I have a 12 month old amplifier called Prosound, a Taiwanese manufacturer, which has stopped outputting audio.
The electronic display appears to be fully functional, which is powered by one main transformer. There are 3 main leads coming from it, yellow/green, black, and the display power. The display power is obviously working, the yellow/green is out putting 30V and 60V, however the black lead is not reading anything.
Question. Could a transformer blow if it still outputs various other voltages? If not, what else could it be? I've checked the fuses and they're still ok.
Yes, but probably not in your case. You've measured 30 and 60 volts referenced to what? If there are only three wires coming out of the transformer, it would probably be a center-tapped 60 volt unit...giving you 30 volts on either side of the black lead. Try measuring from black to yellow, then black to green. I would bet that you will get 30 volts each time, and that yellow to green is where you measured 60 volts. That's entirely normal.
Why have you fixated on the transformer as the source of your trouble? Most likely it lies elsewhere....
Sorry for my misleading description, there are 3 sets of wire.
Black/black - Motherboard
Yellow/yellow/green/green - Motherboard
Mixure - Front display.
We know cable 3 works due to the front display is operational, cable 2 is outputing both 30 and 60 volts, but I cant get a AC or DC voltage out of cable 1. Obviously in AC, but it was worth a try.
I know very little about electronics, but I am able to visually see there are no blown caps, no burnt out transisters, and the 4 fuses are in tact.
The display doesn't read any graph of sound input, so I would guess that the output side of it still works. However, I really don't know what this means :)
I can hear a slight humming noise, but that could be normal for a big transformer, I guess.
Still pretty vague. '3 sets' is confusing. For instance, set #1: 'Black/black'. Is that two wires, both black etc?
Still don't know where you are measuring, from each wire to ground, or from wire to wire...and how many wires are there? Four; two yellow and two green?
Visual cues only go so far. A component can be bad with no visual indication.
There is no 'output side' of a display, unless you count light output.
I'm guessing this is probably beyond your experience level to even get a start at fixing it; but if someone wants to chime in, I'm glad to be wrong.
I agree with jak that it is highly unlikely to be a transformer problem. It is rare for individual windings to fail on the secondary side. It would help to know what the two black wires are connected to. For instance, the AC - AC input of a bridge via one of the fuses ? If this were the case, then at least you would know that there should be some kind of winding between the two blacks, and you could easily measure across them with an ohm meter. However, I tend to agree that blacks would usually, by convention, be winding centre taps, so this is in fact what they might be, and both connected to ground, hence the reason that you get no AC reading across them.
Is there no indication on the transformer as to what windings and output voltages it has ? Transformers often have this information on them, particularly when they have permanently fixed colour coded wires.
Beyond this, I am of the same opinion as jak, that a diagnosis and repair of this type, is probably beyond a beginner with no electronic service experience. Good news is that if nothing is burning up, and all fuses remain intact, then the problem is likely not too serious - assuming that it's actually not the tranny, of course ...
Technical schools and many high vocations schools take in local community projects such as yours. Check locally - and do not hand this unit to a "student want-a-be" - I have seen repairable gear destroyed by that process.
This is one of those areas where experience and skill together make the best technicians and repairman. Many are retiring!!
My guess would be the output transistors are blown, along with likely other parts in the chain. This would cause most amps to shut down and behave similarly. If you know little about electronics then either junk it or have it serviced, you won't get anywhere without some propper tools and knowledge.
Yes all the other comments do apply and the repair scene is getting very sketchy these days. For a lot of newer eqp the manufacturers won't or can't supply any documentation. The comment about the older techs just knowing where to start is very much to the point. Unfortunatly there are repair shops that take things in, charge an estimate fee and then say they can't fix it. "tis a sad state of affairs lads" All that being said: 1. the black wires, just 2? may be the 110 AC input power. You didn't mention any other wires, are there any others? 1.5 just because you measure voltage is not a lot of help. The power supply section could be bad, rectifiers, regulators, etc. 2. most modern amplifiers have a relay to disconnect the speakers from the output. This allows turn on with out a 'thump' and there's usually a circuit that will sense DC on the output and disconnect the speakers to prevent damage. There are a couple of chips designed specifically for this function and they can be troublesome and crap out by them selves. 3. If your finals are blown or partially bad, based on your stated low level of knowledge about electronics, it's probably beyond your expertise to repair. I would seek out a repair shop that specializes in audio. NOT your neighborhood TV shop, which are just about nonexistent these days anyway. Look around the web, there are several that advertise. Be wary of repair shops attached to the "big box" or even small box stores. Be prepared to have to ship, and pay for it, pay an estimate fee up front, and a substantial repair fee, and all this must be balanced against your original purchase price or the replacement cost. A lot of stuff gets thrown away or "abandoned" because of cost issues. "a sad state of affairs indeed" I could offer a couple of other things to check, but if you can't make the repair, can you solder? what's the point. Perhaps the only advantage would be having a reasonably good idea of what's wrong, to know whether the repair shop is padding the bill.
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