I'm repairing a channel of my Denon avr-1400 and I'm looking for new power transistors but I haven't been able to find them in the usual places. The numbers on them are A1491 and C3855. Underneath the numbers is the inscription 7N PZ and by a company (I think) called SK. Are there any other parts I could use?
Thanks for your time
Pete
Thanks for your time
Pete
Denon AVR-1500 Trouble Blown Transistors
Hi Pete & Jan,
I have a Denon AVR-1500 receiver with the same two transistors blown out. It looks like they got real hot because the smaller transistor to the lower right of the bigger two also looks like it got "cooked", not sure though.
Anyhow, what I really would like to know if this thing is worth fixing? Right now if you power it on the red led just blinks..
If I disconnect the blown transistors, should it power up? with one less channel?
I can provide any pictures and tech info needed. It seems like a waste to send this to the dump if it only needs a couple transistors.
Anyhow, any help would be greatly appreciated.
I cant seen to find a service manual either but here are the numbers and locations of the blown components.
Location TR418 - Chip SK A1491 40YZ
Location TR422 - Chip SK C3855 40YZ
Location TR412 - Chip -> This is a very tiny transistor on the heatsink caked in compoun. I cant see any numbers or know if its bad...
Thanks!
Eric
Hi Pete & Jan,
I have a Denon AVR-1500 receiver with the same two transistors blown out. It looks like they got real hot because the smaller transistor to the lower right of the bigger two also looks like it got "cooked", not sure though.
Anyhow, what I really would like to know if this thing is worth fixing? Right now if you power it on the red led just blinks..
If I disconnect the blown transistors, should it power up? with one less channel?
I can provide any pictures and tech info needed. It seems like a waste to send this to the dump if it only needs a couple transistors.
Anyhow, any help would be greatly appreciated.
I cant seen to find a service manual either but here are the numbers and locations of the blown components.
Location TR418 - Chip SK A1491 40YZ
Location TR422 - Chip SK C3855 40YZ
Location TR412 - Chip -> This is a very tiny transistor on the heatsink caked in compoun. I cant see any numbers or know if its bad...
Thanks!
Eric
The best place to get replacement parts for that amp in the USA is mcm electronics. They sometimes purchase components direct from denon electronics USA, the manufaturer of denon equipment in USA so will be able to supply about any replacement parts when it comes to denon. If you can do the repair yourself it would be very cost effective.
just be careful that you get genuine parts and they're in the same beta range. the beta range is the O,P, or Y under the right side of the part number. the date code/ lot number is under the left side of the part number. the dimple under the date code/ beta code, should have well defined sharp edges, and nothing imprinted in it. some counterfeiters put an SK in this dimple which sanken does NOT.
shown here is a picture from sanken:
shown here is a picture from sanken:
Attachments
Hi Eric,
Hi Peter,
Get your transistors from Denon, it's the only way to be sre you are getting the real parts. Your drivers and bias are probably also blown, along with some resistors.
Why is it that everyone thinks they can properly repair their own equipment? From what I see on a constant basis, they can't. They other thing I see lot's of? Most repair shops haven't got a clue either.
Find a good audio service shop or technician. Stick with them, they are your best friend. Believe it.
-Chris
Probably not a good idea. There may (very probably) be other parts blown also.
Get your unit to a proper service person. Otherwise, just throw it out. Which would be too bad since it is well worth fixing. Just not by you.
Hi Peter,
Get your transistors from Denon, it's the only way to be sre you are getting the real parts. Your drivers and bias are probably also blown, along with some resistors.
Why is it that everyone thinks they can properly repair their own equipment? From what I see on a constant basis, they can't. They other thing I see lot's of? Most repair shops haven't got a clue either.
Find a good audio service shop or technician. Stick with them, they are your best friend. Believe it.
