In Reply to: RE: Harman Kardon A410 - Phono Section problems posted by nowave on July 15, 2007 at 16:28:44:
A smallish-value capacitor with one lead held between thumb & forefinger & other lead touched to the Base lead of transistor should produce an audible hum from loudspeaker if circut is conducting. Same result when cap lead is touched to center terminal of input jack if entire following circut is OK. IOW begin @ input jack & each successive transitor until you do hear a hum; the preceeding stage that produced no hum should then be thouroughly checked. An aged electro-chemical constructed capacitor in that stage may also be the culpret rather than the transistor = a $1 replacement from a local Radio Shack discovers. The only problem with this procedure is knowing WHICH transistor lead is the Base vs Emitter & Collector = an HK schematic is useful (as with any diagnostics).
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Follow Ups
- A no instrument signal tracing procedure. - Ron Oehlert 22:25:26 07/15/07 (1)
- RE: A no instrument signal tracing procedure. - Michael Samra 01:51:34 07/16/07 (0)