscilloscope is old-fashioned) method of searching for dead pickups:
http://ep-forum.com/smf/index.php?topic=3839.msg17262#msg17262

The thread below includes the link above, and also the link to the method of pickup replacement:
http://ep-forum.com/smf/index.php?topic=5620.msg27734#msg27734

Sean

[pianotuner steveo]

If you are just trying to determine if the amp works, what i do is connect a different source like an ipod,using adapters to go into the 1/4" jacks on the left side of the suitcase bottom.( keep the volume low!) you can also use a guitar,trying one channel, then the other.

If you have audio, then you know the problem is in the keyboard. If not, the amp needs servicing.( the keyboard still may need service too)