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.

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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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pre65
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Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by pre65 » Wed Apr 22, 2020 10:09 am

Andrew, did you ever get the higher power versions up and running ?

10V @ 10A would be nice. :)
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Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by Andrew » Wed Apr 22, 2020 12:32 pm

Not yet, I never got a round tuit, sorry.

It's on my list, but life keeps getting in the way.
Analogue, the lost world that lies between 0 and 1.

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

Post by pre65 » Wed Apr 22, 2020 12:40 pm

Andrew wrote:
Wed Apr 22, 2020 12:32 pm
Not yet, I never got a round tuit, sorry.

It's on my list, but life keeps getting in the way.
Que Sera, Sera. :)
Life is what happens to you while you're busy making other plans. John Lennon

G-Popz THE easy listening connoisseur. (Philip)

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

Post by simon » Wed Apr 22, 2020 2:11 pm

You got Doris Day's Greatest Hits too G-Popz? :-D

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pre65
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Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by pre65 » Wed Apr 22, 2020 2:30 pm

simon wrote:
Wed Apr 22, 2020 2:11 pm
You got Doris Day's Greatest Hits too G-Popz? :-D
Perhaps, perhaps, perhaps Simon, who wouldn't ? :)
Life is what happens to you while you're busy making other plans. John Lennon

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

Post by simon » Wed Apr 22, 2020 4:03 pm

I'll take that as a rhetorical question :-)

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pre65
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Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by pre65 » Wed Apr 22, 2020 4:46 pm

simon wrote:
Wed Apr 22, 2020 4:03 pm
I'll take that as a rhetorical question :-)
Whatever. (will be, will be) :lol:
Life is what happens to you while you're busy making other plans. John Lennon

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pre65
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Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by pre65 » Sat May 16, 2020 10:46 pm

Another question for Andrew.

I've no experience of your small boards, but I'm thinking of filament bias on a 12A (112A) which would require 256.2 mA @ 14v. Will they cope with this ?

If so, when will you have kits available ?
Life is what happens to you while you're busy making other plans. John Lennon

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

Post by Nick » Sun May 17, 2020 11:18 am

Or 0.25A as the rest of the world would describe it. Some may argue you would need to adjust the current until you get 5v across the filament.
Resistance isn't futile it's V / I.

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pre65
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Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by pre65 » Sun May 17, 2020 11:47 am

Nick wrote:
Sun May 17, 2020 11:18 am
Or 0.25A as the rest of the world would describe it. Some may argue you would need to adjust the current until you get 5v across the filament.


I don't think I've done filament bias before so I'd been looking at how Rod Coleman did things. I printed off his fact sheet so I can understand the details. What you say about the filament voltage sounds right, although I have read that slightly starving filaments may be an improvement.

My plan, if this idea comes to fruition, was to test things out with a 20R resistor in lieu of the filament to see how close to 5V it gets.

Rod recommends a 20-23v transformer to power his modules and I have a pair of 22v toroids.


*
Life is what happens to you while you're busy making other plans. John Lennon

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