AVR-1905 Denon receiver amp fooled me

- J
- jango2
  
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posted
16 years ago

Sun, Sep 9, 2007 12:31 PM

Symptom: does not switch on. Will switch on unpredictably once every

50 tries. Digital 5volts is always available. Clock oscillator can be observed at the syscons pins only if other vertical boards are plugged in. Grounds for digital and analogue seem to be floating. Display may either be blank or have some leds glowing. The first time i powered up it worked. I gave an estimate. Now i'm fooled. Ever since then it switched on just once. Help. What role does the 6ch input board play in the syscons clock oscillator (a 12 Mhz 3 legged ceramic resonnator). Jango

- W
- William Sommerwerck
  
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posted
16 years ago

Sun, Sep 9, 2007 2:43 PM

Ouch. I'm glad I'm not working on that one.

I'm going to make a really stupid suggestion. It sounds like a bad solder joint. Somewhere.

Have you called Denon? It's possible this is a known problem.

- J
- jango2
  
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posted
16 years ago

Thu, Sep 13, 2007 12:43 PM

Hey William, thanks a ton, you were right. I found a print cut leading to pin 40 (RESET) of the syscon. Damn break was under the ic. Your "stupid" suggestion kept ringing in my head and it was'nt until i got the entire mainboard with all the vertical boards plugged in (ground wires soldered from all boards too), off the chassis that i found it. I would have ordered a syscon, replaced it to no avail, next i'd have suspected the VFL drive ic, replaced that too........ Looking back heres a clue that might have given me hope that the syscon was'nt bust, Clock oscillator would be visible only when i'd drain Vcc off the ic (set powered down) and repowered the unit. This should have led me to suspect improper reset. I couldnt access reset pin of the ic as the smd was under the pcb. I did solder a wire to the reset transistor's collector to monitor it and found a clean reset. Thanks again mate, You have a good day :) Jango.