small valves

[Dwight K. Elvey]

>From: "Allison" <ajp166 at bellatlantic.net>
>
>>
>>Subject: Re: small valves
>>   From: "Dwight K. Elvey" <dwight.elvey at amd.com>
>>   Date: Mon, 25 Apr 2005 09:57:08 -0700 (PDT)
>>     To: cctalk at classiccmp.org
>>Hi Stan
>> I've done similar. I've taken one of those small 100W
>>inverters and rewound the transformer on it to provide
>>all the voltages for my older battery powered Atwater
>>set. It just runs from a 12 volt gel cell. I tapped
>>of the primary to provide the filament voltage and
>>used the secondary with tape to provide the rest.
>>As I recall, there was one -C and two +B voltages.
>>I used no regulation, just used the right rinding
>>ratios. One has to remember, these old radios
>>were made to run form carbon-zinc cell in most cases.
>>I did put a pot on my C cell. The original was -4.5v
>>but I found that it works better, with less distortion,
>>when set at about -3.5v.
>>Dwight
>
>Good approach.  I enjoy building and winding my own cores
>be they EI iron or powered iron/ferrite types is part of 
>that.  Switching mode PS design is an art in itself. Part
>of the fun is building for good efficientcy and for powering
>tube designs that means knowing the load.
>
>An aside is don't run regens off inverter or switching supplies
>as the gain is high enough to negate reasonable shielding 
>and bypassing.  For that I find common alkaline 9V batteries 
>in series do well for the typical 27-90v range and exhibit 
>good life.

True but expensive. I do this on my Radiola II.
Dwight