Guitar Synthesizer Repair Tips

My MC1 hold footswitch has stopped working

What seems to be the problem?

I have run across five Ibanez MC1 Guitar-to-MIDI converters. These are great units, but probably four of these units had a problem with the hold footswitch. Everything else in the unit worked perfectly except this one function. Luckily, my tech guru friend Marty happened to be in Los Angeles for work. Over lunch, and a schematic, he explained to me how to check the circuit, in particular the function of the digital transistor, labeled DTA Q101. The hold footswitch connects directly to the Q101.

Indeed, DTA Q101, or more properly a DTA143EF looked like it was the problem! This is a discontinued item, but NTE makes a substitute, a NTE 2368. Replacing the transistor solved the problem. Once I became familiar with this part, I realized that similar digital transistors are everywhere, used as digital switching transistors in the Roland GR-700, US-2 and BC-13, and more. I also used a similar part, the NTE2238, in the SBC+ for switching applications.

Here are the photos of the MC1 footswitch repair:


The yellow arrow points to the bad digital transistor, labeled DTA Q101	The underside of the circuit board, with arrows marking the soldering points.	Completed repair with a new, NTE 2368 digital transitor substituting for the discontinued DTA143EF.