Question about Fisher RS909

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Mystery Voltage Unit trips into protect mode for no aparent reason. Just as msyteriously as it trips in if you shut it off and turn it back on sometime it will work sometimes it will not. Checked for bad solder joints and loose ground, shorted output or output out of range and all seem to checkout just fine. The only real clue I have found is when you meter the voltage at the filter caps and discontinue the voltage one cap will drain completely to zero volts at the proper RC curve. But the other will only drain down to a seven volt load and stay there. But it follows the proper RC curve it just holds the last seven volts. Replaced Both Capacitors, checked the Bridge Rectifier. Seen this in other electronics and could not identify why this is happening. any advice no matter how technical. Will be appreciated

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Re: Mystery Voltage

Well now you did most of what would be recomended. Try this, When the unit trips into protect, check on the output pin on the output IC or if its a transistor output the speaker output BEFORE the protect relay.. If theres any DC voltage on the output pin then you know the problems in that IC or output circuit. If its a transistor type output, I would suspect the differenal circuit. Way up near the input circuit. Its two transistors back to back. They may check good on a regular check so do a high resistive check And see if theres any type of leakage. These I have seen many many times in a Sanyo/Fisher Stereo system to be the problem. If its an IC output, try disconecting that side of the bad output and see if the unit works ok. If theres no DC voltage on the speaker output pins BEFORE the saftey relay then I would suspect the protection circuits bad. Theres op amps in these circuits that are used as comparators and they do go bad. You dont want to dig this deep and get a service diagram, and the units over several years old TOSS it and upgrade!! Good Luck

Posted on Aug 05, 2006

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My kenwood krf-v5300d overloaded? Stand by light flashes if pressed stops flashing if pressed again unit turns on but doesent pass start up and shuts off again havent managed to find a solution from bassic...

This unit is in what is called "protect" mode/ See the link below for an explanation of this. Specifically to your unit, the output components are unique to Kenwood and are not cheap. Further investigation to locate the reason for the protect mode will be necessary prior to any attempt to estimate the cost of repair. Something as simple as a missign voltage can cause this symptom.

Please feel free to update this with any other questions or concerns that you may have.



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1 Answer

Can't open,in protect mode

First disconnect all speakers from the unit and then try turning the unit on too see if it still goes to protect mode. Protect mode is a shut down feature that shuts down the unit because of a shorted speaker or speaker wires are touching each other. If the unit does not shut down after disconnecting all speakers then reconnect them one at a time while turing the unit on after each conncection until you find the shorted speaker. If it shuts down with no speakers attached to it then you have a internal problem with the amplifier section, probably a shorted output transistor in the Amp circuit or preamp circuit.

Jul 08, 2011 | Yamaha Audio & Video Receivers

1 Answer

What does the word "Protect" mean in the display? My receiver AG-D9100 works great and then quits and the word PROTECT comes up in the display. If I turn it off it usually starts right back up ok...for...

Something is shorting out and tripping a safety feature that protects the amplifier from damage.

try a few simple steps to see if the problem is internal or external.

First make sure that none of the speaker terminals have any loose strands of wire that could be grounding out the terminal and that no wires from the red terminals are touching the component or the black terminals / wires.

secondly disconnect all but one speaker test it to see if t causes the amp to go into protect do so for the other speakers until one trips the protect mode. If one of the speakers is tripping the protect mode it could be a damaged / blown component.

just for fun make sure your speakers are 8 ohms this can be found on the manufacturers website or in your manual. Its rare but some speakers are 4 ohm and they can cause amplifier issues such as tripping a protect mode.

You may have to evaluate the "value" of the receiver and determine if its worth repairing. Many shops will charge a "diagnostic" fee which may be $40 to $80 and remember that parts and an hours labor may not make good financial sense especially if you are talking a unit that is 5+ years old.

Hope this helps

Dec 31, 2009 | Teac AG-D9100 Receiver

1 Answer

Denon AVR 2106 Protect Mode


I will will help you with this, but you must follow my instructions. These are not easy unit to repair, and your troubleshooting technic may have even caused more problems. You should never power on a receiver with connectors unplugged. Since the 15 pin connector is used for the audio signals only (CN559) you may be OK, but please do not do this anymore unless you are willing to create a lot of smoke.

