New Dual Linear Power Supply

heiney9

I don't claim to be an electrician, but I did take some general classes way back in HS as electives and we hit the theory and application pretty hard.

First step in my streaming (improvements) was to purchase a linear power supply for my Modem and Wireless router. To get rid of the cheap walwart for each. I'd read that starting here can make the wireless stream more reliable and sound better.

I bought a well reviewed unit from China. Specs are as follows 25VA (watt) 3.5A dual 12V linear supply for 110-115V USA. I looked at the walwarts and the router showed 12V 1.5A output, the modem is 12V 750mA output. I even bought the more expensive Talema branded 25VA transformer. Here's a pic of the guts.



With no load I had it hooked to VOM and it stayed steady at 12.05V and was cool to the touch. Under load with both the Modem and Router hooked up it jumped to 12.2V and I adjusted down to 12.0V, but the case slowly started warming up until it got pretty hot to touch (not as hot as my Aleph30 singled ended Class A amp). But hotter than I think it should get.

No magic smoke or smell..........

Any input or advice appreciated. Pretty sure it's over spec'd for what I'm using it for?

Couple pics





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VR3

I notice my cheap Chinese supplies I use for my auxiliary stuff, fans, etc do get a tad warm, warmer than you would think. They have ran flawlessly though

heiney9

VR3 wrote: »

I notice my cheap Chinese supplies I use for my auxiliary stuff, fans, etc do get a tad warm, warmer than you would think. They have ran flawlessly though

A tad warmer I would be unconcerned about, but this was approaching the Alpeh 30 temp where about 10-12 seconds on the cooling fins before it becomes uncomfortable.

I am going to be gone/in & out all weekend, so I've unhooked it for now until I can further figure out what's going on. Don't want to leave it unsupervised at this point. The walwarts get very warm, but not as warm as this did. Maybe check to make sure the dc output plus and minus are the same? Pretty sure I verified before purchase.

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VR3

Yeah I wouldn't say mine are any where near that hot... I could keep my hand on them indefinitely

F1nut

The specs show the transformer temp at 60C, which is 140F. Hence, all those heatsinks.

tonyp063

The other thing to consider is that it's specc'ed as 110V a/c input, & if your home is like most of us, you'll be getting ~120V at the wall.

The LPS, while regulating, will dissipate the extra bit as *more* heat than design center.

heiney9

According to my Power conditioner in the living room the voltage here fluctuates between 118-124V in the Summer. So perhaps that's part of it. I'll contact the manufacturer and see how hot it's supposed to run at.

I just wasn't expecting it to get that hot just running a modem and router. They don't really do any work. This is more an experiment than anything else, just to see if an LPS makes a difference. I spent less than $100, so if it's a poor build or not really spec'd to work as a dual, not a big loss.

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heiney9

F1nut wrote: »

The specs show the transformer temp at 60C, which is 140F. Hence, all those heatsinks.

If it's like class A and it's designed to run hot, that's fine with me. Just want to make sure it doesn't burn my house down

VR3

It may run Max output regardless of the load presented

heiney9

VR3 wrote: »

It may run Max output regardless of the load presented

When I first received it, I let it run no load for 1/2 day and it never even got slightly warm. Hooked up to the VOM it output a steady 12.03V

The dc cables that came with it are 5.5mm x 2.1mm. I believe that's standard size? Although, now that I think about it should both ends of the cable be interchangeable?

Because they weren't for the modem. One end of the dc cable was too large so I flipped it around and it fit. Both ends of the dc cable fit the LPS. I wonder if this might be something that causes an issue?

Dr_Wu

My Teradaks run pretty much the same way. I rest them on a polyurethane pad (actually a small cutting board). No worries about heat, and some isolation, as well. Plugged into a power regenerator.
Would you happen to know what size LPS I need to replace the wall wart on a Motorola MG7550 modem/router? Thanks!

heiney9

Dr_Wu wrote: »

My Teradaks run pretty much the same way. I rest them on a polyurethane pad (actually a small cutting board). No worries about heat, and some isolation, as well. Plugged into a power regenerator.
Would you happen to know what size LPS I need to replace the wall wart on a Motorola MG7550 modem/router? Thanks!

Thanks for the input.

If you have the walwart, look at the writing on the case. It should say what the output voltage is & amperage. Just remember mA is milliamps, so for example 750 mA = .75 amperes.

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heiney9

I wonder if drilling some holes in the case would help. I will be doing some more experimenting when I can monitor everything for awhile.

I'm just having a hard time understanding as the small little walwarts don't get hot at all. They can't be using great parts.........and I'm sure are spec'd less than this LPS.

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Emlyn

I was thinking about the non-venting of the case when I first looked at the power supply. Could be the designer decided the whole metal case serves as a heat sink of sorts so venting wasn't needed. That transformer is pretty big for a small box though and the heat probably diminishes the longevity of the other parts.

heiney9

I need longer dc cables, so I'm going to order some. Eliminate the cables being an issue right away. Then I'll run each component one at a time and see how that works. Again, no load it doesn't even get warm.

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VR3

I run this one to power my modem and router... Runs ever slightly warm but as you can see it is overbuilt. Cost came out to 150 per unit, not bad at all. Great quality unit too

heiney9

I bought this so I could independently measure the voltage. The LED on the front is very close. I measure 12.08V the LED on front read 12.1V

heiney9

VR3 wrote: »

I run this one to power my modem and router... Runs ever slightly warm but as you can see it is overbuilt. Cost came out to 150 per unit, not bad at all. Great quality unit too

I looked something similar in size, build and spec and maybe I was wrong to determine it was over kill. I used a Welbourne Labs for my Squeeze Box and it never got warm. I guess maybe I underestimated the draw of both together.