-Chris
i've had to start ordering transistor pairs by the denon part numbers for paired devices. one of our shop's part suppliers was subbing transistors from an unknown source when we use the denon part numbers for the single transistors. many of these were either from mismatched beta ranges (i.e.one an "O" and one a "Y") or even worse, counterfeits. since i've been ordering them as pairs, the subbed devices have gone away. another thing is that certain denon models tend to burn up all the way back to the diff amps, so do not try powering the amp up with the outputs removed, you might just let more smoke out. i agree with anatech, find a qualified tech. denon will not be helpful to any tech who isn't certified by them, and that's the policy of most manufacturers. denon's amps are simple(circuit-wise) but their receivers are very complex machines which will trigger shutdown mode at the slightest hint of a problem. it's kind of similar to modern cars. they still have an internal combustion engine under the hood, but damage an unimportant-looking component there under the hood, and you're not going anywhere, even if it is a nonessential part, because the car's CPU says so....
Hi unclejed613,
You are sooooo right on every count there.
A good shop or audio technician will have a source of good parts and common stock. The lower grade service people will shop on price, which pretty much guarantees bad parts. That and you must understand that the most expensive component is the circuit board. Rough servicing will damage the circuit board, which you will have to live with. They are not replaceable.
One last comment. The better technicians will not be the least expensive per hour, but they are the most cost effective per job. Flat rate guys are also a problem, the quality of service suffers. Also, good technicians / shops will have a waiting time. Good guys are busy, the others may have time on their hands.
-Chris
You are sooooo right on every count there.
A good shop or audio technician will have a source of good parts and common stock. The lower grade service people will shop on price, which pretty much guarantees bad parts. That and you must understand that the most expensive component is the circuit board. Rough servicing will damage the circuit board, which you will have to live with. They are not replaceable.
One last comment. The better technicians will not be the least expensive per hour, but they are the most cost effective per job. Flat rate guys are also a problem, the quality of service suffers. Also, good technicians / shops will have a waiting time. Good guys are busy, the others may have time on their hands.
-Chris
Thank you for all the reply's here.
From what I have read I definitely see that I am not going to have this repaired, I already have a replacement to this unit. That being said, I have heard another review saying the center channel blew out, I am guessing the same has happened here but perhaps the "explosion" was more detrimental to mine causing it to not even power up (just a blinking red light).
So If i am going to trash it anyhow, if I cut the two transistors (all 3 wires each) stand back and power it on. If it powers up and works in stereo mode then great! If the red light continues to blink then so be it, I will send it to be recycled at electronic heaven or give it to a local repair shop.
What do you think? If the Transistors are burnt and are shorted the wrong way couldn't this cause the protection? I have seen burnt transistors and stereo equipment continue to function with limited functionality (one less channel or something). Should all three leads on the transistor be cut? Or just certain ones? (Emitter, Base, Collector)
Thanks!
From what I have read I definitely see that I am not going to have this repaired, I already have a replacement to this unit. That being said, I have heard another review saying the center channel blew out, I am guessing the same has happened here but perhaps the "explosion" was more detrimental to mine causing it to not even power up (just a blinking red light).
So If i am going to trash it anyhow, if I cut the two transistors (all 3 wires each) stand back and power it on. If it powers up and works in stereo mode then great! If the red light continues to blink then so be it, I will send it to be recycled at electronic heaven or give it to a local repair shop.
What do you think? If the Transistors are burnt and are shorted the wrong way couldn't this cause the protection? I have seen burnt transistors and stereo equipment continue to function with limited functionality (one less channel or something). Should all three leads on the transistor be cut? Or just certain ones? (Emitter, Base, Collector)
Thanks!
Hi Todd,
Not really, it's far more basic than that. It's like a computer guy figuring he is equipped to actually service audio to the component level.
Hi Eric,
It's a nice receiver, better than most in the same power class. Just because you have bought a replacement for it (without even getting a repair estimate??) doesn't mean you should throw it away. I guess you are just a reflection of the way society thinks right now, on many levels.
I guess you've thought about this rationally then. This has got to be like the "new math", 'cause nothing is adding up here for me.
Look, not many people understand how an amplifier works - really. Many service technicians don't know either, but just because you don't understand how to repair something, is that any reason to destroy it?
