Any way to modify noisy power supply?

[alpard]

I have this Lab power supply made in China.  It has digital read out for voltage and also currents, and is fully adjustable continuosly via the dial from 0 - 30V, and it is rated 10A max.

It is great to power up project stuff, but when it is connected to SW radio, the radio gets noisy due to the power supply generated noise.  Is there any way to modify or implement something on the psu, and make it usable working with Shortwave radios?

[Charlie_Dont_Surf]

There probably isn't a lot of room to place a filter inside the chassis but you can fit an external filter to cut the noise down.
You would place the filter in line between the output of the supply and the device that you wish to power. I do this with some of my switching supplies, even for lab use. (I don't power radios off them.)

Something like this would work. I bought a few of something with a very similar appearance a few years ago from Drok (if I recall correctly) and they seem fine.

https://www.ebay.com/itm/334340331698?mkevt=1&mkcid=1&mkrid=711-53200-19255-0&campid=5338678874&toolid=20006&customid=2dcb9d6c815615459e9ef509571b2325%7C%7C&gclid=2dcb9d6c815615459e9ef509571b2325

[alpard]

Thanks for your info and advice.  Yes, that looks a great filter for the psu noise problems.  But the price seems rather high for a filter.
If it were cheaper, it would be a very attractive device to add into the link.

But maybe I must try to implement battery pack for 12VDC made up of multiple AA batteries. 8x AA batteries are needed for 12VDC. Or buy a high quality psu?  WIll think for the options. 

[ChrisSmolinski]

You can often find good used quality linear power supplies (Linear One, Lambda, etc.) on eBay for a decent price. Easier, much better, and and in the end likely cheaper, than trying to filter a noisy Pride Of China power supply.

[alpard]

I once had an old linear power supply (made by quite famous company - but now cannot recall the brand). The power supply was 20A rated one 13.8V for full 100W Txing on amateur radios.  The psu was powering on an old ICOM IC-751 transceiver for just SWLing.

One day, the psu went bang with smoke and flames.  I quickly switched it off before it caught fire.  Luckily the IC751 was not damaged in any way, but the psu was totally damaged beyond repair.  I got it few days before the incident from eBay business dealer mostly selling used radio gear, and was able to return it for full refund.

After that, I am apprehensive about any linear power supplies, and even switching psu, they can blow any time  causing possible damage to the radios and even more.
Maybe it happened due to the age of the power supply, but then I just have this idea that it can happen to any power supplies.  I try to avoid using power supplies whenever possible.  They are also noisy due to the fans (if have them), and definitely noisier on the radios than battery powered radios.

But maybe it was just one off experience I had, and maybe they are safe to use I don't know. 

[redhat]

Batteries can go bang and catch fire too, ya know...

It should be noted that how filtering is installed will have a large impact on how effective it is.  Understanding how circulating current flows through grounds, chassis parts, etc and how to address them is key to RFI and noise abatement.

+-RH

[alpard]

Making up 12V battery pack with 8x AA batteries were absolutely no use at all.  It powered on the radio OK.  But the radio draws about 500 - 600mW on standby.  The 8x AA battery power pack lasted about 1 hour, and then the radio died off.  I measured the voltage from the power pack, and it was 10V.  12V to 10V in one hour, and the radio needs new 8x AA batteries.   So, it would be ok for emergency use or for repairing 12V radios or devices for powering on for 30 min. to 1 hour, but no use for daily use of powering the radio.

I went to Amazon, and bought a new switching PSU 13.8V rated at Max 30A.  It does the job.  The PSU seems solid, accurate and quiet enough running the radio.  Hope it will last for years with no problems.  It would be handy later, when / if I decided to go for transmitting with HF / VHF transceivers too.

[alpard]

The new switching power supply is actually very noisy with the constant fan going in the psu.  And the digital meter reading on the front of the psu for current reading is not working.   Not ideal.

[Charlie_Dont_Surf]

Well, you can still obtain linear power supplies, but they will likely have/need a fan too.

The other thing to note is that, sadly, because every fraction of a cent matters in Chinese manufactured consumer electronics, these guys put the cheapest fans they can get in the power supplies and these fans...well...really blow. (Pun intended.) I have replaced the fans in many of my power supplies with fans that are quieter and push similar or higher amounts of air. (My sanity is worth a few more dollars.)

Fans at this price point are generally in standard sizes so likely to find replacement of the same size. Noise and air flow are generally listed in the selection tables on Farnell, Digikey, Mouser, Newark, etc. (For noise, look for lower dBA.)

[alpard]

The fan in the new switching psu seems to come on all the time even when the radio is off.   But when the radio is on, the fan gets louder and faster.
It seems to had been set to come on at certain temperature within the psu using some electronic programming chip in the factory?     But the output voltage seems to be solid.  The radios seem happy and on all day with no concern over the running out batteries like before when using the 8x AA battery pack.  When the input voltage from the psu drops to 12V or less, the radio gets noisy. At below 11V DC, the radio doesn't function properly.  It needs good solid 13V+ for working properly.  The new switching psu has no problem for providing the set voltage to any radios.

I am not going to open the psu and change anything because it would invalidate the warranty.