One board solved, my second board had the same problem with the missing jumper for the large cap. The problem is during my testing TP1/2 the TP2 lead fell out and shorted out on the board.
At the time, both fuses and R53/54 burned. I've just replaced the resistors and put resistors in for the fuses. On power up, R53 burned immediately. IVe gone over the board searching for anything that looks like it may have been damaged but visual inspection is OK. I tested all resistors and they look good. I've tested the diodes and D5 is bad, it does not conduct either way.
If D5 was bad, would that account for the burning of R53?
At the time, both fuses and R53/54 burned. I've just replaced the resistors and put resistors in for the fuses. On power up, R53 burned immediately. IVe gone over the board searching for anything that looks like it may have been damaged but visual inspection is OK. I tested all resistors and they look good. I've tested the diodes and D5 is bad, it does not conduct either way.
If D5 was bad, would that account for the burning of R53?
Will the circuit perform fine with a significantly lower gain? My input signal is ~3VRMS so I would only really need less than 1/3 of the gain that the amp provides by default. Obviously there is no point in me having a voltage gain of ~40.
What is the ideal way to change this circuit in order to reduce the overall voltage gain?
What is the ideal way to change this circuit in order to reduce the overall voltage gain?
Thanks for the help, but in digging further,post 441 seems to contradict these values. Now I am definitely not sure what is correct.
you can increase the value of the shunt resistor in the feedback loop, R5 which is 820 ohms can be increased to say 1200 ohms to lower gain....
Good news, bad news!
The side that didn't spark is working great! The side that sparked and damaged Q19 and D5 has a lot of hum when powered up and when playing music sounds like the highs are muffled out.
Before I go and buy an HFE tester, does this sound like a specific issue? I'm thinking a few more transistors probably blew out and instead of a tester I may be better off just buying a new set (minus Q19).
The side that didn't spark is working great! The side that sparked and damaged Q19 and D5 has a lot of hum when powered up and when playing music sounds like the highs are muffled out.
Before I go and buy an HFE tester, does this sound like a specific issue? I'm thinking a few more transistors probably blew out and instead of a tester I may be better off just buying a new set (minus Q19).
The humming was user error, after assembling the chassis and taking readings from the speaker terminals, I got -30mv on the noising side! I had a hard time adjusting that earlier, the mv would creep around a lot. Now both sides are down to 0.1-2mv and holding steady.
R14 is measuring 8.44v on both sides and TP1/2 measured around 30mv. I'm going to let the amp warm up for a while before taking readings again.
Right now, the side with the issue still sounds a bit muffled/muted on the high end. I could do a REW measurement if that would narrow down the problem, otherwise I may just end up ordering a new set of transistors from digikey.