An electrician isn't the right guy for this job, they're schooled in working with AC wiring, not this delicate stuff.
What you need is an old fashioned TV/Radio/Amp repair guy, not many of these left. Look for someone who services guitar amps, they should have the skill set.
What needs to be done is each connection should be taken apart, soldered correctly and shrink wrapped. Electrical tape has no place in a connector like this.