Sansui 5000 suddenly loses tuner output

findaname

New Member
Hi,

I have been trying to locate an older thread on this issue but have had to give up.

I suddenly lost output from the tuner of my Sansui 5000 tuner/amp (lovely machine). I can see on the tuning meter that signals are being received powerfully, but suddenly no output to the speakers. Everything else is functioning perfectly (Aux, Tape Heads, Phono). I have no sound from either AM or FM bands.

I noticed in that very old thread which I was trying to find again, that someone knew the cause/remedy of this fault.

Very, very, very grateful for any good ideas/tips.
 
Odd if the voltage was off to the front end or IF strip you would have no signal meters or fm stereo. The function/input knob turns on power to the FM section,dial lights and switches the input to the equalizer amp board which is is the back right corner under a cover by all the jacks. I'll have to dig into the schematic but my guess is something there is heating up or goofing up knocking out the signal pass thru from the tuners to the pre-amp section. Assume you have used some deoxit on the input selector? It's shaft driven
 
Thanks both (all) lot for valuable feedback. Much appreciated.

I have only toggled all the switches and find that I do in fact have AM signal - and output. Zilch output from the FM although apparently strong signals being received - as evidenced by the meter.

I have not opened up the machine yet - lots and lots of cables and stuff - in the hope that such may not be necessary.

Isn't it rather strange that the tuner functions with AM but not on FM?
 
No FM sound

Thanks a lot, GeoKost.

Unfortunately, the tip on page 7 did not help - a simple solutions would have been great. All knobs have been twiddled and switches switched, many times. All connections at the back back have been checked (leads taken out and put back again) several times. Nothing of this helps.

I notice a good strong FM signal on the meter but no FM sound. I do not receive any Stereo indicator light when I find an FM station on the Stereo Only mode. I wonder what that indicates. Does this information help in an arms-length diagnostic?

This beautiful machine has served me well for 40 years and I consider it a good friend. Would do a lot to get in back in order. Help very much appreciated.
 
No. No hiss at all on either FM or FM Stereo Only, muting On or Off.
However, I do faintly hear an FM signal if I turn the volume fully up. Very faint but definately there.
 
You put a jumper in as indicated on the f-1120 board where mpl251 is? From what I gathered on that thread, if mpl251 fails, it will act as if the mute switch is in all the time.

If you tried that, then something else is going on.

George.
 
Sorry to say I am rather a novice with electronics. I have not opened the box and really don't know which is the f-1120 board. Interesting theory. How would I go about putting a "jumper" on it?.

The only test equipment I have is an ohm/voltmeter for cars. Would that be any use?
 
I suggest that you have a tech look at it. Or, I typed this up:

Looks like your going to have to go into it.

I'm going to first say a few things, hoping you do know the precautions of the voltages inside the radio, and how to use the volt/ohm meter.

Download the manual and schematic for the receiver. I am also talking about the Sansui 5000 here. No X or A model.

Get to board f-1137, and with the meter set to DC voltage, check point OG for 12vdc. 12vdc feeds the FM and AM boards.

At least I feel like thats a starting point.

On my receiver, I had to replace tr002 on the f-1137 board. In other words, I had no 12v, and no FM or AM.

But, you say you have signal needle movement, which makes me think it is the muting board.

Vigman can jump in here to or someone else.

If something needs correcting here, by all means someone jump on in the thread.

George.
 
This is the circuit board you are looking for, could be the cause of your problem, maybe not. With all other functions working correctly you can narrow down the area where the problem is by getting into the schematic. But this is probably a job for an experienced technician. The old Sansui is well worth the cost.

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The MPL piece is a lamp of sorts, if burned out it will kill the FM output.
 
Hi guys.

This is just great. Thank you all for your excellent help. I have decided not to trust my soldering skills on such a beautiful HIFI instrument, so I am ordering each one of these boards on the internet. Trusting that they are both working. When they arrive I shall start the major task of dismantling my bookshelf, removing the 5000 and extracting the two suspect boards. Hope it is just a plug-and-play solution. You guys are great. Thanks and I shall let you know of the result.
Best regards
 
It is not plug and play.

Judging by your responses, go back to my original first sentence on my last post and take it to a tech.

Have fun.

George.
 
The MPL is an opto isolator.... it has a small light bulb in 1 end & a photo resistor on the other side... and is a PITA!
 
Hi guys.

This is just great. Thank you GeoKost and Tom3 for your excellent help. I have decided not to trust my soldering skills on such a beautiful HIFI instrument, so I am ordering each one of these boards on the internet. Trusting that they are both working. When they arrive I shall start the major task of dismantling my bookshelf, removing the 5000 and extracting the two suspect boards. Hope it is just a plug-and-play solution. You guys are great. Thanks and I shall let you know of the result.
Best regards
 
Find a name...... Finding a good tech is difficult ... but will be a better way to go IMHO...
If you don't trust your soldering skills... there will be ALOT of soldering to replace these boards... Now it might be a good idea to have these boards for parts.... but a wholesale swap, with unknown hardware.... NOT a good choice...
 
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