Hello everyone,
I would need help in repairing a zapco 2000.1.
The amplifier immediately goes into protection as soon as the rem is connected, because I accidentally send + 12v to the audio output.
I have already removed all the audio mosfets and I have checked the driver transistor (q12 q6 q5 q9 q16 q20 q21 q23) on the audio driver board (dwm1216x_v20) and they seem to be ok. I also tried to turn on the amplifier without the audio driver board, but it always comes on in protection. what else can I check?
http://www.diyaudio.com/forums/attachment.php?attachmentid=690088&stc=1&d=1530655179
I would need help in repairing a zapco 2000.1.
The amplifier immediately goes into protection as soon as the rem is connected, because I accidentally send + 12v to the audio output.
I have already removed all the audio mosfets and I have checked the driver transistor (q12 q6 q5 q9 q16 q20 q21 q23) on the audio driver board (dwm1216x_v20) and they seem to be ok. I also tried to turn on the amplifier without the audio driver board, but it always comes on in protection. what else can I check?
http://www.diyaudio.com/forums/attachment.php?attachmentid=690088&stc=1&d=1530655179
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if the amp goes into protect mode also without output mosfet, probably the issue is localized in other area.
If I were you, to find the problem, I would not install the output mosfets and try to get out of the protection (check the protection circuit).
Next, I would make sure that the audio driver card works properly (with oscilloscope) and then proceed with the installation of the mosfets (even if your actual output mosfet are good).
If I were you, to find the problem, I would not install the output mosfets and try to get out of the protection (check the protection circuit).
Next, I would make sure that the audio driver card works properly (with oscilloscope) and then proceed with the installation of the mosfets (even if your actual output mosfet are good).
I'm checking the protection circuit, but I can not find what it does to block the TL494. I checked the voltage on the lm293 and they are perfect. (the same as a working 2000 zapco). These are the voltages of lm293:
pin1 = 0.1v
pin 2 = 12v
pin3 = 5v
pin4 = gnd
pin 5 = 1.7V
pin6 = 4v
pin 7 = 0.1v
pin8 = 12v
I also tried to connect the pin4 of the t494 to ground to bypass the protector and the power supply starts for less than a second and immediately return to protection
pin1 = 0.1v
pin 2 = 12v
pin3 = 5v
pin4 = gnd
pin 5 = 1.7V
pin6 = 4v
pin 7 = 0.1v
pin8 = 12v
I also tried to connect the pin4 of the t494 to ground to bypass the protector and the power supply starts for less than a second and immediately return to protection
I found the problem, I have the q11 transistor shorted and the diode d12 burned on the power supply driver board.
without these two, the power supply starts and I have the rail voltage. (+ 75v & -75v)
I'm still trying without the audio mosfets.
the transistor q11 is marked on the diagram as 2sa1980, and marked on the transistor (cayn). I can not find this smd transistor on the internet, with which transistor can I replace it?
without these two, the power supply starts and I have the rail voltage. (+ 75v & -75v)
I'm still trying without the audio mosfets.
the transistor q11 is marked on the diagram as 2sa1980, and marked on the transistor (cayn). I can not find this smd transistor on the internet, with which transistor can I replace it?
there are only smd component on zapco2000 driver board, but on your schematic you can see only TH component; generally you can use general purpose pnp transistor that share the same package and pinout of the original (actual) transistor. for example, probably you can use this BC856 pdf, BC856 description, BC856 datasheets, BC856 view ::: ALLDATASHEET :::
I replaced the damaged components, and now the power supply and its driver board are ok. Now, however, after the power supply starts, I have protection again immediately after the relay is engaged. this is because I have DC Offset on the output. (I measure 75v a moment before entering protection).
I specify that I'm trying without output mosfet and now I also removed the driver transistor on the audio driver board, but I still have 75v on the output.
I specify that I'm trying without output mosfet and now I also removed the driver transistor on the audio driver board, but I still have 75v on the output.
if you do not have the output mosfets installed, it is virtually impossible to have DC output.
it is more likely that during the removal of the mosfet, you have left some tin bridges between drain and source in the rheophores of some mosfet.
Check better.
you were right, there was a small piece of tin between drain and source.
without output mosfet the amplifier switches on normally and the relay engages.
But by mounting the output mosfets, when I turn on the amplifier it absorbs a lot of current, more than when my bench power supply can stand (10A).
I noticed that by removing only the P mosfets, the amplifier turns on normally and the N mosfets are driven.
There seems to be a problem with the piloting of the P. mosfet
I have already replaced all the transistors and all the ICs on the audio driver board, but the problem remains.
I also checked all the voltage stabilizers and they are ok.
From now on, in order to understand where the problem is, you have to use an oscilloscope, it is very important to know how to use the oscilloscope, it is not enough to have it.
You could have some broken mosfet, find it and get it out of the circuit, try the amp without the broken mosfet and see if it works, if it does, you'll have to replace all the mosfets in that bank.
If instead there are no broken mosfet, unfortunately the problem is (surely) on the driver board.
I told you from the beginning, certain repairs require some preparation, it is not for everyone to find and solve the problem simply by replacing random components.
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