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I am trying to build a simple LED flasher circuit with a PUT 2N6027.

I have a bunch of transistors and some are marked 2N6027 110, and some are marked 2N6027 B09.

When I use the B09s, I have no problem and the circuit works perfectly. When I plug in any of my 110s, I get no flash at all.

Are there 2N6027 variants?

If 110 is a batch/date number, and they are all bad transistors I won't be happy since 90% of what I have are 110s.

These people have the same problem (but different numbers).

I suspect this guy has a similar problem as well.

UPDATE:

I tried replacing R2 with a 4.7k resistor and R3 with a 10k resistor. Same result. With my multimeter I see 6.18v on the gate, and the full 9v on the anode (since there is no voltage drop over R1). Isn't this exactly the condition under which the LED path should become closed? I am starting to think I just have 18 bad transistors and 2 good ones.

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This happened to me also. I had the Make:Electronics kit bought from Makershed and the 2N6027's labelled 110 were faulty. I replaced them with components from Mouser and the experiments worked fine. I think they had a bad batch in the kits.

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I know I'm a bit late to the party, but I just wanted to share an experience I had with some cheap 2N6027's I got off eBay recently. I was also using them for an LED flasher, and could not make it work no matter how I tweaked the circuit. After a bit of testing I discovered that the devices were actually low voltage thyristors, and not PUT's. I suspect they were mislabeled at the factory and somehow ended up on the market - which is probably what you should expect when buying cheap ($1.13 for 10pcs and free shipping) unbranded stuff from Hong Kong.

@user64540: Interestingly enough, the ones I got were also marked 413.

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Looks like kind of a marginal circuit to me (typical of the sort of crud one finds deposited on the internet, I'm afraid).

Try changing R2/R3 to 5.1K/11K (basically, halve the value of each).

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  • \$\begingroup\$ Updated my question with more info. I tried halving the resistor values, and see the exact same problem (B09s work, 110s don't). Any other ideas? \$\endgroup\$
    – dbyrne
    Commented Jan 8, 2015 at 0:22
  • \$\begingroup\$ Not really. Maybe try probing on diode setting with a multimeter and see if the pin outs look the same-- pretty long shot, though. Are they eBay or other dubious source? We probably used tens of thousands of these things back in the day. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Jan 8, 2015 at 1:14
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    \$\begingroup\$ Yes, they are from a dubious source (AliExpress). They were super cheap, so even though I only got two working ones it is not a big financial loss compared to if I had sourced them from Digikey or Mouser. Its just a pain since I'll need to reorder more. \$\endgroup\$
    – dbyrne
    Commented Jan 8, 2015 at 1:24
  • \$\begingroup\$ Same thing here. 110's don't work for the flasher circuit. ( got 10 for 2.80 euro from ebay ) Went to the store and bought a 413. ( 1 for 1,60 euro) The 413 Worked fine. \$\endgroup\$
    – user64540
    Commented Jan 16, 2015 at 18:25
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    \$\begingroup\$ And that is why you don't buy electronic components from eBay... \$\endgroup\$
    – Matt Young
    Commented Jan 16, 2015 at 19:22

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