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I'm laid up recovering from knee surgery, and have been listening to the H845 quite a bit lately. Yesterday, I got to thinking about something that happened to me back when I was in the repair business.
I had replaced the filter caps in a set with a selenium rectifier. As it sat on the bench playing, the volume started to get lower and within a minute the selenium rectifier started smoking. I pulled the plug, but not before the whole building stunk to high heaven with the most pungent odor outside that of a skunk that I had ever smelled.
Now, I use my Zenith as a bedside radio. If that selenium were to go south, the bedroom is not the place I would want that to happen. Taking all that into consideration, I decided to put in a diode. I left the selenium rectifier in it's place on the outside front of the chassis and soldered in a diode underneath the chassis. This model has a full metal cover underneath the chassis, so nobody would ever know it was there unless they slid the chassis out and removed the cover.
I played it for an hour, and noticed no difference in the sound quality or tuning capabilities. I did note, however, that with the volume turned all the way down you could still hear it pretty well. When I checked the B+, it was a little higher than I wanted it to be, and the filter cap can seemed a little warm.
I ended up adding a 100 ohm 10 watt resistor, and that brought everything back down to normal. I know 10 watts is overkill, but it's what I had. It's connected to the diode underneath the chassis, so I was a bit concerned with the amount of heat it would dissapate there. I left the radio on for 3 hours, and removed the bottom chassis cover and found it was not hot at all.
With the diode and resistor in place, the set performs exactly like it did with the selenium rectifier and I don't have to worry about smelling up the house. This set gets used on a daily basis, and often stays on all night (because I doze off and forget to turn it off). Despite the fact I wanted to leave this radio as it left the factory, I just think it was best to go on the safe side and bypass that old selenium rectifier.
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