Question about Denon AVR 3808Ci Receiver

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Blown Channel on an amplifier

If i've blown a channel on a stereo amplifier. what do i check on the board to be replaced besides the transistors.

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Look for low valued resistors that may look ok, but be open. Check the emitter resistors (.22 or .47 ohms). Check the transistors in the driver circuit as well.
Dan

Posted on Jun 06, 2008

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Determine if an analog receiver has blown a channel


When you need to replace the output transistors, do them both at the same time with a matched pair. That way you won't unbalance the power supply and will be assured of the same power out is available on both channels.

Feb 18, 2016 | Sansui Audio & Video Receivers

1 Answer

MY MHC-GNZ7D MUSIC SYSTEM ONLY SHIWING PLEASE WAIT , ITS NOT WORKING PLEASEGIVE ME SUJETION


One possibility is that the power-on speaker protection delay is stuck on. The most common cause of this is a shorted transistor in one of the power amplifier channels. In that case, you will need to replace the speaker driver transistors in that channel. I don't have service information on your particular model; it may use power amplifier modules rather than individual transistors.

The tricky part is identifying the amplifier power and speaker output terminals to test for this problem. To find a shorted output transistor, you need to measure the resistance between the output of each channel and the plus, then the minus power supply connections. There is a relay between the amplifier output and each speaker terminal on the back; this relay is turned off by the speaker protection circuit, so you can't measure from the speaker terminals. If you have a fried transistor, one of the tests will show a resistance of a fraction of an ohm. A good transistor will have a very high resistance or read open. This will be the case whether you have modular amplifiers or discrete transistors.

If you see a blown fuse, that is a strong indication that you do have a fried transistor. Sometimes the speaker protector circuit shuts down fast enough to save the fuse, but not always.

Apr 27, 2011 | Sony Audio & Video Receivers

2 Answers

Pioneer vsx_D710S whatever can be the input source,the flag " poweroff" apears and switch off the system. Seems to have no time rules, shut down frequency connected with hazard ...... No...


I'm not sure what kind of an answer you are looking for. If you are not qualified to do some soldering rework and ready to spend some money (could be as much as 50$) for parts, you better look for a professional service that in most cases will cost as mush (or more) as your receiver.

If you are still reading then here you are. This is a common symptom of a blown hybrid amplifier IC caused by shorting speaker output while it's powered on. There are two protection circuits for amplifier output, Overload and DC output. In your case, most probably, DC output protection is the one that shuts down amplifier to prevent further damage. Find schematics (service manual). To confirm this, look for amplifier inputs connector, measure DC DET. signal, normally it should be around +4.85V. If right after power up it goes down to almost 0V, then it is for sure a blown output on a Hybrid IC. Check whether receiver shuts down with that cable unplugged. If not than get ready to do some rework.

There are two big Hybrid amplifier ICs, one that outputs two channels (usually front left and front right) and 3 channels (for the rest). One of the outputs (if not more) one one of them (if not both) is blown. In most of the 5.1 Pioneer receivers 2 channel IC is PAC010A and 3 channel one is PAC011A. If you want to get original parts and will find those for less then 40$ each you are lucky. There are however cheaper replacements from SANYO, those you can find for around 10-15$.

Find schematics, unsolder resistors one by one that connect AMP outputs to DC detection circuit on each IC and check which one is blown. There are 2 for 2 channel one and 3 for the other. Usually if one output is blown all others on the same IC are blown.

There could be a chance that only one channel on IC is blown, if you want to fix it you still need to replace whole IC. Also, instead of spending on new IC you may want to sacrifice one working channel (center for example) to output the blown one (so you'll get 4.1 :) ).

Nov 11, 2010 | Pioneer VSX-D710S Receiver

1 Answer

Onkyo TX-DS696. No right channel speaker sound


hello there 2 transistor 1 for the right channel and 1 for the left first thing 2 do is a visual check in good light check for any burn't part or any bulging capacitors if everythink looks ok then check underneath the board for dry joints if then you will need a mulitmeter to start testing components

regards
shasun

May 15, 2010 | Onkyo TX-DS696 Receiver

1 Answer

AVR2106 blown channel parts list


Though any transistor(s) might well have gone and the capacitor could be changed, I see no reason to change any resistor unless it's burnt up or giving an incorrect resistance reading. A multi-meter will tell you if a resistor is working or not, if it's not dead or weak it won't make a lot of difference to the circuit, but replacing it will simply cost you more money!

