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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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AVR-1905 Denon receiver amp fooled me
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 |
#2
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AVR-1905 Denon receiver amp fooled me
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. |
#3
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AVR-1905 Denon receiver amp fooled me
I'm going to make a really stupid suggestion. It sounds like a bad solder
joint. Somewhere. 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. |
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