[R-390] 26Z5W replacement

[Bob Camp]

Hi

The radios were designed in an era of 110V power. A typical wall outlet would read 110 +0/-5 volts in most areas most of the time. Yes, that's pretty low. These days a wall outlet may well read above 120V (as in 120 +5/-0 volts. That plus the solid state rectifiers pushes the B+ a bit higher than the designers would have thought. 

That said, I agree with Charles, I've never seen a problem in an R-390A that was related to "high B+".

Bob

On Sep 16, 2013, at 8:11 PM, Roger Ruszkowski <flowertime01 at wmconnect.com> wrote:

> 
> Fellows,
> 
> What if we added a thermistor in with the diode?
> It would limit inrush current.
> Offer a bit of voltage drop.
> Not be overly hot.
> 
> The few extra volts of B+ we get from solid stating the rectifiers does not
> run the receivers out of their design range. 
> 
> I have no idea what a good part number or spec for the thermistor should be.
> 
> Roger AI4NI
> 
> 
> Charles,As always, thank you for your insight and thoughtful comments.  I reallyliked your past analysis of the choke input power supply.It looks like you have thought a bit about the problem of ramp up,certainly more than I have.  I could not see an easy way to do it from thepower supply end, which would be part of the point.  If I were going to doa lot of work, it would probably be to design a switching power supply, andI'm not ready to tackle that one today.I decided to move onto the main point, which is getting a working radio.JP
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