Why do you think there are electronics courses in university? Why do good technicians take years to learn to be a really good service person? I have the feeling that you think that servicing an amplifier is dead easy. Well, it is - for me and many other trained people. It is most definitely not easy for the average person.
My point?
I guess I hate to see things needlessly destroyed. You may not have liked what I told you, but I am telling you the truth. I am having trouble understanding why you are willing to throw the money you paid for this set away.
Can I make a suggestion to you? Find a good, young technician who is learning, but shows neat workmanship and a desire to do a good job. Give the darn receiver to him (or her) to keep. That way someone else can enjoy it and it's out of your life. For heaven's sake, don't give it to someone so they can destroy it. That's just as bad as you destroying it. A total waste.
BTW, you seem to be basing your opinion of this set on one single review that appears in many places. There are far worse receivers out there than this one.
-Chris
Not really, it's far more basic than that. It's like a computer guy figuring he is equipped to actually service audio to the component level.
Hi Eric,
Very odd logic to your thinking. This is really too bad.
It's a nice receiver, better than most in the same power class. Just because you have bought a replacement for it (without even getting a repair estimate??) doesn't mean you should throw it away. I guess you are just a reflection of the way society thinks right now, on many levels.
There are many reasons for an amplifier to fail, that review was one, single person. That person did have it repaired as well and seems to be still using it. Could be you needed a higher powered unit for the levels you play at.
I guess you've thought about this rationally then. This has got to be like the "new math", 'cause nothing is adding up here for me.
I have to know why you expect it to work by doing this? It will probably not work because there are other components that are likely damaged as well. I told you that already.
Look, not many people understand how an amplifier works - really. Many service technicians don't know either, but just because you don't understand how to repair something, is that any reason to destroy it?
Why do you think there are electronics courses in university? Why do good technicians take years to learn to be a really good service person? I have the feeling that you think that servicing an amplifier is dead easy. Well, it is - for me and many other trained people. It is most definitely not easy for the average person.
My point?
I guess I hate to see things needlessly destroyed. You may not have liked what I told you, but I am telling you the truth. I am having trouble understanding why you are willing to throw the money you paid for this set away.
Can I make a suggestion to you? Find a good, young technician who is learning, but shows neat workmanship and a desire to do a good job. Give the darn receiver to him (or her) to keep. That way someone else can enjoy it and it's out of your life. For heaven's sake, don't give it to someone so they can destroy it. That's just as bad as you destroying it. A total waste.
BTW, you seem to be basing your opinion of this set on one single review that appears in many places. There are far worse receivers out there than this one.
-Chris
Hi Bob,
Thanks, but in truth it's just my very strong biases showing. I don't like where society is going, or the sense of values that seems to be coming more common these days.
I guess that makes us dinosaurs in today's world. And here I was thinking our world is finally going green. Nope. Just garbage bag green it would seem.
Eric,
You touched on a subject that concerns me greatly. My comments are really a comment on society. In the 70s, everything was for fun. In the 80s, we saw some of the most selfish people ever created come out of the woodwork. The 90s looked like people just gave up and grabbed what they could for themselves. Now we are seeing where the previous decades brought us. We like to talk "green", but all I see in our youth are people who were not taught any values it seems. A watered down version of the 80s where no one seems to care about much, and has lost the sense of pride for family and community. The "chuck it" attitude appeared in the computing profession first, and seems to be the way everyone thinks. This will truly cost us all in a while. It's this attitude that I see is without morals. No thought for our fellow people at all.
Rant over. It's my way of saying you caught some of the fallout from larger issues.
Remember one thing Eric. No one snowflake in an avalanche ever feels responsible. Chew on that for a bit.
-Chris
Thanks, but in truth it's just my very strong biases showing. I don't like where society is going, or the sense of values that seems to be coming more common these days.
I guess that makes us dinosaurs in today's world. And here I was thinking our world is finally going green. Nope. Just garbage bag green it would seem.
