Sansui 5000A - FM needs 5 minutes to be on - Stereo light out

A

anti-doom

Well-Known Member
Hi,

My 5000A has FM issue. First turn on and select FM, it needs about 5 minutes to turn FM on. AM works right away at the moment I turn it on and switch to AM. Once the receiver is warm enough, then FM works right away. Only FM has this issue and only happen when first turn it on after long shut down.

Also, stereo light is out even on strong station. I measure 7.65 V on both ends of stereo lamp. Short one end to ground then lamp is on.

Any though/recommendation would be much appreciated.

Thank you.
 
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1st off clean your selector switch (might as well do all of them) with DeOxit D-5 and work the living bejesus out of it / them.

The Stereo lamp works on a differential Voltage.....One side from the Power supply and the other from the Multiplex circuit. Both voltages are the same when the lamp is off If it never comes on, it means that the Multiplexer is either out of alignment, or not picking up the stereo signal from the Tuner (which could very well be out of alignment). Having said that, it's a gold plated bitch to fix unless you have a STRONG background in electronics, and RF, IF and MPX circuits. It could be something as simple as an out of tolerance transistor, resistor, capacitor or a combination of 2 or more of them.

Put the FM in MONO and start it up after overnight. See if it comes up faster. It could be any number of issues, but it sounds like to me that a transistor is failing and takes an inordinate amount of time to warm up. Or you could have a failing cap in the FM Front end, IF STRIP (which has a boat load of IC's (one of them could be going bad)) or the multiplex. Putting it in MONO, bypasses the MULTIPLEXER. If it comes up fast, the problem is in the multiplexer. If not, you got problems in the RF AMP(Front end), or IF Strip.

But it could be something as simple as a dirty contact in the selector. Expect the worst, Hope for the easiest solution.
 
Larry,

Thanks for the input. I have sprayed a lot of Deoxit into the switches and buttons so maybe not the switches/buttons.

I recapped all the caps om MPX board and still have same issue. I will try bypass the MPX by using MONO only to see what happens. That is good point. I suspect some transistors on MPX board but not sure. Now, it takes long time to turn on FM even Tuning meter is moving.

I just notice one point. When I press/depress FM Stereo only button, I can hear pop sound thru the woofer of the speakers.

Thanks.
 
But did you exercise the pots and switches. The softening action of DeOxit PLUS friction of exercising, cleans the contact point. On a rotary switch you'll see a very thin line on th contact plate that is shiny. The finger will also be shiny where it contacts the rotary plate. Same thing on a pot. On a pushbutton or slide switch you'll also see a thin line that's clean and the finger will have a clean point. I have a 1000A where it took 9-10 applications over a month's period to get all the switches, pots etc., cleaned up when I got it 12 years ago. It was really bad. Have a couple of pioneers that were dirty but not as bad as the 1000A.
 
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