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I Can't Find a 2SC945A - What To Do?

KingBubba

KingBubba

"Too Much Stuff"
I am presently repairing an Onkyo TX-4500MkII and between Mouser and Digikey, have been able to find the items I need except for a transistor labeled 2SC945A. On the schematic it is marked as Q507, for those of you who might have a SM for this item, PM me if you would like to look at the SM. This item is marked as "thermo", as opposed to "power amp", on the parts list. It was bridged from the PC board to the heat sink for the outputs with a metal bracket.

I wondered if this was part of a protection circuit that would be activated when the heat sink got to a certain temperature. When tested, the component showed no continuity between any of the contacts, completely open on all.

Is this component fried? or does it need higher temperatures to activate. Does anyone know anything about this item, its use in the circuit, if it is really shot, and most of all where can I find one if I really need it.

Also, in regard to this project I need to get a 2sc1625 o and a 2sa815 o. Mouser has these but there is no letter following the numbers. Is this letter of importance to me. Mouser's replacement was a TIP30C for the 2sa815 and TIP29C for the 2sc1625. Would anyone know if this is a correct replacement for these transistors?

Thanks for any help rendered.

Gary
 
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MCM Electronics lists the 2SC945 as in-stock $.08 each, NEC Brand.
http://www.mcminone.com/product.asp?product_id=2SC945&catalog_name=MCMProducts
This is an NPN transistor, and is probably part of the bias circuitry.

2SC1625 is out of stock, but they list 2SC2344 as a sub, $1.23, Sanyo Brand
http://www.mcminone.com/product.asp?product_id=2SC2344&catalog_name=MCMProducts
2SA815 is also out of stock, but they list 2SA1008 as a sub, $1.73, NEC Brand.
http://www.mcminone.com/product.asp?product_id=2SA1008&catalog_name=MCMProducts

The letter suffix on the part number generally refers to the beta, MCM doesn't indicate what suffix they are selling. This may or may not be an issue in your application, I suspect not.

Tom
 
2SC945
Vceo=60V
Ic=100mA
Pc=250mW
B=200
Ft=250MHz

Fairly generic. I can find no specs on an 'A' variant, but let's assume that the 'A' indicates a higher Vceo, as it usually does. The Panasonic 2SC1509 (80V) would work, as long as you can use a TO-92L package.

The letter after the part number (if something other than 'A', 'B', or 'C', which are used to indicate a higher-voltage part) is usually the gain grouping. Manufacturers specify the minimum gain group that will maintain rated specifications. If the seller does not indicate what you're getting, you simply have to hope that it'll do the job properly (and the odds are heavily weighed in your favor in this regard).

Edit: MCM sells a lot of cheap remarked Chinese parts that have little to no relation to the original Japanese part. I do not trust those guys. Digikey, Mouser, and B&D are three of the few that I do trust.
 
The NTE cross-reference site lists 20 varieties for your 2SC945A. Usually a PDF of the specs are available so you can make comparisons to the original device, if you have the data, or get an inkling if you do not.

You can always take that info and broaden the search, so to speak, to find other compatible crosses or at least understand a bit more of what function the device was expected to fulfill. Quite often, at least in non-critical audio applications, many different PNP or NPN types will often have enough gain, voltage and heat dissipation, not to mention similar packaging and pinout, to suit the circuit's requirements.

Man, it just about hurt my fingers to type that! Hope it made sense to you, my basic point is that most transistors can be used in pretty wide-ranging applications. They do not always need to be exact, as long as the intended replacement meets or exceeds the specs of the original. How else could RCA in the 1970's, for example, advertise that only a few thousand-odd replacements could be substituted for over 178,000 original devices?

http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/69d5aa3584d015ce85256e780056e56f?CreateDocument

-Ed
 
Thanks, I have been looking for a cross reference place and also had completely forgotten about MCM. As usual AK comes to the rescue and so quickly too. Was it NTE that was getting such a bad reputation for selling lousy product?
 
OK...one last time so you do not miss it...buy ORIGINAL parts, not cheap-ass Chinese remarks, which is what MCM will sell you.

Between the Pansonic parts at Digikey, the Fairchild parts at Mouser, and the Sanyo parts from B&D, you can have nearly all the small-signal transistors covered and not one will be a Chinese remark.
 
EchoWars said:
OK...one last time so you do not miss it...buy ORIGINAL parts, not cheap-ass Chinese remarks, which is what MCM will sell you.

