Sansui eight with relay - weak FM signal

[Jomp]

Hi AKers, I am an electronics novice but a Sansui lover. I need your help with my Sansui eight that has a relay - it has 3 problems:
1. the FM signal maxes out at 4 and the Mono button must be pushed in to get sound from both speakers. If the Mono button is not pushed in I only get sound from the left channel - in both situations, the Stereo light works OK when a station is tuned in.
2. the AM band is very noisy and can hardly pick up any station
3. when the unit is turned off, the relay unclicks but at the same time there is a thump from both speakers. The unit is DC offset and bias as per the manual and they are OK.
Appreciate any ideas/views/advice about these problems. BTW I have adjusted the frontend pots for the FM signals but no improvement
Cheers
YL

 

[LBPete]

1) If you are looking at the signal meter when you say it maxes out at 4, that's pretty close to normal. If it receives stations clearly,it's probably OK. If you want the meter to read hire, there is usually a trimmer on the FM board that adjusts the level of the meter.
2) probably needs to have the tuner capacitor cleaned. There is a very good thread in the tuner forum on how to do that.
3) if the mono button restores both channels, you have a drop out in the preamp before the mono switch. The usual suspects are simply dirty controls. All of the controls on the front panel have a switch or a potentiometer behind them, all of them need to be cleaned.

Please post the serial number for the database. Click on the link in my signature block.

- Pete

 

[Jomp]

Thank you Pete for your thorough reply. I have sprayed electronics lube and clean into all the switches and pots and twitched and turned them numerous times but the Mono button still needs to be pushed in to get FM sound from both speakers. I will investigate the preamp to see if I can see anything obvious.

About the serial number, can you tell me where I can find it. I looked everywhere, the back panel, inside, front, underneath but could not see any serial number. Do you want the serial number for my eight Deluxe too?

 

[LBPete]

Dropping a channel like this is a very common issue for a 45 year old receiver. If it comes and goes with the mono button, it's definitely dropping out in the preamp at a point before the mono button. A dirty control is still the #1 suspect but it could also be a bad solder joint or something touching and dragging down the signal. An oscilloscope would be a big help in isolating it.

I want all your Sansui Serial Numbers for the database. There should be a paper label with a 9 digit number on the back panel. Here's an image pulled off the internet.




- Pete

 

[kevzep]

I'd say you have an issue with the Multiplex circuit if the mono FM signal is coming from both speakers.
Tuning cap will need cleaning as Pete says, and also you probably need an alignment with a bit of trouble shooting in the MPX circuit...

 

[Skywatcher]

Hi AKers, I am an electronics novice but a Sansui lover. I need your help with my Sansui eight that has a relay - it has 3 problems:
1. the FM signal maxes out at 4 and the Mono button must be pushed in to get sound from both speakers. If the Mono button is not pushed in I only get sound from the left channel - in both situations, the Stereo light works OK when a station is tuned in.
2. the AM band is very noisy and can hardly pick up any station
3. when the unit is turned off, the relay unclicks but at the same time there is a thump from both speakers. The unit is DC offset and bias as per the manual and they are OK.
Appreciate any ideas/views/advice about these problems. BTW I have adjusted the frontend pots for the FM signals but no improvement
Cheers
YL

Check the coupling caps for the L/R output on the tuner board. They're old and one may have gained enough ESR to prevent the signal from passing through. I've found this on a few different Sansui tuner boards. My SIX being one of them.
The "thump" could be caused by some dried out electrolytic capacitors that are no longer able to filter DC voltage. More than likely on the relay board.

 

[stereofun]

I used to have a relay Eight that was recapped. I always heard a little thump and muted pop when relay clicked out. Not saying it normal, but probably not unusual either.

The push switches are really prone to gunking up and cut a channel - they are also very hard to spray with de-ox, so in addition, make sure you work the switches repeatedly - They seem to have some ability to self-clean that way.

 

[Skywatcher]

I used to have a relay Eight that was recapped. I always heard a little thump and muted pop when relay clicked out. Not saying it normal, but probably not unusual either.

The push switches are really prone to gunking up and cut a channel - they are also very hard to spray with de-ox, so in addition, make sure you work the switches repeatedly - They seem to have some ability to self-clean that way.

Pretty much all the push switches are prone to problems with age. I've had some go completely "open". However they are silver coated and get heavily tarnished so Deoxit doesn't do much for them anyways. I take them apart and dip them in silver tarnish remover and they come out like new. The short ones are easy, but the long switches can be a little more involved because of the multiple slide contacts. The compound switches add another dimension. lol!