[Heath] Heath SB200 Input

[Kenneth G. Gordon]

On 18 May 2011 at 10:00, JF wrote:

> Actually, the Harbach replacement PS board does fix that HV
> metering problem because it includes a new properly designed
> resistor string.

Oh. OK. Thanks, John, I was not aware of that.

BTW, it is not necessary to replace the SB-200's HV filter caps with the caps of 
the original value, 125 MFD. I used 470 mfd caps, and Rich Measures sells 560 
mfd caps for that purpose.

Modern caps are much smaller than the old ones, and have much less leakage, 
and the greater capacitance greatly improves dynamic regulation.

I used 105 degree C versions, which I bought off eBay.

I replaced mine when one finally shorted out and took out a couple of diodes. 
When I measured those remaining, all had deteriorated, and the maximum 
capacitance any showed was 75 mfd. Some were down to 30 mfd.

Although using some form of "soft start" is a good idea, with the Heathkit amps, it 
is not really necessary, since the power transformers in the SB-200 and SB-220 
were especially designed to limit inrush current to a safe value.

Ken Gordon W7EKB