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Old 9th January 2013, 05:35 PM   #1
gmarsh is offline gmarsh  Canada
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Default Darlington output transistor hunting..

I've got a Sony tuner that a co-worker gave me to fix, which has a blown output channel. Devices are Sanken 2SD2439/2SB1588, and the amplifier runs from +-45V rails.

Unfortunately my usual electronics distributors (mouser, digikey, whatnot) don't stock Sanken, and I can't seem to find anyone else making an equivalent transistor - high Hfe and a >100V Vce seem to be mutually exclusive. There's a few dealers in the US that I can order from, but between shipping/customs it'll be $40-$50 by the time they reach my doorstep - which is past my co-worker's budget. And I fear ordering them off eBay.

TIP142/147 seems like a common choice, but I'd be running them close to their 100V Vce limit with +-45V rails - it won't take much of a power surge to take them out. I'm contemplating a "homemade darlington" approach, made with 4281/4302's from my junk box and a bodged on predriver, but I'd like to save that approach as a last resort.

Anyone have any part suggestions? Thanks!
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Old 9th January 2013, 05:58 PM   #2
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Might try looking for mj11015/16 pairs.
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Old 9th January 2013, 06:01 PM   #3
cihtog is offline cihtog  United States
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Old 9th January 2013, 06:09 PM   #4
Mooly is offline Mooly  United Kingdom
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Have a look at the BDTxxx devices that Philips used such as the BDT64C and 65C which are 120 volt rated.
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Old 9th January 2013, 06:44 PM   #5
gmarsh is offline gmarsh  Canada
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Quote:
Originally Posted by cihtog View Post
Awesome. Thanks!

Dismantling the amp now to see if anything else blew up, fingers crossed..
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Old 9th January 2013, 07:17 PM   #6
gmarsh is offline gmarsh  Canada
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And the rest of the amp is OK, which is the good news.

Unfortunately futurlec doesn't have the 2SB1588, or other PNP darlington that's really suitable. 1101x's are only available in a TO-3 metal can. The BDT64C/65C Hfe is a fair bit lower, and the second stage of this amp looks fairly wimpy so I'd like to keep the number up.

I contemplated ripping out the audio amps entirely and bolting a couple of chipamps to the heatsink, but the +-45V rails won't let that happen either...
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Old 9th January 2013, 09:01 PM   #7
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To keep within your requirements and budget, then making your own darlingtons seems to be the only viable route here. Digikey has the MJW3281AG/1302AG pairs available, pair them with the drivers of your choice with a 68 ohm resistor from base to emitter and there you go.
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Old 9th January 2013, 09:05 PM   #8
jaycee is offline jaycee  United Kingdom
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TIP142/147 will be vastly inferior and will probably just cause hassle as they are dreadfully slow in comparison to the 50MHz fT of the original Sankens

Unfortunately this sort of audio darlington is an area Sanken specialise in - there are not many alternatives.

Digikey do stock Sanken. It looks like 2SD2439/2SB1560 will drop in. You would need to use insulating washers compared to the originals though.
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Old 9th January 2013, 09:29 PM   #9
cihtog is offline cihtog  United States
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google turned up lots of leads for parts... just have to sift through the alibabas, and datasheet sites.

2SB1588

mcm list the one below as a sub

-180V -15A 85W Bce Sanken Transistor Fm100 | SANKEN | Distributed By MCM
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Old 9th January 2013, 10:11 PM   #10
jaycee is offline jaycee  United Kingdom
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And they would be completely wrong. 2SA1673 is not a Darlington. Furthermore, it is obsolete.

2SD2390/2SB1560 matches the specs of the 2SD2439/2SB1588 exactly - the only difference is the case type.
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