Because the resisitors drive FET,if remove them from the board to check them,the FET will not be damaged,then you can measure FET,if the resistance of D pole to the S pole is about 09l,and S to D ia about 0.5L,then it is OK.Your focus should be placed on measurement and replacement of the resistor, I think so.
Because the small board seemed damaged I focused on that and the top side of the main board. I just realized the R41 resistor was connected to the D26 diode from the bottom of the board. I checked D26 and there is a short so I know I need to replace that. I'm going to do that now if I can get the same one. D26 is connected to a large piece of copper in the board that supplies a bunch of resistors, capacitors and a couple transistors. I checked the transistors and they seem ok. I checked some of the capacitors and resistors but there's a lot so I think I should just replace the diode as long as I won't do damage by turning on the amp after if something else is wrong.
I got a IN5819 1amp diode, the FR105 1amp one I'm replacing says its a fast recovery diode. The guy at the store said it would work but he didn't know if the new one was fast recovery. It doesn't say fast recovery on the data sheet so I'm not completely sure. I'll take his advice though and install the new one and see if the amp powers up.
I installed the diode and small board and the amp didn't go into protect! I guess I had the answer the whole time, I just was looking in the wrong spot. Now to figure out why the fets seem ok but there is no speaker jack voltage. I'm going to do my best to figure it out, do you have any suggestions Perry?
Ok thanks for the advice, I thought it seemed weird that there was so much dcv in the amp but not at the terminals. I can hear the relay click and the amp doesnt go into protect but there is no sound. Do you have any ideas? I've been checking around but I haven't found anything. Does it seem normal to get 19.5k ohms between pins 1-3 of the output fets but 73.8 and 70dcv on pins 1 and 3. The middle one isn't readable because it is very jumpy. Is that because of the 12v regulator mentioned by Perry? I remember reading about unrectified signals and I'm thinking the middle pin is not readable because of the type of signal.
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I think that it is complicated, for example，when you checked the R41 resistance and it is 10 ohms,then we can judge this resistor is good,as we know that the resistance of a resistor is not reduced when it's damaged.As far as FET does not work, the main reason is the control signal is not available to the gate.
There have been so many failures, I suggest you use the oscilloscope take a measurement of the signals of G pole and D pole.If the signal amplitude of G-pole is relatively stable and considerable,then view the signal amplitude of D pole can be driven enough.
There have been so many failures, I suggest you use the oscilloscope take a measurement of the signals of G pole and D pole.If the signal amplitude of G-pole is relatively stable and considerable,then view the signal amplitude of D pole can be driven enough.
Ok thanks jekat I'll look into an Oscilloscope to test the signal properly.
I checked the Q225 and Q225 and Q226 had OL on every pin so I replaced it (A1266) with PN2 907A with advice from the electronics store. Do Q225 and Q226 need to be equal pairs as far as replacement?
When I power up the amp it now goes straight into protect, I'm suspecting the IC (IC1) which is after Q226. I get 0 resistance on pins 11-12 and I get 0.00dcv on pins 9 10 13 14 15 16 with the amp in protect.
I checked the Q225 and Q225 and Q226 had OL on every pin so I replaced it (A1266) with PN2 907A with advice from the electronics store. Do Q225 and Q226 need to be equal pairs as far as replacement?
When I power up the amp it now goes straight into protect, I'm suspecting the IC (IC1) which is after Q226. I get 0 resistance on pins 11-12 and I get 0.00dcv on pins 9 10 13 14 15 16 with the amp in protect.
I've heard with d-class amps you shouldn't substitiute many things so I wasn't sure about substituting. Do you mean Q225 and Q226 should be consistent with the original or with matching replacements? The electronics sales person said sometimes Japanese parts are hard to find and it would be easier and equal to use these american ones.
Sorry, by push pull do you mean the positive and negative of the speaker output section?
Sorry, by push pull do you mean the positive and negative of the speaker output section?
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I just wanted to say thanks to you three for your help. I wish I could be of more help. I'm soaking it all in though but there is a lot of different things to learn with electronics, from vocabulary to parts to testing to systems .......... I had this amp given to me broken so it's just for learning off of mostly.
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Do you think the reason the amp powered up with a bad Q226 and it goes into protect now is beacuse I didn't also replace Q225 with it's counterpart transistor? The originals were K819 and K820 and the guy at the store gave me something different but similar for Q226. Q225 is still the K... transistor.
Perry maybe? Or anyone else?
Perry maybe? Or anyone else?
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