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'[OT]: Transistor identification'
2001\03\09@091530 by William Bross

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I have recently acquired a large pile of compact fluorescent lightbulbs
that died -- all with less than 10 hours on them.  I have found the bad
part but cannot identify it.  It appears to be a NPN in a TO220 package
marked   'DK55'.

I did a fairly thorough web search but came up totally blank.  Any ideas?

Thanks,
Bill





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2001\03\09@095504 by Roman Black

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William Bross wrote:
>
> I have recently acquired a large pile of compact fluorescent lightbulbs
> that died -- all with less than 10 hours on them.  I have found the bad
> part but cannot identify it.  It appears to be a NPN in a TO220 package
> marked   'DK55'.
>
> I did a fairly thorough web search but came up totally blank.  Any ideas?


It's not a 2SK55, wrong package.
How do you know if it's an NPN when it
is blown? Surely they blow short circuit?

Years ago I built some kit fluoro electronic
starters that used a TO220 pack SCR as the
main semi. ??
Good luck. :o)
-Roman

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2001\03\09@102453 by William Bross

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Well, there are two in each bulb -- one blown and one good -- always the
same ones.  The good ones certainly look like an NPN on the ohm meter.
But, I could be wrong. I don't regularly play with SCRs and triacs.
Tonight I'll trace out the circuit just for fun and see if I can calculate
a suitable substitute if I don't get any hits.
Thanks,
Bill

At 01:55 AM 03/10/2001 +1100, you wrote:
{Quote hidden}

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2001\03\09@104953 by Alan B. Pearce

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>> I have recently acquired a large pile of compact fluorescent lightbulbs
>> that died -- all with less than 10 hours on them.  I have found the bad
>> part but cannot identify it.  It appears to be a NPN in a TO220 package
>> marked   'DK55'.

at one stage companies like RCA and I think Motorola made TO220 devices in both
PNP and NPN types with part numbers along this style. I cannot remember the
exact families of devices though, and the ones I do vaguely remember would not
have had voltage ratings suitable for mains use.

Do also check to see if there is a small fusible resistor in the supply line. I
heard a not so funny story about a chicken house on a farm that went dark after
a opossum climbed a power pole and bridged the 400V distribution line onto a
230V line at a step down transformer causing all the bulbs in the chicken shed
to fuse this resistor. The guy that told me the story said they just replaced
all the resistors and the bulbs were then OK.

From the brief description you have given it sounds like a totem pole transistor
arrangement used with a centre tap capacitor arrangement so by swapping one
jumper it can be run as 230 or 115 volt.

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2001\03\09@114709 by Chris Carr

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Are there any other active devices such as an IC ?
That might help identify the circuit which in turn would help identify
the transistors.

Regards
Chris

{Original Message removed}

2001\03\10@005146 by Roman Black

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William Bross wrote:
>
> Well, there are two in each bulb -- one blown and one good -- always the
> same ones.  The good ones certainly look like an NPN on the ohm meter.
> But, I could be wrong. I don't regularly play with SCRs and triacs.
> Tonight I'll trace out the circuit just for fun and see if I can calculate
> a suitable substitute if I don't get any hits.
> Thanks,
> Bill

Bill, try a 2SC2335, these are a good rugged
high volt transistor in TO220. We use them
a lot in TVs if we can't get the exact spec part,
as the 2SC2335 has better specs than most parts
in that package. They are common and cheap,
<$2 US.
-Roman

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