Sansui 7070 right channel cutting out.

spiderx

New Member
I bought a Sansui 7070 in used condition. It was working okay but it started to cut out on the right side. Anyone know a cause for this or have experienced this problem? It gets much quieter than the left side. You turn it up and then it comes back on for a few minutes but grows soft again. You can see the peak meter voltage isnt pushing as much as the opposite volt meter on the unit.
Could it be a transformer problem?
 
I bought a Sansui 7070 in used condition. It was working okay but it started to cut out on the right side. Anyone know a cause for this or have experienced this problem? It gets much quieter than the left side. You turn it up and then it comes back on for a few minutes but grows soft again. You can see the peak meter voltage isnt pushing as much as the opposite volt meter on the unit.
Could it be a transformer problem?
I had a bad solder joint (I think) in mine. I ended up solving the problem by hitting the mute buttong, turning the balance all the way left, and turning the volume way up. I guess the current in the circuit got it hot enough to improve the solder connection? Anyhow, I haven't had a problem since letting it run at high volume for a few minutes.
 
It probably just needs to be cleaned and serviced after all it is at least 40 years old. Please post the serial number for the database. Click on the link in my signature block.

- Pete
 
Pete I will as soon as I get it back from the guy I bought it from. He has it for some time and hasnt figured out the problem. It was suppose to be in for 2 weeks and we are going on 4 years. :( I keep in contact with him and he touches base but he seems to be having a problem pinpointing what the cause is. He offered to sell me another receiver even two of them but I want the sansui.

Thanks dr*audio. I will mention that to him and see what he says. I would love to get this back and complete my system again.
 
If you can solder you can fix this yourself. This is a simple problem and if the seller can't fix it he is no technician.
 
Pete I will as soon as I get it back from the guy I bought it from. He has it for some time and hasnt figured out the problem. It was suppose to be in for 2 weeks and we are going on 4 years. :( I keep in contact with him and he touches base but he seems to be having a problem pinpointing what the cause is. He offered to sell me another receiver even two of them but I want the sansui.

Thanks dr*audio. I will mention that to him and see what he says. I would love to get this back and complete my system again.
If this guy hasn't figured out this issue in 4 years, I would get it back from him ASAP, if you can.
 
I think the guy travels alot. He seems very knowledgeable as I have meet him a few times. Its hard to find someone good in my small community. I know he knows his stuff as I asked plenty of questions but I think time and travel is factoring in. I messaged him a online search that I found and heard back from him the next day. He said he found the issue and has the part. Not sure any more details on that but planning on asking more ?'s. He is out of town once again so I have his number and a date to contact him. Fingers crossed & hoping. I do understand and agree with what you guys are saying. I know he even said after the 3rd year that he is really busy and hasnt worked on it much. He seemed honest enough to wait it out and see what happens.
dr*audio what is the issue with it? Cold solder joints? I read this on fixya with someone having a similar issue.
 
Most likely it is a bad speaker relay. All one has to do it tap on the relay and if the channel cuts out or comes back in you know the relay is bad.
 
Ah, Ya wouldnt have any links to a photo of what it looks like or the location on the unit would ya? Im just curious as I would lodge this info in my memory banks for possible future incidents with it. Can the speaker relay but fixed or does it have to be replaced? Also are they still available on the market for replacement or is it best taking it from a donor unit?
I found these photos from the website classic receivers. Is the speaker relay where the speaker wires connect(upper right hand corner of the unit)?
sansui-7070-back.jpg
 
The relay is located on the main power supply board. Its a 2 pole double throw relay, probably can be be replaced by a MY2-02 relay from Mouser. You need to see what voltage rating the coil of the relay has. Its typically marked on the clear plastic case. It is probably 24v DC, or 48 VDC, but could be 12 VDC. Assuming its 24v the part number would be MY2-02-24dc
The relay can be cleaned by removing the cover and cleaning/polishing the contacts and reinstalling.
 
The relay is located on the main power supply board. Its a 2 pole double throw relay, probably can be be replaced by a MY2-02 relay from Mouser. You need to see what voltage rating the coil of the relay has. Its typically marked on the clear plastic case. It is probably 24v DC, or 48 VDC, but could be 12 VDC. Assuming its 24v the part number would be MY2-02-24dc
The relay can be cleaned by removing the cover and cleaning/polishing the contacts and reinstalling.
Looks like it's 24 Volts:
24780729531_5a0fee5e73_o.jpg


From this thread: http://audiokarma.org/forums/index.php?threads/7070-restoration.700459/
 
The relay must be replaced. The plating on the contacts gets worn and then the contacts start to oxidize. Cleaning it will only work for about a month. The relay is located inside the unit on a circuit board. You must de-solder it and solder a new one in. You use de-soldering braid to desolder it. Place the braid on top of the solder joint and place the tip of the iron on the braid. The solder will wick up onto the braid. Do not use too much pressure on the iron or you will damage the traces on the board.
 
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