Since this unit does turn on without that one connector plugged in, I will assume that you do not have a blown channel even though it is the most common reason for these to go into "Protect Mode" which is what yours is doing. They go into protect mode to keep the receiver from causing more damage to the circuits and to prevent fires.

I think the most likely reason your unit is going into protect mode is because the negative 15 volt regulator on the main board is bad. This regulator is located by ref # IC102 and is on a small heat sink in the power supply area of the main amp board. Since you have the manual for this unit you should be able to find the part number and location very easy.

The second most likely reason for your problem is a resistor, ref # R184, it is a 10 ohm 1 watt resistor and it is right next to the pre-amp board on the main board. It is near CP501 but on the other side of the pre-amp board towards the output transistors a little. Check this resistor first with an ohm meter, see if it is at 10 ohms. If not, get a 10 ohm 1 watt flameproof resistor and replace it. Then make sure everything is plugged in right and try it again.

If the resistor is good, then go to the voltage regulator, you can check it by measuring the voltage at resistors R145 and R146. If you look at the schematic for that area, you will see that those resistors are connected to both the positive 15 regulator and the negative 15 volt regulator. One side of R146 should measure -15 volts and the other side of R146 should be at 0 volts. Then measure R145. You should have +15 volts on one side and 0 volts on the other side. If the voltage you measure there is not within a couple of tenths of a volt either way, change the voltage regulator that is bad. If all you get is positive voltage on R146 and no negative voltage, then IC102.

Now you are probably wondering, how can you check those voltage if the unit is shutting off right away. Here is how. Have you meter probes in place before turn the unit on, watch the meter while is is turning on. You only need a few seconds to check each one. Check R146 first, then after the unit shuts off, check R145 when you turn it back on again. This is much safer than unplugging connectors and letting the amp idle with unbalanced voltages which could cause an extreme current draw if left on too long.

If you can not verify any problems with those two things above, then you really do need to check the amp circuits. You can do this with no power connected, but you must take out the main board with the big heat sink. Once you get it out, check the output transistors and start with the pair that is located at the inner most spot of the heat sink. The area close to the display and CNT board. That is the most common channel to go bad. If either one of those transistors mounted on the big heat sink measures shorted of very low in ohms, that is the bad channel. If you have a bad channel, there will be many more parts to replace, I will let you knwo what those are if you find any shorted output transistors. You can not check the amp circuit any other way, you will only be getting a reading across the relays if you try to check it at the speaker outputs. The speaker relays never open unless the unit comes out of protect mode first.

Let me know if I have explained this good enough for you, if not I will give it another try.

Good luck,

Dec 02, 2008 | Audio & Video Receivers

1 Answer


It is going into protect mode. It is a common problem, but is not an easy problem to fix. It will go into protect for 3 main reasons. I work at an authorized Denon service center and have repaired many of these models, so I know what I am telling you is correct.

Reason 1

The receiver has a blown channel. This will require the replacement of many parts. The output transistors, supply resistors, driver transistors, and a capacitor in the driver circuit of the affected channel. It is usually the channel that is located closest to the display board on the main heat sink.

Reason 2

A bad voltage regulator in the power supply. It has several voltage regulators all on their own small heat sinks. It is usually ref # IC101 or ref # IC102.
IC101 is a positive 15 volt regulator and IC102 is a negative 15 volt regulator. More often than not, it is the negative regulator that has gone bad.

Reason 3

The amplifier circuit has a 10 ohm resistor that supplies a high voltage to it and that resistor opens up and must be replaced. It is ref # R184. It is a 10 ohm 1 watt resistor.

Those are the 3 main reasons for your problem. It is not an easy unit to fix, but it is well worth the cost of a repair considering how much these receivers cost to purchase a new one. If you do not have the proper tools to fix this unit, please do yourself a favor and have a service center fix it for you. You will need a multimeter, soldering iron, solder, solder wick, and a # 2 phillips screwdriver. You will also need to isolate whcih of these 3 problems is causing the unit to go into protect. If you have a multimeter I can help you with it, but you still need the soldering equipment and must be skilled at using it.

Let me know if you require more help,


Oct 28, 2008 | Audio & Video Receivers

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