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Sansui 551 FM Muting is Too Strong ! ?

Zekeman

Zekeman

AK Subscriber
Subscriber
I just restored a little Sansui 551 receiver. I recapped the whole unit. The muting will only let in the strongest signals. In order to pick up all stations I need to turn the muting off. The reception with the muting off is quite good for most if not all stations...I am impressed with how sensitive this little units tuner is!

Anyway there is no pot to adjust in this unit like its bigger brothers in the XX1 series. In the service manuals troubleshooting chart is suggests replacing the TR 7 and 8 if muting is an issue....which I did with no change to the muting. I am looking for ideas as to why this would occur...

Any guidance will be appreciated.

Thank You!!

Zeke
 
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No...the Chicago area has many strong stations.....with he muting on it only lets through a handful of stations.
 
"The reception with the muting off is quite good for most if not all stations" ... I don't get the issue. The muting is doing what it is supposed to do.

Depending on where you're located and what antenna (indoor or outdoor) you're using 'directional' or 'omnidirectional' will make a huge difference (I'm assuming you're using either a 300 or 75 ohm dipole indoor, assure one lead is connected to the ground the other to the specific terminal.)

Note that About nine FM stations in the Chicago market use the Hancock for their primary if so you might locate that then try repositioning the ant. Also sometimes using a weaker gain antenna can help to reduce the 'mud'.

hope it helps.
 
Great information..........thanks.

To clarify.....I need to turn the muting OFF....in order to pick up most stations....so the muting is so rigid, if you will, that it is not letting the signals "break" through.
 
Yes that is correct. Muting turned on will eliminate other weaker signals. i.e. if you're unit was hooked up to a high mounted antenna with good gain and a rotor you could position the antenna to tune into say.. Montreal. but you might be getting some cross signals mixed in.. So you would then use the mute button to focus the signal.

http://www.amfmreception.com/fm-radio/fm-reception-guide

There are other similar guides out there. You might even contact some radio club in your town and ask them.. they might even have DIY design.. antenna kits and even used ones for indoor or outdoor are pretty cheap, too. look on line for DIY antenna i.e. fm am etc..

just in.. check this link, too for the J-pole link
http://www.audiokarma.org/forums/showthread.php?t=221021
 
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"but you might be getting some cross signals mixed in.. So you would then use the mute button to focus the signal."

The muting circuit does not actually focus the signal.

There are two basic types of muting circuits, both turn off (mute) the FM audio on weak signals or when there is no signal at all.

There are basically two types of muting circuits. One type operates based on just signal strength, the audio is turned off when the signal is weaker than a preset level.

The other type looks at the high frequency content of the demodulated IF (intermediate frequency). The theory is that the weaker the signal, the greater high frequency content (hiss) in the demodulated signal.

This type of muting circuit looks at the amount of quieting (reduction in high frequency hiss) and mutes the audio when the quieting is below a predetermine value.

This type of muting circuit is based more on signal quality than signal strength, although both of these are related.

In simple terms the muting function is just an automatic turning of the FM audio on or off based on signal strength/signal quality.
 
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