Modified or pure sine wave inverter?

Thepipdoc

Thepipdoc

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I'm considering buying a smallish inverter to run a tv and free sat receiver box when no 240v is available.
Do I need a pure sine wave inverter or will a modified type be OK? (modified substantially cheaper)
 
It depends entirely on the quality of the modified sine wave (ie how close it is to a true sine wave in terms of harmonics) and the tolerance of the equipment to it. In other words, suck it and see. A pure sine wave inverter should be fine, but many will not maintain a true sine wave when a load is imposed which is close to the maximum capability of the inverter.

For that and for reasons of efficiency, you'd be far better off buying a 12V telly and satellite receiver.
 
A pure sine inverter will run everything a modified sine wave inverter will and more. Unless there's a significant reason not to (price may be one) I can't see why you'd buy anything other than a pure sine wave inverter. You may be OK at the moment but subsequently find you're that not after getting some new piece of kit. Some laptop chargers need a pure sine wave for example, so a new laptop in the family could mean a new invererter or not being to charge the laptop on the boat.
 
Thepipdoc said:
I'm considering buying a smallish inverter to run a tv and free sat receiver box when no 240v is available.
Do I need a pure sine wave inverter or will a modified type be OK? (modified substantially cheaper)
Click to expand...

Will you be able to hold the bore-sight of the receiving dish on the satellite away from a pontoon, or even if you are on a pontoon for that matter? ;)
 
Asuming it's an LCD TV, both the devices that you want to run are low-voltage internally - so you're proposing to take a 12-volt supply, boost it to 240 volts, then connect devices that will internally drop the voltage back down to 12 volts again - not very efficient! However, a modified sine-wave inverter should do the job, if it doesn't work then take it back to the supplier as 'unsuitable for your purposes' and get a refund. A proper sine-wave inverter will be so much more expensive that it will almost certainly be cheaper to buy a 12v receiver and TV.
 
Sine wave inveter

I would say if you can afford it buy a pure sine wave inveter. A modified sine wave can cause inefficiencies that can cause things to overheat and waste battery power when you don't know it. good luck olewill
 
lenseman said:
Will you be able to hold the bore-sight of the receiving dish on the satellite away from a pontoon, or even if you are on a pontoon for that matter? ;)
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This a valid question.
Whilstmy home berth and most Marinas provide electricity - some don't.
I'm currently in Torquay town dock marina and on this occasions I've been fortunate to pick up one of the 240v supplies, but one of the draw backs to this marina is the fact that you can't always get 240v. Having said that, terrestrial TV is very good here so I don't need to use the satellite receiver.

....... and having said all that, I have 12volt Maxview decoder box but I fried the inside bits last week and I'm trying to get my electronic wizard friend to repair it. He's identified the part that has frazzled he just needs to locate a supplier.
If he repairs it I wont need to buy a inverter.
 
Thepipdoc said:
. . . . . and having said all that, I have 12volt Maxview decoder box but I fried the inside bits last week and I'm trying to get my electronic wizard friend to repair it. . . . .
Click to expand...

Methinks someone connected the red and black the wrong way round by the sound of things. Hopefully that won't be too difficult to fix? :p
 
lenseman said:
Methinks someone connected the red and black the wrong way round by the sound of things. Hopefully that won't be too difficult to fix? :p
Click to expand...

Nah, it wasn't quite like that. I ignored the instruction to ensure the power was switched off before any "wires" were disconnected - this instruction apparently includes the co-ax cable.
Apparently I blew a transistor!
 
lenseman said:
What transistor do you require, do you know that type number and is it an obscure type? :(
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I don't have the number of the transistor but the friend that's hoping to repair it does. It seemed to be readily available but because the immediate area around where the transistor used to be now has a hole the much greater than the transistor he's going to have to find a replacement with "tails" ( i don't know if that's the correct description).
RS Components don't stock this type - any suggestions?
 
