My other stuff...

Saturday, March 29, 2014

1985 Gibson Chet Atkins Classical ~ pickup preamp


Hard to believe it's been five months since the last post ~ where does the time go?


Here's a fantastic Chet in rare white (aged to blonde) finish.  The owner complained of a pickup issue wherein some of the strings were considerably quieter than others, making this guitar unplayable when plugged in.  This pickup configuration is quite rare and acquiring parts or repairing the transducer is nearly impossible, so the challenge was to repair the problem while keeping it all original.  The very expensive alternative would be to replace the saddle completely and install a new pickup system, which would be rather arbitrary and likely unnecessary.






This was a very innovative system for 1985.  There is a transducer for each string integral to the saddle and connected to a preamp via a ribbon
cable.  On the circuit board of the preamp itself is a trim-pot to adjust the volume of each string individually, allowing the player to customize the EQ of the instrument for more bass, mid, or trebbly output.  Quite cleaver.  Then there is a conventional master volume and tone control easily accessible on the upper bout of the body.

After a thorough cleaning of each internal and external pot as well as the area in and around the saddle itself, there was still a noticeable drop in volume from the low E, D, B and high E strings.  My fear was that there was a break somewhere along the ribbon cable itself, but it didn't make sense that only those strings would be affected.  While the solder connections at the circuit board that connect the ribbon cable appeared intact, a much closer inspection revealed that the fragile ribbon cable had somehow been folded downward along the bottom edge, severing the connection at the solder joint.  It then became obvious why ~ the battery had no clip and was housed rather loosely beside the circuit board, and had bumped against the connection to sever the link.  In turn, the plastic in the ribbon cable had become very brittle and delicate over the years so it was an accident waiting to happen.




So I put my Dentist hat on and armed myself with a tongue suppressor, some dental tools and a magnifying glass to isolate the wire from the ribbon cable and the pin connector at the problem strings.  Once complete, each link was re-soldered into a much more robust connection.  I also had to add a very small 5mm length of three strands of hair-thin wire to the high E connection to bridge the gap.  A very delicate process indeed.  Once complete and after confirming that the problem was resolved, I coated the connections with a generous amount of transparent super glue to strengthen the entire area.

It was then time to address the battery.  Unfortunately, I didn't have a suitable battery clip in stock to install.  Instead of making the trip to the store to purchase one, adding another hour to the job, I decided the more economical way was to make one.  I have various scraps of metal for just such a thing!  A piece 55mm (that's about 2 11/64" for you non-conformists!) in length would do.






Bending it in the vice leaving 17mm (21/32") for the thin side of the battery, then pinching together the opening slightly to add a spring effect made this a very strong clip.




Installed with industrial double-sidded tape (to negate drilling any holes for mounting screws) and this job was complete.  Very happy to have kept it all original.  This guitar is ready for another 29 years of classical wizardry!  I hope Chet would be proud...