I have been working on this amp forever it is very simple class ab I can't believe I am having so much trouble with it. The amp goes on and off with only 11 volts 2 amps applied to it using a linear power supply to power it, that supply does not go over three amps, I have checked everything, with my scope, I have replaced all the pnp transistors out of tolerance, none of the zeneers show any leakage or any signs of getting hot, the amp looks brand new, I know the guy had to of crossed the positive and negative because of the transistors I replaced, I pulled the main zeneer the runs from positive and negative terminals on the amp it's fine shows no backwards continuity meaning using fluke meter with the leads crossed on the zenner, I have replaced a op amp that was out of tolerance but still should have been good, I have pulled every fet n as well as p channel and checked all the transistors running those fets the pnp ones. All the caps are good any ideas because I feel like a idiot lol. I have never had a amp give me this much trouble, that includes jl amps I can fix those np at all lol
I mean it pulls excessive current and the power supply shuts down at 3 amps then turns back on keeps doing the same thing
Measure the DC voltage across each of the emitter resistors. Does one resistor or a group of resistors read greater than 0.000v DC.
Here are a couple pics of the amp
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With the amp disconnected from everything, what's the resistance from the B+ terminal to the RCA shields?
From the non-bridging speaker terminals to the RCAs shields?
From the non-bridging speaker terminals to the RCAs shields?
If you have 0.2 ohms from the B+ terminal to the RCA shields, the transformer is likely shorted. With the meter on those two points, twist the transformer to see if the resistance goes up significantly.
Those appear to be OK.
Having -10v on the secondary ground is strange. You could try connecting one of the non-bridging speaker terminals to the amp ground to see what gets hot. Have all transistors clamped to the sink if/when you do this.
Having -10v on the secondary ground is strange. You could try connecting one of the non-bridging speaker terminals to the amp ground to see what gets hot. Have all transistors clamped to the sink if/when you do this.
Should I keep my little three amp power supply connected because as I said it shuts down at 3 amps, I have a ten and a fifty amp as well
Try it with the 3 amp supply first. You may need to go to the 10 amp. You won't need the 50 amp for this.
ok it does nothing different with the three amp however just a question d105 and d205 in the audio section of the amp have no voltage drop
one more thing that is strange, when i used my scope I was showing both + and - at the same time when the amp tried to power up, on the black end of all the zenners, the white end was fine.
Almost sounds like a z44 is stuck open but as i said I have had them all out of the amp and checked them, they are all also showing both + and - when the amp tries to power up but only for a split second, just when the amp is at full power, anything under 12 volts is stable
I have had all the caps out tested them with my cap tester at full voltage including the 6800 uf there was none leaking or shorting, of course i have not taken any of the small caps out, just checked those for shorting with my meter
D105 and D205 are likely for the protection circuit and would not have voltage across them unless the amp was going into protect mode.
What do you mean 'showing + and -'? Can you post a photo of the scope display?
What do you mean 'showing + and -'? Can you post a photo of the scope display?
I mean the trace splits the same time up and down twelve volts, thats why the amp is shutting down because the protection kicks in as soon as it powers up
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