I remeasured and it is 1.78V at WH.I and still 85V voltage drop. Maybe the amp was longer time on last time. I will keep it now on some time.
Btw. the predriver transistors are running very hot I can barely keep my hand in the small heatsinks were they are connected, but it is almost same in the right channel.
Btw. the predriver transistors are running very hot I can barely keep my hand in the small heatsinks were they are connected, but it is almost same in the right channel.
I don't trust the current situation, since you have tried to turn the pot without success when suddenly the lamps had 85 Volt.
Nobody knows if the pot is again in the right position !
So switch the amp off, let it cool down and then try to adjust 40 to 50 Volt on the Lamps with pot R124.
If not possible anymore to adjust the lamp voltage with the pot, put it in the max 500 Ohm position.
Then let it warm up and try to push and pull a bit on the board until you have the 85 V back on the lamps.
Be aware that when the voltage over the lamps is 85 Volt, that the predrivers Q29,Q39 and Q40 on the + side, and Q41,Q42 and Q52 on the - side are no longer able to conduct and that the 1.2 Volt over R50, being 30mA, must be supplied from somewhere, so what is this somewhere, how is this possible ??
But we are almost there. This is pure luxury to be able to measure while nothing breaks down.
Predrivers that are getting hot, you probaby mean Q23, Q25 and Q26 , right ?
Especially Q23 will get very hot, 16mA over 160 Volt is 2.6 Watt.
Hans
Nobody knows if the pot is again in the right position !
So switch the amp off, let it cool down and then try to adjust 40 to 50 Volt on the Lamps with pot R124.
If not possible anymore to adjust the lamp voltage with the pot, put it in the max 500 Ohm position.
Then let it warm up and try to push and pull a bit on the board until you have the 85 V back on the lamps.
Be aware that when the voltage over the lamps is 85 Volt, that the predrivers Q29,Q39 and Q40 on the + side, and Q41,Q42 and Q52 on the - side are no longer able to conduct and that the 1.2 Volt over R50, being 30mA, must be supplied from somewhere, so what is this somewhere, how is this possible ??
But we are almost there. This is pure luxury to be able to measure while nothing breaks down.
Predrivers that are getting hot, you probaby mean Q23, Q25 and Q26 , right ?
Especially Q23 will get very hot, 16mA over 160 Volt is 2.6 Watt.
Hans
Wow, that is alarming.
I see two strange resistor called R99 Sat and R70 Sat.
This component can influence the output voltage to a large degree.
Could you try to find out what component this is.
Without this component, output voltage will be D6*(R101+R100+R143)/(R100+R143)=47V*(25k/15K)= 78 Volt.
So if you can't find this R99 Sat and R70 Sat, just pull out their connectors from this board, and we'll search for it later.
Working with +/- 78 Volt is no problem.
Let's first try to find the problem with your amp.
Hans
You measured 361K between what and what ?
When power is off, you should see between +Vcc Reg and Gnd resp R101, R100, and R143 a total of 25KOhm.
When there is also a SAT resistor ( the first time I hear
) it should be even a bit less.Exactly the same resistance between -Vcc Reg and Gnd
Hans
You measured 361K between what and what ?
When power is off, you should see between +Vcc Reg and Gnd resp R101, R100, and R143 a total of 25KOhm.
When there is also a SAT resistor ( the first time I hear
Exactly the same resistance between -Vcc Reg and Gnd
Hans
Can you measure with resp to gnd the voltages on R93, R96 and R98.
Hans
I do not understand how D16 can break down, but it explains at least a bit of the 111 volt.
A 1N4936 is supposed to be able to handle 400V DC, 1 Amp continous and 30 Amp peak ??
Q31 if broken can be easy replaced, it's still a current transistor only costing a few Euro's.
Hans