Between the Pansonic parts at Digikey, the Fairchild parts at Mouser, and the Sanyo parts from B&D, you can have nearly all the small-signal transistors covered and not one will be a Chinese remark.
Click to expand...

Glenn,
Thanks for the info on MCM. I thought that if the part was marked Sanyo or NEC or some other reliable mfg, that they would be genuine. I know anything labeled 'MOSPEC' is junk.
Tom
 
The reason I asked the NTE question was because the 2SC1509 reference comes up as an NTE product at the mouser site. Echowars, you made no reference to a Fairchild part at Mouser in your first post, so when I looked 2SC1509 up on the mouser site and NTE came up, I was leery from what I have read from your posts in the past about NTE. I feel like I have been doing my best to absorb all information as it comes my way, but I am not a mind reader. I have never even heard of Fairchild before, so how would I know to look for it. I trying my very best here. Thanks.
 
...and I'll help when I can, but I can't really give classes through forum posts, and I've got my own fish to fry as well. Which is my way of saying that I want to help, but (1) there's 1,000,000 things you need to know and take for granted to do this, and (2) I can't always be there to hold anyone's hand. Some of this stuff ya'all just need to toss into Google and start reading links.

(FWIW, the 2SC1509 is a current part, and can only legally be made by Panasonic...but I'm sure the Chinese have a few million parts around with this number on it. The real thing is sold at Digikey. Mouser crosses you to an NTE85, since they don't sell Panasonic products.)

Fairchild has been around since the advent of the first transistors. Gordon Moore, who later went on to found Intel, started at Fairchild in the 50's, IIRC. Fairchild has a line of pseudo-Japanese transistors, the 'KS' line. Japanese transistors all start with a 2SA, 2SB, 2SC, or 2SD designation. Fairchild has copied a number of these devices, and 'renamed' them to KSA, KSB, KSC, and KSD. Very good transistors, and Mouser sells them.

I have no idea what Parts Express sells on any given day. I still buy a lot of parts from them, but NOT transistors. They burned me more than once with blatent counterfeit junk transistors, and some piss-poor Chinese remarks at other times. Why roll the dice when you can buy an authentic decent part made by Panasonic or Fairchild? Like I said, between Mouser, Digikey, and B&D, 98% of the semiconductors I need are a couple of mouse clicks away (but you WILL have to learn how to substitute one device for another by reading datasheets and specifications...I have yet to see a substitution/cross reference program on the net that was worth a damn).

Thanks to the Chinese, crap transistors are everywhere, and you really do have to be careful who you buy from...unless you just plain don't care. I'm just trying to give ya'all the benefit of the thousand or two dollars I've wasted buying crap that wasn't fit to line the bottom of a bird cage. You can heed this advice, or learn for yourself.
 
KingBubba said:
The reason I asked the NTE question was because the 2SC1509 reference comes up as an NTE product at the mouser site. Echowars, you made no reference to a Fairchild part at Mouser in your first post, so when I looked 2SC1509 up on the mouser site and NTE came up, I was leery from what I have read from your posts in the past about NTE. I feel like I have been doing my best to absorb all information as it comes my way, but I am not a mind reader. I have never even heard of Fairchild before, so how would I know to look for it. I trying my very best here. Thanks.
Click to expand...

The mouser cross reference isn't that great and it seems to lean towards nte, because nte provides so many matching numbers for it.

2sc945 to-92 eCb 50v .1a .25w 250mhz 50-600hfe

http://www.onsemi.com/PowerSolutions/home.do cross references 2sc945 (not 945a) to the bc182..

http://www.fairchildsemi.com/crossref/crossref.do using 2sc945 (NOT 945A)

will come up with 39 pages of cross references... BUT I have done my homework on this one before: ksc945 is the LAST one and BC182 is the first. The output SEEMS to be alphabetically weighted....

bc182 and ksc945(Fairchild) will get you lots of hits in mouser.

