DHT Heater using VCCS - PCB or Kit (Possible Group buy)

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RhythMick
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Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by RhythMick » Sun Mar 08, 2020 7:25 pm

I can also highly recommend Andrews boards. I run the standard boards (as opposed to the large) with 300B no issue. Make sure you size the transformer with plenty to spare - I had a buzz which eventually tracked back to toroidal overload.

jc123
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Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by jc123 » Mon Mar 09, 2020 3:50 am

Thanks RhythMick, what is the least voltage input for normal operation on Andrews board for 300B ?

RhythMick
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Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by RhythMick » Mon Mar 09, 2020 7:08 am

Allow 4v for regulation. So for a 300B

(5v + 4v) is 9v peak, over 1.414 is 6.36v RMS

6.3v tx should be ok. 6v might be if your primary is 5% high. I went for a dual 7v toroidal with 4.4A secondaries to give plenty of headroom.

I also used the 63mm heatsinks for the 300B. These are onboard the smaller boards. I'm not using any forced air circulation and I regularly measure the temperature of both the heatsink and the transistor casings, usually about 60 degrees.

jc123
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Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by jc123 » Mon Mar 09, 2020 3:15 pm

RhythMick wrote:
Mon Mar 09, 2020 7:08 am
Allow 4v for regulation. So for a 300B

(5v + 4v) is 9v peak, over 1.414 is 6.36v RMS

6.3v tx should be ok. 6v might be if your primary is 5% high. I went for a dual 7v toroidal with 4.4A secondaries to give plenty of headroom.

I also used the 63mm heatsinks for the 300B. These are onboard the smaller boards. I'm not using any forced air circulation and I regularly measure the temperature of both the heatsink and the transistor casings, usually about 60 degrees.
Thanks !

Andrew
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Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by Andrew » Wed Mar 25, 2020 9:36 am

Got more PCB on the way, had run out.
Analogue, the lost world that lies between 0 and 1.

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