Sony ES receiver "popping" when powered off...?

cwilson

Member
Howdy AK,

I'm a bit of a rare poster here, but I need a bit of help with my 2nd system. I have been building a "vintage powerhouse" system of 2nd hand purchases, currently just a pair of Mission Argonauts powered by a Sony GX800ES. Occasionally when I turn off the receiver (1 in 20?), as the relay clicks from within, I'll hear a loud "POP" from the right speaker, and right only. I recall a different Sony receiver I had doing the same, but that left years ago and wasn't worth repairing...

I do, however, feel like this ES unit is worth tinkering. Not only is this a 2nd system, but the receiver is still a semi-new purchase (less than a year?), and works flawlessly 99.99% of the time. I paid $70, which is about the going rate, and my total investment for the entire system is still only $120! The amp in the GX800ES really makes it special. It has a push-pull amp rated at 185w @ 4 ohms, and is also 2 ohm(!) stable in 2ch mode. I feel like getting any other similarly rated power source for my 4 ohm Missions would surely cost more... so I feel like this is worth investigating/repairing.

So..... would this be a power relay? Easy fix? My electronics DIY experience is limited, esp. with audio, but feel like I am a semi-technical guy. I have successfully soldered wires in my car, and have access to such equipment.

I know this is semi-vague, but any directions towards common problems, places to look, schematics, etc. you folks could point me in would be much appreciated!!

THANKS!
 
The speaker protection relay should open instantly when the receiver is turned off. If you're getting a pop through the speakers, the protection relay is sticking or not opening fast enough.
 
Hifiengine has the service manual, but I wouldn't recommend troubleshooting this model for a beginner because of its complexity. All of the low-power stages of the power amplifier are in a single IC for each channel. I don't see any trimmers for DC offset null (or bias current), so it's a fair bet that IC751 (STK350-130A) is kaput. You might be able to confirm this by using freeze spray on it (go easy!) while monitoring DC offset at the speaker output terminal after that offset develops. And it's probably not a great idea to continue operating this guy with speakers attached until it's fixed. It could cook your woofer voice coil and burn its protection relay contacts from arcing at turn-off time.
 
So I know this is a very old thread I started, but I put the ES back in rotation... as I think I have found a way around the issue above.

There is a speaker A/B/OFF switch that is a physical knob. Turning to OFF gives a nice, assuring click within the unit, without any odd sounds. The unit can then be turned off worry free, as this has so far had a 100% success... I have yet to hear this again!

Can anyone quickly comment that this will indeed avoid the issue and not damage my Mission speaker while using the receiver? I dont expect 20yrs operating it like this, but can I at least put this off of the current worry list? :)
 
I would check for DC offset, but other than that I can for see no issues. I would get another opinion besides mine though.
 
As faber12 has said, check for DC offset during operation. Any sign of offset drift or spiking is cause for alarm. Suggest you use inline speaker fuses until the other shoe drops.
 
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