Thepipdoc said:
I don't have the number of the transistor but the friend that's hoping to repair it does. It seemed to be readily available but because the immediate area around where the transistor used to be now has a hole the much greater than the transistor he's going to have to find a replacement with "tails" ( i don't know if that's the correct description).
RS Components don't stock this type - any suggestions?
Click to expand...

I fully understand what you mean "with tails" ;)

You will have to be sure that the replacement transistor is not part of any 'radio frequency' circuit. If it is, and you change the fundamental layout of the circuitry, this could introduce stray RF eddies and cause howl-round, but I am sure you will be OK. ;)

Without knowing the part number, it is difficult to suggest a place to buy but I have many transistors in my 'spares' department as I have been in radio ever since Noah . . . . no; make that Marconi. :)

By the sound of the description, it shorted with quite high current to create a hole in the PCB! :eek:


Ask your repair chap to have a good look at the surrounding electrolytic capacitors near the burnt out transistor. Get him to see if they are 'bulging' on their bases and also look for any other scorch marks particularly under resistors near by specifically those routing down to earth? Your guy will know what to look for. I suspect everything will be OK if the transistor went off with such a bang as to form a crater in the board there would be little time for anything else to get even mildly warm let alone scorch any part of the PCB. :o

As long as you are aware of the cause, ie: you did something wrong, then replacement should be fairly straight forward and hopefully you haven't fused another part of the board causing your new transistor to blow when you turn it back on?

If you can get the part number and post on this forum or text me, I am sure we on these forums can find a replacement for you in very short order. :)
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Thepipdoc said:
RS Components don't stock this type - any suggestions?
Click to expand...

Farnell could be a better bet, but if your friend knows what he's doing, I expect he will have already tried them. Another possibility is DigiKey - they're in the USA, but deliver very quickly to the UK, but there will be a small order carriage charge, and VAT to pay on deliver. Otherwise google the part number.
 
If your still thinking of getting an inverter, the setup i use is a modified sine wave 3.5kw inverter for things that draw lots of power, i occasionally use the microwave off it and the hoover, and for everything else electronic that needs 240v, i have a APC UPS that i got off ebay for £20, took the buzzer out and wired it direct to the house batteries on my boat and it provides very very clean power to everything under 750watts, so i get the best of both worlds and it cost less than £100 for both inverters
 
lenseman said:
I fully understand what you mean "with tails" ;)

You will have to be sure that the replacement transistor is not part of any 'radio frequency' circuit. If it is, and you change the fundamental layout of the circuitry, this could introduce stray RF eddies and cause howl-round, but I am sure you will be OK. ;)

Without knowing the part number, it is difficult to suggest a place to buy but I have many transistors in my 'spares' department as I have been in radio ever since Noah . . . . no; make that Marconi. :)

By the sound of the description, it shorted with quite high current to create a hole in the PCB! :eek:


Ask your repair chap to have a good look at the surrounding electrolytic capacitors near the burnt out transistor. Get him to see if they are 'bulging' on their bases and also look for any other scorch marks particularly under resistors near by specifically those routing down to earth? Your guy will know what to look for. I suspect everything will be OK if the transistor went off with such a bang as to form a crater in the board there would be little time for anything else to get even mildly warm let alone scorch any part of the PCB. :o

As long as you are aware of the cause, ie: you did something wrong, then replacement should be fairly straight forward and hopefully you haven't fused another part of the board causing your new transistor to blow when you turn it back on?

If you can get the part number and post on this forum or text me, I am sure we on these forums can find a replacement for you in very short order. :)
.
.
Click to expand...
Brilliant stuff - thanks.
unfortunately my repairer is away from work all this week (he works for me) and I'm off to New York next week so I won't actually touch base with him for a couple of weeks.
I've forwarded your post to him - he also speaks this strange "Techie" language that the un-techie don't understand! :o
I have a feeling he wrote the transistor number down on a piece of paper prior to going on holiday and if so I'll post the number sometime tomorrow.
Thanks for your help.
Bernie
 
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