ok the amp isn't going into protect; i think the led just stays that dim; idk.......
but the reason i say that it does NOT go into protect is because 3 of the 4 fet pairs get signal that corresponds with music going in. the 4th one does not. I know it is in H bridge (read up on class d amps earlier, these things are complicated!) so i guess 3 of the 4 are fine one has an issue.......... I did probe on the control chips and all 4 output pins are normal so the problem is between the output pin on the control chip and the FETs.
I get the following wave forms on the left most pin (looking at the face) of the different fet channels. I forgot to remember which one was which not that it matters. FYI the probe was in x10 mode and i did calibrate the pot with the calibrate pin on my scope
Here is the one that is not right. I had to drop the voltage scale way down to even see anything.
but the reason i say that it does NOT go into protect is because 3 of the 4 fet pairs get signal that corresponds with music going in. the 4th one does not. I know it is in H bridge (read up on class d amps earlier, these things are complicated!) so i guess 3 of the 4 are fine one has an issue.......... I did probe on the control chips and all 4 output pins are normal so the problem is between the output pin on the control chip and the FETs.
I get the following wave forms on the left most pin (looking at the face) of the different fet channels. I forgot to remember which one was which not that it matters. FYI the probe was in x10 mode and i did calibrate the pot with the calibrate pin on my scope
Here is the one that is not right. I had to drop the voltage scale way down to even see anything.
on the left of the board ther are 4 output fets; the right two are the ones i'm referring to. all of these are output. power supply is fine so i wont refer to them. The pair that has no signal was one half of the blown up output FETs.
I dont know how to label them +/- low high. I haven't traced out what part of the h bridge that pair goes to.
I also just noticed that the first two pics are from the same pair of output fets. Two pairs go posative when they're signaling two go negative. Well one goes negative the other doesn't do anything. All readings were taken with the negative/ground on the scope to the negative battery terminal
I dont know how to label them +/- low high. I haven't traced out what part of the h bridge that pair goes to.
I also just noticed that the first two pics are from the same pair of output fets. Two pairs go posative when they're signaling two go negative. Well one goes negative the other doesn't do anything. All readings were taken with the negative/ground on the scope to the negative battery terminal
grenadier, parry said:
I asked if I should still do that even though all output fets are removed.
I asked if I should still do that even though all output fets are removed.
bwuahahaha success!!!
I had some MPSA56 (fairchild to-92 equivilent of a pzta56) laying around; twisted the base and collector around so they're in the right spot. soldered it on in q206 spot:
Now i'm getting this waveform on q208/q209:
now i think i'm going to try and put in those fairchild to-220 fets i got as samples and see if i can't get audio out of this thing or just completely smoke it!!!!
I had some MPSA56 (fairchild to-92 equivilent of a pzta56) laying around; twisted the base and collector around so they're in the right spot. soldered it on in q206 spot:
Now i'm getting this waveform on q208/q209:
now i think i'm going to try and put in those fairchild to-220 fets i got as samples and see if i can't get audio out of this thing or just completely smoke it!!!!
well there was good and bad....
put all 8 fdp2614 fets in; powered it up and i'm getting a good looking wave form coming from q211-q214 which were the output fets that were not blown out.
however now i'm getting nothing on q207-q210.
looking at the schematics i traced the signal back to U202 (schematic version 5 is the closest though i dont think its exact), pins 6 and 11 were not generating the same signal that pins 6/11 were generating on Q204 like it was BEFORE i put in these output fets....
SO, i lifted pins 6/11 on U202 and the waveform is there.... so something else is pulling it down... i'm thinking the drive trafo T200 is bad
any way to test that or replace it?!
mind you all of these measurements were taken with no load and no signal; just power/ground/remote...
Also one thing to note the q211-q214 fets get fairly warm after about 5sec of the amp being "on" but i have no heat sync on them
put all 8 fdp2614 fets in; powered it up and i'm getting a good looking wave form coming from q211-q214 which were the output fets that were not blown out.
however now i'm getting nothing on q207-q210.
looking at the schematics i traced the signal back to U202 (schematic version 5 is the closest though i dont think its exact), pins 6 and 11 were not generating the same signal that pins 6/11 were generating on Q204 like it was BEFORE i put in these output fets....
SO, i lifted pins 6/11 on U202 and the waveform is there.... so something else is pulling it down... i'm thinking the drive trafo T200 is bad
any way to test that or replace it?!mind you all of these measurements were taken with no load and no signal; just power/ground/remote...
Also one thing to note the q211-q214 fets get fairly warm after about 5sec of the amp being "on" but i have no heat sync on them
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