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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 17th Jul 2019, 11:56 pm   #1
Fokale
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Default 2n6027 as a replacement for BRY39 PUT

Hello everyone,
I am planning to replace a bry39 with a 2n6027 in a motor control circuit in an old pfaff sewing machine. The problem is, although people suggest using the 2n6027 as a substitude, the 2n6027 does not have a cathode gate. So 3 pins vs 4 pins on the bry39.
The circuit is in the attachment. Any ideas about how to implement the 2n6027 into the circuit will be highly appreciated. There is an old closed topic about bry39 and 2n6027 in the forum but unfortunately it did not quite help.
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Old 18th Jul 2019, 12:08 am   #2
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Default Re: 2n6027 as a replacement for BRY39 PUT

Hi there, by an odd chance one turned up the other day, you're welcome to it, save faffing about with a substitution.
Greg.
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Old 18th Jul 2019, 4:30 am   #3
Fokale
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Default Re: 2n6027 as a replacement for BRY39 PUT

Thanks a lot for your kind offer Greg, I wish I lived a little more nearby
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Old 18th Jul 2019, 6:22 am   #4
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Default Re: 2n6027 as a replacement for BRY39 PUT

How many BRY39's do you want, got bags of em, happy to post you a few if you pay postage.

Andy.
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Old 18th Jul 2019, 10:36 am   #5
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Default Re: 2n6027 as a replacement for BRY39 PUT

The 2N6027 has electrodes cathode, anode, and anode-gate. It may work in the circuit (you just wouldn't have the 750k resistor connected to anything).

I have found the BRY39 gives a bit of trouble working at frequencies of 20kHz, turn-off takes a few microseconds. I have used a resistor between cathode-gate and cathode to allow stored charge to be removed - (I also used the cathode-gate as an extra trigger input). It seems that the BRY39 in the circuit above triggers, puts a pulse into the transformer in the cathode circuit, and then turns off, so most of the time the 750k resistor is doing very little, but when the pulse is present the resistor actually takes the cathode-gate to a voltage more negative than cathode so raises the valley current of the BRY39 and prevents it staying 'on'.

However, DA's kind offer of some BRY39's probably makes this redundant!
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Old 18th Jul 2019, 4:52 pm   #6
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Default Re: 2n6027 as a replacement for BRY39 PUT

There you go then, two offers and some theory, can't be bad, i can certainly post one to you if you like.
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Old 18th Jul 2019, 5:40 pm   #7
Fokale
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Default Re: 2n6027 as a replacement for BRY39 PUT

Wow guys, I am above the clouds Thank you all for the practical and theoretical help. But I am afraid it does not worth the hassle of sending and receiving a parcel abroad. The motor control works fine at the moment, the part involving the bry39 probably controls the maximum rpm of the motor. Nothing vital.
I am planning to give 2n6027 a try. If it does not work, I will leave it as it is.
Thanks all for your help again.
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Old 18th Jul 2019, 7:07 pm   #8
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Default Re: 2n6027 as a replacement for BRY39 PUT

I don't know if it was ever exported to Turkey, but the power supply of a Philips K9 chassis colour TV should contain 1 or 2 pieces BRY39 in the control module (also a BR101, similar but not the same). A French Philips chassis from around the same time (1972-1976) uses that circuit, too.
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Old 18th Jul 2019, 11:07 pm   #9
Fokale
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Default Re: 2n6027 as a replacement for BRY39 PUT

Thanks for the info Marteen, I will keep that in mind
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Old 18th Jul 2019, 11:34 pm   #10
Fokale
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Default Re: 2n6027 as a replacement for BRY39 PUT

And a final note, I have just soldered a 2n6027 omitting the 710k resistor and everything works as intended now. I am able to adjust the maximum rpm via the N trimpot. Case closed, thank you all for your help again.
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Old 19th Jul 2019, 5:54 am   #11
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Default Re: 2n6027 as a replacement for BRY39 PUT

Glad you got it sorted, no worries.

Andy.
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Old 19th Jul 2019, 11:21 am   #12
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Default Re: 2n6027 as a replacement for BRY39 PUT

Super! Thanks for letting us know details of the closure!
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