From: "Saved by Internet Explorer 11" Subject: YAMAHA TECH TIP Date: Tue, 16 Jun 2015 22:06:51 -0700 MIME-Version: 1.0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Content-Location: file://C:\Users\DM Fraser\Documents\Schematics\New Web Site\Audio\Products - General Audio\W-Z\Yamaha\Yamaha Tech Tip.htm X-MimeOLE: Produced By Microsoft MimeOLE V6.1.7601.17609 YAMAHA TECH TIP=20 =20 =20 =20
MODEL RX-V800 /=20 HTR-5280
TYPE SYMPTOM/REPAIR
SUBJECT I-PROTECTION, BUT = AMPLIFIERS=20 ARE GOOD
SYMPTOM:  UNIT =20 IMMEDIATELY SHUTS OFF DUE TO OVER-CURRENT PROTECTION = (I-PROTECT).  =20 ALL AMPLIFIERS CHECK GOOD WITH NO EXCESSIVE LINE CURRENT = MEASURED WHEN=20 THE POWER RELAY IS BYPASSED USING A VARIAC.  THE = COLLECTOR=20 VOLTAGE AT Q35 MEASURES THE SAME DC VOLTAGE AS THE PRI = TERMINAL TO=20 THE MICROPROCESSOR.  (NO VOLTAGE DROP ACROSS R92 AND = Q35 IS NOT=20 TURNED ON.)  THE VOLTAGE ON PRI CAN BE BETWEEN 1V AND=20 4V. =20

CAUSE:  THE MEMORY = BACKUP=20 CAPACITOR (C633) HAS LEAKED ELECTROLYTE ONTO THE FUNCTION = CIRCUIT=20 BOARD CAUSING VOLTAGE TO LEAK INTO THE PRI CIRCUIT.  = THE=20 LEAKAGE MAY NOT BE VISIBLE ON THE BOARD.

SOLUTION:  ONCE A = TRUE=20 OVER-CURRENT PROTECTION IS RULED OUT, REMOVE C633 AND CLEAN = THE=20 CIRCUIT BOARD CAREFULLY TO REMOVE ALL ELECTROLYTE = RESIDUE. =20 REPLACE C633 WITH A NEW PART.  CLEAR THE PROTECTION = HISTORY=20 USING STEP 9 (PRESET RESERVED) IN THE DIAGNOSTIC MODE ON = PAGE 19 OF=20 THE SERVICE = MANUAL.


BY: =20 JGB


ENTERED:  =20 = 03/07/03