Eric,
You touched on a subject that concerns me greatly. My comments are really a comment on society. In the 70s, everything was for fun. In the 80s, we saw some of the most selfish people ever created come out of the woodwork. The 90s looked like people just gave up and grabbed what they could for themselves. Now we are seeing where the previous decades brought us. We like to talk "green", but all I see in our youth are people who were not taught any values it seems. A watered down version of the 80s where no one seems to care about much, and has lost the sense of pride for family and community. The "chuck it" attitude appeared in the computing profession first, and seems to be the way everyone thinks. This will truly cost us all in a while. It's this attitude that I see is without morals. No thought for our fellow people at all.
Rant over. It's my way of saying you caught some of the fallout from larger issues.
Remember one thing Eric. No one snowflake in an avalanche ever feels responsible. Chew on that for a bit.
-Chris
Wow, that wasn't the response I was expecting.
But please do notice what you wrote here Chris:
"
Please read the last sentence of my posting you are referring too:
This would mean exactly what I wrote, It will be recycled or perhaps repaired by someone who has more expertise than I do.
I recycle as much as possible, this receiver would be no exception.
By the way I like your post about describing the generations, family and morals (Post #13). I don't think a day goes by when I don't think about sustainability, from driving to work or watching someone throw away a Starbucks cup.. It seems so easy to throw something out but I always wonder if people really understand the consequences of their actions. The same goes for always wanting something new. I actually have a very small solar array setup because I love the fact that a portion (very small of course) of electricity is created from a renewable source. Then you think about what was involved to create those panels, batteries, and charge controllers.. I doubt it was "green" solar energy.. Anyways, we could chat on this forever but the fact of the matter is that we really need to put more R&D to alternative energy sources and recycling options. And yes, family values and morals are extremely important!!
Now, I tested the resistance at the transistors and they were open circuits anyhow so cutting them would do nothing. The smaller one was burnt and shorted. I cut that one out and the red light continues to blink. And no, I don't feel that i destroyed the unit by removing one burnt transistor..
As someone pointed out Denon seems to have good protection circuitry, perhaps it knows there it a problem with those transistors and will not power up?
What I found interesting is that there are three sets of transistors and supporting circuits behind them (all identical) I was going to test the components (transistor back) and it they all register good I am thinking about replacing the blown transistors.
Any comments on if this might be a viable approach or a waste of time?
Also the last transistor was so small and "crisp" that I cant figure out what model it was. The other two that are still good are doused in heat compound and I hate to pull one back just to see the code..
Pete, did you ever find your transistors? Any luck fixing your unit?
Thanks
But please do notice what you wrote here Chris:
"
Please read the last sentence of my posting you are referring too:
This would mean exactly what I wrote, It will be recycled or perhaps repaired by someone who has more expertise than I do.
I recycle as much as possible, this receiver would be no exception.
By the way I like your post about describing the generations, family and morals (Post #13). I don't think a day goes by when I don't think about sustainability, from driving to work or watching someone throw away a Starbucks cup.. It seems so easy to throw something out but I always wonder if people really understand the consequences of their actions. The same goes for always wanting something new. I actually have a very small solar array setup because I love the fact that a portion (very small of course) of electricity is created from a renewable source. Then you think about what was involved to create those panels, batteries, and charge controllers.. I doubt it was "green" solar energy.. Anyways, we could chat on this forever but the fact of the matter is that we really need to put more R&D to alternative energy sources and recycling options. And yes, family values and morals are extremely important!!
Now, I tested the resistance at the transistors and they were open circuits anyhow so cutting them would do nothing. The smaller one was burnt and shorted. I cut that one out and the red light continues to blink. And no, I don't feel that i destroyed the unit by removing one burnt transistor..
As someone pointed out Denon seems to have good protection circuitry, perhaps it knows there it a problem with those transistors and will not power up?
What I found interesting is that there are three sets of transistors and supporting circuits behind them (all identical) I was going to test the components (transistor back) and it they all register good I am thinking about replacing the blown transistors.
Any comments on if this might be a viable approach or a waste of time?
Also the last transistor was so small and "crisp" that I cant figure out what model it was. The other two that are still good are doused in heat compound and I hate to pull one back just to see the code..
Pete, did you ever find your transistors? Any luck fixing your unit?
