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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 8th Jan 2024, 10:17 am   #21
Julesomega
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Default Re: ECC81 with broken glass envelope meets 2 x LND150 transistors

Quote:
Originally Posted by dougietamson View Post
Here's the pinout:

Anode pins 1&6 = Source
Grid pins 2&7 = Gate
Cathode pins 3&8 = Drain
Thanks for the discussion: there was a lead time of many months for the LND150 transistors to arrive at the local RS, and then I started looking for the 'circuit', which is defined only as above, and would mean N-chan MOSFETs being reverse pol'd. Further, the photo of the device being tested seems to show the devices with the round side facing out through the envelope, and the pin connections are indiscernible.
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Old 11th Jan 2024, 1:42 pm   #22
dougietamson
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Default Re: ECC81 with broken glass envelope meets 2 x LND150 transistors

Quote:
Originally Posted by Julesomega View Post
Quote:
Originally Posted by dougietamson View Post
Here's the pinout:

Anode pins 1&6 = Source
Grid pins 2&7 = Gate
Cathode pins 3&8 = Drain
Thanks for the discussion: there was a lead time of many months for the LND150 transistors to arrive at the local RS, and then I started looking for the 'circuit', which is defined only as above, and would mean N-chan MOSFETs being reverse pol'd. Further, the photo of the device being tested seems to show the devices with the round side facing out through the envelope, and the pin connections are indiscernible.
I've just tried the LND150's in a PI slot of an amp with the flat side facing out.

It didn't work! - complete silence. I then tried them facing in and all is good, they survived the test and sounded good.

Doug.
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Old 11th Jan 2024, 3:12 pm   #23
Radio Wrangler
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Default Re: ECC81 with broken glass envelope meets 2 x LND150 transistors

If they are MOSFETs or DMOS, then there will be a back gate tied to probably the source pin. This will definitely make them asymmetric.

Some JFETs are symmetric and can be used either way. Some transceiver designs used this in bilateral amplifiers where by swapping the bias supply for the drain from one end to the other, the amplifier would reverse and amplify in the opposite direction!

David
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Old 11th Jan 2024, 5:00 pm   #24
Julesomega
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Default Re: ECC81 with broken glass envelope meets 2 x LND150 transistors

Thanks Doug - very interesting! They are indeed DMOS, and N-channel depletion mode, so Source to Cathode, Drain to Anode!
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Last edited by Julesomega; 11th Jan 2024 at 5:06 pm.
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