Sony STR-KSL40 "protect" message.

[rad]

Hi. I wonder if anyone could help with this problem. I have a Sony STR-KSL40 home cinema box/processor. The fault with the system is that after varying degrees of time the sound will trip off with a loud clicking sound and a flashing "PROTECT" message appears on the front screen of the box. I have tried isolating each speaker in turn but have had no success. I suspect an internal component failing due to heat/time but don't know where to look. Any help would be much appreciated.

[blakew]

usually a system like that would "protect" itself from speaker wire shortages, or being turned up too loud. i suggest checking each speaker and its corresponding wires, and make sure that they aren't shorting out (although the speakers themselves should have an impedance between 4-16 ohms)

if none of that makes sense then i apologise.

[UNDRCOVR]

i have the same problem.. have u managed to find a solution yet?

[OceanOver]

First of all... Hello to all the Googlers who have been searching for a solution to the same problem as us!

I have the exact same problem. When you power up the unit, you can hear a relay on the power supply board making a loud "click", the display will light up and then 2 seconds later, the words "PROTECT" start flashing on the screen.

Here is what I have done and am going to do (still haven't got a solution yet).

* Disconnected all speakers, sub-woofer, RCA inputs and outputs, etc and powered on. Got the "PROTECT" message.

* Performed an "Initialisation Reset" (powering off the unit and then holding the power button for 5 seconds as the unit comes back on). The initialisation process completes then the unit returns to Protect Mode.

* Performed an FM Station "Auto-Betical" Scan (whatever the hell that is?). Powered off the box then powered back on while holing the "Input Selector" button down. It successfully completes a full FM Band scan (even detecting stations with RDS). But as soon as it finishes, it resumes Protect Mode again.

* I took the cover off the unit to inspect for possible shorts or burn marks near the speaker connectors. These all looked good - used a multimeter to confirm no short circuits there.

* I visualised the insides of the unit as separated into 4 main sections.

1. The Power Supply (takes the incoming mains and converts it to DC suitable for the rest of the unit)

2. The Power Amplifier Board (contains the audio input/output jacks, fibre optic inputs, the PA stages, speaker jacks, etc.

3. The Logic/Controller card (where the brains of the unit are (Optical fibre processing, decoding software, etc

4. The Display/Faceplate card (controls the LED display, responds to IR Remote Controls, volume, front buttons, etc.

* At first glance inside the unit, all looked pretty normal. The cooling fan appeared to operate for a few moments when the unit was powered on and would spin down after the unit returned to Protect mode. So it is getting power ok. There was not much dust on the PCB's (amazingly). I could not see any evidence of arc damage either (to begin with).

* Next I disconnected what I called the Power Amplifier Board and lifted it out. I spun it upside down and finally saw something that could be wrong. There was evidence of HUGE amounts of heat traveling through the board. Underneath the output transistors (there are 5 of them - one for each speaker - all 5 are mounted up against the big rectangular heatsink down the middle), I noticed brown burn marks on the PCB. The closer I looked, more and more became visible. The green coating on the silicon board appeared wavy and wet looking. More evidence of extreme heat. Even the plastic lugs used to hold various parts down onto the board looked like they had melted and cooled multiple times with little solidified air bubbles. Not good.

* Even so, the overall damage doesn't appear to look as devastating as it sounds. I did some quick continuity tests with the multimeter at various locations to confirm none of the tracks had been badly broken. I also tested the resistance of as many Resistors as I could - all ok.

* While I had the PA Board out, I could get a much better view of the Power Supply. Two round arc marks on the sides facing toward the PA card. Dammit. And a look under the lid of the chassis, a big square burn mark above the power supply. Ouch.

The plan is to now assess how much a new power supply is and possibly a new PA board and compare this to the cost of a new unit with more features.

It's a pity, I really liked this receiver. Very powerful sound and easy to use. I'll let you know if we have any luck soon.

Ocean.

[dodo]

hello to you all,

i personally followed every single step that OceanOver recommended and at the end i figured out to clean my fan completely so i would highly advice you all to take a vacuum cleaner and suck the dust out of it up wait aroun 5 min and than plug everything back in and start your receiver,enjoy it

[mtumzima]

I have this old DAV-DZ340 theatre and i am experiencing this problem of Power protect. Apparently i established the power supply IC STR F6168 was blown having verified using a multitester. I replaced the IC but still the same problem but the Amplifier power from the supply is still at zero. Every thing seems ok. Could someone advise what could be the beef with this machine.

Michel,
[email protected]