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Bullseye
| | Posted on Wednesday, July 16, 2003 - 8:38 pm: | 
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I have been looking at some Astron power supplies and was wondering what,if any,advantages there are to the variable VS the non variable power supplies? Never really messed with this until now so I don't know I usually just bought what Wal-Mart or Rat Shack had and called it good but now I'm looking for a good one to last "forever". |
Bullet
| | Posted on Thursday, July 17, 2003 - 1:18 pm: |
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you can adjust the voltage being feed into whatever device you using. were as you cant with the other types |
2600
| | Posted on Thursday, July 17, 2003 - 4:23 pm: |
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If you are doing service work, this is a way to see that the radio will still perform at the lower voltage you get when the vehicle's motor is turned off, and you are running the radio from the vehicle battery alone. With the motor running, you will have 13.5 to 14 Volts on the radio. With the motor off, it will be closer to 12 Volts. Other than this kind of service work, it's just another "decorative" knob with little practical value.
Astron is a good choice. It contains the protection circuits that cheaper power supplies don't. A power supply breakdown can fry a radio or amplifier in an eyeblink, if it doesn't contain an overvoltage detector and "crowbar". All the Astron power supplies DO.
73 |
Bullseye
| | Posted on Thursday, July 17, 2003 - 11:06 pm: |
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So in other words I,basically,can turn the voltage down and it would show how a particular piece of equipment would perform when running on just a battery BUT I can also turn the voltage up to get maximum performance out of said piece of equipment? Now,also,with adjustable amperage I could use the same power supply for multiple amplifiers such as adjusting down to 14 amps. for a ModV+ then up to 26 amps. for a 250HDV and then up to 40 amps for a 500V and so on. Also,just out of curiosity,what would be the max voltage that a "12 volt" piece of equipment(ie one designed to be used in a vehicle) could safely be run at? |
frasiercrane
| | Posted on Friday, July 18, 2003 - 12:46 am: |
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when a power supply has adjustable current (amps) it's usually a current limit, meaning if you set it at 10 amps, whatever you hook up to it won't be able to draw any more than 10 amps(above 10 the voltage will cut back), if the equipment normally draws 5 amps and you set the supply at 10, it will still only draw 5, it won't force more current through it. This is generally used as a safety feature when testing stuff, and on some supplies can be useful for charging batteries at a constant current.
vehicle equipment is usually designed for 13.8 volts, probably up to 14.2 would be reasonably safe as most cars will reach that voltage while running, but it depends on the equipment.. stick to 13.8 and you should be fine.. |
Tech671
| | Posted on Friday, July 18, 2003 - 5:32 am: |
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The adjustability is the voltage, not amperage. Your example of different amplifiers is of their "amperage" draw, not voltage. The supply will feed whatever amperage is demanded from it. If you have a 70a Astron supply and run a mod V on it, the supply will produce only what the mod V asks for (12a or so) and you can adjust the voltage usually from 12-15. The Astron will not exceed a voltage that will damage any of those if it is working properly, which is usually about 15v.
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Kc0gxz
| | Posted on Friday, July 18, 2003 - 6:11 am: |
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Bullseye
I see no point in a power supply where the amperage can be adjusted. Perhaps in a Lab maybe. But if you want a power supply that will do it all, get one that has a high amperage rating. The higher the better.
For example, if you have a radio that has a maximum draw of 5 Amps, don't get a 7 Amp. Get a 10 or 12 Amp. That way, the power supply will never break a sweat. And do not use the same power supply for both the radio and the amplifier. Always use separate supplys. Especially when working sideband.
Having a power supply that has a Amp meter on it is always a plus. If the Amp meter goes to the minus when you say "aaaaaaaaaahh" into your mic on AM, then you will know that you have downwards power. If the amp meter goes up while you're doing the "aaaaaaaaaahh" thing, then you will definately know that you are using more power. Verrrrry few people know how to set their power meters in order to check for downwards power. "But that's another subject".
When spending your hard earned money on a power supply, do your homework. Compare specs and compare prices ampere for ampere. What ever you do, don't buy Radio Shacks big dollar supply. The most outstanding feature it has is the guarentee that it will shut off when unpluged from the wall. Well, I guess that IS a good feature.
I have (from stupidity) destroyed quite a few (brand name) power supplys in my years working with radios. But now, I personally prefer the Pyramids. The ones that are rated at 26 Amps and above are a little harder for me to hurt. When they over heat, they shut down. Also over-voltage protected. There are other features but I don't remember them all.
However, here is a feature on the big 46 and 52 Amp Pyramids that (to the best of my knowledge) no other power supply can do. Hook a wire to the positive post and one to the negative post. While the power supple is turned on, touch the two wires together. The Pyramid will shut itself down. Other brand name power supplys will (in a heartbeat) usually blow something internally. From what I've been told, that is a Pyramid exclusive on their high dollar supplys. Now that's what I call a power supply. I don't think the smaller Pyramids will do that so I wouldn't put it to the test if I were you.
I think the big Pyramids are built for stupid idiots like me who are always accidently shorting wires together while working at the bench. I sometimes don't have enough sense to unplug the wires when I'm done with them. Like a moron, I just leave them lay on the bench.
