This amplifier have problem with right channel amplifier board, left works fine. I have replaced some defective components as shown but now the amp runs for about 10-15second then it blows a few part in the "red" area.
Problem is that i dont have time to measure before it blows again.
Bulb and variac does not help.
My idea is to disconnect something in circuit to eliminate some parts or maybe bypass "turn on board" so i can use variac.
I am thinking that some active component starts to drift in value when it warms up.
I quickly turn on amp and when it goes out of protection i turn it off within a few seconds before it blows up and there is no DC on output and none of the small components are hot in the red area.
I am stubborn and any help is appreciated.
Problem is that i dont have time to measure before it blows again.
Bulb and variac does not help.
My idea is to disconnect something in circuit to eliminate some parts or maybe bypass "turn on board" so i can use variac.
I am thinking that some active component starts to drift in value when it warms up.
I quickly turn on amp and when it goes out of protection i turn it off within a few seconds before it blows up and there is no DC on output and none of the small components are hot in the red area.
I am stubborn and any help is appreciated.
Attachments
Can't do that (run IPS in isolation) with a current feedback amplifier (CFA). This amps
feedback/operation is dependent on the low impedance of the output stages.
Looks like this amp is also a stupid CFP output stage (my favorite -sarcasm) , Most likely runaway oscillation ....
OS
Weird bit is that on the schematic they used 2sa970/2sc2240 but on the boards they used 2sa992/2sc1845. Maybe my replacement transistors cant handle the current. Will se if i got any 2sa970/2sc2240. Is it better to test with a load to limit any oscillation while testing?
Have you got any digital scope? Without that I am afraid that you will only be guessing what is going on - example from my Yamaha A-700:
I have all the equipment that i need, reason, for the thread is to see if there is a faster aproach to fault finding in circuit. I will defenetivly find the fault but sometimes when things are a bit slow i need some new ideas too not get caught up in a thinking thats incorrect. I have probably repaired around 250 class A/B amplifiers and too be totaly honest i use the income to finance buying even more defective amplifiers. Its sick, but its me. Anyway i keep the best sounding (for me) . Whenever the best sounding bunch is more then 20 amplifiers i always sell a few. Do i keep the best ones? Do i keep the most expensive ones? Its a hobby and i really dont care much about the money. If you ask me which one i prefer its difficult but only the best A/B can keep up with a good class D. A few harman/sansui/nad is what a generally listens to.
Feedback signal seems to be directed "upstream" via P102B connector (and cabling?) - have you checked these?
Yeah thats a great idea. Not sure if it is glued but i will try to measue that module with smd components. Its the shiny module close to the NAD logo on the mainboard
