[Boatanchors] OT: The DC battery system for my ":shack" (long monologue)

Phil ko6bb1 at gmail.com
Wed Jun 15 17:17:05 EDT 2016


Hi,

OT for this list, but then the Astron 50A supply qualifies as a 
"boatanchor" at ~48lbs!

Just thought some of you might be interested in how I power nearly ALL 
equipment here, or at least anything that runs on 12 Volts.  That 
basically includes everything but the computer equipment and the 
homebrewed tube type regen.

The PRIMARY power source is an Astron RS-20M (metered) 13.6V power 
supply that's tied into the main DC power buss under the operating 
bench.  The 24/7 'standby' power draw on the supply runs about a 
conservative 5 Amps.  The "On 24/7 equipment is typically the TYT dual 
band Xceiver, Icom IC-7200 Xceiver, 4 port multicoupler, DSL Modem & 
router, float-charging the battery bank.  In addition during operations 
(such as a CLE) the R-75, Icom IC-735, Pre-amp/control center, Softrock 
system etc may all be left on all weekend, running the 'standby' current 
up to about 8 Amps (still almost conservative for the PS).

Also tied into the 12VDC system is a 300W 110VAC inverter that can let 
me have a small amount of AC during a power failure for items such as a 
fan on a hot day, computer etc.

BUT, IF I transmit on any of the Xceivers with most of the auxiliary 
equipment turned on the the PS Ammeter pegs hard at >20 Amps (it IS 
supposed to be current limited, but I've never tested it to see what 
that limit is).  On the Astron supplies, the model# number indicates the 
intermittent current rating and they should NEVER be operated 24/7 at 
more than half of that rating!!!  To do so invites disaster.

My Astron has been running just fine for well over 15 years now, but as 
I've added more equipment it does seem to run somewhat warmer, though 
not excessively so.  THAT IS, unless there is an extended power outage 
and the supply has to bring the battery bank back up to full charge!  
Then the supply gets pretty warm (even with the muffin fan I put on the 
heatsink).

In any case, I wanted to get a larger supply and it was on my list of 
"future things to do".

Well, last Saturday, at the usual Saturday Ham Radio "Coffee Klatch" at 
the mall one of the old timers asked me if I'd repair an Astron 50 amp 
(linear) power supply for him.  Said he has two needing repair, IF I 
fixed one for him I could have the other.  One has meters, one not, he 
wants to keep the metered one.  I told him sure and dragged the 
unmetered one he'd brought home (they weigh ~48 lbs each).

Checking it out I found that it put out 13.6VDC, BUT had a lot of ripple 
and noise on the DC output.  I pulled ALL 8 of the pass transistors 
(known to fail).  They tested good so I re-greased them and put them 
back in. Further troubleshooting turned up an open emitter equalizing 
resistor on one of the pass transistors, but all that'd do is reduce the 
current capacity by about 1/8th.

Further troubleshooting showed ripple and noise on the output of the 
LM723 regulator chip.  Hmmm, found that the 'lytic capacitors on the 
main board were all dried out,and in fact the 2200uF capacitor in the 
(low current) PS for the regulator itself was open (a separate supply 
from the main humongous filter capacitors of the main circuit).  
Replaced ALL the small 'lytic capacitors on the board (4), found one 
lead on the 2200uF cap was burnt open, rechecked PS.  VOILA!  It works 
as it should! Still need to replace that one open resistor to restore 
the 8th Pass transistor in the circuit (each of the 8 pass Xistors has 
an .05 Ohm 5W equalizing resistor in the emitter).

At this point, since this is an 'early' Astron (1984 date codes) I went 
ahead and did the recommended upgrades to it, including adding the 
protective resistor that protects the LM723 IC when used with a 
"float-charged" battery bank (after all, this will be 'my' supply when 
I've finished the 2nd one.

**************************************

Since this Astron is the one that doesn't have Voltage/Current meters, 
AFTER it's mine I intend to add metering to it, and will use a digital 
meter to display Voltage, Current, Watts and accumulated "energy".  
Don't need the last feature, but I liked this particular meter MUCH 
better than the ones that only showed Voltge/current.  I'll put the 100A 
current shunt INSIDE the Astron and Velcro the meter to the front face.  
There's enough room inside for the shunt. I ordered the needed .05 Ohm 5 
Watt resistors for the PS AND the meter etc just this morning.  But 
won't install the meter until I've confirmed that I can repair the other 
unit (I'm sure I can) and that this one is mine. . .

I ordered this meter (with 100A shunt).

https://www.amazon.com/gp/product/B013PKYILS/ref=od_aui_detailpages00?ie=UTF8&psc=1


*******************************

Change of subject.

*****************************

I've long been wanting to wire in a "disconnect switch" between the PS 
and the rest of the DC Buss circuitry (I.E. the Heavy DC fuse-blocks 
under the bench, the heavy (it's either 4ga or 6ga) DC cable going to 
the battery bank in the shed just the other side of the outside wall and 
so forth.  Since we're talking heavy currents and relatively low 
Voltages (13.6V), even a small Voltage drop would effect overall system 
effectiveness.  I'd considered a really heavy relay on the output of the 
PS that would drop open when the AC power fails (or is turned off).

I would be just as happy to be able to manually disconnect the PS from 
the rest of the system.  Then I ran across this behemoth of a DC switch, 
rated 275 Amps continuous, 475 Amps intermittent!!!  Designed for Marine 
and RV service it should do the job.  In fact, IF I like it well enough 
I'll probably get a 2nd one to use in the DC cable going to the battery 
bank.  Make it easy to disconnect the battery system when servicing them 
(right now I just remove one of the big-honkin' fuses to do that.

Here is the switch. The funny thing is, I wasn't looking for it at all, 
but while looking for the volt/ammeter it popped up as a "related item". 
Which led me on a search for switches.  This one, while not the cheapest 
one on Amazon, looked like about the best for the price (you can spend 
well over $100 for a battery disconnect switch).

https://www.amazon.com/gp/product/B005DUUL9W/ref=od_aui_detailpages00?ie=UTF8&psc=1 


Comments, suggestions?


-- 
73 From "The Beaconeer's Lair"
Phil, KO6BB
http://www.qsl.net/ko6bb/  (Web Page)

HF/LF RADIOS:
Grundigs: S-350 (~2006), G6 (2011) & S450DLX (2014).
HOMEBREW: 7 Tube+Rect 1v3 Regenerative RX for LF (built 2015)
Icom:     IC-735 Transceiver (~1990).
Icom:     R-75, Cascaded 250/125Hz CW-Filt, Panadapter. (~2009)
Icom:     IC-7200 Transceiver (~2015).
R-Shack:  DX-380 digital portable (~1990).
SDR:      Softrock Ensemble II LF (built from a kit 2015).
Zenith:   Royal-7000 Transoceanic Portable (~1968).

ACC:   HOMEBREW  LF-MF Pre-Amp, MFJ-993B HF Auto-Tuner.
        HOMEBREW  4 Port Multicoupler, Feeds Antenna to 4 RX's.
        HOMEBREW  8 Hz Audio Filter.
        Timewave  DSP-599zx Audio Filter.
        Behringer 1202fx Audio Mixer (for mixing/routing audio).

ANTENNAS: 88 foot Long Ladder-line fed dipole, 35 feet AGL for MW/SW.
           Active Mini-Whip, 36 Feet AGL for LF/MW/SW.
           37 foot "Low Noise Vertical", 11 feet AGL for LF/MW/SW.

Merced, Central California, 37, 18, 37N   120, 30, 6W CM97rh



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