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Author Topic: Power On-Off at Rig or at Power Supply?  (Read 3528 times)
AF3Y
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Posts: 3737




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« on: November 09, 2012, 03:13:47 PM »

Does it really matter?  If so, which is better?

I have always used the Power Supply switch to power up and shut down the rig, but have been told that is not good.
When I asked why it was not good, I could not get an answer besides "someone said that". Roll Eyes

I am sure I will get answers both ways, but just curious as to your opinions.

73, Gene AF3Y
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KD0REQ
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Posts: 925




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« Reply #1 on: November 09, 2012, 03:18:19 PM »

both.

turn on: power supply, then rig

turn off:  rig, then power supply.

this way, any transients or hiccups in the regulator are NOT going to raise hob in the radio.
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WB2WIK
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« Reply #2 on: November 09, 2012, 03:37:54 PM »

Power supplies don't go from zero to full voltage in a millisecond, nor can they turn off that way.

I leave my shack power supplies on 24/7/365 and only use the switches on the equipment.
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N4NYY
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Posts: 4758




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« Reply #3 on: November 09, 2012, 04:12:37 PM »

both.

turn on: power supply, then rig

turn off:  rig, then power supply.

this way, any transients or hiccups in the regulator are NOT going to raise hob in the radio.

Exactly
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SWMAN
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Posts: 562




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« Reply #4 on: November 09, 2012, 04:15:13 PM »

 I know that in the owners manual for my Kenwood 570 it says to turn off the radio by its switch and not by the power supply. But it not say why not to switch from the power supply.
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K8AXW
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« Reply #5 on: November 09, 2012, 08:29:59 PM »

It can and will be argued forever on rather a power supply "hiccups" when power is applied or shut off.  No doubt there are many who has done this "power supply first, radio left on all the time" routine all their lives.

But, why take a chance?  I would agree with REQ.

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N4NYY
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« Reply #6 on: November 10, 2012, 04:54:29 AM »

Quote
It can and will be argued forever on rather a power supply "hiccups" when power is applied or shut off.  No doubt there are many who has done this "power supply first, radio left on all the time" routine all their lives.

I did this to my 746, and the dreaded backlight blew out. The only time I ever did it.
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AA4PB
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« Reply #7 on: November 10, 2012, 05:11:03 AM »

I had a radio that intermittently lost all memory settings if I turned off the power supply while leaving the radio on. That's because when you turn off a power supply the voltage gradually drops as the filter capacitors discharge. Some microprocessors in the radio can have problems when their operating voltage gets too low. It is better to turn off the radio first so that the voltage goes immediatly to zero.
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WX7G
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« Reply #8 on: November 10, 2012, 07:32:42 AM »

AA4PB has described the possible problem; how does the radio respond during the time the voltage is between zero and full? Strange things may happen in some circuits but the short period of time saves the radio from damage.

As a test, take your radio and raise the voltage over a period of one minute from from zero to full. Now lower the voltage over a period of one minute from full to zero.   
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W8JX
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« Reply #9 on: November 10, 2012, 07:39:15 AM »

Quote
It can and will be argued forever on rather a power supply "hiccups" when power is applied or shut off.  No doubt there are many who has done this "power supply first, radio left on all the time" routine all their lives.

I did this to my 746, and the dreaded backlight blew out. The only time I ever did it.

I have a 100,000 mfd cap in parallel with my supply and have for many year. It softens peak demands on supply during SSB and absorbs any transit surges too. 
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K7KBN
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Posts: 2801




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« Reply #10 on: November 10, 2012, 08:11:28 AM »

I know that in the owners manual for my Kenwood 570 it says to turn off the radio by its switch and not by the power supply. But it not say why not to switch from the power supply.

"Why" is simply "because the manufacturer specifically says not to".

The manufacturer knows his product.  Failure to follow manufacturers' instructions may create problems not covered by warranty.

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73
Pat K7KBN
CWO4 USNR Ret.
WX7G
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Posts: 6028




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« Reply #11 on: November 10, 2012, 08:51:16 AM »

Quote
It can and will be argued forever on rather a power supply "hiccups" when power is applied or shut off.  No doubt there are many who has done this "power supply first, radio left on all the time" routine all their lives.

I did this to my 746, and the dreaded backlight blew out. The only time I ever did it.

I have a 100,000 mfd cap in parallel with my supply and have for many year. It softens peak demands on supply during SSB and absorbs any transit surges too.  

Having designed many regulated power supplies for industry I can say that adding capacitance to the output of a regulated power supply will alter the feedback loop response and can cause it to oscillate. Oscillation can be masked by the large capacitance but the power supply may still in a high stress mode (slamming the output transistors off/on and going into current limit with each cycle).

I do not recommend additional capacitance or that the existing power supply output capacitor be replaced with one having a lower ESR.
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KG6AF
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Posts: 354




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« Reply #12 on: November 10, 2012, 12:06:51 PM »

Even if the power supply turns on and off glitchlessly, there's at least one reason to always switch the rig off while the power supply is on.  In modern rigs, the transceiver may do some housekeeping, like writing information to Flash, in the time between the rig's off button being pushed and the power being turned off.  If you turn off the power supply first, the rig may not have the time to do this housekeeping before power disappears.  Best case, some of the rig's state isn't saved, and you have to re-enter information when the rig is next turned on; worst case, the state of the rig is scrambled, and you have a repair job to do.  I know that the K3 manual has a warning that the rig should be turned off before the power supply.



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NO2A
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Posts: 779




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« Reply #13 on: November 10, 2012, 01:32:55 PM »

I think this is similiar to why you don`t start a generator with a load on it.
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KE3WD
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Posts: 5689




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« Reply #14 on: November 10, 2012, 03:43:57 PM »

Modern rigs with internal processors should be turned both on and off via the rig's intended power switch.  There is both a bootup routine to consider here as well as a power down routine.  Many of these rigs, the power switch is in software rather than an old design switch that simply cuts power at the base level. 

Of course, you can turn the Power Supply on and off as well, just be sure to turn it on first, then power the rig, and at power down, the opposite applies, turn off the rig first, then turn of the Power Supply.

Experimenting won't prove much of anything, for these routines happen fairly quickly and you are just playing the odds.  Most times, the design of the rig is such that it can survive a sudden power cut, but there's that one time...

Don't risk scrambling the bits. 

73
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