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New Member with DOA Sansui 7070

visman

visman

AK Subscriber
Subscriber
Hello all - and what an awesome website.

Recently I added a Sansui 7070 to my vintage electronics collection and it needs a little help. I've tried to follow the threads here but couldn't find the answers.

I suspect I have a fuse resistor issue - but here goes ... My 7070 powers up (lights come on - at least those working) - but no sound through the speakers. I do not hear any relay "click" after powering on (like my Marantz 2240 does).

I do have a multi meter and can work a soldering iron - but do not have a schematic for this receiver.

For those interested I bought on craigs list (with a really cool projector) for $50.00 - thanks
 
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Welcome to AK, pal- sorry to hear yr 'Sui is sick, but I'm sure somebody will chime in here w/suggestions...
 
The 7070 uses the same driver board as the 9090DB. It is prone to the same issues with the fusible resistors. Do a search for 9090DB resistors. There is a ton of information available.

- Pete
 
Visman, welcome to AK and the [Exclusively Sansui] forum. This is the place for all thigs Sansui! :thmbsp:

You need to clean all the switches and controls first before you go any farther. It is not uncommon to loose both channels due to a dirty function switch.

Next, assuming you're still dead, you must determine if the power output section is functioning or if the preamp/tone circuits are dead. Get an external source and plug it into the AUX and connect a set of headphones to the headphone jack. Do you get sound?

As Pete said, the driver cards on these Sansui's do fail -- especially the fuse resistors. However, it is more usual to have just 1 channel out so I wonder if you have a more central problem.
Paul
 
Thanks for the advice - I have a can of deoxit and I'll give the controls and switches a good cleaning.

After that I'll input a source through the aux and see if anything happens (including headphones).

I'll report back soon.
 
Paul when the fusable resistors fail, the unit goes into protection. The 7070 doesn't have a protection LED but it's a good bet it's in protection if he is not hearing the relay click. Cleaning the controls is inportant but this baby will need additional therapy.

PS: Visman, welcome to AudioKarma. Good to hear from another local audio nut.

- Pete
 
Thanks - all!

OK I've cleaned the pots (removed the faceplate etc). Sprayed and worked them all.

Got out my headphones and noticed that I have a very very faint sound coming out of the left channel only (on am radio). It is only moticeable on full volume.

thanks
 
By the way - thanks Pete.

I've been hooked on vintage electronics forever (since I bought my first Pioneer SX636 back in the 70's).

This Sansui looks like it should be terrific - I'm going to match it with a pair of KLH model 6's which I recently picked up at a yard sale.
 
Go to the protection relay. At one end you have the drive coil, which I suspect is currently not energized.

The other connections are for the channels, two going to the amplifiers and two going to the speaker selector matrix.

If you find a DC voltage on one of the signal pins going to the amps, what this means is that an amp has failed (is generating a big DC offset) and is activating the protector, thus refusing to fire the relay.

Fred
 
I've pulled the F2624 board and indeed 6 of the fuse resisters show open.

The odd thing is the resistors that I think should be 150 ohm are more like 3900 ohms (if my color code reading is right - looks like orange-white-red-gold). I've attached a photo.

The red arrows show all open resistors on the board.

Also there are a couple of resistors soldered onto the back side of the board - is this normal?

Thanks for your help!
 

Attachments

  • Sansui F-2624.jpg
    Sansui F-2624.jpg
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Fred, that is certainly possible but the reading will not be a true indicator if the fusible resistors on the driver board are open or out of range. They need to be checked first. It's a known issue with this driver board. I have two 7070s, both were in protection when I got them and in both cases replacing a handful of the fuse resitors fixed them.

- Pete
 
You beat me to it. Sansui does sometimes put resistors on the back of boards but I don't remember if this board has them or not. I wouldn't worry about them unless you see other evidence of tampering.

- Pete
 
Pete can you help me identify the correct ohms for the resistors I've marked as "open"?

Basically the four corners and then the third in from the bottom left and right.

They are all matching so I have nothing to compare to for readings.

Thanks
 
R33/34 in the corners by the big plug are 180 ohm. R35 and 36 are 4.7 ohm. It would be very unusual for R38/37 to be open but they are 3.9k ohm. I'm not sure which ones you are pointing to at the bottom but that row has a couple of 4.7 ohm and a 150 ohm. Also check R43/44. They are 150 ohm.

- Pete
 
At this stage, it is probably a good idea to consider replacing all of the the fuse resistors on that board while you are at it!
 
Good idea - I will replace the lot.
Thanks all for your help - I'll let you know how it turns out.

By the way any recommendations for a fuse resistor source?
 
All the fuse resistors on the board are covered by these values:
4.7 ohm
10 ohm
150 ohm
180 ohm

- Pete
 
Another point... it is common practice to use flame-proof metal film or carbon film resistors instead of the original fusible type resistors.

Also, the 1/4 watt resistors can be replaced with 1/2 watt rated resistors.

Any electronics supply house should be able to supply suitable resistors, but if you cannot find them locally, try Digikey.
 
Well tonite I soldered in the new resistors and plugged the board in and turned on the power ...... and heard a beautiful "click" and then music from my Sansui!

Thanks to everyone for helping me bring my Sansui back to life!

Now to figure out how to get at those dial lamps .....

Thanks all!
 
dial lamps

they come out by removing the couple screws on the white light bezel, takes a #2 phillips.
Fuse type lamps, originals were 7v 300ma, available everywhere are 8v 250ma.
Member Dwojo has them, Vetco in Bellevue WA has the 7v ones, cost a buck each plus shipping.
Reflow the solder joints on the back of that light bezel prior to re-installation.
Can't recall if the 7070 has watt meters, those lamps are a pita to change.
Casey
 
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