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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 25th Feb 2021, 8:36 pm   #1
G6Tanuki
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Default Transistors from old CFL bulbs.

I was having a chucking-out and came across a box of old CFL bulbs - still working but long since replaced with LEDs.

I cut some of them open to see what was in the electronic ballast; the answer being a bunch of diodes, a small 400V-rated electrolytic capacitor, some other 1Kv-ated capacitors, a coil or two - and - in one - a couple of decently-beefy TO220 transistors.

These are marked E13005 - the closest to this I've tracked down is MJE13005 - which are rated for a collector-emitter voltage of 400V, DC collector-current of 4A, Ft of 4MHz. 75W collector dissipation [with suitable heatsinking of course]

Only downer is that Hfe is listed as being between 8 and 40 - so hardly spectacular!

Any suggestions as to use? I was initially thinking of trying to build a transformer-coupled amplifier [imagine the classic two-OC81-in-push-pull revisioned using a valve push-pull output transistor and 250V HT] but the low Hfe makes me think this would be a fool's errand.

I might just see if I can use them in a "solid-state vibrator replacement" Royer-type oscillator for one of my R209 receivers.
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Old 25th Feb 2021, 9:41 pm   #2
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Default Re: Transistors from old CFL bulbs.

High voltage transistors frequently have low Hfe. In the case of BU208 I seem to remember could be as low as 2. CFLs frequently have high voltage TO92 devices, sometimes TO126; I have yet to find TO220s
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Old 25th Feb 2021, 11:32 pm   #3
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Default Re: Transistors from old CFL bulbs.

They are Fairchild KSE13005 devices.

Similar specs to the MJE13005's.
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Old 25th Feb 2021, 11:55 pm   #4
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Default Re: Transistors from old CFL bulbs.

Quote:
Originally Posted by G6Tanuki View Post
I was having a chucking-out and came across a box of old CFL bulbs - still working but long since replaced with LEDs. ...
Any suggestions as to use?
Landfill ?
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Old 25th Feb 2021, 11:57 pm   #5
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Default Re: Transistors from old CFL bulbs.

Those CFLs started off with BJTs but soon moved over to MOSFETs. A wonderful source of interesting parts, but after you've struggled to strip one or two you come to realise that life's too short
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Old 26th Feb 2021, 8:04 am   #6
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Default Re: Transistors from old CFL bulbs.

I'd still use the bulbs, still way better than an incandescent, if not those tranny's would make a reasonable HV CCS or could be connected with an MPS42 as a Darlington pair for extra hfe.That said I thought if used as an OP device hfe isn't that important, the voltage amplification done previously the OP device just used to shift current.

Andy.
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Old 26th Feb 2021, 8:41 am   #7
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Default Re: Transistors from old CFL bulbs.

There's an interesting article in Sprat (G-QRP), issue 138, Spring 2009 - Das DereLicht - A CW transmitter made from a light bulb. You need a crystal and a few components for the output LPF and the others come from the bulb. He found a BUL128B transistor in the bulb. The transmitter produces up to 1.5w on 80m. Neat!

Best wishes

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Old 26th Feb 2021, 7:55 pm   #8
G6Tanuki
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Default Re: Transistors from old CFL bulbs.

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Landfill ?
That's my conclusion too: they're truly poverty-spec transistors not worth trying to do anything serious with.

Transistors, and the bucketfull of disassembled CFLs, will duly be consigned to a tip somewhere in Westbury.
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Old 26th Feb 2021, 8:52 pm   #9
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Default Re: Transistors from old CFL bulbs.

Quote:
Originally Posted by Julesomega View Post
but after you've struggled to strip one or two you come to realise that life's too short
That was kinda my conclusion too after eviscerating a few integrated examples and, bearing in mind that there was always strong competition to make the most unobtrusive and svelte (well-crammed) fitting on the market, the electronics bit will inevitably be well fried and weary after a few thousand hours service (especially relevant with capacitors). That crammedness also means minimal length components, adding to the un-usefulness. At the end of the day, there's nothing inside that couldn't be purchased new for not much- an HV electrolytic of a few uF and the afore-mentioned HV transistors. If nothing else, the part numbers of the latter give an example of something to search in future!

An insight into an application of an HF version of the Baxandall-modified Royer oscillator, though, so sort of educational.

The one time I bothered with component reclamation was on finding a few hundred NOS installation-type CFL drivers in a skip on an industrial estate, things about the size of two fag-packets with a screw-hole at each corner and a choc-strip along one edge- each had a RIFA 6.8uF 450V 125 degree axial elko with long leads, these were harvested and feature in various things here. Even so, I doubt they'd be more than about a quid each. (They also featured a pair of the afore-mentioned E13005 devices, presumably made by the gazillion for this market).
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Old 27th Feb 2021, 2:33 pm   #10
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Default Re: Transistors from old CFL bulbs.

Some time ago I was given a non-working service type SA, a Cushman CE-15.
https://www.radiomuseum.org/r/cushma...tor_ce_15.html
One of the horizontal amp's final transistors was faulty.
A transistor salvaged from a faulty CFL-light was a good match for the other transistor.
If I remember correctly the beta was around 30 or so.
It is still working fine.

Peter
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Old 27th Feb 2021, 3:02 pm   #11
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Default Re: Transistors from old CFL bulbs.

Quote:
Originally Posted by turretslug View Post
The one time I bothered with component reclamation was on finding a few hundred NOS installation-type CFL drivers in a skip on an industrial estate, things about the size of two fag-packets with a screw-hole at each corner and a choc-strip along one edge- each had a RIFA 6.8uF 450V 125 degree axial elko with long leads, these were harvested and feature in various things here. Even so, I doubt they'd be more than about a quid each. (They also featured a pair of the afore-mentioned E13005 devices, presumably made by the gazillion for this market).
Those RIFA (now Kemet) axial capacitors are excellent quality and quite expensive, I can't find a 125C but the 105C at 6.8uF 450V is 2.10 each in quantities of 1000, lower quantities if I could find them would be much higher priced.

David
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Old 27th Feb 2021, 8:05 pm   #12
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Default Re: Transistors from old CFL bulbs.

Maybe I should have stuffed the lot in the boot- with hindsight, it's the sort of thing I would have done if only to pass on the bulk of such good caps to others as a favour. I didn't have the brass neck to take more than about a dozen- it's the "funny looks" thing! You're right, the higher voltage PEG124s are only rated to 105 degrees, rather than the 125 degrees of the lower voltage series,

Colin
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