MR8100 Power Supply

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UPMan

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Difficult to know with certainty. The voltage/amps is fine. But, being a switching supply, there is always a chance it will be RF noisy (sometimes you can reduce the noise using a ferrite choke on the cord).
 

kruser

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Hey all. Just picked up a mr8100 for cheap online and i was wondering if this power supply is good enough for it.

DC 12V 2Amp Adapter / Transformer / Power Supply / UL LISTED | eBay

Thanks
Mike
That should work just fine. Just be careful about getting the polarity correct when you splice the wires. Even better would be to install an inline power jack on the wire leads from the MR8100. Radio Shack sells a couple female inline jacks that may work.

UPMan is correct about the switching type supplies causing noise. I try and avoid them and often I will power a radio from a large linear power supply I have here that also maintains a bank of batteries for when the power goes out which was very often until they moved some of the main feeders underground.
Honestly, I've not had many problems with switching type supplies for anything above 40 MHz or so. If you do not do any VHF Low band monitoring, you may be ok.
If you detect new noise in the MR8100 and have another radio that also hears the same noise, unplug the new MR8100 supply from the wall and see if the noise stops on the other radio. That simple test will tell you if your new supply is radiating any crud.
 
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kruser

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Thanks for the heads up. I do a lot of HF monitoring and i wont get that one but how would something like this work out

Ps3 3-amp 13.8-volt Power Supply | Buy MP Master List, Pyramid Online
Those work OK. They are linear so not much chance of any RF noise.
Plus that one will do 3 amps constant so you could power three receivers from it if needed although it will run warm to touch especially if you run it at the full 3 amps. I've seen a few of the Pyramid models run warm even with just a half amp load but I can't say I've ever seen one fail.
It is really no different then the supply that radio shack sold (maybe they still sell one) that looked just like it. I would not be surprised if Pyramid did not make the ones that radio shack sold really. That one is probably overkill for just the MR8100 but the price is OK and it will run more then one scanner with ease should you ever need that capability.
 

SCPD

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Kruser thanks again for the help and advice. I sent him an offer for 30.00 total. If i do get my ham ticket i can use this PS and if i don't i will run my 996t hp1 and 8100 off it :) abd free up 2 outlets under my desk.
 

kruser

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Good luck on the ham ticket!

Be warned that the little 3 amp supply is not going to run much if you are hooking a transceiver to it. You mentioned something about using it if you get your ham ticket.
Maybe some small 10 or 2 meter or 440 MHz low power (5-10 watts max) mobile rigs would be ok.
Anything HF is going to need a 20 to 30 amp supply if it is a 100 watt HF radio. I like to keep the current draw at no more than about 75-80% of the power supplies rated continuous load.
That gives the supply a little breathing room as you are not pushing it to the limit all the time.

The little 3 amp supply like in your link will run an HF transceiver in receive mode only just fine. Just don't key up the transmitter!

EDIT: *** Don't run the HP-1 directly from the 12 volt power supply! *** The HP-1 has a 9 VDC input. The HP-1 comes with a car cigarette lighter plug cord that has a 12 to 9 volt regulator built into the large plug. You could use that to power the HP1 if you first wire up a cigarette lighter socket onto the power supplies output and then plug the supplied cig cord into that. Ironically, the AC adapter that powers the HP-1 is also of the switching type that can cause noise which is exactly what UPMan warned about being a possible source of noise!
Now I have checked my HP-1's AC supply and I've not found any RFI issues from it. If you do find noise in your HF receivers (or scanners for that matter) first try unplugging any switching type supplies you have around your radios. Most supplies for external computer devices like routers and modems are also switching types. Like I said before, switching type wall wart supplies are usually very lightweight so they are easy to identify for the most part.
Using the HP-1 cigarette lighter adapter may be the way to go if you find that the AC wall adapter does cause noise. The cigarette adapter just has a simple voltage regulator in it that does not cause any noise. Oh well, this is really a topic for a new thread but should get you going with your power supply project.
 
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pro92b

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Two things to note regarding the Pyramid PS3: It is rated at only 2 Amps continuous and 3 Amps peak. There is no over-voltage protection listed in the specifications. A failure in the power supply could fry the radio connected to it.

I use a Samlex RPS1204 rated at 3 Amps continuous with over-voltage protection. It has run continuously for the last 10 years with no failures. This is a better, safer unit than the Pyramid.
 

kruser

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Two things to note regarding the Pyramid PS3: It is rated at only 2 Amps continuous and 3 Amps peak. There is no over-voltage protection listed in the specifications. A failure in the power supply could fry the radio connected to it.

I use a Samlex RPS1204 rated at 3 Amps continuous with over-voltage protection. It has run continuously for the last 10 years with no failures. This is a better, safer unit than the Pyramid.
The unit he linked to shows the PS-3KX which does show overload protection but no over voltage protection. That is a good catch.
The link the OP posted also says 3 amps constant and 5 amps surge.
I checked some other sites specs on the KX series and they all showed a max of 2.5 amps constant but still no OVP.
I also found several sites that again claimed the 3 amp constant but I'd figure 2.5 myself now that I found so much misinformation.

