Faulty TV aerial distribution amplifier?

What you describe is typical of the amplifier having lost its power supply, and the signal is just what's capacitively leaking through the unit. Does it make any difference if you actually switch the power to it off?

Thanks for replying... The power is definitely on, as the on/off switch lights up, and when you switch it off there is no picture at all. I should add that I've managed to get one TV to have a reasonable picture by connecting it up to the single "Full" output. But even then it's not as good as if I bypass the amplifier altogether.

Have you tired disconnecting all the outputs, then trying to connect just one (and if that is a bad picture, try another port, then if that is still bad, try another run to a different room?)

Just thinking maybe one of the outputs has got shorted, and this is dragging the whole lot down?

Sparks...

Timbo expressed precisely :

After reading your other submission, it does sound as if the unit has failed. Certainly they can suffer storm damage (lightning). Even if not a direct strike, it can damage the front end.

I mostly did my testing using a portable TV in the loft, firstly plugged into a spare output, and then having unplugged all the other outputs. Didn't seem to make much difference. I don't think I tried it in every one of the outputs, though. What causes shorting? (Just occurred to me that as my aerial is in the loft, a storm seems an unlikely reason??)

Thanks. Just occurred to me that as my aerial is in the loft, a storm seems an unlikely reason??

I wonder if it has just partially failed due to a component or something.

Shorting could be caused by nailing through a cable, or a crap connector at one end (or a fault in a TV/VCR Etc.)

If you tried a few, with all other outputs disconnected, it sounds like the unit has failed for whatever reason.

Do you have a mast head amplifier too (another box of tricks, usually right next to the Ariel)?

Sparks...

Timbo formulated the question :

Most likely the actual amplifier, the FET. Look for a component which looks like a transistor... Three legs, probably black plastic cased. If you can work out the part number on the side, then it should be possible to buy a replacement. Not a guaranteed fix, but it is difficult diagnosing at a distance.

In article , Timbo writes

Very likely to be a lightning belt, this happened to ours a few weeks ago. Identical symptoms. Unless you can recognise the appropriate transistors then replacement is the only cure!.

Don't worry about it being in the loft, the one that did ours in hit a house 400 yards away!....

Thanks Harry.

I'm a complete novice at that sort of thing, so I think I'll probably try replacing the whole unit - thanks for all the help!

Not sure about the masthead, will check it out when I can, won't be for a day or two though. But as I said, the picture is fantastic when I simply bypass the amp unit. Thanks for your help thus far, I'm inclined to try replacing the amp box.

tony sayer explained :

Agreed, I had similar happen a few years ago. It took a printer, modem and an expensive satellite system out. Indoors only improves its chances of surviving, it will not guarantee it.

Are these tiny ? My amp has gone a bit iffy recently, although cycling the power and/or wiggling a few of the leads around seems to restore normal operation for a time. I opened it up expecting to see a decent set of circuitry and maybe the odd suspect component, and found hardly anything inside !

A lightning strike anywhere within half a mile can induce a pretty massive voltage into any cable. You don't need a direct strike or anything LIKE it.

Yes. Some of the RF transistors have a nasty chemical in them. Can't remember what it is, but the datasheets have dire warnings about breaking them open, disposing of them or burning them.

One transistor, a few tiny capacitors and coils is quite typical. Some of them use one of the hybrid RF amplifier modules.

That would indicate dry solder joints, rather than actual failed components. Most probably solder connection to the sockets.

There is almost nothing inside...

Power supply; basic amplifier; perhaps filter components and then some impendence matching to each output socket.

Interesting! Thanks. Definitely going to try a replacement then.

Beryllium oxide.

Mainly higher power devices in the '70s and possibly '80s. More modern devices are usually Beryllia free.