Hiwatt custom tranformer 70v bias question

Brianvcskin

Member
2016-03-12 12:16 pm
Bias voltage mod

Am building a hiwatt DR103 clone 90% complete but am looking getting a transformer built with 70v bias tap. Stock is 50v but hiwatt always run hot(not enough bias voltage) wondering if this would work. And what I should change the bias resistors to. Here is the bias circuit I'm looking at using for a basis the Dr103 with one pot. Thanks people hope you can help.:)
 

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Brianvcskin

Member
2016-03-12 12:16 pm
Bias voltage mod hiwatt

Am 90% complete with my hiwatt DR103 (4xel34) clone but want to do improve the anemic bias circuit. Haven't purchased a PT yet but am looking at betting a custom toroidal build with a 70v bias tap as the stock 50v is not enough they run hot usually around 38v. There is a mid circuit with one pot I was going to use. Need to know if a 70v tap will work if so what value should my resistors be. Thanks in advance.
 

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Brianvcskin

Member
2016-03-12 12:16 pm
Am 90% complete with my hiwatt DR103 (4xel34) clone but want to do improve the anemic bias circuit. Haven't purchased a PT yet but am looking at betting a custom toroidal build with a 70v bias tap as the stock 50v is not enough they run hot usually around 38v. There is a mid circuit with one pot I was going to use. Need to know if a 70v tap will work if so what value should my resistors be. Thanks in advance.
 

Brianvcskin

Member
2016-03-12 12:16 pm
The current of a bias ciruit is very low. Therefore simple voltage doubler works fine with original power transformer.
You do not need to have a custom transformer just for bias.

voldoub.gif

For the cost of shipping a mercury magnetics(120v primary only I believe) or Hammond or partridge clone I can have a toroidal built to my spec cheaper . This is why I was looking at this route . Or should I just get one built with 50v and use the doubler circuit?