Marantz SR7005 AC Receiver Pop on 2nd Startup Relay

[bighalf]

Hi guys, I have the subject receiver and it has developed a loudish momentary pop when starting up. The process seems the receiver turns on, prepares itself for a few seconds, and then a relay clicks and sound starts. Most of the time it’s fine, but occasionally on that second (delayed) relay click, there’s a pop.

I wonder if anyone has had a similar experience, and identified what was the cause? It’s a 10 year old unit, but I can’t see any obvious caps bulging etc, and don’t want to replace stuff unnecessarily!

[Martin72]

Hi,

Normally the delay after power on and switching the output should prevent a popping sound(Time to stabilize the circuits).
I would check the speaker outputs for a DC offset voltage, measuring with a multimeter.
Then checking the railvoltages for being appx similar, e.g. +/-50V.
If there´s a remarkable difference between + and - rails, check the electrolytic caps, they could be weak without any optical signs.
 
(Further things:
- Is the popping sound on every output ? That would speak for the "Electrolytic cap damage theory", when all channels are affected.
- Unbalanced rail voltages causes the offset on the output, when the offset voltage is gone after popping it´s another point which speaks for a damaged/weak cap(s).)