Sony Amplifier and Schematics

Symptoms?

What format is the schematic?

It's a PDF of only the one page. I have all of the pages as seperate pdfs.

there are two ways fro you to post the file from pdf,

1, enlarge the pdf file, then post it as a picture of format of jpg by clipboard.

2, convey it into word format from adobe reader or take advantage of reader to clipboard then post here. it s easy job.

your instrumnet is great can do the inspection. no problem.

is it a power amp or preamp? I think we can help with it.

or send me email and I can post it here.

I use Adobe Reader 9.0 and Foxit Reader. Both have a snapshot feature. Just select "Snapshot" and select the area that you want to copy to the clipboard. The copying is automatic, just select the area.

Next, open Paint and Paste. Click on File and Save As. Give it a name and select either jpeg or gif for your format.

Go to CR4 and open the editor, click on the camera icon, select your saved file and Submit.

You're done.

As a former radio/tv technician, however, I suspect that you have a shorted speaker or speaker wire. The power amplifiers I worked on had the same feature and I almost always found that the speaker was shorted when the amplifier's protection circuit was triggered.

regards,

Vulcan

Sometimes this happens when the sound amp IC is blown.

your unit most likly has blown (shorted) output transistors either on the main channels

or the surround outputs step one is to diode check all power transistors when you find all the bad parts around that channel, trace it back to the preamp ic and replace that also. check all bias components around the shorted pair of output devices replace all bad parts and try to power up (smoke test) also resolder all bad connections especialy around preamp i.c.'s

Step one...

Remove the +/- Voltage supplies to the outputs (transitors or IC) one at a time. Turn the unit on and see if if comes of "protect" mode. (This will narrow it down "most" of the time)

Step two....

Once you find the channel that has the problem your going to want to work backwards. Depending on the unit alot of Sony amps tend to be "direct coupled" from stage to stage meaning that if the outputs blow it will just work its way backward until it hits something that can handle the current load or opens.

Step three....

Very important...The gentleman from the Phillipens is right. MOST all blown outputs are caused by a speaker problem. What he did not mention is that once you fix your amp you have to check your speaker wires and speaker to make sure you don't just blow the unit up again.

Sony prints are usually pretty good and there should be power and signal lines pretty clearly defined. Post the output stage and I will look it over.

Please also remember its been about 10 years since I fixed any consumer electronics. But I rode that pony for nearly 15 years! I am sure it will come back to me.

Good luck!

bill12780

I'm not sure this will be readable.

There are 8 transistors that can cause this Protector mode to come on.

OK what i would do to start is the Left and right channels ouputs that would be q605 and q606 for left and q655 and q656 for right. Just disconnect pin 3 or take them out completely to be sure one set at a time and see if the unit come out of protect.

If left and right are working then move to the Center channel and then the SLeft and SRight.

Remember to not have any speakers hooked up and to get the volume turned down the second you can. Just cause you bring it out of protect does not mean that it wont blow up the speakers or that the speaker that is bad is now hooked to the oppisite side and will blow up the other stage.

When you find the bad set of outputs you need to start to check the low resistance Resistors there is one in particular the DC offset Resistor (I think that is what its called...been awhile) for example its R615 and R618 for the left channel. You should also check the fuselinks R612 and R613. (They are usually ok but should check them just to make sure)

Another thing. If you did not notice there are 4 or 5 VERY large capaitors over in the power supply. I would recommend shorting those out before working on the unit everytime you plug it in and turn it on. Use a jumper lead with a 1K 1/2 watt resistor so they dont snap at ya and hold it there for about 5-10 seconds. This will keep you from getting wacked.

Let me know what you find.

bill12780

PS I am assuming that since you own a tek scope you have the basic knowledge to do this. Just remember an isolation transformer when using that nice scope!

Hey Bill,

Thanks for your reply, when you say pin 3 are you meaning the e or the c, just want to make sure?

Hey,

It would be the collector of the device. NPN should hook to the B+ and PNP should hook to the PNP device.

I did not pull up the print on this answer...(I am at work and have a meeting in just a few) so I might be wrong but that is how most amplifier design is.

just make sure they are totally disconnected best to just remove the devices completely or you will screw with the experiment! hahaha!

let me know..

bill12780

seem you familiar with amplifier. so you can help him to solve the problem.

I removed Q607 & Q657 with no change. Should I put them back and continue?

