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Pioneer SX-D7000 Stereo Receiver
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Author:  CrazzyAbtTubes [ 08 Jul 2009, 14:12 ]
Post subject:  Pioneer SX-D7000 Stereo Receiver

Not even a day ago, I was at a friends house, and her dad wanted to show me this stereo he found on the curb. It was in the garage, he hooked up speakers and we powered it up... all the lights came on but it was obviouse that something was horribly wrong. First of all two of the input switches were obviously not triggering properly (AM and AUX stayed pushed in and lit) and secondly I found there to be a strange heat and odour coming out of the chassis, no smoke just a smelly burnt odour. There was no audio ither, no his no noise, nothing at all.

So in the end I got a free-bee! yay another broken or partially broken stereo to add to the ever growing collection, and not only that but this one happens to be a golden boat ancor with one blown up channel!!! :bawling:

But wait.... this time is different, I have the full user manual and schematic! :sing: And unlike the LXI amplifier I can completely bipass the preamp stage until I fix the switches, too bad it wasn't just the switches.

I will post pictures of the redisection soon and the unfindable SCHEMATIC, but for now I am in the search of 2SA1076/2SC2526 substitute replacements here: http://www.diyaudio.com/forums/showthre ... adid=37265

Author:  roggom [ 08 Jul 2009, 16:14 ]
Post subject:  Re: Pioneer SX-D7000 Stereo Receiver

I always liked the blue displays on the older Pioneers. The 2SA1076 crossed over to an NTE93 PnP HiFi power Audio amp http://www.nteinc.com/specs/10to99/pdf/nte92.pdf The specs look very close to the specs in your other link. The second transistor did not cross but if they are complementary in the same circuit I am sure it is the NTE92. Just check the specs a little further.
Some of the older amps will have a pungent almost hot and sour smell if the owners smoked. 20~30 years of nicotine can rest in the circuitry and get rather funky.

Author:  CrazzyAbtTubes [ 08 Jul 2009, 16:29 ]
Post subject:  Re: Pioneer SX-D7000 Stereo Receiver

Thanks roggom, the NTE units actually have the same package as the originals, but how would they compare to some of the other subs like the ONsemi?

Author:  roggom [ 08 Jul 2009, 17:27 ]
Post subject:  Re: Pioneer SX-D7000 Stereo Receiver

Well, many techs/ repair guys scoff at the NTE because in many cases they are too generic. I have used them in Marantz rebuilds and have had great success. Just match the voltage, current and Hfe and then make sure to calibrate the idle current. I have not used onsemi so I can not compare. This is also a good opportunity for a recap project of the main amp board.

Rogers

Author:  CrazzyAbtTubes [ 08 Jul 2009, 21:41 ]
Post subject:  Re: Pioneer SX-D7000 Stereo Receiver

Well I guess I will go for it then, the store I order parts from sells me NTE products all the time, I just bought an LA4270 chip but is the NTE version. :up:

I will be replacing allot of numorus components on the main board, 3 very crispy resistors and two small TO-92 transistors I found missing their tops, and the drivers may be blown as well, so this could be a major rebuild, but one thing is for sure someone tried to fix other parts of the receiver as well because of some obvious not original parts in the tuner PS.

I have taken lots of pictures and have yet to draw up my version of the schematic, but thanks for the help. :up:

Author:  roggom [ 08 Jul 2009, 22:04 ]
Post subject:  Re: Pioneer SX-D7000 Stereo Receiver

Not sure if I have suggested this in past threads, but I really suggest making a "poor mans variac" this allows you to troubleshoot and if the short is still in the circuit the lamp will go on, instead of frying the output transistors. Variacs are good but some do not have current protection. You can make one with a power strip and a small desk lamp around 40watt bulb. Just put the lamp in series with the hot wire.

Hopefully you can find the root of the problem as those amps are really stylish.

Author:  CrazzyAbtTubes [ 09 Jul 2009, 18:26 ]
Post subject:  Re: Pioneer SX-D7000 Stereo Receiver

Actually, I have a pair of 12V 2-3A regulated power supplies that I could use to test the amplifier at a lower voltage where I can monitor for shorts and at least make sure that there is audio coming out. Because this is of much lower power I can easily use the light bulb technique to make sure that there are no shorts, and like I said, things don't seem to blaow up as fast. ;)

I guess all I have to really take into account is how to rebias the amplifier to work at this voltage, which gives me the idea that I could attempt class "A" bias, but there would be an insane amount of heat, and would definetly need larger PS. :down:

I am gathering a parts list so I am far away from testing this beast.

Author:  CrazzyAbtTubes [ 21 Jul 2009, 10:41 ]
Post subject:  Re: Pioneer SX-D7000 Stereo Receiver

I guess I have to put this project in a box for a while.... The matched NTE's are going to cost me 200 dollars!!!! :hot: :( :bawling:

Is this amplifier really worth the money? I really want to get it working but I have too many other projects to spend that kind of money, unless there are cheaper substitutes but those NTE's are beasts and I don't even know how blown up the main board is yet but was thinking that for now I could get cheaper outputs just to make sure the amplifier works, like cheap TIP36/35's, have piles of them.

I suppose I could just get four NTE's to get the blown up channel working since the transistors on the other channel don"t have shorts and test good on my anologue meter at 10-12 ohms? :confused:

Author:  roggom [ 21 Jul 2009, 12:17 ]
Post subject:  Re: Pioneer SX-D7000 Stereo Receiver

Looks like mouser has them for $40 http://www.mouser.com/Search/ProductDet ... L8CxfuM%3d, still, that is quite a bit of money for trannies. I would put a request on audio karma or something for a parts unit. If you are lucky you can find another with a working channel and more spare parts.

Rogers

Author:  CrazzyAbtTubes [ 21 Jul 2009, 22:10 ]
Post subject:  Re: Pioneer SX-D7000 Stereo Receiver

I guess that would be a good idea if I didn't all ready have enough broken equipment parts as it is, but I'm not out of ideas yet.

I think I may all ready know the answer to this question, but will ask it any ways, is it ok to mix different brands of transistors at the output? The store I went to had all whole lot of cross references to those NTE's, some were beefy Sankens and there were RCA and ONsemi I think, is it ok to use these others even if the NPN's and PNP's are different brands? :xfingers:

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