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Old 25th September 2005, 11:36 AM   #1
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Default Totally Unfamiliar Transistor Numbers...???

Got a Sansui AU-999, and one of the driver boards has an intermittent problem that may be a flaky transistor. Unfortunately, these transistor part numbers are totally whacked!!

XA495?
CDC8002-1?
9002-1?

What in the world?? Are these Germanium?

They are certainly bizarre-looking....little white 'flying saucers' with black tops.

These numbers ring a bell with anyone?
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Old 25th September 2005, 11:46 AM   #2
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Found this link

http://www.ecadata.de/suchneu/such.php?ECA_KEY=CDC8002

If you register there seems to be datasheets for it also
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Old 25th September 2005, 01:10 PM   #3
ilimzn is offline ilimzn  Croatia
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CDC8002/9002 are complementary pairs similar to 2N4033 and complement which at the moment escapes me. You couldeasily replace them with anything of the general sort (80V / 1A).
XA495 you could replace with whatever favorite front end transistor you use

If your intermittent problem is occasional sudden DC spike resulting in blown fuses, you may save yourself a complete change of components (which is what I did on a 999 that had this problem before figuring it out), and use a good PCB cleaner and thouroughly clean all the PCBs! Believe it or not, that was the root cause - apparently the flux used seems to be the predecessor of the infamous Sansui glue
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Old 25th September 2005, 09:36 PM   #4
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No blown fuses...what happens is that I get a gentle 'thump' through one of the channels...yes, you could call it a DC spike, but is it a gentle one. The driver boards are easily swapped from L to R and the 'thump' follows the board.

So...there is nothing really too oddball about these transistors except the looks of them?
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Old 26th September 2005, 12:32 AM   #5
anatech is offline anatech  Canada
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Hi Glenn,
Did you check the polarity? It sounds like unequal cap charging on the front end supplies. Could be your error amp is slow coming up on one side too.

-Chris
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Old 26th September 2005, 07:39 AM   #6
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Well, I went on a hunch, and replaced TR807. Haven't heard anything wierd from the amp since.
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Old 26th September 2005, 11:45 AM   #7
ilimzn is offline ilimzn  Croatia
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Quote:
Originally posted by EchoWars
So...there is nothing really too oddball about these transistors except the looks of them?
Exactly, and in fact, the oddball looks are the first iteration of non-metalic packaging. The package is a sort of ceramic base, plastic cover version of the TO style metal can. Even the pinout is the same. The smaller version as used on the input transistors is the predecessor of the TO92 case.

The 999 power amp is a bit of an odd-ball. On one hand it is quite advanced for the times, on the other it has a curious omission - resistor terminated VAS (from a separate higher voltage rail, this is similar to Mac amps). As a result it actually has a rather low open loop gain.

BTW you should think about replacing both transistors in the differential VAS... not overly important even though it is likely your replacement has higehr gain, there is considerable emitter degeneration... it's just... well, for me it would be like a persistant itch ;-)
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Old 26th September 2005, 01:41 PM   #8
anatech is offline anatech  Canada
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Good call. Now, if it stays fixed ....

I agree with ilimzn, change the others before they get you.

-Chris
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Old 26th September 2005, 08:54 PM   #9
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Both VAS have been replaced. The first was simply to get it working properly.

I used Zetex ZTX694B's for replacements. Amps sounds very good.

One thing is odd...amp is rated at 50WPC, and that is nearly exactly where it begins to clip...0db of headroom.
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Old 26th September 2005, 09:02 PM   #10
anatech is offline anatech  Canada
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Try measuring with a pulsed waveform. With a constant signal the supply will be loaded down.
Still close.

-Chris
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