Reversed Electrolytics redux

[Jay Jaeger]

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.

JRJ

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
> regulator
>> serving as a voltage reference for a TIP-3055 so the supply can provide
> more
>> 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...
> 
> http://www.bristolwatch.com/ele/basic_power_supplies.htm
> 
>>
>> 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.
>>
>> JRJ
>>
>>
>> JRJ
> 
>