Kenwood KA-5002 - null balance button?

ilkka313

New Member
I just got this unit. What the weird 'null balance' button should do? Should it lock down when pressed? My one doesn't lock and I haven't found any affects in sound when pressing it.
 
My guess is that it blends the two channels to mono and inverts one in phase relative to the other. My further guess, then, is that one holds the "null" button in (i.e., it is a "momentary contact" switch) and adjusts something (probably the balance control --or individual level trim pots if so equipped) until no sound is heard. At that point, the two channels are perfectly balanced (nulled).
 
Well, null button doesn't work with headphones. Also there's no signal at all from speaker outputs, but headphone output works perfectly. Where to find schema for this unit?

Ok, found the schema, have to check the speaker selector first.
 
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It's the Null switch giving the problem - no earth on speaker terminals. I opend it, two levers with contact points on each end and all are dirty, no contact. Let's see if I can still get it together, there are tiny springs and balls inside.... Headphone signal is taken before this switch, therefore it works.
 
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