How long should a TV masthead amplifier last?

[kevt296]

Hi All

I have an Optima MA20-4 (4-way) masthead amp fitted in loft and connected to a loft installed aerial. It was installed in Aug 2010 and feeds 2 TV's. We use only terrestrial tv signals through freeview boxes. Loft is standard, gets cold and damp in winter but no signs of water damage or ingress to any part of loft.

We have been away for a couple of days and on return we have no signal to either tv. The smaller tv with built in freeview just about gets a frozen image but the main tv, nothing at all despite the freeview recorder stating that signal strength to most of the channels is above 70%.
We live just South of Oxford but I cannot find any problems reported with Transmitter and none of our local friends seem to be experiencing problems.

How long would you expect a tv amp to last (nominally) and if it sounds like the amp is at fault can anyone recommended alternatives or is the 4 way Optima MA20 still a good choice!

Thanks

 

[Lucid]

It's designed for outdoor use, so the fact that it is indoors should give it an easier life. Others in the trade might have differing experiences, but my first instincts would be to check that the power supply (PSU) is on, then check that none of the cables in and out of the PSU have been snagged or come loose. If they're okay then I'd look for water in the cable from the aerial to the amp and (if the run goes outdoors) the amp to the PSU. Water gets in to cables either because of chaffing due to unsecured/poorly secured drop lead and inadequate termination.

If anything is likely to have given up then it's the power supply.

 

[kevt296]

Hi Lucid
Thanks for your reply.

All equipment inc. aerial is inside loft. Both psu and distribution unit are securely attached to roof beam with plenty of slack in the cables. There are no signs of any water penetration/ingress to cables or amp. Green light on psu is lit and cannot find anything obvious.

 

[kevt296]

Hi Lucid
I dismantled the psu and checked voltages across transformer. I was getting ac mains voltage on the input side but no 12v dc on the output (direct output from transformer). So I guess a new amplifier then! Any recommendations? Particularly one that is designed to cope with interference from 4G?
Thanks

 

[Lucid]

If the power supply is faulty then you could just replace that bit. The masthead amp is likely to be fine. But if you want 4G filtering (LTE) then there's an Optima with that on this page http://www.satcure.co.uk/accs/page11c.htm

The whole install seems a bit odd though. Masthead amps can be mounted in the loft, but the idea really is for them to be as close to the aerial as possible in order to get the cleanest signal i.e. on the aerial mast. Second, the idea of having the phantom power supply sending 12V up one of the downleads is so that one doesn't have to have a 240V device running 24/7 unattended in an area that undergoes some quite large temperature variations. The PSU should really be somewhere in the house. I can think of a couple of reasons that would prevent this such as DC blocking wall plates, but in general the PSU would be happier in the main body of the house and you'd be able to switch it off if not needed when the house is empty.

 

[kevt296]

Hi Lucid
Thanks again for your reply and the link. Will check it out.
In my case the amp box is approx 8 feet from the aerial, both of which are in the loft. The psu is right next to it. I agree with what you are saying. I find it a little weird that the psu is series linked into the main TV cable and not directly connected to the amp distribution box. I would have thought
I guess I could always fit the replacement in the lounge where it would not be affected by temperature and as you say, could be switched off when not required. However, would this not cause a reduced strength signal to the other TV that is being fed from the amp box, as the power output is now being fed along a much longer cable before it reaches the amp box?

Your help has been appreciated
Regards

 

[Sam Gangee]

You can't switch the PSU off if you want a signal anywhere.

Masthead amplifiers are designed to tolerate a certain temperature range as experienced outdoors. Most lofts experience extremes of temperature, being almost as cold as outdoors in winter and as hot as you can imagine in summer! This extreme may shorten the life of a masthead amp and will almost certainly kill a PSU designed to operate within normal room temperature range. In brief, the PSU should not be in a loft because it's usually too hot in summer, and for safety reasons. It should be mounted on a wall where it gets good ventilation. Never lie it on a carpet or on loft insulation; it will overheat.

For the record, I've had several masthead amp systems fail:

1. Electrical storm caused static to build up on the aerial. This discharged through the amp.
2. Rain water got inside because the aerial connection hadn't been sealed.
3. Rain water got inside because the amp had been mounted upside down.
4. Power supply failed because it overheated. (It wasn't mine so I don't know why.)

More info.: http://www.satcure.co.uk/tech/amps.htm

 

[Lucid]

I find it a little weird that the psu is series linked into the main TV cable and not directly connected to the amp distribution box...

I could always fit the replacement in the lounge where it would not be affected by temperature and as you say, could be switched off when not required.

..
would this not cause a reduced strength signal to the other TV that is being fed from the amp box

There's nothing really that weird about how the PSU is connected. It is done this way for the safety issues previously mentioned, and also to avoid the cost of running power in to the loft from a ring main on a lower floor [because you wouldn't wire in the the lighting circuit... right.... right???]

The PSU will definitely be happier in the body of the house.

Where the PSU lives should have no effect on the masthead amp so long as the signal cable between them is of decent quality.

Sam Gangees' comment about never switching off the PSU only applies when the house is occupied or if you have a Freeview recorder and want to make unattended timer recordings. I think he may have just skim read the replies and presumed we were talking about switching it off each night. That would of course have the effect of disabling the aerial amp and so stop Freeview reception to any device. But that's not what we were discussing.

 

[Sam Gangee]

(The PSU) ... could be switched off when not required. However, would this not cause a reduced strength signal to the other TV that is being fed from the amp box, as the power output is now being fed along a much longer cable before it reaches the amp box?

You can't switch the PSU off if you want a signal anywhere.

Because if you switch the PSU off you will get zero signal from the Amp on all outputs.