Sony amp "protect" issue

[pentium]

Re: Sony amp "protect" issue

Okay, I'll do what you say.

[pentium]

Re: Sony amp "protect" issue

No more. This is crap.
I have spent my whole damn night going over this thing with everything I got and I still can't find the goddamned source of the problem!
@#$% it, I'm going to see if any of the shops in town want to give it a shot without charging me $75 an hour to let it sit in the shop for two weeks before anyone even glimpses at it (yes, I'm talking to you Giddens. )

[Gianni]

Re: Sony amp "protect" issue

Hi pentium, look in the attachment I don't know if it can help you.

Good luck
Gianni

[pentium]

Re: Sony amp "protect" issue

Thanks but I already posted the service manual. Check the other page.

[chipper]

Re: Sony amp "protect" issue

Wait, so you pretty much recommend I go with the iron and just reheat every joint on the board?
I really did not understand your last post.

I agree that there is far too much grease on the IC's attached to the heatsinks , and there is even grease on the transisters at the base. You need to wipe these off with a Q-tip and a few dampened tissues.

I wanted to read all of the posts to be sure I hadn't missed anything before I offered some of my own suggestions or thoughts , but it appears , like you are thinking and have reacted to : there seems to be a heat problem , which may have melted the grease the way it is.

Before I check your notes on the service manual locations provided , I want to offer you an immediate explanation according to past experiences I have had with stereo. I used to have a 8' x 10' audio (only) wall cabinet of sound equipment , so I know them. (all built by me custom)

With larger , more powerful amplifiers , come taxed and ready power transformers installed in circuit , that is why you added heatsinks and found alot of heat there. Personally , I never bought , nor used any sort of gas guzzler type of amp , while I also ran a pre-amp for this very reason. Combined units , seem to suffer from being relied upon in the power transformer department , and this is the result. A pesky pre-test , or self test nightmare.

I used to hate the "CLICK" of my pre-amp , but knew my amp was safe. So , my first suggestion is that the system is "Protected" by this self test for the amplifier's sake , which rules it out. But , the transformer is checked before it turns the amp on , if it fails the self check , the light comes on and stays on. It will not power up the amp. So , I think you should be showing the transformer , not the heat it made , or the amp made from it.

Let me look at the schems.

[chipper]

Re: Sony amp "protect" issue

Without going into extreme detail about the schematics , I see 3 badly burned areas at their contact points to the board at the 3 resistors located between R806 & the Nichicon cap at C810. After cleaning the entire board of that gobbly gook white stuff , I would remove the Nichicon cap so that I had room to either A : resolder the resistor joints from above (shown in picture) to fill in the holes so that they contact the board , or B: use a fine drill bit to drill new holes in the traces underneath to renew their contact to the board properly on both sides of them all.

Accordingly , it seems SONY put way too much grease on those IC's , not paying any attention to the fact that IC manufacturer instructions say that a minimum or small smear of grease should be used behind the IC's before installation. And , that if too much is used it may crack or fracture the IC when it is tightened to the heatsink.

This looks to be the case in both areas of heatsinks. In other words , it is not even necessary or needed to have the mounting screws threads filled with grease either. All of this contributes to heat build up and reduces the transfer of heat to the heatsink , which can cause the IC's to fail or run far too hot. Between those 2 overheating sources , the resistors have heated up to their maximum.

I hope that you can resolder those , and that is why it started to work when you reassembled it. I'll bet they are loose or contaminated by the melted board material , which amounts to what a bad or missing solder would do - it would disconnect those resistors , which is being detected and has effected your self-test at start up.

As far as the power of that amplifier and it's quality , it is not great , but common amongst receivers or even home theatre applications. Everything is balled up into 1 unit. Pre-amplifiers resolve the heat that is built up in the main power supply , by powering the amplifier - which is by itself . Pre-amplifier's also shut down any amp that has a problem with it's built in protection circuit before damage can occur. This is what has happened to your unit , it has powered down , as it should , when there is a problem - not just heat.

