Insignia progressive scan home theatre unit power transformer output

Subtract 2 zero's off of that and youd more likely have the correct wattage.

Probably should give it a thorough visual under very good lighting and see if you can determine what smoked. Surely there will be some evidence as smoke leaves residue and also component distortion.

Could there be an overvoltage protection (a MOV) be present at the mains input? That one would blow a fuse, and the rest might still be working. That happend here when somebody put a computer from the USA on 240 volts. He switched it to 240, but the MOVS were still meant for 120 volts and kind of got smoked.

The first thing to note is that any output power quoted on these Chinese HC and hifi systems, is a total power, so with 6 channels of output, that takes it down to 180 watts per channel before you start. The next thing to note is that the power quoted is back-pedalling-mid-winter-differential-peak-garage-music-with-a-following-wind power, which is aproximately 50 times RMS output power, so 3.6 watts RMS into 4 ohms per channel, is about what you can expect to get ...

As far as what exactly was powered when the excess voltage was applied, you can by no means assume that it was only the standby supply. Many such items will come fully or briefly fully to life, after power is reaplied from a full power down. This allows the system control micro to do a status check on the machine's current mechanical condition, and also allows the system to check for such things as pending timer events, or to resume playing and so on, after a power interuption, which may be due to an external power line interuption, outside the user's control. Many units 'remember' whether they were on, before the power was removed, for just this reason.

Further, if a switcher is hit with double the voltage it's expecting, then after being very lucky that the side of the chopper transistor didn't zoom off into space, there's no telling what unpredictable things that the power supply may have done as a result.

There are not too many places that a "cloud of white smoke" can have come from, without any obvious damage being visible. My best bet would be that it came from the main filter cap. If the power supply is designed for 110v operation, then the chances are that this cap is rated to only about 200v. If 220v ac was applied to the unit, the voltage across this cap will have been in excess of 300v. Release of the magic white smoke is the usual result of doing this to an electrolytic.

Without any further messing about, the very first thing that I would do, is to replace that cap. It could well be damaged, and be causing the supply to suffer excess primary-side ripple. This in turn, can lead to erratic operation, and excessive noise on the secondary rails, which may well result in poor playability issues. I do, however, feel that lack of output on one front channel compared to the other, is unlikely to be a power supply issue. I would feel inclined to investigate this by putting a CD test disc with audio tones on it, into the machine, and then comparing levels between channels, with a 'scope. Is the value of the unit sufficient to warrant your time getting into this to component level, though ... ?

Arfa

Thanks for the input guys: you have hit the nail right on the thumb with this one as I wanted to know if anyone had any experience with these units precisely because it is unlikely to be worth spending any money on it. Yes, my reference to the power figures of the 1960s was indicative of what I think this unit is capable of and what continuous RMS power means in relation to the 1000W output quoted. Incidentally I had to play a trick to get the sub to work 'properly'. There is only one channel output to the sub, a positive wire and a ground wire. My sub which is 8 Ohms obviously has two channels going into it. SO I connected both positives and both grounds to each other (therefore in parallel) to connect the sub to the amp, thinking that I am halving the impedance to 4 Ohms, which might well be more in line with what the amp is expecting. If this induces anyone to clutch stomachs laughing and fall off chairs etc, please post because the sub does actually work and produce some slightly sybaritic sound.

I freely admit that I may ultimately have to connect a line level output to an external amp however.

The test CD is a good idea if I can find one cheaply enough on eBay or somewhere though the only scope I have is on a 1970s Marantz tuner (don't laugh) and it doesn't have a time line. As I indicated, I am curious about that left front channel not sounding correct and cant believe that the power through some transformer to a power transistor could have been in any way turned on when the unit is in standby mode.

I tried looking for the filter caps when I was inside the unit because when I first saw the board looking fine, I thought that the white smoke was most likely the oily insulation between the coiled up parts of some cap or other. But as it is so cheaply made, they don't exactly look gigantic and all caps inside the unit look vaguely similar. None of them look burned out or 'melted' unless there is some carbonisation on the underside of the board which I cant see. But if there was, I doubt the unit would work. I am just a bit surprised that with this level of cheapness in the power transistor transformers and the level of money saving in the heat sinking, a unit which had suffered such 'damage' could continue to work AND have no appreciable symptoms. But I am intrigued by your reference to "excessive noise on the secondary rails". There IS an excessive ringing on the front right channel which might not be present on the left channel because the output is so deficient in that part of the spectrum. As I say, I will probably ultimately have to connect a line level output to an external amp

BTW on further enquiry, when the unit was plugged in, flashing lights started looking as if they were 'blowing' all over the front panel (while it was presumably clearing its memories etc). I am just a bit surprised that no appreciable processors have blown. The unit IS very slow to respond to the remote control however. But the owner says it was always a bit slow to respond to commands like OPEN TRAY etc.

Anyone got any ideas on the choppy video or is THAT indicative of some processor being blown?

I love it... "The first thing to note is that any output power quoted on these Chinese HC and hifi systems, is a total power, so with 6 channels of output, that takes it down to 180 watts per channel before you start. The next thing to note is that the power quoted is back-pedalling-mid-winter-differential-peak-garage-music-with-a-following-wind

power, which is aproximately 50 times RMS output power, so 3.6 watts RMS into 4 ohms per channel, is about what you can expect to get ..."

And that is exactly true. I've noticed that about 3-4 yrs ago and I thought I was losing my hearing. My 20 yo Marantz 100 w/channel stereo receiver coupled with my JBL studio speakers will rattle the windows at

2/3rds full volume. I've always wanted to do a power test on these units but never had the time...I just assign them to the 'junk' catagory and move on to real units...Too bad though, now the Chinese are redefining a 'watt' to a milli-watt....sigh...wonder how the mfg are allowed to get away with it. The equations for power, and the conditions under which it is measured is (was?) pretty much a standard. Hmmm, maybe the speakers are extremely inefficient?!?!? lol

-J