Reversed Electrolytics redux
cube1 at charter.net
Sat Aug 22 19:45:45 CDT 2015
I figured as much. And, with a 10K ohm bleeder resistor that I added on
the output (another added safety feature), the voltage dropped down to
5.2 and change - within spec.
On 8/22/2015 6:19 PM, Dave G4UGM wrote:
>> Also, I now know why the +5 V is high. It has a UA 7805 3 terminal
>> serving as a voltage reference for a TIP-3055 so the supply can provide
>> current. That 7805 has a forward biased diode between the center terminal
>> and ground, thus raising the output voltage by right around 0.5v. I
> expect I
>> will leave it alone.
> When used as series pass transistor the TIP-3055 will usually drop 0.6v
> across the emitter under any significant load. Adding a silicon diode in the
> 7805 base is the normal fix...
>> The same design is used for the +24V, which comes out at 24.2V.
>> So, odds are that this supply could drive two floppy drives.
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