Apr 05, 2010 | Denon AVR-2106 Receiver

1 Answer

Distorted sound in channel


PLEASE :) wear saftey goggles, no jewelry or watches while troubleshooting a live amp. Tube amps have up to 600V dc on some points so rubber gloves will improve the saftey margin. My primary suggestion is to take it to a pro. Please be safe if you are inexperienced. I can't be liable for my fixya suggestions.

I think you meant "changed" Left speaker with Right Speaker and visa versa. Some receivers have speaker A and B selections from a switch on the front, which is why I ask. I think you tried each speaker on the bad channel to find if the speaker was blown. If the speakers are OK make sure that the speaker wiring is good too. Sometimes they can be compromised so use two short lengths of new wire for trouble shooting. Try the other functions like tape, cd, phono, aux, dvd, ect. and if there is no problem with them then it is your tuning system. Check your antenna first. Make sure you are tuned to the station with max power received. Sometimes you can lose Stereo with analog tuners or be tuned to a harmonic frequency close to the target frequency. Check all of the fuses. Sometimes slo-blo fuses can blow incompletely resulting in a high resistance that causes a voltage drop. If the problem is still there you have trouble in the RF receiving/pre-amplification circuit or blown components in the output transformer/tube/transistor circuit. This is verified by having the same problem with the other functions above. In either case, you will need to take the unit to a repair service or get a service manual and test your voltage points to determine which components are bad. Without a service manual, I would start with the Left output transistor. Check the AC and DC voltages with respect to ground (chassis or negative output/input) on the good channel at all nodes and compare them to the same ones on the bad channel. Again, start with the output circuit for the amplifier. There will be one or more transistors per channel. They will be screwed to a heat sink. Also look for brown, cracked or melted components. Keep in mind that replacing these does not necessarily fix your problem as there is usually a failure elsewhere which caused them to go bad. Work your way back to the actual input signal and you will have hopefully found the problem. Good luck, be careful, and seek some local advice from your friends or repair technician. Happy Shooting!

Jul 08, 2009 | Pioneer Audio & Video Receivers

1 Answer

Audio distorsionado en canal izqierdo


the input selector switches if they are dirty can make the amplifier sound like it has a blown channel.
compare voltages from the left and right channel and make sure they are identical as well as the power supply,typically + and - 65vdc .check the regulators for the pream,they run panel lights off the same circuit + - 14vdc

May 26, 2009 | Marantz Audio & Video Receivers

1 Answer

My marantz sr19ex amplifier has stopped outputting sound


I am working on one right now, it has blown output transistors and several upstream transistors and burned resistors as well. This channel of the amp will need a rebuild.

Use a volt meter and, with black lead on the chassis, check the voltages at the 3 conductor connectors going to the board at the rear speaker terminals. These are the outputs coming from the amp and if there is voltage on any of these (unit at idle, no volume), the protection circuit will keep the output from getting to the speakers. High voltage here means blown amp, most likely.

feel free to contact me regarding the repair... www.irebuildmarantz.com

Aug 27, 2008 | Audio & Video Receivers

2 Answers

DENON AVR 1906


Units dc protect mode is probably activating due to Blown channel (shorted output transistors) I work for a Denon Authorized repair Center in Michigan If shipping to Michigan is economical let me know kstahl65@att.net

Feb 05, 2008 | Denon AVR-1906 Receiver

5 Answers

Marantz SR18-no sound


I have worked exclusivly on marantz recievers, for the last seven years, the loud 'pop' you heard, and smoke, was 90% that one of the amplifier channels, on the amp block, has blown, and consiquently the unit stays in protect mode. It will power up, and decode audio, and even show an f.m. stereo on the tuner, but you won't get the 'happy click' of the protection relays, until the channel is repaired. also replace the 5fd memory capacitor on the front micro board behind the front panel. If you have someone repair the channel, make sure that the tech resolders all of the connections on the molex connectors on the amp block. there are 10 of them, five male and five female, The bad solder on these are what caused the problem in the first place.

Nov 29, 2007 | Marantz SR-18EX Receiver

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