HP-23 upgrade

[Kenneth G. Gordon]

On 29 Jan 2009 at 18:08, Dick KF4NS wrote:

> I have the article by Mike Bryce WB8VGE which was in OCT '03 QST

I'll have to dig that out.

> (parts ID same as original schematic)
> I already have four new Xicon 100uf 450V caps so will use them for
> C1-C2 in HV ckt unless a higher value is a better idea.

I used 470 uf at 450 vdc 105 degree C caps in my two HP-23(*) supplies. 
I did this in the interests of better dynamic regulation after reading an 
article from a GE Ham News. I have had no problems with the higher 
capacitance. 

The originals were 125 uf at 450 vdc. When I checked mine, most had 
deteriorated to around 75 uf.

> Why the
> position swap of C5/R5 and increasing C5 to 220uf in the LV circuit?

I'll have to look at the article to answer that.

> Do I really need to change C3-C4 to 220uf?

Again, I'll have to look at the article.

> As far the bleeder
> resistors go, what is the reason for reducing bleeder current?

Because the newer caps have significantly less leakage current, and 
don't need the lower resistance for equalization purposes. AND that 
reduces the heat in the power supply by quite a bit.

> All
> diodes will be changed to 1N4007's. C6-C7 will be same value; new
> 20mfd 150V Sprague ATOMs.
> 
> I will test all the resistors but wonder about the need  to increase
> them to 3W.

I'm not sure it is the wattage that is the important thing here: usually 3 W 
resistors are rated at higher voltage. ALL resistors have a maximum 
voltage rating. The 1 watters are marginal in this service.

Ken Gordon W7EKB

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