Switch mode power supplies for masthead amplifiers.

[Antennaman]

For many years, I have used DC plug packs (transformer/bridge rectifier/capacitor filter) for nominally AC powered masthead amplifiers I install. It is now getting reasonably difficult (for me) to source these locally, as the ones I prefer to use are no longer being supplied.

They have been replaced with switch mode varieties, however, I seem to be replacing ones that have failed after only a short period of time, (some of which I have installed), which is annoying.


eg:

I smelt this one as soon as I walked into the house.

So, I have gone back to using AC plug packs, which still use iron, & keeping my small supply of DC ones for special occasions on an as needed basis.

Just wondering what the experience of others has been with switched mode plug pack failures, for plug packs that are left on continuously, as could be expected for those used in powering masthead amplifiers?

(I have also encountered these types of plug packs causing wideband RF interference as they head towards failure, usually in a domestic environment, when they are used for charging household items, powering electronic picture frames etc.)

[mtv]

I've been using switchmode MH supplies for a few years and haven't had any issues so far.

It's not a good sign of things to come though, if you are seeing them fail.

[Shadow mask]

Yes, I have seen this also. Had two 14VDC switch modes faulty out of the box and one in the field.

[beeblebrox]

Yep see this often with any switch mode supplies. Especially after a power problem. I'd do one a month at the moment. Had a few unearthed matv power supplies pop of late... All switch mode... None that I installed as mine are all earthed...
The iron cores are pretty solid but as you say harder and harder to buy them.


What's even more annoying is sometimes they go but are still producing what looks like ok power until you put them on a cro either filter caps are shot or controller. Had two from an matv system today both gone bad, still putting out correct voltage with the multimeter but huge ripple current.

so you get an amplifier actually look like it's working, but is producing garbage ie 80dbuv but not lock poor or no ber....

First thing I check if there's any amp in a system now is the power supply

Had two jobs where someone else had been in quoted all new multiswitches for $$$$$$ and I replace the power supply for a couple of hundred bucks.