Thanks

if you hve less experience of fixing board, I suggest you;d better have it repired to services, so that will not enlarge fault.

you upload only one paper which only one part, there may be up to 60 papers..

from the diagram, the protect transistor pair are q010 and 011,longtail, output is 010 collector. and 007, 707,988 etc are all protectors.

so you hve to check which one is possible.

studio,

The diagram gives voltages for various points which you can use to diagnose the circuit. These are usually for quiescent (no music or sound signal going into the circuit).

Check the voltages at the points where indicated and do your analysis from there. Check the components where you find discrepancies with the power off (and, as our friend Bill12780 said, discharge the capacitor - I've been bitten once, won't happen again).

Hope you find the problem and solve it.

regards,

Vulcan

No...Your on the wrong transistors.

Replace the protect transistors your took out. More then likely if the problem was there the unit would NOT be going into protect mode and would have bellowed smoke out! hahaha!

Stick with the outputs to start with, experience tells me that is where you problem is (you got like a 95% chance). They will be big boys and usually screwed to a large heatsink. Yours are as follows:

q605 and q606 left channel

q655 and q656 right channel

look at the print closely you will see that its basically 5 of the same circuit Left, Right Center and Surround left/right. look for the ne-XXX numbered parts on the print. Follow the emitters and you will see they come together and work through way out to the actual speaker terminals (through that DC offset or Emitter resistor like a .68 ohm or something)

Work through them in that order. L/R channels, Center, then your surrounds. There is no reason why other then most people have L/R speakers not everyone has Center and Surrounds. And like someone mentioned above its usually a bad speaker that starts this all. So no speaker...Usually no problem in the circuit!

Remove one set of transistors at a time and try it. If it does not work put them back in (so you don't get them mixed-up) Once you get the thing out of Protect Mode you may still have other problems. So its important to keep everything has it was.

I will be in meetings most of the day but will check back this afternoon.

Good luck and for god sake please be careful. Remember to discharge those caps (make sure and use a 1K 1/2 watt or better resistor and DONT hold the resistor it could get pretty hot pretty damn fast)

It probably wont kill ya but it does feel like getting kicked in the chest by a mule! Remember its DC so there will be no skin effect! So it will hurt! Or you might make your problem worse!

bill12780

Hi Bill,

I have a 2 ohm 225w will it work?

sounds like a load resistor...

You need at least 1k to pad thet spark and at least 1/2 watt. You should be able to get one at any rat shack!

Gotta bail...

bill12780

Of course, there isn't a short circuit across the speaker outlet terminals, is there....

No, this is with nothing hooked up.

Disconnected in pairs and tested the following.

R Q656 & Q655

L Q606 & Q605

C Q006 & Q005

SL Q706 & Q 705

SR Q756 & Q757

It never did come out of Protector mode.

Well.....So much for the easy stuff.

Next Check both the B+ and B- (+/- 58VDC) and make sure they are there and are pretty darn close 58V.

(BE CAREFUL HERE! its only 58 volts but those caps carry quite a kick!)

Check all the fusable links in the power supply R911 and R912

Once the Power supply is verified start looking at the protect circuit. if you look at the print. You will see the protect transistors I would start removing them and checking them

Q657,607,757,707,007 if these are all ok move forward and check the switch circuit. Q010 and 011.

Make sure you remove all the transistor to check them. The way they are configured will make checking them in circuit impossible.

And of course watch for burnt resitors and bad solder connections(sonys "use" to be notorious for burning up small little resistor and they are sometimes hard to see so watch carfully)

If all this fails...Start looking for really low ohm resistors on the print and check them.

At this point if your still not fixed you may have a control problem. But with out the rest of the print I not sure where to tell you to go.

These kind of problems are rare in audio equipment its almost always the output section. If you want to continue to tinker I will answer any questions you may have. But from here your going to have to do live troubleshooting with power on. Unless your are an experience tech. I would NOT recommend a high power amplifier to be your first victim---I mean subject (hahaha).

one or more of your outputs may be failing under load. Your power supply might have a but load of AC on it. The list is endless to the possibilities.

What I am saying is if you check all the stuff I told you those are the easy things. Proceed from there at your own risk!

Please post back if you find anything or have any clues like burnt resistors or hotspots on the PCB or have any questions. I am subscribed to the this thread so I get an email when someone posts to it.

Good luck!

Bill12780

Earlier I had taken these out, Q607 & Q657 with no change.

