Reads PROTECT on the display of my Onkyo TX-SV525 ???
I have traced the amplifier circuit and found one shorted final transistor with a burned resistor associated with the transistor.The bad transistor was the left rear channel.I replaced both rear channel transistors with a new matched set and the burned resistor.I found no other problems in the circuit.I powered it up and the display reads PROTECT,with no output.I have a service manual,but I can find nothing about the protection circuit....
Re: Reads PROTECT on the display of my Onkyo TX-SV525 ???
HOWDY, NOW YOU COULD TRY THIS ONE: POWER THE RECEIVER UP , THEN PUSH&HOLD !THE VIDEO 1 BUTTON, THEN TURN THE PIECE IN THE OFF (STANDBY MODE ) ,IT WILL SAY "CLEAR SO IT SHOULD BE BACK TO IT,S ORIGINAL FACTORY SPECIFICATION,S.
SUCCES ! AMSTERDAMCOWBOY-HOLLAND-NOW FLORIDA! 4-EVER
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There are several reasons. If you find one shorted transistor in a push-pull stage you should always replace both. One might be faulty but not shorted, but when in operation it does the other one in. You might have also missed another shorted part such as a diode or voltage regulator. Hunt around looking at the circuit of the confirmed shorted parts and test or replace anything off that circuit.
Finally check your speakers and wiring to them. Shorted output transistors have generally two ways of going like that. Wires touching each other or bad speakers, or having it too loud!
hot transistors are usually shorted out, or driving a short!!
a multimeter across the 3 transistor legs (TO-3 transistors have 2 legs & the case which is the 3rd leg) will reveal if they're dead (remove the transistors first as the circuit may give a false reading) - if you get a zero ohms reading between any of the legs it's dead - don't forget to check the smaller driver transistors too,, as a dead main transistor will kill its smaller driver transistor
speakers are marked,, usually 4 ohms or 8, though sometimes 16 ohms - use a multimeter to ensure you have something very close to these values according to the label on the speaker box & measure from the wires at the point where they connect to the amp
power the unit without any speakers or speaker wires connected,, if the transistors still get hot, you're very likely looking at bad transistors
most likely you have played your with either spk bad or bad wiring i have the same exact amp played it hard for more than two year and still have it sitting right now just bench test it last week still drive hard i think you make bad connection some for that to burn like that
When replacing output transistors on amplifiers it is generally a good practice to replace the output capacitors as well as the biasing resistors.
Just because one transistor is bad does not mean that that is the whole problem.
Look for what caused the problem.
Bad speakers,bad wires,defective traces on circuit board,poor soldering.
Also when mounting the transistor make sure it is insulated and grease it with a dab of silicone heat sink compound.
Whenever I service a board I examine all components for tolerance as well.
A resistor marked at 1% tolerance,example 1k ohm + or - 1% should read no less than 990 ohms and no more than 1010 ohms. Anything else your asking for trouble.
Another point is that some amplifiers use matching pairs.
Pairs complement each other in an output stage and must be replaced in pairs.
I repaired a Sansui Amplifier a while back and it looked as if a power output resistor was burned.
Comparing the two channels I figured the matching value from the other side and replaced all of them and the system has worked flawlessly for years now.
I am a retired electrical engineer and have worked in a few areas of electronics for over 35 years.
Hope this information helps you.
If the circuit board has a charred area, you have another problem besides the resistor. A short or overload likely caused the resistor to burn. Probably a blown output transistor(s) or chip(s), which generally short when they fail. This creates an overload in the circuit which burns up the load resistor - probably.
You have a shorted output channel. You probably see burnt resistors and very heat stressed areas of the board. That is a sign of the outputs being shorted. Unless you have experience in repaired amplifiers you will not be able to repair this yourself. If you change the burnt resistors, they will most likely burn up again. The output transistors for one of the channels are also shorted. They must be replaced along with every other bad component. If you miss just one of the bad components you will most likely burn up all the good parts you just put in. Resistors must be checked to make sure they are within the rated tolerance, capacitors must be checked for being shorted or being dry, diodes must be checked for being open or shorted, output transistors and driver transistors must be checked for being open or shorted, and the list goes on. It is a very difficult job for anybody not experienced in repairing electronics.
Take it to a reapir center that will work on those type of amplifiers, not all repair centers will.
I am very sorry to give you such bad news, but it is the problem you are having.
If you need any additonal help feel free to ask, if you decide you are going to try and fix it yourself I can tell you what to look for and how to check them, but without the proper equipment you will not be able to do this.
If you found this information helpful a rating of "FixYa" would be appreciated. The "FixYa" ratings is not just for helping you fix your equipment yourself, it is also for helping you decide if you can even fix it yourself or not.
My receiver has a similar problem. So far I have found a pair of output transistors fried shorted E to B to C (Q6051 and Q6061) and the associated ceramic current limiting resistor array (R6101) failed open. These bad components will definitely be sensed by the protection circuitry as an overload condition. I ordered some replacement transistors from Mouser (2STC4467 and 2STA1694) and the resistor (RSS2WK-0.22 ) from Encompass.
I will let you know if this corrects the problem once the parts are installed. I also got a service manual from www.user-manuals.com which helps a lot.
It is likely that the PA stage has developed an offset voltage in the output stage. The faulty amplifier channel can be found by progressively disconnecting the collectors of the of the power transistors until the protection fault disappears. Once the faulty channel is found the the cause of the offset has to be traced to the faulty transistor or resistor. Don't forget that if you can smell smoke or burning then there are likely to be components(esp transistors) that have been damaged by the fault. I had a Luxman unit that destroyed 5 transistors in the output stage that was due to an open .5W resistor in the driver stage. Good luck.