Antiference PS12F - Masthead Amplifier PSU - Page 1
Forum section: electronics / general

author: TheBay
author_rank: Unknown
timestamp: October 08, 2018, 10:52:23 pm
content: Decided to fit a new Masthead Amp, so bought an Antiference 4 way Masthead Amp that comes with a PSU,These usually come with a tried and tested Linear PSU, however when the kit arrived I noticed they had switched to a cheap little SMPS.I decided to try it, this little PSU was causing lots RFI, it even caused interference to the TV!I opened it up for a nose, they claim it's "Screened" but it isn't, it was sort of "potted" but that came off quite easily, Antiference said that's the Screening...They must have some magic potting compound I've never heard of.The design leaves a lot to be desired. Lack of mains filtration, safety features and it also comes with a FAKE BS Rated Fuse in a UK Plug of questionable quality.Just look at how those F Connectors are mounted, they have their own little antennas!It's in the hands of Trading standards at the moment, but thought I'd share some pictures of this awful little device so anyone here can avoid.I did e-mail Antiference and was basically told it was a cost cutting exercise, when I highlighted issues with this product they didn't want to know.I since replaced it with a Wolsley Linear(Last picture) which functions as it should and is built 100x better and safer.

author: Ian.M
author_rank: Super Contributor
timestamp: October 08, 2018, 11:45:41 pm
content: The primary to secondary creepage distance is a lot higher than typical cheap unsafe far east PSUs, though its a pity they compromised it with C9 under the optocoupler. The number of electrolytics, chokes and semiconductors indicates that the circuit design hasn't been muntzed. If the PSU had been supplied with an external fully screened F bias-T, I suspect it would have been entirely satisfactory to all except HAM DXers. Unfortunately unscreened SMPSUs are more or less unavoidable nowadays - just about every CFL and reasonable quality LED bulb, and every personal gadget has one, so this one's contribution to local RFI conditions is only notable because of the close coupling between it and the RF signal on the amplifier's down-lead.Their decision to run a RF signal along an unscreened, non-impedance controlled track on the PCB, next to the secondary winding rectifier, which is probably acting as a harmonic multiplier of the switching frequency, is extremely unfortunate.The dangerous fake BS1362 fuses don't meet the technical parts of the BS1362 standard. If the fuse has a blast resistant thick-walled ceramic tube, substantially flat ended well attached end caps, a sand filling, and the correct gauge fuse wire, its entirely possible for it to meet BS1362 specs.

author: TheBay
author_rank: Unknown
timestamp: October 09, 2018, 12:06:35 am
content: Quote from: Ian.M on October 08, 2018, 11:45:41 pmAgree with the above and the fuse is completely fake, no sand or a thick wall. That was my main reason to report it to TS.They advertise it as screened though and it doesn't do its job properly it will make a TV signal worse as it radiates interference via the Coax and mains cable, bitof a pointless device really, yes it supplies power to the Masthead Amp, but it itself degrades the signal.I'm a Radio Ham btw, so yeah was causing considerable QRM here. More so than any SMPS I've come across.Here is a video I did when I first suspected the fuse being Non BS compliant:

author: Cyberdragon
author_rank: Super Contributor
timestamp: October 09, 2018, 12:34:47 am
content: I've had a pocket FM transmitter totally mess up the TV before, it doesn't take much. But yeah, the thing is still illegal Chinese garbage, at least it's not as dangerous as it could be (unless that transformer is nasty).

author: TheBay
author_rank: Unknown
timestamp: October 09, 2018, 07:25:06 pm
content: Quote from: Cyberdragon on October 09, 2018, 12:34:47 amI'm half tempted to unwind the transformer and have a look.