512-KSC945CGBU to-92 eCb 50v .15a .25w 180mhz 40-700hfe $0.05 ea
or
512-KSC945GBU to-92 ebc 50v .15a .25w 180mhz 40-700hfe $0.05 ea are the ones I use.....

the c means center collector eCb available on some of them, otherwise they are eBc lead arrangement....

the next letter (r, o, y, g or l) is the gain classification EchoWars refers to
r 40-80
o 70-140
y 120-240
g 200-400
l 350-700

in this case the L transistors with the absolute highest gain in ecb aren't as available, but you are welcome to look....

then the last two letters are -bu- or -ta-
bu is bulk
ta is "ammo pack" which is a cardboard strip with the transistors leads formed out a bit and then inserted into the cardboard strip. Sometimes the strip is all that's stocked, BUT it's not hard to get them out

I did want to find a CL ksc945CL** (ecb) and a ksc945L** (ebc) the highest gain available.
They have:
512-KSC945LBU (ebc)
but NO 945CL(ecb) high gain (512-KSC945CLTA) in stock right now


have fun........ now you begin to see the barest minimum we have to deal with behind the scenes..... before we fix or post

AND, THIS just gives me the datasheets to start comparing to each other for suitability... I DON'T TRUST CROSS REFERENCES (either)
 
To all of you who contribute to assisting and educating those of us without the complete picture, a huge thank you. I'll do my best to learn how to read a data sheet. I would be happy to not bother the likes of echowars and markthefixer and the many other people who are so busy and knowledgeable and helpful. I've seen the data sheets on Digikey and Mouser and elsewhere but barring starting at the top of a list of data sheets and reading through every one, is there a method to know where to start? That would be the biggest problem for us less knowledgeable individuals, what is the process of starting a search through thousands of data sheets? It is very daunting to open up the transistor section of the Mouser or Digikey catalog with no reasonable method of cross referencing.

If I have a transistor or other component that is obsolete, how do I get the data on it, in the first place, to use when checking other component data sheets? I would be thrilled to know how to compare data sheets, but it is the starting process that is the most difficult.

I promise to use search functions first before I ask any more questions. I'm doing my best to learn. Thanks again.
 
KingBubba said:
If I have a transistor or other component that is obsolete, how do I get the data on it, in the first place, to use when checking other component data sheets? I would be thrilled to know how to compare data sheets, but it is the starting process that is the most difficult.

I promise to use search functions first before I ask any more questions. I'm doing my best to learn. Thanks again.
Click to expand...

This very discussion happened recently with basicblues....

I start with google, usually ending up in datasheetarchive.com or datasheetcatalog.com and get the data and pick out as much of the relevent information as possible. Then I try the cross references I mentioned (onsemi & fairchild) to see what they recommend. datasheetarchive.com and datasheetcatalog.com also tend to have cross references or equivalents listed as well. Then you find THEM and start comparing and looking for something that you can actually BUY....

This is the thread:http://www.audiokarma.org/forums/showthread.php?t=142375&page=3
and while my substitutions for sx-1250 amplifier transistors starts at post #37, there is a very LONG analysis of HOW I got to the results on post #37, defending my choices. You will be most interested in the first post on page 4 (post #46) where I outlined the major characteristics of the transistors. The SAME ones EW mentions...

BUT it should take you SEVERAL days to digest that thread, it not only occurred over several days, but it also represents several full evenings of work for two people. There are links to MEGS of datasheets

in my last post I gave you a WEALTH of information to work with, but I guess I will have to spell it out:

These two lines:

2sc945 to-92 eCb 50v .1a .25w 250mhz 50-600hfe
512-KSC945CGBU to-92 eCb 50v .15a .25w 180mhz 40-700hfe $0.05 ea

specify the transistor case style to-92
the transistor lead layout ECB
the collector to emitter voltage 50v fifty volts
the maximum collector current .1a is 0.1 amperes
the power dissapation .25w is 0.25 watt
the unity gain frequency of 250mhz
the beta or gain or hfe 50-600hfe

the AK forum won't support extra spaces that would have made the columns stand out more clearly...
 
Thanks again to all. I am going to print this thread out and all the other info that has so kindly been provided to me and spend about a month reading and attempting to understand what I read. I hope at least some will sink in.

My goal, aside from repairing the Onkyo I now have on the bench and the others lined up behind it, is to be able to come on this forum and answer questions for some noob trying to fix some great old piece of equipment that deserves better than to be tossed in the dump or stripped of its parts and sold on The Site. Obviously my work is cut out for me. Thanks.
 
Sorry fellers, had no idea Parts Express was not that credible.
Bought some for a Luxman L-85V i'm working on and had no idea Parts Express MIGHT list them as an NEC part and not be sure they weren't genuine.
Once again sorry about that.
 
PE buys parts from distributors, not manufacturers. They have no clue of its pedigree, and likely care even less.

It's no crime not to know all this. Takes time and a lot of wasted dollars before you can learn who to trust and who to ignore.
 
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