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Old 19th May 2010, 10:47 AM   #1
bobcat is offline bobcat  United Kingdom
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Default Transistor substitutes

Hi all i have managed to locate a schematic for my stageline sta 750 from this forum & thanks,
but iam unable to locate some of the transistors from my usual suppliers
so was hoping that some kind person out there
could help with some substitutes
they are
2sd667
2sb647
2sc1815
2sa1837
2sc4793
2sd669a
all assistance is greatly appreciated
also can someone suggest a good semiconductor equivalent book available in the uk.
regards Bobcat
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Old 19th May 2010, 12:26 PM   #2
Mooly is offline Mooly  United Kingdom
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Well this is good for most data sheets,
Datasheet catalog for integrated circuits, diodes, triacs, and other semiconductors, view

As to books... T.D. Towers was the one to have.
Amazon.co.uk: towers transistor selector
don't know the last edition though and the web has kind of made all these obsolete.

2sd667/2sb647 are complementary pair... can't think of anything common in that package as equivalents, you will have to search the catalogues. MJE340/350 are a common choice TO126 package but only 0.5 amp rating... is it enough for your application ?

2SC1815 is general purpose... they are in everything and should be easily available, BC546 is fine, as is 2N5551 etc, but the pinouts are different. Anything will work for these as long as it's rated similarly.

2SA1837/2SC4793 are another complementary pair... high voltage TO220 package. Can't think of anything similar off hand.

2SD669... again is 0.5 amp enough... MJE 340 again.

I'll have a think
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Old 19th May 2010, 03:24 PM   #3
AndrewT is online now AndrewT  Scotland
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2sd669ac is a 1.5A device with hFE>100 @ Ic=150mA and 20W <=40Vce

You will struggle to source an equivalent. Which parameters are absolutely necessary and which can be relaxed?
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Old 28th October 2016, 12:23 PM   #4
OXAUDIO is offline OXAUDIO  United Kingdom
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The 2SD667/2SB647 are used in supply voltage regulator circuits in the Harman-Kardon HK1400 (and possibly HK1200 HiFi Amplifiers, where they are used to provide stabilised +20.5 &-20.5 v. rails for the preamplifier circuits. A quite conventional Transistor assisted zener circuit is used for this purpose, which is supplied with + & -40v from bridge rectifier D20. I need to source a 2SD667 (& possibly 2SB647) or eqivalents for this circuit, and would guess that transistors rated at 30-40v(Vce) and ca 0.5A Max would be more than adequate. If they were in TO-92MOD packages fitting them would be easier, though an alternative package type could be used. Does anyone have any suggestions as to either a source from which to buy the original types, or suitable alternative types. I have a load of transistors of various types, mainly European BCxxx devices, so maybe I can find suitable ones in my parts 'stock'. Is it advisable to replace both transistors with a closely matched pair? The 2SB647 checks out OK, but the 2SD667 is seriously leaky between all 3 terminals, though I've no idea what caused it to fail.
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Old 28th October 2016, 08:03 PM   #5
Mooly is offline Mooly  United Kingdom
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I'm assuming no heatsinks are used. If so then BD139/140 should be suitable. Pretty much anything will be OK for duty such as this as long as its rated accordingly. Even TIP41/42 as long as there is room and all these will have much increased reliability being larger and able to dissipate the heat better.

I wouldn't give it a second thought, just replace them. No matching or anything like that is required.
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Old 28th October 2016, 09:21 PM   #6
OXAUDIO is offline OXAUDIO  United Kingdom
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I did think of using something like TIP31/32, Mooly, although the originals are TO-92MOD rather than TIP case style. Earlier today I fitted a MPSA42 to replace the failed 2SD667, with a temporary 33 ohm resistor in series with the collector, pending getting some 22ohm fusible types. I was getting 36v at the collector of the replacement transistor, but 0v at both the base and emitter. The associated zener diode checks out OK, but I haven't yet checked other peripheral components.
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Old 29th October 2016, 06:06 AM   #7
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The obsolete Hitachi types (2SD667,9 etc.) are all presently common Ebay copy types and I think it would be best to begin there, oddly enough. I've had good results over several 100 ea. lots so far with those copies.

2SC1815 could be any low noise, small signal NPN. KSC1845 is an improved high voltage type or perhaps BC550 or any of its many similar low noise BC types will replace it, allowing for the different pinouts of euro BC types and checking Vceo rating is adequate. The Toshiba drivers you can get as Unisonic copies from Profusion PLC. You won't find all those types or close substitutes in one big traditional suppliers catalogue though.
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Last edited by Ian Finch; 29th October 2016 at 06:21 AM.
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Old 29th October 2016, 08:18 AM   #8
OXAUDIO is offline OXAUDIO  United Kingdom
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Most of your reply, Ian, relates to the original post, rather than to my comments/questions concerning the HK1400, in whick, AFAIK at this stage, all the preamplifier devices downstream of the voltage regulator circuits are OK, but I may look on eBay to see if clones of the2SD667 & 2SB647 are avaliable, although I can see no reason why an MPSA42 could not be used as the series pass transistor in this case.
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Old 29th October 2016, 08:21 AM   #9
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by OXAUDIO View Post
I did think of using something like TIP31/32, Mooly, although the originals are TO-92MOD rather than TIP case style. Earlier today I fitted a MPSA42 to replace the failed 2SD667, with a temporary 33 ohm resistor in series with the collector, pending getting some 22ohm fusible types. I was getting 36v at the collector of the replacement transistor, but 0v at both the base and emitter. The associated zener diode checks out OK, but I haven't yet checked other peripheral components.
It would help to see the circuit but having zero volts on the base suggests a basic problem somewhere. 36V on the collector suggests no current is being drawn from the supply. So where has the base voltage gone ?
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Old 29th October 2016, 09:05 AM   #10
OXAUDIO is offline OXAUDIO  United Kingdom
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The circuits of both the positive and negative voltage regulators are standard series pass transistor assisted zener types, Mooly. I have the diagrams, which came from HiFi Engine, so I'm not sure that I should scan them & post them on here.
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