I would summize that you may be pushing the amp too hard with a set of maybe 300 watt speakers or more - but the THD (total harmonic distortion is 0.09) on the amp , and the frequency response is only 40k hz - 20k hz - which is not putting out base.
The human ear can hear 20k to 20k - mine used to do that at 0.00001 THD. Meanwhile you are only putting out some 70watts/channel as well.

Mine was putting out 300watts/channel and this is all important , as "hiss" should not be heard in any good amplifier when it is turned up to at least half to 3/4 volume. If hiss is heard at 1/4 - the amp is no good to buy or use at high volumes or for recording. Heck , I even had a remote control on the volume knob that ran up and down on mine.

Coincidentally , I have a Sony amplifier / signal controller something like yours in the living room that is a STR D511 , but it is only hooked to 2 small bookshelf speakers , not to any floor models. It works fine but does heat up anyways.

Keep off the loudness control if you are using it now and try resoldering and restarting to see if you are able to run it then. Good Luck.

[Gianni]

Re: Sony amp "protect" issue

Thanks but I already posted the service manual. Check the other page.

Sorry I didn't see the link.

Gianni

[pentium]

Re: Sony amp "protect" issue

You know, I still have not gotten around to getting this thing in the shop.

[pentium]

Re: Sony amp "protect" issue

Well, here I finally managed to get another probable location.
It was mentioned on another forum but the main symptom is the same.

I remember when my 595 borked. Massive blue arcs and way too much smoke, it set the smoke alarm off! though it was just a little transistor that appears damaged I could fix it... shows 'protect' and refuses to turn on now.

Well arcs or no arcs, I guess it is worth looking into the transistor.

[pentium]

Re: Sony amp "protect" issue

Well a bit of an unnecessary followup but I have a new amp.
I found the same model amp at the landfill and after swapping parts around (most notably the main logic board) I had one working amp.

[pentium]

Re: Sony amp "protect" issue

BINGO!
Turns out that the problem with my old amp was not a bad soldering joint but a bad part.
I noticed that in the amp I found that I was missing a component so when I pulled the missing part from the old amp into the new one, the new amp powered up but gave me the "protect" problem and the old amp no longer gave me any issue (though the center channel was now missing).

It's an STK530-230 (check that photo I posted, It's the other black thing on the left of the part I thought was bad) which seems to be some sort of linear IC that seems to be available for incredibly cheap. I just need to go buy two of them and I will have two working amps.

[Wizard]

Re: Sony amp "protect" issue

You will need to buy it from sony or other reputable electronic supplier. I tried bdent.com for that part and came up nothing.

Also you will need to check the ESR of some capacitors that are near hot stuff.

Cheers, Wizard

[pentium]

Re: Sony amp "protect" issue

I can do that.
We have three stores that deal with stuff like this. RTS electronics is the closest thing we have to a store-version of DigiKey, then there is another store that is tucked under the bridge on ramp (cramped but the guy knows his stuff) and...Giddens Electronics who are at least certified to service Sony stuff.

[Wizard]

Re: Sony amp "protect" issue

awesome!

Cheers, Wizard

[zandrax]

Re: Sony amp "protect" issue

Hurrah: at least you found the culprit.
Update us when you can solder the replacements.

Zandrax

[pentium]

Re: Sony amp "protect" issue

While no shops in town have the part in stock, that shop under the bridge saves me again. They can order and sell one to me for $25, Giddens can do it for $48 (the greedy bastards tried to gouge me again) and RTS electronics can't get it at all.

[mbates14]

Re: Sony amp "protect" issue

electronix.com

[pentium]

Re: Sony amp "protect" issue

It took almost four months but the part came in today and it did indeed fix the problem with both of my Sony amps. I guess this is just a problematic part.

[shadow99]

Re: Sony amp "protect" issue

And yes, Sony is SLOPPY wth heatsink grease! :p

Cheers, Wizard

I'd bet that thing has been worked on before. Factory originals arent THAT sloppy with heatsink grease....normally.

[fastvideo]

Re: Sony amp "protect" issue

If all output transistors measures good, replace the STK ic.