The Samlex RPS1024 also has the cigarette lighter socket the OP needs if he intends on powering his HP-1 from it.

Now that you pointed this out, I agree that the Pyramid PS-3 may not be a good choice for some of the expensive items he talked about powering from it. The site in his link is also misleading. The item is called the PS-3 but the picture shows the PS-3KX. The KX does have a slightly higher rated output over the PS-3 but who knows which he will get. Plus they reversed the constant and surge ratings in the specs they listed!
The Samlex model is a little costlier and I'm not sure how much the OP can afford but I do agree that the Samlex is the better choice.

XENO194, I think I agree with pro92b and the Samlex model he mentioned would be a safer choice especially after you mentioned hooking up the 996 and HP1 to it! That right there is close to a grand worth of receivers so why take a chance of frying them from overvoltage when you can spend a little more and get a better supply that will shutdown from over voltage.
I just did a really fast search on the Samlex model and the 1st link offered it for $35 bucks so I'd imagine you could do even better. Don't overlook what I added into my previous post about not powering the HP-1 directly from a 12 volt supply!

pro92b, do you know what the Samlex OVP shutdown voltage is and can it be adjusted? How about the actual output voltage, can that be changed internally via a pot adjustment?

I'm glad you spotted this. I saw overcurrent but my brain did not translate that into no OVP. All of my large supplies have both, OVP and OCP plus I have external voltage monitors (at the loads) on them as they charge banks of batteries so I take no chances that something may fail. I even monitor battery temps in between some of the large SLA cells. Those sensors will not shut the supply down but they will alarm me just like a smoke detector would should they trip.
I also use current limiting resistors to limit the initial charge current into the battery banks should the power fail and deplete the batteries while I'm away. They limit the charge current to 10 amps max. The batteries can handle 15 to 20 amps initial charge current.
I do shut all of this down if I leave for an extended time though.
Nothing better than a little piece of mind when away on vacation!
 

pro92b

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The manual for the PS-3KX lists 2 Amps continuous output current. The various dealers do list several other values but I would go with the manufacturer's specs. Interestingly there is a schematic in the manual and the output voltage can be adjusted with an internal potentiometer.

The Samlex supply doesn't list the over-voltage threshold value and I have not tested it. I also never opened the supply to see if there are adjustments inside. The output is very close to 13.8 volts with very little noise or ripple.
 

SCPD

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I think i will just use it for my mr8100 and not mess with my other gear :) thanks for pointing all this out to me. I was was going to use it with 2 way gear it would be a very simple dual band mobile unit. Nothing to crazy.

Thanks again
Mike
 

kruser

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The manual for the PS-3KX lists 2 Amps continuous output current. The various dealers do list several other values but I would go with the manufacturer's specs.
I agree fully with going with the manufacturer's specs all the way.
I did not dig for the manual so that was also a good thing you dug up.

In Pyramid's credit, I have owned several of their large supplies over the years and I think they all had adjustable outputs via internal pots.
Some even had adjustable current limiting but for both you needed to study the schematic to figure out what the pots even did.
I cannot recall any of them coming without a schematic. Pyramid was always real good about that.

I'd imagine the OP will still be OK with the PS-3 if he orders it before seeing this. I know several that have had them (pyramid's) running for years without any problems including my old ones that I sold or gave away. I think the smallest I had was a PS-6 or 7 maybe.
I'll also take back my 3 radio limit and reduce that to two scanner type radios only on this PS-3 model. I think as long as he does not run it at or near its normal limit (2 amps now) that it will hold up.

I realize now that I still have a Pyramid supply ready for use here. It is a PS-35 Phase III thing with a claimed 35 amp continuous output and 37 amp surge.
It does have external voltage and current adjustments on the front panel along with meters for both. I modified it though and added a fan on the rear heat sinks and I replaced the cheap voltage adjustment pot with a quality 3 turn pot. I have had this thing for ages. I also got rid of the cheap binding posts they used and mounted a large power block on it. It also does not have any OVP like their smaller models but it does have an alarm that has never sounded. I have no idea what the alarm does. Run it into an overcurrent condition and the alarm buzzer does not get any power so it does not appear to be for that. I never did figure out what the alarm does! I powered an Icom 725 from it for a good 10 years without any problems along with several receivers.

I do not use it for anything other than bench testing these days though so it sits collecting dust mainly until I need it for current regulation when powering up suspected shorted devices. It works well for that purpose.
 

kruser

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I think i will just use it for my mr8100 and not mess with my other gear :) thanks for pointing all this out to me. I was was going to use it with 2 way gear it would be a very simple dual band mobile unit. Nothing to crazy.

Thanks again
Mike
I'm glad you came back and saw all this! I think you should invest in a better 10 amp or higher model for the dual band mobile.
I know you can buy a simple dual band mobile for much cheaper then you paid for the 996T these days but you may as well get a decent supply for the future. Get something that does 35 or 40 amps and you will be all set for running mobile HF and V/UHF rigs from home along with the digital equipment you may get into as the hobby progress's:)
This hobby can turn very evil and drain your bank accounts very quickly!
 
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