i am fixing 2 of these amps simultaniously and i have run out of things to fix on one amp so i thought i could switch to this one.
this amp is the exact same amp as this thread
http://www.diyaudio.com/forums/showthread.php?s=&threadid=126125
with this amp i am getting 0v at the op amp and +- 2-3 volt at the regulators. the rail voltage is 2v and i cant see any obvious melt downs or burn marks. i checked the R106 location and surrounding components and everything measures fine.
where do i look now?
this amp is the exact same amp as this thread
http://www.diyaudio.com/forums/showthread.php?s=&threadid=126125
with this amp i am getting 0v at the op amp and +- 2-3 volt at the regulators. the rail voltage is 2v and i cant see any obvious melt downs or burn marks. i checked the R106 location and surrounding components and everything measures fine.
where do i look now?
It sounds like the power supply is inoperative. What is the DC voltage on each of the legs of FET102 and FET104?
FET102
1.
2.
3.
FET104
1.
2.
3.
Don't plug this amp's preamp board into the other amp. If there's something wrong with the other amp that's causing the op-amps to fail, it will damage the op-amps on this preamp board also.
FET102
1.
2.
3.
FET104
1.
2.
3.
Don't plug this amp's preamp board into the other amp. If there's something wrong with the other amp that's causing the op-amps to fail, it will damage the op-amps on this preamp board also.
ok i wont plug the pre amp board in
when i check for power on those transistors i get +8v only on the middle leg of each transistor the other legs are 0v
when i check for power on those transistors i get +8v only on the middle leg of each transistor the other legs are 0v
It sounds like the power supply you're using is set too low or is being dragged down by the amplifier. Does the voltage go higher (on the power supply) when you disconnect the amp?
The amp has low voltage protection (if I'm not mistaken) so it may not power up with only 8v.
Does the supply voltage remain at/near 12v without applying remote voltage to the amplifier?
The amp has low voltage protection (if I'm not mistaken) so it may not power up with only 8v.
Does the supply voltage remain at/near 12v without applying remote voltage to the amplifier?
yes that is exactly what is happening. it is 13.5v till i hook it to the amp then it drops down. i am using a resistor to power the amp for testing but even without the resistor this still happens.
Does the supply voltage get pulled down if you don't connect the remote turn on?
If not, check the output transistors (FET401-404) to see if any are shorted (no power applied, meter set to ohms or diode-check).
If not, check the output transistors (FET401-404) to see if any are shorted (no power applied, meter set to ohms or diode-check).
no i dont get a short (really high resistance on some) but nothing to make my meter beep.
if i apply power to only rem or B+ then it doesnt drag down the power, only when the 2 of them have voltage does it happen.
if i apply power to only rem or B+ then it doesnt drag down the power, only when the 2 of them have voltage does it happen.
If the voltage drops the same with/without the resistor, your DC power supply would seem to be faulty.
What's the current rating of the supply?
What value resistor are you using?
What's the current rating of the supply?
What value resistor are you using?
power supply is 5A 65 watt and im using 2 ceramic resistors 20W and 4 ohm they are tied parrellel and measure at 2 ohm
this power supply lights up the other amp which is identical to this one
should i get more power for this?
this power supply lights up the other amp which is identical to this one
should i get more power for this?
5 amps should be enough to power it up.
How low does the supply voltage drop without the resistor?
How low does the supply voltage drop with the resistor?
Measure the voltage at the terminal block of the amplifier.
I think the amp may be drawing just enough current to trip the low voltage protection.
How low does the supply voltage drop without the resistor?
How low does the supply voltage drop with the resistor?
Measure the voltage at the terminal block of the amplifier.
I think the amp may be drawing just enough current to trip the low voltage protection.
it gives the exact symptoms with or without the resistor, the cooling fan comes on for a fraction of a second then it drops to 8v if i leave the full voltage applied for about 5 mins then the heatsink starts to get warm. i have 2 lights on the back of the amp labeled "thermal" and "short" neither of these light up.
i am measuring voltrage for the amp right at the terminals where you feed the power into the amp.
i am measuring voltrage for the amp right at the terminals where you feed the power into the amp.
What components are on the area of the heatsink that begins to heat up.
Does anything else on the board heat up?
Does anything else on the board heat up?
right around the FET 101 and 102 on the same side the opposite side is a little warm but not as much .
no where else on the board gets warm or smokes
no where else on the board gets warm or smokes
Pull the rectifiers (rec101, 102).
You'll need to keep them under the clamp so you can power up the amp without risk to the regulators. After pulling them, flip them, place them under the clamp (legs up) and tighten the clamp.
Then power up the amp through the resistor. If it powers up, the power supply components (including the transformer) are likely OK. There will be no rail or regulated voltage. The only point where you may find voltage (other than that supplied from the 12v supply), is where rec104 and rec105 are connected. That should be ~20v.
You'll need to keep them under the clamp so you can power up the amp without risk to the regulators. After pulling them, flip them, place them under the clamp (legs up) and tighten the clamp.
Then power up the amp through the resistor. If it powers up, the power supply components (including the transformer) are likely OK. There will be no rail or regulated voltage. The only point where you may find voltage (other than that supplied from the 12v supply), is where rec104 and rec105 are connected. That should be ~20v.
against everything i have read i pulled the clamps off and put power to the amp eek!!
it is quite obvious i am getting 4 of these rectifiers super hot.
FET 101,102,103 AND 104 all of them have the same part number 75339p. it only takes about 1-2 seconds for all 4 of them to get super hot. way too hot to touch.
should i flip all 4 of them upside down? or did i find the problem?
i promise i will never power it up with the heat sink unbolted ever again LOL
it is quite obvious i am getting 4 of these rectifiers super hot.
FET 101,102,103 AND 104 all of them have the same part number 75339p. it only takes about 1-2 seconds for all 4 of them to get super hot. way too hot to touch.
should i flip all 4 of them upside down? or did i find the problem?
i promise i will never power it up with the heat sink unbolted ever again LOL
Did the amp power up properly with REC101 and REC102 out of the circuit or does it still drag the supply voltage down to 8v?
All of the FETs must be in the circuit.
All of the FETs must be in the circuit.
no go!! i hve the rec 101 and 102 with the legs in the air and rec 103 and 104 with 8v on the middle legs
and the cooling fan still starts for a fraction of a second when i first put power to the board
and the cooling fan still starts for a fraction of a second when i first put power to the board
oops yes i am
the 4 FETs are all getting hot so i pulled 2 of them out, but ill put them back in and pull out the rec 101 and rec 102
the 4 FETs are all getting hot so i pulled 2 of them out, but ill put them back in and pull out the rec 101 and rec 102
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