Dr_Wu

fwiw, I like the DC cables from this company:
https://ghentaudio.com/part/dc-4s8.html
No affiliation

mhardy6647

heiney9 wrote: »

I bought this so I could independently measure the voltage. The LED on the front is very close. I measure 12.08V the LED on front read 12.1V

THIS IS MY KIND OF PRODUCT! FIVE STARS!

heiney9

So, I bought new dc cables for this thinking maybe the one supplied were somehow defective and causing the unit to run hard, elevating the operating temp.

It's been sitting unused and today I decided to just hook up the router. It still gets very warm to what I would say is hot.

Those that have the smaller chassis LPS, does yours run hot? I can touch the top of the case and keep my hand there (unlike my Pass amp), but it is hotter than I think it should be. It seems to be the same temp as when I was running both the modem and router as it is a dual 12V 3A 25W LPS.

I figured I'd run one, even though it's a dual output LPS. If this is normal it would make me feel better. I bought it from China and English is not the sellers first language. It got great reviews, but no mention of operating temperature.

I could drill holes in the case to help vent the heat, unless it's normal to run this temp. My Welbourne Labs I used for my SQB Touch never ran warm.

My Netgear router ps is 120V 2.5A

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heiney9

The lower sides and the bottom are almost too hot to touch for more than 15-20 seconds.

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heiney9

What am I missing here? Is this somehow underrated for the job?

https://www.ebay.com/itm/353093629947?hash=item52360537fb:g:9F4AAOSwS7Be1PYO

I even selected the better Talema transformer.

???????

heiney9

I am not smelling anything burning or getting too hot? Usually that's a sign.....lol

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msg

Where are you seeing the current draw spec on the unit?

Been a while since I've done these kinds of calcs, but going by those wallwart specs, looks like you might be a little underspecced, which could explain the heat?

W = VA

W = (12v x 1.5A) + (12v x 0.75A)
W = 18VA + 9VA
W = 27VA

And this unit's specced for 25VA, right?

Maybe my maff's off.
I also don't know whether modems and routers run at constant current draw.


There's another similar looking one on Ebay that has this in the description, where they say that 3.5A is the max output current, and that that max output current will vary, depending on the voltage chosen for the unit. There also seems to be some "overhead" required, because these numbers don't match exactly.

Voltage: 5V 7.5V 9V 12V 16V 24V ( if not specified , will ship 12v version by default)

Maximum output power: 25W

Maximum output current: 3.5A (depending on the output voltage, e.g. 24V maximum current is 1A, 5V can reach 3.5A)

They don't spec what the max output current is for the 12V version, but extrapolating based on the note in the above description that only the 5V unit can reach 3.5A and that the 24V can reach only 1A, I'm guessing you don't really have 3.5A to play with, and that you might be overdrawing based on that Wattage calc above.

How does it run with just one device connected?

heiney9

It's the same running 1 or 2 devices. It is fused and I get no "hot" smell. I took the top off and the tranny is hot. Like F1 noted The specs show the transformer temp at 60C, which is 140F. Hence, all those heatsinks.

I need to find another 12V device to run to see if it gets as hot. I will drill some holes in the case if need be.

I'm fine if this is normal, but it was getting a bit to hot for my liking to leave it on 24/7 unattended.

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VR3

Why not go with the teradak 200w? It runs very cool and is dual output

My smaller dual output power supplies are warm to the touch but not hot enough to be uncomfortable

mhardy6647

Did you measure the actual current draw of the device(s) you have hooked to the P/S?
Do you know if it the the hot spot's the power transformer or the regulator?

That power transformer temp spec would be a "flat out" full power value -- it shouldn't get that hot in normal use.

On the bright side, the PT says the primary's 115 V, and not 110V. The latter is not uncommon on some Asian-sourced components (albeit typically cheap tube amplifiers of somewhat dubious provenance).

If it is hot (as opposed to warm), the life of the P/S will likely be nasty, brutish, and short.

heiney9

VR3 wrote: »

Why not go with the teradak 200w? It runs very cool and is dual output

My smaller dual output power supplies are warm to the touch but not hot enough to be uncomfortable

Because I bought this and before spending more money I want to see if I can make it work. My thoughts now are maybe I underspecc'd it. But it gets the same temp running one or two devices, so that doesn't seem logical.

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mhardy6647

EDIT: oops, I re-read the OP. All set, sorry!

heiney9

I am going to do more experimenting with the LPS I have. As far as Dr. Hardy's inquiries, I believe it's the transformer getting so hot, not the regulator(s).

The one thing that doesn't make much sense is the heat seems to be the same if I have one or components hooked-up. I would think adding using the second output would put double the stress on it.

Currently I will be hooking up an external HD to it and see if that gets just as warm. I can't think of anything else I have here that would use 12V dc. I currently have the cover off the LPS.

This is a really nice LPS or rather it seems to use some good parts. I didn't expect to see Nichicon PS caps.

Trey - is this the one you are suggesting?

https://kamaudio.com/TeraDak-DC-200W-Dual-Output-LPS-Linear-power-supply




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