Emphaser EA15000SPL problem

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MarioRestucci

MarioRestucci

Member
Joined 2012
Perry Babin said:
How can you explain why it's not limiting the voltage from the 820 ohm resistor to the forward voltage of the be junction?

I posted the modeled circuit and it's clearly clamping the positive part of the waveform.
Click to expand...
VERY very very strange!
Since this problem has persisted for the past two weeks, BOTH MMBTA92 have been replaced to make sure they have no problems with them, but even after replacing them the result is the same.
The ground at the bases of the 2D is solid and apparently even the 2.4k resistors to -rail are ok.
I no longer know what to think, today I will try to replace MMBTA92 again, but I think it will be the same thing.
 
MarioRestucci

MarioRestucci

Member
Joined 2012
Perry Babin said:
Are they OK after you remove them?

How can they be limiting your meter to 0.6v but not the drive circuit?

Install a diode in place of the transistor's BE junction and see if that perform like the model showed.
Click to expand...
Incredible but true, I unveiled the arcane.
COLD WELDING !!!
I removed the 2D, clean the pitches by removing the old tin and put the same 2D again with new tin, as if by magic, now everything works, but mounting IRS I realized that they go to shut down because of faulty MAX, in fact without MAX it works perfectly and produces the signals on the low sides of all IRSs.
Since MAX can not be easily found in my country, what can be used in its place?
I saw a 12volt VEBO for muting transistors, is it strictly necessary?



Thank you so much Perry, you opened my eyes, without your help I never thought to remove the 2D and redo the new welds
 
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