4300 dropping audio

68kaiser

Active Member
Hello. I have a 4300 that I got from a friend that said it was broke. He was right but this thing sounds sweet when it is working. It has a mind of its own. I had it on the bench and could not get a steady reading for bias or DC of set. It will come out of protection no problem. I pulled the driver boards checked things out and played around with it for a while.
Put the boards back in and checked DC again and it was stable! So I set it then set the bias. Both where stable and looked good.. Hooked up speakers and listened to FM... All was good. Took it it on the house and it worked for 15 mins then.. Audio faded out and a crackling poking sound came in. It sound's just like a record that has played past the music and you are listening to dirt and lint on the blank record at high volume. I checked the DC at speaker terminals and sure enough its up and down all over the place.. In all chanels.
While still not coming out of protection. Is the problem in the power supply? Any help would be great thanks.
 
Hi,

Check the speaker relay contacts, they get oxidized and then become quite intermittent - the relay can be opened and the contacts burnished, do not use a file or heavy sandpaper, mainly deoxit on a piece of paper dragged across a number of times. However, the best answer may be to replace the relay with a new one. Tap on the relay to see if it improves the situation.

Also, some people would check the relay coil driver components because sometimes they get weak and can't pull the relay contacts tight enough to be good.

Usually this problem will partially clear by turning up the volume control to send more signal voltage through the relay contacts and temporarily get a current to flow. But it will drop out again. Common problem.
 
I will check them in the morning.. It does it with both main and remote speakers.. Each have their own relay.. I hope that's all it is. Really want to play this thing load and see what it does what I have heard from it so far it sounds great. Thanks again...
 
You may also want to DeOxit (with power off) the 2 channel / 4 channel switch on the back (never move it with power on), and the various pushbutton switches and selector switches. All of them carry signal and all are suspect when signal drops out.

Also, good idea to clean up all the RCA input and output jacks, any jumpers from pre out to amp in, and check for any bad solder joints to the speaker connectors.
 
I am checking things out now.. I tested the power supply voltage and the manual calls for 35v out put.. My output is fluctuating 18-35 volts. Will not stabilize. Digging into it now
 
I found the problem and she is singing sweet nothings to me now... It was a transistor D331 i replaces it and its partner with D313 transistors that i had on hand. Saw on another thread they where a good sub. don't remember what number it was on the board. The power supply is now running smooth and stable. DC and bias adjusted out perfectly. Thanks for the help
 
Good to hear you got it going, sounds like the power board was sagging out or dying under load?
 
Yes.. It would work at times then just go to hell..I got to say this receiver has a set of brass balls, lots of power to spare. I love this receiver and it is one sexy piece as well.
 
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