Sansui 6060 -- issue, need help

[D Chas]

@D Chas - look at the replies above for detailed explanations, but you could have either 1) DC offset or 2) a defective protect circuit. The DC offset can be measured at the outputs of L and R channels (before the relay), but it may be easier to measure the two channels as they feed into the protect circuit. If those aren't engaging the protect function, you could have some bad components in the protect circuit itself. When NOT in protect mode, the protect circuit should be driving the coils of the protect relay. If you measure full voltage, the relay should be engaged. If I understand the operation of the protect circuit, the transistor in the attached schematic should be off (Voltage from base to emitter < 0.6volts). If either output (highlighted in yellow) has too high a voltage, this transistor will keep the relay turned off. You can easily check the voltage across the coil (i.e. the power supply voltage feeding the protect circuit) to be sure it is the correct value (it's hard to read in the image, but it looks like 27V to my eyes - this is on the right/coil side of the 220 ohm resistor. Let us know what you find.

View attachment 2900397

@D Chas - look at the replies above for detailed explanations, but you could have either 1) DC offset or 2) a defective protect circuit. The DC offset can be measured at the outputs of L and R channels (before the relay), but it may be easier to measure the two channels as they feed into the protect circuit. If those aren't engaging the protect function, you could have some bad components in the protect circuit itself. When NOT in protect mode, the protect circuit should be driving the coils of the protect relay. If you measure full voltage, the relay should be engaged. If I understand the operation of the protect circuit, the transistor in the attached schematic should be off (Voltage from base to emitter < 0.6volts). If either output (highlighted in yellow) has too high a voltage, this transistor will keep the relay turned off. You can easily check the voltage across the coil (i.e. the power supply voltage feeding the protect circuit) to be sure it is the correct value (it's hard to read in the image, but it looks like 27V to my eyes - this is on the right/coil side of the 220 ohm resistor. Let us know what you find.

View attachment 2900397

Jeff, it’s 43 v at where zd602 and R606 meet.
Funny thing though, I’ve noticed that my R606 is actually a 1K ohm. Schematic says 220. My R604 is 220k.

 

[D Chas]

That's your problem. That voltage should be very close to zero especially with the driver board out. Odds are your output transistors are blown.

- Pete

Ok, I measured the outputs. 31v for the top mom’s and on the bottom pnp’s. 0 v for one channel and 7 v for the other. Are you saying that the transistor reading 7 Vbe should be replaced?

 

[Jefft91]

Jeff, it’s 43 v at where zd602 and R606 meet.
Funny thing though, I’ve noticed that my R606 is actually a 1K ohm. Schematic says 220. My R604 is 220k.

I see ZD602 but not R606 in my schematic. In any case, this is not getting you closer to the problem. Since you report seeing 7V on one of the outputs, you need to fix that - it's causing the protect circuit to keep the relay from engaging. Just to confirm, you're measuring the node where the emitter resistors (r07 & r05, r06 & r08) meet.

Now you need to trace backwards through that amp channel to find the bad components. I think I'll defer to those who are better than I at walking you through this process. It is not necessarily the output transistors . It can be components upstream that are faulty.

 

[D Chas]

Yes, measured at the nodes that you mentioned and it’s 0v pretty much on each side
Thanks again for your help in narrowing this down.

 

[Jefft91]

@D Chas I thought you said one side was 7V. If both sides are 0V as you just stated, then this does not explain why the relay is not pulling in.

[EDIT] What is the voltage you see across the relay coil?

 

[D Chas]

Yes, sorry for the confusion. Per my earlier post:

“On my board the resistors next to the coils are R05 and R06. a 2701 board. Without the driver board I measure7v on R05 and 6.5 on R06. I installed the 2647driver board and I measured 35v on R05 and .04von R06.”

The 0 volts readings were taken at the power emitters like in the diagram

 

[Jefft91]

If I understand your reply (which I'm not so sure I do), you have a bad channel. The offset isn't measured at the outside ends of the resistors as shown in the diagram you attached. Instead, it's measured at the common terminal between the emitter resistors. The diagram you attached has different component numbers that in your unit. I attached the schematic that I THINK matches your unit. Please confirm. I have put arrows pointing to the two nodes I was referring to in my previous post.

We need to speak the same language in order to communicate clearly.

 

[D Chas]

My board is 2701 but the nodes you’re referencing are laid out the same. I get 6.7v and 6.2v. See diagram. (Also I’ve added the rest of the power supply board 2700)

 

[Jefft91]

@D Chas - I re-read all of your posts. Sorry I didn't follow things better. With the DC offset you report, you need to be able to test transistors and other components of the amp circuit to determine what's causing such high offset. You may wish to consult a tech in your local area unless you possess the skills to debug this yourself.

 

[D Chas]

Jefft91- Thank you for your help and getting me this far. I think that I’m that much closer to finding where the high dc offset is coming from.

 

[time-pilot]

I noticed your post, I have a 6060 on the bench right now with the same problem, well it did, it's fixed now. I'm attaching a picture with all the voltages you need. It came down to the usual suspects on this on, the old green/black button diodes. Replacing those fixed the protection circuit. This unit is also getting a re-cap and a short tracing done. Also you don't need the power transistors workiing or installed to have the protection circuit work, you also don't need the driver installed either. The protection circuit functions separately, but later integrates to the driver board.

 

[D Chas]

I noticed your post, I have a 6060 on the bench right now with the same problem, well it did, it's fixed now. I'm attaching a picture with all the voltages you need. It came down to the usual suspects on this on, the old green/black button diodes. Replacing those fixed the protection circuit. This unit is also getting a re-cap and a short tracing done. Also you don't need the power transistors workiing or installed to have the protection circuit work, you also don't need the driver installed either. The protection circuit functions separately, but later integrates to the driver board.

Wow, thats all great to hear! I'll let you know if I can get mine up and running. Thanks time-pilot

 

[misterguitar]

Time pilot, I have the same Receiver on my desk getting a total rebuild. what did you use as a sub for the black and green dot button diodes? D610 and D611? The later revision schematic doesn't match the parts list.

 

[D Chas]

Time pilot, I have the same Receiver on my desk getting a total rebuild. what did you use as a sub for the black and green dot button diodes? D610 and D611? The later revision schematic doesn't match the parts list.

For the 2700 rectifier board I used 1N4148 for D610 and 1N34A for D611.
Not sure about the button diodes on your board.

 

[Crodrig]

I'm here for the solutions too, mine had same symptoms and had fuse resistors replaced with metal film, worked for a couple weeks now it's gone again.