[Boatanchors] Amp Supply LK500-ZC Amplifier Question

[Jim Wiley]

Any of the rest of the Boatanchors gang want to chime in on this one?


- Jim, KL7CC



On 8/3/2015 8:22 AM, WA5CAB--- via Boatanchors wrote:
> Sorry again, but again no.  It's only a matter of terminolgy but the DC
> value is the average, period.
>
> Robert Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
>
> In a message dated 08/02/2015 23:54:59 PM Central Daylight Time,

> jwiley at gci.net writes:
>> Au contraire, mon ami:
>>
>> While a DC voltage can vary in magnitude from a few microvolts or even
>> picovolts to many hundreds of kilovolts (or more), it is still DC.    Nowhere
>> does it say that a DC voltage has to remain constant in amplitude for it to
>> classified as DC.  Unless and until it reverses polarity, no matter how
>> briefly, or ceases to flow altogether,  it is still DC.
>>
>> - Jim, KL7CC
>>
>>   
>>
>> On 8/2/2015 8:29 PM, WA5CAB at cs.com wrote:
>>
>>>> I'm sorry, but the phrase "DC Peak" is a contradiction in terms.  DC is
>>> forever.  Or at least many half cycles.
>>>
>>> In a message dated 08/02/2015 23:11:31 PM Central Daylight Time,
>>> jwiley at gci.net writes:
>>>> Actually, there is another way, and in my opinion, better:
>>>>
>>>> No filter capacitor at all, but instead 2 diodes, one connected as a
>>>> "half-wave" rectifier, in the normal manner, with  the other across the
>>>> relay coil, connected so as to absorb the "reverse EMF" generated by the
>>>> collapsing magnetic field.
>>>>
>>>> This configuration works because the current created by the collapsing
>>>> field, shunted through the diode across the field, maintains the field
>>>> until the next half cycle of the driving voltage arrives.
>>>>
>>>> Because the half-wave rectifier generates almost 18 volts of peak DC
>>>> from a 12.6 VAC source, or 28.3 volts DC peak from a 20 VAC source, either
>>>> should be enough to activate a 24-volt (nominal) DC relay.
>>>>
>>>> In a practical sense, it is helpful to remember that it takes much less
>>>> magnetic field strength to hold a relay closed than is required to
>>>> initiate closure.
>>>>
>>>> Also, the 2-diode configuration is much less expensive (parts wise) than
>>>> the diode plus electrolytic capacitor, and it  has the advantage of not
>>>> having to worry about the capacitor drying out at some future date.
>>>>
>>>> Parts budget:  2 diodes (1N4007) between 1.1 and 20 cents each,
>>>> depending on initial quantity purchased, vs, 1 diode plus one capacitor: 60 cents
>>>> to perhaps a dollar or more.   Since many hams find purchases of  1N4007
>>>> diodes in 1000 quantities (about $11 worth) makes sense, the 2-diode
>>>> approach becomes a more practical alternative.
>>>>
>>>> -  Jim, KL7CC
>>>