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This one had been sitting in a barn for years. Powered it up and the large power transistors on the heat sink would get hot
after a time....and the heat sink would also get quite hot. Speakers sounded like they had some DC on them....with a loud thump

Found the manual on Hi-Fi engine,
[ http://www.mediafire.com/file/b8mlsu7q3pz0bvf/hfe_nad_3140_service.pdf/file ]
and saw a video on youtube saying lots of capacitors dry out
due to their locations near resistors that get very hot, I guess sorta a poor
design. Went in and recapped almost the entire
product save for the (4) large 50V PS caps which appear to check ok.None of
the high power or driver transistors
mounted to the main heat sink were shorted..

Powered on but no audio, and noticed the fuses to Bridge D805 were melted open.
I believe they were ok before.
Replaced them and they started to light up like fiilaments, so shut down,
removed the bridge D805, then checked it, its ok.

There is about a 16 ohm short on the + / - lands where the bridge was. It
seems like something I did maybe is causing this,
like a capacitor in backwards, which I am doing alot of lately for some
reason.

Turns out, yep I put C805 (470/ 63) In backwards ! Capacitor still checks
ok, so will re-use it.

Short is still there though Im guessing R803 is adding in 5.6 ohms or so,
that means theres a 10 ohm short someplace. Q801, 802 arent reading short,
and looks like this becomes a +43V ps feed.

Any ideas out there on what to check next? I am guessing this cap in
backwards caused the voltage applied to a component to be
reverse and its shorted. Or would this be normal with a reversed cap installed,
and putting it in right would be how to fix it?

Steve Hearns
Technotronic Dimensions [USA]
WWW.TECHNOTRONIC-DIMENSIONS.COM
 

Buongiorno,cercavo schema equalizzatore Behringer DEQ 2496, in particolare  lo stadio di alimentazione che fa' saltare 
fusibile protezione generale,circuito TOP245YN perforato Ko!
Grazie 

Üdv! Creative Soundworks 500DAB készülékben elhagyta magát ez a modul. Egyik SMD ellenállás értéke kéne. Persze séma nincs hozzá sehol, csak abban bízhatok, hogy valamelyikteknek van ilyenje, és hajlandó belemérni. A többit priviben...

Sziasztok, Segítségeteket szeretném kérni. Elakadtam a fent nevezett hifivel. Semmi életjelet nem ad. Elméletileg villámcsapás volt a közelben és utána nem működött. Ami zárlatos volt az D1S31 es dióda. Seconder oldalon semmi fesz nincs még stan by sem. Prímer puffer kondin 330V. Tehát a PFC nem indul. PWM ic tápja megvan HV1 és HV2 ott van a 330V. Primer körben diódátak, ellenállásokat rendben találtam. OPTO-t is cseréltem próbára. Bármilyen segítséget megköszönök. Üdv.: Gy