• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Sister Sony on the bench (STR 6060)

I know ,
I have to check voltages
(I have to compare to good channel.
I was just exhausted last night.
Just physically and mentally empty.
I'll have to re approach with a full tank. I'll look at schematic and try and figure a logical path. I'll likely be back asking questions:rolleyes:
 
First I know AK had serious issues over the weekend.
I'm sure a few (if not a lot) didn't get much sleep in the last three days, so I hope this doesn t come off as complaining.
I posted A sort of long post regarding some testing showing some discrepancies between the 2 channels but it appears to be gone:dunno:.
I'll have to reconstruct the investigation for you later:eek:
 
No, (Thanks for asking)
I took a bunch of measurements and posted Friday night.
They were lost in the great AK crash of '18.
I took new measurements last night but was too tired to post.
For reference, I'm doing all measurements on a DBT.
So they're all low. I'm measuring both channels at the same time (assumption is where they differentiate is where problem is , or nearby.
Clearly they start out the same and at one point one channel's voltage drops significantly from the other (good channel).
I'm apparently not savvy enough to figure what's going on.
I was writing on the output (power amp board drawing) (the actual PCB drawing)
I was going to spend some time and transfer them to the schematic so it makes helping me easier.
Thanks for the continued help.
Oh ,
I did test the emitter resistors . Unfortunately
(Or fortunately?) They were good.
It would have been nice if it were that simple.
 
Last edited:
You adjusted center voltage to 38.5 volts. Yes?
And you can't adjust bias..... Sometimes with multiturns somehow or another you neeed to turn and turn before something happens, just monitor DMM all the time.


I see the protection circuit (current limiting to outputs) is split for the two channels L&R. QX13,14 &15
Can you compare voltages between the two (including the thermistor attached to the outputs) and see if this throws up any clues?
 
Its been a bit hectic here.
Hopefully somebody is still paying attention. For point of reference all these reading done on a DBT. The top # i note is the good channel. The lower number the bad channel. What does this mean?power amp test voltages.JPG
 
I got your PM, NJ Phoenix. I see you've got an STR-6060 but I don't see a schematic for one over on HiFi Engine. They've got the -6060FW version there so I used it. A couple of things:

- It is great that you've taken both channel voltages for comparison. The hard part is that those are better used with the schematic rather than the physical board layout. This greatly helps analysis. I spent a bit of time translating the voltages over to the 6060FW schematic, although there are likely minor differences.

- The power amp is a quasi-complimentary design. This means that the final output devices can literally be removed and the amp will still operate but at far lower voltages. This is a plus for the diagnostics because we can confirm whether the circuit is/is not working with them removed. Yep, its a pain in the butt, though, since there are no TO3 sockets.

- From my transfer of the voltages to the 6060FW schematic, it appears the 3rd stage back, Q608, is where they are off. The first stage voltages appear to be ok if I read it correctly.

- This amp has a Protection circuit that appears intended to limit current flow through the final transistors when driven hard. This is similar to McIntosh and other circuits of the same era. The thing is that we need to be sure that's not causing the problem so it can be disconnected. It is a separate board that has Q613-Q615 for one channel and Q713-Q715 for the other.

Effectively, what this is doing is to eliminate circuits that can affect what you're reading. I know this adds a lot more complexity to the diagnostics, though.

Cheers,

David
 
i might have a hard copy for the 6060 .. will try and remember to sift through thousands of manuals in daylight and scan the schematics
 
I can make an effort to transpose those #s to the schematic.
Hardest part is getting a clear image of schematic to post on
 
If I take a step back.
Just so I have this straight.
I might add this worked prior to recap.
You want me to pull the outputs and then proceed troubleshooting.
There must be a logical approach.
I'm just too naive to see it.
I'm all ears and I'll follow it by the #s.
Thanks for the help!:thumbsup:
 
if it worked then maybe its something you did wrong . or its because it made something better and the next stage was ready to go and new parts gave it a push ..
i would first check human error .
 
Pete,
I agree if it worked before I started I more than likely was the cause.
I have gone back more than once.
My values seem good.
My polarities seem good.
I don't see any bridges or damaged traces ( which doesn t prove neither is the case).
I am at a point where the symptom will probably have to lead me to the problem.
As you said , the recap might have pushed something on the edge over. (I hope that's the case).
As far as pulling outputs (I don't understand why they're not socketed)
I'm thinking just unsolder the 2 pins and heatshrink the ends of the leads for testing.
I'll be watching space (not sure I can get to it today). Thanks again
 
nj pheonix said:
If I take a step back.
Just so I have this straight.
I might add this worked prior to recap.
You want me to pull the outputs and then proceed troubleshooting.
There must be a logical approach.
I'm just too naive to see it.
I'm all ears and I'll follow it by the #s.
Thanks for the help!:thumbsup:
Click to expand...

Checking in on the progress......

If it worked prior to the recap, then the next question is, where along the way did you power it up and test it?

Generally, I'll do one or 2 caps per channel at the same point in the signal chain. Then, I'll run a signal through it to be sure things are still working as expected. This way, any problem introduced is well-bounded.

If this wasn't the case, then, the only way forward is to isolate the parts of the signal chain that are known good. By default, what's left is where the problem is. This takes diligence and patience. By taking the voltages and recording them plus simplifying the signal chain and any other circuits that can influence it is the way we can isolate what's known to work. Once that's done and the root cause fixed, you can start adding back the other parts (output devices and limiter circuit) to be sure it remains working.

Cheers,

David
 
You must log in or register to reply here.
Back
Top Bottom