LinnDrum. This time the Snare Drum / Sidestick was not working and some, meanwhile common, boot issues. This LinnDrum has been modified to easily swap the sound eproms. With this modification it can happen to put in the eproms in the wrong direction. If that is the issue some instruments only play a short trigger click.
I traced down the fault to a dead AM6070 digital to analog converter. I found a replacement on ebay and the instrument(s) came back to life.
I found some leaky capacitors in the individual audio outputs that needed to be replaced. I used nichicon audio grade capacitors for the replacement.
Then I noticed this audio jack and I swapped it with the click jack, which is not so heavily used like the stereo outputs. Both are still working.
Overall I found weak or questionable solder joints, which I re-flowed. I also re-flowed and cleaned up all the molex, since there was battery corrosion spotted from a previous damage.
All the slider potentiometer sounded and looked very dirty and scratchy, so I sugested to clean them professionally. Open, clean, close ... no contact spray used.
Finally I modified the power safe circuit and used a modern reset IC. The old IC was heavily corroded and the original circuit isn't that great anyway.
There are lethal voltage exposed in electronic devices. Unless you know what you are doing, don’t try this. If you following along, you doing so at your own risk.
I’m documenting repairs for my reference and yours.
I do synth restorations and repair with a specialty in vintage synthesizers, drum computer and other vintage gear, based in Düsseldorf, GER. Get in touch about your synth situation!