Thanks
Well said , koo's.
It is such a shame the extreme level of electronic (PC ,AV and
industrial) waste that goes into landfills here (U.S.). I
wish I could spread the habits that I adhere to. In the last
year , 850+ PC's (steel cases crushed , all aluminum HS's
separated , PCB's collected and turned in to the city's
recycling program) same goes for amp's and receivers..
of course I keep all the working sound cards , P4 cpu's
400VA trafo's , larger amplifier HS's for DIY use.
CRT monitors just get the Aluminum HS's taken , the rest to the city.
Flatscreens usually have SMPS trouble .. easy $$$.
Amplifiers and receivers can have a second life as well ,
"gut em' ,reuse the trafo/ heatsink, rear inputs and speaker
connects... put a pair of $20 DX amps - P3A's ,etc.. good for
the kids.
As far as those sanken units ( SK A1491 /SK C3855 ),
$1.40 njw0281/0302 (to-3P)seem to be the best match, in fact
EXACT (Cob /Hfe/ Ft) except the On's have a little higher
breakdown voltage and wattage.
never had a returnusing those as substitutes.
OS
Hi Eric,
If you wish to service your set, the very first thing you should do is get a service manual for it. I think Denon is reasonable in the 'States for pricing. The original paper manual is far better than a PDF scan. You will be able to identify any and all components you need to look at. It will also give you test points and procedures for setting it up properly. Please note that just replacing parts is not considered a repair. I have no idea what equipment you have, or experience. I have the feeling you don't have that much experience though.
To do this, you will need the following things. A solder sucker and solder wick, solder, thermal compound (fresh, computer stuff may not work) and a decent soldering station. Most soldering irons are not very good for PCB work and may have enough AC leakage current to damage what you are working on. You will need replacement parts and new mica insulators (preferred), or single use compressible types. You will also require a decent multimeter and a transistor tester that can measure leakage and beta (gain). You can build a jig for this also, there is information all over the place on this site. You really should have an oscilloscope and an audio oscillator. You can burn a CD and use that as an oscillator, a CD player output.
When you remove the damaged parts, clean all traces of material from the heat sink surface. This must be clean and flat. You will also be torquing the new parts to the proper clamping pressure. Do not over tighten these parts. Any burning on the PCB must be removed, it may become conductive. Scraping it away is fine. If you end up with a hole, mix up some epoxy and fill the hole before going further.
As ostripper mentioned, the On Semi NJW0281 and NJW0302 are fantastic devices. Highly recommended. You can buy everything you need from Digikey. Don't forget to measure the resistors in those areas. As a resistor fails, they generally will drop in value before climbing up and going open. You should lift one end of the part off the PCB to measure it to ensure an accurate reading. When you have got everything installed, it's time to inspect your work. Remove all flux from your work and watch for small short circuits and bad connections. Now comes the hard part. When powering up a new repair, there is nothing that says it won't go bang right away. Use a variable, bipolar DC power supply if you can get one. If not, i will generally short out the power relay and apply AC power through a "variac" while watching the current draw, bias current and DC offset. Just plugging it in and turning it on is not a good way to save money! Sometimes, having a light bulb in series with the test socket may save you from exploding parts, maybe not. Do not short the power relay unless you are in fact going to use a variac to slowly apply power to the unit.
I hope you find that helpful. I follow that procedure pretty closely myself. I didn't list the other equipment I commonly use, like a distortion analyzer for one. Please do keep your wits about you and work carefully. Take great care not to damage any PCB foil.
-Chris
If you wish to service your set, the very first thing you should do is get a service manual for it. I think Denon is reasonable in the 'States for pricing. The original paper manual is far better than a PDF scan. You will be able to identify any and all components you need to look at. It will also give you test points and procedures for setting it up properly. Please note that just replacing parts is not considered a repair. I have no idea what equipment you have, or experience. I have the feeling you don't have that much experience though.
