Power Supply Help Requested

Hi to all you very fine Charlie Tangos,

I do hope you're all keeping well and enjoying your radio pursuits.  


I have a couple of questions for anyone that can help me out if you'd be so kind.

Being housebound disabled I don't exactly get the opportunity to visit radio outlet emporiums and just as well really because I'd have questions they may not be able to answer or be too happy if I arrived armed with screwdrivers and test meters.

Unfortunately as past experience has shown not many are that happy to receive telephone calls with the type of questions I ask either!

I need something beyond the physical dimensions, pretty LED colour it comes with or apparent 'recommendations' and customer reviews.
("Does exactly what it says on the tin" or "Arrived later than expected" is hardly helpful.)

So onto my question....


Does anyone own one of these power supply units (they're all the same just badged differently) :-

Nissei SPS-1335

Nevada PS-1335

Sharman SB-30BB

Amongst other names stamped on them out there but the back looks like this :-



This looks for all it's worth like a good power supply for my needs and I do love the inclusion of the 'battery' option so that it can trickle charge and switch over to battery backup should there be a mains failure. (We still get them in my village although not as often as times of old but 'brown-outs', fluctuations and sometimes noisy switch-overs still occur.)

What I do need to know though is whether the "-", negative or black terminal post is isolated from the mains/chassis 'Earth'.

If anyone has such a power supply and access to a multimeter (DMM or otherwise) could you tell me the continuity or resistance reading (marked Ohms on a meter) between the aforementioned connections. (Whether that be the screw post marked with an earth symbol, the fan guard screws or the central pin of the mains connector to the negative black terminal post.)

Unfortunately as this is a current production unit I cannot seem to find a service manual/schematic/circuit diagram for it and manufacturer emails remain unanswered. Therefore I've run out of options to check for myself.

The other really handy thing would be a picture of the internals if anyone can perform this safely. (There's a big 300 Volts or so of DC power that sits inside them and the internal capacitors for some time even after switch off!) Please don't concern yourself though if you feel unsure about opening such stuff or worried about voiding any warranty.

This will help me in finding a suitable replacement for my currently utilised power supply which was kindly donated but required some work from myself to isolate the negative from the Earth along with an external mains filter and power factor correction choking. I'd rather not repeat that excercise for a purchased unit to which I would have had to save up me pennies.


Any help would be most appreciated, given a 'like', a 'thanks' vote, your brain rewarding you with a serotonin & dopamine rush and much admiration from myself.

It may even be handy for other Charlie Tango members now or in the future and wouldn't that be a great thing.  


All the very best,
Victor

Hi Victor,

I had a look myself on the internet and like you couldn't find anything. I can only suggest asking Nevada if they know or at least do a test of one of their units. I'm sure they wouldn't mind.

Nigel

yes it's always worth a try

Good luck in setting up.

Cheers for the responses so far all.

I don't think I'm going to get to the bottom of this with any sort of ease so I might go the old fashioned route of a linear power supply and save up a few more pennies. At least that way I know what I'm getting.

Thanks again.

73,
Victor

Hi Victor,

Been doing a bit more digging about. Got this info from hamradio.co.uk (M.J.S Martin Lynch and sons)

MyDEL PS1335 switch mode Power Supply.

This could be a clue, got it from product information,

CAUTION 

Even though the chassis of the unit is negatively grounded, use correct terminals to connect cable 


Hope this might help,


Nigel

Much appreciated there Nigel and thanks for taking the time.

I've been digging through a fair amount of datasheets & instructions finding myself disappointed with manufacturers specifications.

Along with some recent experiments switching between battery and mains driven power sources of various kinds (receiving doesn't require that much current) I've been shocked that despite my efforts in cleaning up my shack RFI wise there's a big difference in noise levels between them all.

With that in mind I will be looking at other options than the power supplies I originally noted at the start of this posting.


Thanks again to all.

All the best,
Victor

You're welcome Victor, I try and help out where I can. I had a similar issue with RFI noise but trying to nail it down was was right pain as I wasted time thinking maybe it was a cheap power supply somewhere, the kind you get with mobile phones. Worked out it wasn't coming from inside the house at all and traced it to my neighbours plasma TV! Thankfully they moved so things improved a lot.

Hope you get it sorted,

Nigel

That's a great attitude there Nigel and one we warmly welcome as well as promote here at Charlie Tango.  

Yep, you can fair old chase your tail locating QRM noise sources as many of us can attest to!

It seems my good wife has overheard my shenanigans and kindly offered an early Birthday gift to me of a new power supply. I have a couple of 'linear' options available.....So I'm off shopping!

Much appreciated again.

73,
Victor

well done Victor hope you have success with your shopping trip 

So did you get your pressie then Victor ?

I did David, I very much did.  

Sharman PS-LM40 linear loveliness....has a few quirks, (which I can easily fix ), weighs a ton but fits in my radio shelf perfectly and was worth about 1.5 ~ 2 S-units reduction in wideband hash on the lower bands!!

Not quite an Astron or Microset but a lot cheaper.
(Not complaining, my wife bought me the perfect Ham pressie!)

Good choice Victor.

Having run similar for a while now, but badged under a different name, I can guess the main quirk to address. I will mod mine inside at a later date, but it's been running fine with an outside of case fan running at low speed (HERE) pulling air through the side vents, I've tidied the voltage reducer away in a little box btw. With this, and with the low power I draw from the PSU, the internal fan rarely comes on now.

Hi Neal mate,

Ah, just saw your link and hope your happy with your version. (I think they come in QJE flavours amongst others and reminds me of the older Alinco DM340 too.)

Yep, you guessed it - Although the fan isn't particularly loud it did take me by surprise the first time it went off but luckily it doesn't go off too often with my QRP limits. My take on this was to hook up two 60mm Evercool 12v fans wired in series which is almost silent but provides sufficient extra cooling. These run continuously wired to the back of the cigarette lighter style socket and if one of the fans fails the other will only get 12v max so just become a little noisier. Luckily I have a drawer full of them (bargain buy) so can always replace them but quick calculations shows they'll last years. So far the main fan hasn't come on once since.  

The other 'quirk' was the poor choice in main power terminals from the manufacturer that aren't the best and don't fully unscrew. Luckily I have some old 1960's British made 1/4" shaft types that are currently bolted onto a homebrew power strip but will adorn the PSU eventually.

I've also added a simple comparator overvoltage protection circuit to my power distribution box just to give that little extra reassurance. (Old style 'crowbars' are a bit savage and still rely on blowing a fuse.)

I did have a USB outlet socket wired to my additional powerstrip but the damn thing uses a 'buck' convertor and noticed it was horrendously noisy RFI wise on 160/80/40m so that b*gger has come straight out!

Overall a very happy bunny and pretty sure it'll outlive me.  

73