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Old 3rd February 2004, 05:43 AM   #1
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Default Denon Transistors

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
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Old 3rd February 2004, 06:14 AM   #2
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If you google 2SA1491 and 2SC3855 you find several sources for them.

Jan Didden
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Old 22nd March 2009, 10:18 PM   #3
koocuz is offline koocuz  United States
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Default 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
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Old 22nd March 2009, 10:26 PM   #4
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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.
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Old 22nd March 2009, 11:27 PM   #5
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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:
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File Type: jpg tn2sa1491-sanken.jpg (3.1 KB, 371 views)
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Old 22nd March 2009, 11:41 PM   #6
anatech is offline anatech  Canada
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Hi Eric,
Quote:
If I disconnect the blown transistors, should it power up? with one less channel?
Probably not a good idea. There may (very probably) be other parts blown also.

Quote:
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.
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
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Old 23rd March 2009, 12:39 AM   #7
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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....
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Old 23rd March 2009, 02:48 AM   #8
anatech is offline anatech  Canada
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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
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Old 23rd March 2009, 04:56 AM   #9
taj is offline taj
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So, what you're saying Chris, is if the Check Engine light is on in your 2009 Ferrari, your successful experience with a tuneup of that 1973 Briggs and Stratton lawn mower engine just ain't gonna cut it, right?

..Todd
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Old 23rd March 2009, 05:48 AM   #10
koocuz is offline koocuz  United States
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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!
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