At first the yamaha piano wouldn't turn on But after resoldering the chip back in I was greeted with piano noise. When i would play it loud it would cut out and sometimes reboot. After lifting the other circuit board I found the metal dimpled upwards making slight contact with the circuit board. After hammering it down and reinstalling everything. It doesn't cut out or reboot anymore. Someone had put a bolt in that was too long and it bent the metal towards the board.
Q1 and Q2 removed I'm getting about 32 volts into a 4.2 ohm load so looking at around 250watts Which should be roughly right seeing as it says a 300 watt amp(though we all know amp wattages are like politicians).
Q1 and Q2 are j111 (a npn chopper transistor) What would be a downside to permantly leaving these out?
304v is what I'm getting. So all the rails look good now I have to hit the output section, because 1k .5 v input into a 8ohm load I only get about 10v on the output which I believe is around 12.5watts definately not even close to what it should be doing.
Input was into CH1 I realize now I should try the aux and other inputs to narrow some down. In the power amp input about what voltage should I be inputting there( I have an hp200 signal generator I think it will put out at least 20v) For preamps I normally use about half a volt.
This one reared its head as u3 failed putting out only about 5v. I replaced it and 15v rail is good now. What I'm missing now is the 300v rail. q11 is getting 56vacI'm going to check voltage at c44 and D1 to see what I'm getting there.
D1-D4 what kind of circuit is that? A rectifier or somekind of voltage doubler, trippler, etc?
This is how your guessing. Goober over at this other site said doing this fixed his amp what can I buy to fix my amp ?
Get voltages at your rails to really see if you have a power supply issue. The transformer and caps are only a part of the power supply, just as oil and water and gas are only parts of a car engine.
People come here to learn and to hopefully pass it on. Maybe their cost benefit isn't worth your time. Ask for help be ready to supply some answers, if its not worth your time why be here? It's one of those days so excuse me nosaj