To do this, you will need the following things. A solder sucker and solder wick, solder, thermal compound (fresh, computer stuff may not work) and a decent soldering station. Most soldering irons are not very good for PCB work and may have enough AC leakage current to damage what you are working on. You will need replacement parts and new mica insulators (preferred), or single use compressible types. You will also require a decent multimeter and a transistor tester that can measure leakage and beta (gain). You can build a jig for this also, there is information all over the place on this site. You really should have an oscilloscope and an audio oscillator. You can burn a CD and use that as an oscillator, a CD player output.
When you remove the damaged parts, clean all traces of material from the heat sink surface. This must be clean and flat. You will also be torquing the new parts to the proper clamping pressure. Do not over tighten these parts. Any burning on the PCB must be removed, it may become conductive. Scraping it away is fine. If you end up with a hole, mix up some epoxy and fill the hole before going further.
As ostripper mentioned, the On Semi NJW0281 and NJW0302 are fantastic devices. Highly recommended. You can buy everything you need from Digikey. Don't forget to measure the resistors in those areas. As a resistor fails, they generally will drop in value before climbing up and going open. You should lift one end of the part off the PCB to measure it to ensure an accurate reading. When you have got everything installed, it's time to inspect your work. Remove all flux from your work and watch for small short circuits and bad connections. Now comes the hard part. When powering up a new repair, there is nothing that says it won't go bang right away. Use a variable, bipolar DC power supply if you can get one. If not, i will generally short out the power relay and apply AC power through a "variac" while watching the current draw, bias current and DC offset. Just plugging it in and turning it on is not a good way to save money! Sometimes, having a light bulb in series with the test socket may save you from exploding parts, maybe not. Do not short the power relay unless you are in fact going to use a variac to slowly apply power to the unit.
I hope you find that helpful. I follow that procedure pretty closely myself. I didn't list the other equipment I commonly use, like a distortion analyzer for one. Please do keep your wits about you and work carefully. Take great care not to damage any PCB foil.
-Chris
hey, koo's..
you can upload here..
http://71.203.202.56/upload/~upload
real quick..
Or Email me to keep private ,attach
photo..
Duhhh , I have never "PM'ed" on this site..
you have no email button.
OS
you can upload here..
http://71.203.202.56/upload/~upload
real quick..
Or Email me to keep private ,attach
photo..
Duhhh , I have never "PM'ed" on this site..
you have no email button.
OS
some denon models also have a few surface mount diodes, usually 4 (2 signal diodes and 2 zeners) these should be replaced as well. the signal diodes can be leaky if not shorted, and the zeners can have a changed conduction voltage if they've been stressed. these diodes are supposed to limit the base bias on the drivers. some models have them as thru-hole devices. the light bulb trick works well as long as you select the correct wattage bulb for the idle wattage of the amp. my guess in your case would be a 150W bulb. i use 100W for 50W/ch surround receivers, 150 for between 50-100W/ch receivers, and 200W for larger receivers. with a properly operating denon receiver, the bulb will light brightly at first, and the power relay will cycle a few times and each time the bulb will light dimmer, until it's glowing a dull red-orange and the relay stays in. before attempting to test a repaired channel, turn the bias pot fully counterclockwise, which reminds me, check the bias pot, as denons occasionally burn them open. depending on the density of circuit boards in the receiver, you may want to make a "magic wand" to plug into the channel to monitor the idle current. you will notice that there are probably some 3 pin connectors in each channel near the bias pot. you will want a 3 pin connector that mates with these and a long skinny piece of circuit board to glue the connector to. the outside two pins are connected to the emitters of the output devices and read a voltage proportional to the current flowing through the transistors. you should read 2 to 10 millivolts across this connector with the amp idling and no signal or load. let the amp warm up for 5 minutes, and adjust the bias for 5mV across the test points. wait another 5 to 10 minutes and adjust for 8 to 10mV across the test points. do NOTt glue the pot in place, the glue can get into the contact surfaces and open the pot. let the amp idle for about 15 minutes and make sure the current remains stable. you should also test for DC offset on the output. it should be less than +/-50mV, much more than that and you may also have a bad cap in the feedback loop. after these tests are done, you can attach a load and apply signal.
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