If I take the rest of them out one at a time, would it come out of Protector mode and show where to look, or does a good transistor have to been in place.

I am not a very good engineer (I will admit that...I just play one on TV)

But I think that if you just remove it from the circuit that it should come out of protect mode..

Here is the problem. Make DANG sure your outputs are not shorted. If it runs out of protect mode and there is a catastrophic problem it will get even worse! like pouring gas on a fire! hahaha

But from just quickly looking at the print I think I am right. Maybe some one better at reverse engineering could look at the print and tell you. Just to make sure.

Bill12780

How would I check if there is nothing hooked up and I went thru all of the channels to check them.

The other thing I noticed you mentioned to be carefull of those caps, can you be specific which ones, when I was doing each channel I would short c985, c986, c987 & c988 but it never seemed like they were ever charged?? NO bite or sparks when using the resistor to short them. Are these the ones you were thinking about?

Steve

I have adviced you to have it repaired in a service station. now it seems you will do it to end.

do careful. just remember, capacitor cannt be short any time. if you od that, all is the worst. it can be opened.

the best steps are,

first of all, observe all print board to see if there is any burned components, then

1, close power, wait a moment and check by your multimeter at resistor step,

a) from power supply to beginning terminal. obevers if thee is any short circuit ( means resistance nearly zero), they may caused by tr,cap, diode etc.

2. make sure no short circuit, apply to power, check by voltage step,

measure quiescent work point marking at paper according to Vulcan said at 18#

emphasese at teh transistors you list above. to see if there are any broken out, and then change them

3 routine to another paper listed by index, and check.

from these steps, you can find most of faults, if not, it will be some trouble, youd better ask servier for help at home.

your amplifier seems large power, do pay attention. as the voltae is higher.

OK here is the deal....

Q957 looks like the regulator for the 38V display tube. It may be a problem...But its not THE problem

Yes that relay is the relay that supply's the +/-58V to the output transistors and the protect circuit is shutting it off to keep from doing any more damage (The whole job of the protect circuit)

Measure the voltages on q010, 011, 012.

Either the output stage has a problem or the protect circuit does.

Since you took out all the outputs I have to "assume" two things. 1) the amplifiers are ok and 2) the protect circuit is not smart enough to know when the circuit it OPEN. (I have never seen one. But it would not surprise me to know there are such animals)

So check those voltage and post back

If this gets much worse you may have to take it to the Service Center for repair. Just make sure you clean up your tracks or they will charge you double! hahaha!

Only have one meeting today. So should be around. post back.

bill12780

These are the before and after voltages(Protector mode turn on).

GND to B+ 55.6 39.0

B- -55.6 -39.0

Q012 B -.6 -.6

E 0 0

C 0 0

Q011 B -45 -32

C -45 -32

E -45 -32

Q010 B -.6 -.6

C -.6 -.6

E 0 0

Well nothing spectacular there.

I spent sometime in the print. It looks like this baby has a Pre-amp stage.

I would one at a time remove IC601, 651, 001 They are over on the input board. They too could be causing the protect to kick in.

They are STK IC's Big boys about the size of a business card SIP packages. (by the way they are pretty notorious for failing especially in Big Screen convergence sections)

Remove them one and a time and see if it come out of protect mode.

After this I am not sure what to tell you. I know we could fix it if we were both sitting at a bench. But over the internet that is about it.

Let me know what you find and I will keep looking at the print. Maybe something will come to me!

Bill12780

I think your looking at the protect line.

The +/- 58 Volts drives those IC's too and they are monitored by the same protect circuit that we just went through.

They are the pre amp.

It looks like the vcc and vss (the +/- 58 volts) is being watched. and that is what is happening. your 58V is low and drops when the protect is activated.

My guess is that one of those stk's is shorted and dragging down the power supply.

It may be a protect circuit problem. But its my experience to go after the hardest working circuit first and the amp stages are for sure hard working sections.

Try the IC's or if you can just isolate the +/- 58 volts going to that board. just make sure you don't disconnect the protect line (so don't just undo the plug...pull the wires out of the connector or something...hard to give advice on this with out being there to see how its actually put together)

Let me know.

bill12780

Please check me!

If I lift pins 4&6 @ "R" connector on the input board & 1&3 @ "S". Is that it for starters.

Yes,

I believe that will do the trick...

bill12780

No Change.

Hi Bill

Have any ideas I'm thinking q010,q011,q012????

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