Amp came in from a friend, who said his local techs couldn't fix the issue. Amp goes in protect as soon as You apply any signal into the RCA input jack. Idles fine with no signal.
CF1 obviously has exploded badly for unknown reason to me at some point and now there are 2 film caps in series (doesn't seem right to me)?! I can't actually tell what are the CF1, CF2, CF3, CF4. Firstly I thought they are film caps, but pulling out CF4 has showed it is a resistor on my both testers ? Schematic from this amp, the pre-amp input section is attached. I don't know how or why has CF1 exploded as it's used in the output, not in the input and i pretty sure my friend does not use the output signal RCA jacks. So what is CF1 ?
Lifting one of the ends of R21 on the driver board (the 4.7ohm resistor used in the prot circuit) makes the amp produce clean output.
Fitting it back, in reference to the secondary ground, once the relay clicks in, some kind of a half sinewave pulses on R21 can be seen and amp starts restarting/recycling in a loop.
Obviously there is an issue with the protection circuit. Nothing is in short but I have my doubts on the MAX transistor as this have been my experience in the past.
I really would not want to pull out the driver board, is there anything else I can check and are issues with the blown CF1 and the protection somehow connected to each other ?
CF1 obviously has exploded badly for unknown reason to me at some point and now there are 2 film caps in series (doesn't seem right to me)?! I can't actually tell what are the CF1, CF2, CF3, CF4. Firstly I thought they are film caps, but pulling out CF4 has showed it is a resistor on my both testers ? Schematic from this amp, the pre-amp input section is attached. I don't know how or why has CF1 exploded as it's used in the output, not in the input and i pretty sure my friend does not use the output signal RCA jacks. So what is CF1 ?
Lifting one of the ends of R21 on the driver board (the 4.7ohm resistor used in the prot circuit) makes the amp produce clean output.
Fitting it back, in reference to the secondary ground, once the relay clicks in, some kind of a half sinewave pulses on R21 can be seen and amp starts restarting/recycling in a loop.
Obviously there is an issue with the protection circuit. Nothing is in short but I have my doubts on the MAX transistor as this have been my experience in the past.
I really would not want to pull out the driver board, is there anything else I can check and are issues with the blown CF1 and the protection somehow connected to each other ?
Attachments
What's the DC voltage on terminals 1 and 7 of U6 on the driver board?
Use the negative rail as the reference.
Use the negative rail as the reference.
On the tester they are showing just fine, but i've already have had parts showing OK in the tester, but not working properly.
I don't know what've touched while measuring but now amp doesn't go into protect with no load while injecting test tone into the RCA....but the current draw increases with the gain which with no load is not a good sign. The current draw should be decreasing a bit, not going from 1.8A to full gain 3.6A with no load attached.
I don't know what've touched while measuring but now amp doesn't go into protect with no load while injecting test tone into the RCA....but the current draw increases with the gain which with no load is not a good sign. The current draw should be decreasing a bit, not going from 1.8A to full gain 3.6A with no load attached.
These amplifiers draw a considerable current at idle, the fault is the current which is wasted as heat on some high power 10ohm resistors and the overall efficiency of the whole system (amplifier).
It is REALLY normal for this amplifier to first draw 1.8A and then suddenly to 3.6A when switched on (indeed, it is strangely very quiet) because when you apply the REMOTE, the power supply starts working first, and then after a short while of time the output stage is activated, moreover, it is also quite normal that (with no load applied) the absorption increases slightly when you apply a signal and raise the gain, in fact, part of that signal is certainly filtered by the inductors and thrown to the ground through the capacitors and filter resistors.
Class D is simple, but strange, if there is no load, paradoxically its energy efficiency is low.
It is REALLY normal for this amplifier to first draw 1.8A and then suddenly to 3.6A when switched on (indeed, it is strangely very quiet) because when you apply the REMOTE, the power supply starts working first, and then after a short while of time the output stage is activated, moreover, it is also quite normal that (with no load applied) the absorption increases slightly when you apply a signal and raise the gain, in fact, part of that signal is certainly filtered by the inductors and thrown to the ground through the capacitors and filter resistors.
Class D is simple, but strange, if there is no load, paradoxically its energy efficiency is low.
"Class D is simple, but strange, if there is no load, paradoxically its energy efficiency is low." - this is some kind of inverse logic at first glance but true.
But it contradicts, at least to me - if I put less weight on the bar in the gym, it would be easier for me and my energy expenditure would be overally less, not more.
With no signal applied it stays at 1.8A. But when You apply some signal the current draw almost follows the gain in a linear fashion to 3.6A full gain, which is kind of odd to me, since not every class D exhibits this behaviour.
Well maybe it's easily predictable for You guys, but it is logically strange to my limited knowledge.
But it contradicts, at least to me - if I put less weight on the bar in the gym, it would be easier for me and my energy expenditure would be overally less, not more.
With no signal applied it stays at 1.8A. But when You apply some signal the current draw almost follows the gain in a linear fashion to 3.6A full gain, which is kind of odd to me, since not every class D exhibits this behaviour.
Well maybe it's easily predictable for You guys, but it is logically strange to my limited knowledge.
Hello!
I have encountered a similar problem with this type.
Check the 100nF ceramic capacitors near the output connector, they may be leaking.
I have encountered a similar problem with this type.
Check the 100nF ceramic capacitors near the output connector, they may be leaking.