I have a pair of Pyramid 52s paralleled for amplifier repair/testing and a Pyramid 46 for my radio repair/testing and general bench work. With the many times I have dead-shorted them, I have yet to smoke them. (knock on wood)
Jeff, kc0gxz. |
Bullseye
| | Posted on Friday, July 18, 2003 - 10:39 am: |
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So,more or less,the adjustability is'nt really going to do much for me. Just using it to run amps. and such,from what I'm reading here,I would be just as well off to buy a straight 70 amp with meters and the power supply will only allow what voltage and amperage that is required to be used. Another advantage is with the 70 I would only need it and the 20 I've got now to run most any amp./radio combination correct. |
Kc0gxz
| | Posted on Friday, July 18, 2003 - 12:40 pm: |
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Bullseye
You got it my friend. But varible voltage is nice to have. 2600 explained it best.
WOW. A 20 an a 70? Great combination!! Just don't drop the 70 on your foot.
Jeff, kc0gxz. |
Bullseye
| | Posted on Friday, July 18, 2003 - 4:54 pm: |
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One more question. I am planning on,for right now,running a Texas Star 350HDV and have a chance to get a Pyramid PS36KX. Now at 32 amps constant and 35 peak will this supply be enough to run this amp or will I be better off getting a bigger one? A guy at work has one one I'm looking at still in the box for $100.00. It was bought by his wife and she did'nt realize he wanted a PS52KX and not the 36. |
Bigbob
| | Posted on Friday, July 18, 2003 - 8:48 pm: |
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I got a home-made PS built in a 4.5" square aluminum tube 14" long muffin fan at one end,transformer on outside has dual windings,primary/secondary,can run 220-110,7.5-15-32 volts out.PS will do 40 amps continously,75 amps intermittant. |
Kc0gxz
| | Posted on Friday, July 18, 2003 - 11:00 pm: |
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Bullseye
The Texas Star will pretty much tax the 32 Amp supply if you drive the amplifier hard on SSB.
The best way to do this on AM is to drive the amp with 1.5 to 2 watts but you didn't give us a clue as to what your radio is capable of peak power wise.
I could give you a better idea of what to expect with more information.
Jeff, kc0gxz. |
Bullseye
| | Posted on Saturday, July 19, 2003 - 6:56 am: |
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I'm not sure what power (DK & SW)my new radio will do but its a peaked and tuned Saturn so. I just got it and the antennas going up today so I'll tell you then. I don't do SSB to much so thats not generally going to be a problem. |
Bullseye
| | Posted on Monday, July 21, 2003 - 10:46 pm: |
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HEY JEFF Thanks for all the advice which I took. I found a PS52KX "Like New" on Ebay for $100.00 so I went ahead and got it. I know like new on Ebay is questionable occasionally but I have bought from this outfit before and been pleased both times so I'm pretty confident in this one. Once again Thanks for all the input and advice. THIS IS WHAT MAKES THIS FORUM GREAT!!!!!!!!!!!!!!! |
Kc0gxz
| | Posted on Monday, July 21, 2003 - 11:06 pm: |
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Bullseye
There aren't enough good things ever said about this forum. I'm very impressed with it too.
Jeff, kc0gxz. |
Bullseye
| | Posted on Thursday, July 24, 2003 - 4:27 pm: |
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Jeff, This is gonna sound stupid,if I could say it to ya that is,and I think I know the answer but just to be on the safe side exactly how do you run 2 power supplies "paralleled". I was still looking for a 70 amp Astron but if I can do this I can get another Pyramid and,effectively, have 80 to 100 amps instead a max of 70 and can you run more than 2 this way(3-4-5-6-7 etc...)  |
Hootyal
| | Posted on Thursday, July 24, 2003 - 5:31 pm: |
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My Astron rs-70m has an extra terminal(+) just for running them parallel. Just wish the meters had lights. |
Kc0gxz
| | Posted on Friday, July 25, 2003 - 12:49 am: |
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Bullseye
Look at the power supplys as being two batterys. When you want to double your amperage supply, you tie the two positive posts together and you do the same thing with the negative posts. Doing so will double your amperage.
BUT, THEY HAVE TO BE IDENTICAL BATTERYS.
To make a long story short, all you're doing is wiring them together in paralell.
Now, here is the way I did it with a pair of Pyramid 52s. And I'm sure there are some people out there that won't like this method. But, it works for my purposes since it is ONLY used for amplifier work. My radio work is done on a Pyramid 46.
The first thing I did was to install heavy duty binding posts on the rear of both supplys. From inside the supplys, I wired 10 gauge wire from the front + and - posts to the newly installed rear + and - posts. From there, I ran 10 gauge wire from both rear positive and negative terminals of both supplys into a small metal box with heavy duty + and - terminals. The metal box I then bolted under the shelf over my work bench.
WORD OF CAUTION: And I can not stress this enough. Make very, very sure the power supplys are set at the EXACT SAME OUTPUT VOLTAGE. Those voltage control knobs are large and very easy to bump with your hands while connecting wire to the front terminals. Personally, I do not like the large knobs on them just for that reason.
One more thing. Set the voltage for both power supplys at 14.0 volts with a GOOD digital volt meter. DO NOT use the volt meters on the supplys to set the voltage with. I can guarantee you that they are not very accurate.
When you're done with this project, stack the supplys on top of one another so they arent taking up so much space. The front terminals can still be used in the regular manner.
By the way, that 52 amp is a surge rating. In reality, the actual true constant amp rating is probably more like 45-48 amp. Power supply companys always over rate their amperage the way that antenna companys give you out-of-this-world Db ratings. The problem is, most people that aren't-in-the-know, actually believe these ratings. Especially with antennas. But I don't want to go there now.
If I can think of anything else, I'll post it for you.
Jeff, kc0gxz. |
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