try DMI
These guys took over the bench work for the Data Marine line of instruments. You can Google them through "DMI" and go the their web site. I think they do bench work on all sorts of marine cockpit instruments. They have a phone number listed on their site and I called them and talked to a tech before I sent my depth sounder in. They had good turn around time, weren't too expensive ($30 I think), and identified the problem for me which turned out to be a bad through hull transducer which they sent me and I replaced and all is well since. All in all a good bunch of folks to work with. Give them a call I think they are on the Atlantic coast somewhere.