[Hammarlund] HQ-129x recap

[Kenneth G. Gordon]

On 8 Aug 2011 at 13:03, William A Kulze wrote:

> Back in Jan I picked up an early model(red letter) 129x and have begun
> a recap. Someone previously had done a partial job of it. The can
> electrolytic was 3 sections of 20mf, 2 at 250V and one at 25V, with a
> separate 8mf/250V cap for one of the 10mf sections. My question is, is
> having 20mf of filtering ok on this instead of the 10mf? I've heard
> some things of over filtering and that some issues can arise
> concerning charge/discharge times and in-rush current at power up. I
> can get the 10mf caps if I need to, but I'd like to know what problems
> can come up with 20mf instead.

I think if you examine the original electrolytic caps carefully, you 
will find that their specs are something like "10 mfd +100/-80 
percent", or something very similar.

Therefore, using a 20 MFD cap in place of a 10 MFD cap could still be 
within spec.

I wouldn't worry about it.

What you are referring to is that higher capacitance in a capacitor-
input filter can raise the peak current both at the rectifier and the 
power transformer to unacceptable levels. However, the increase in 
capacitance must be VERY substantial in order for this to adversely 
effect the power transformer or rectifier tube.

In your case, as I said, I wouldn't worry about it.

Ken W7EKB