sansui 7070

[decaturron]

Today my mom, bless her heart picked me up a Sansui 7070 receiver. Its really dirty and kind of beat up. I turned it on and the speaker protection kicked in and then right back out. Where is this circuit located on the receiver? What should I check first? thanks.

 

[kevzep]

What do you mean kicked in and then right back out?

When you turn the amplifier on the protection will be on until the amplifier stablizes and then it will engage the speaker relay in a normal operating condition state.....

 

[decaturron]

What I meant is it clicked and about 2 seconds later clicked again

 

[petehall347]

service manual here ..http://www.hifiengine.com/manuals/sansui/7070.shtml
it explains how the circuit works on page 15 of the pdf .

 

[Robisme]

Could be high DC voltage. Put a meter on the speaker terminals and see what the DC voltage is after it comes out of protection, and before it goes into protection.

Also, pull the driver board and check the fuse resistors. There are a few that go out of spec.

Rob

 

[LBPete]

You can't measure DC offset at the speaker terminals if it's in protection. You need to find a point before the relay.

- Pete

 

[decaturron]

I pulled the driver board and there are several suspect resistors that are blue-gray in color. They look like they are flaking away. r33 and 34. Can they be measured with the board out of the circuit? thanks

 

[Robisme]

You can't measure DC offset at the speaker terminals if it's in protection. You need to find a point before the relay.

- Pete

He has two seconds to check for DC at the speaker terminals before it goes into protection.

A quick meter would catch it.

Rob

 

[tchuck]

The two fusible resistors that kept mine from coming out of protection mode (by being open) were on the main board. I can't remember their item # off the top of my head but they are on the main board, on the left side near the tone controls.

 

[LBPete]

R33 and R34 are the most likely ones to have failed and will put the unit into protection. Replace them with 180 ohm 1/2watt metal film resistors. Also check R43/44 and R41/42 the are 150 ohm and are also likely to be out of spec.

There is lots of information on that board and those resistors. Do a search for the board number and start reading.

- Pete

- Pete