Blown TE1501DR need help

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I have all these components blown and replaced them:

c413
r118
q106
q110
r145
r146
fet191
d104
q107

Amp fired up with diagnostic LEDs lit where they should be... however i had no sound, and the VU LED action from the EFX board wasnt working either....

So i removed the upper ribbon connected board which the pots reside one, and found 2 blown TL074 op amps and a couple of burned resistors plus 2 open resistors. Swapped all these out, and still had no sound with no VU action, heard the thump in the speaker like most of the MTXes do on powerup. One of the 074s got hot and then all those new components i replaced blew up again, nice light show... I am thinking all these components made up a switching or possibly linear 15V regulator as it has a 15V zener inside its circuit. which failed shorted along with numerous other components on the explodition rampage.

Why do these MTX Class-D amps have to be such a pain in the ******* ***?

I had another thread elsewhere in this forum, and found out it was in the wrong area. so i reposted it here. sorry....
 
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Yea i know, i had to fight and fight and fight with that stupid heatsink, because the output transistors are TO-247 based i think is the type, and they wouldnt rest right without hitting a lip.

But yes, i had it all clamped down. the regulator was blown up when i got it. I replaced all those parts, and it ran again. but no sound. the service LED was lit, and a LED near the 2 NE5532 op amps and the mosfet driver opto-isolators was lit. I repalced both those op amps and drivers because there was a 10uf 25V cap popped up in that area. so i didnt wanna take the risk, and replaced those parts. I also replaced the LM311 as well.... checked all those areas for shorted diodes/transistors, came up empty.

However, i had no audio, and no action from the LEDs on top. usually when audio hits the amp, the LEDs start chanigng colors and pulsating, they were doing nothing. staying on one color.

Thats when i discovered the two highly overheated TL074s, and couple burnt resistors and 2 open resistors. This is probably how the regulator blew in the first place.....

So i swapped all 4 resistors, they were all 10ohm, and replaced both TL074s from another scrap amp board. i didnt have new ones, which may have been a problem, but i doubt it.

Tried to fire the amp up again, and same deal. no sound. then eventually after dicking with it for awhile, the 2 1ohm resistors blew again, and the IRF540 mosfet shorted again, all the same parts i replaced the first time around blew again..... while i noticed one of the TL074s started getting hot again. I think that EFX board where the 074s are located is shot, taking out regulators. heck i dunno.

Also, there are 2 LEDs near the RCA jack chip, whcih is a TL072 i believe, and netiher of thoes LEDs ever lit up. the short and protect LEDs were off as well...
 
The LEDs near the RCAs only light up when there is DC on the RCA jacks (as when driving it directly with a head unit's speaker outputs).

Get it working without the preamp board. Jump the pins in the header as shown in the attached image. The audio won't be loud but you can get it working and determine if the regulator is going to be reliable. The fans operate off of this regulator so you may want to disconnect them (they're likely damaged) while you're troubleshooting.
 

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I rebuilt the regulators again, I have verified a positive and negative 15V on the RCA jack op amps. I replaced the NE5532s again just to be on the safe side, as this is the driver circuits for the outputs i assume.

Anyway, on power up, when the red LED comes on, i get some hiss and a motorboating sound that declines in frequency as the amp is left on longer..... Also i DO hear sound from the speaker, although very weak. But audiable none the less, HOWEVER after a few seconds when the motorboating and hiss settles down, the audio fades away to nothing.

so im lost. any ideas?
 
yeap i chekced all those. I used old TL074s which are bad apparently. So i will need to replace all the TL074s and a handfull of the 10ohm resistors.

But what I am asking you, with the pre-amp board removed, and jumpers in place, is there supposed to be some motorboating and hiss? i DO have audio with this hiss and motorboating, then when the motorboating goes away, i still have audio, then the audio will distort a little bit and fade out to nothing along with all the hiss, so it goes dead silent after a few seconds.... Is this normal without the preamp board? Also the motorboating and hiss go totalyl away when preamp board plugged in.


Its hard to explain it, i would almost have to record a sound clip. when amp first power up with jumpers in place, it motorboats with hiss. the motorboat sound eventually goes away, but whats left behind is some of the hiss with the music sound. then the music sound fades away into distortion along with the hiss, before the amp goes dead silent. no hiss, no motorboat, nothing. have to let the caps drain by recycling the power before it will do it again. When pre-amp board is plugged in like normal, no motorboat, no hiss, but no sound either.

Also keep in mind when all this happens, the B+ supplies are solid as a rock. both the high B+/B- and the 15V B+/B-
 
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Also this is a monoblock amp, it is not stereo, also it was motorboating/hiss with or without the jumpers. Just not when the actual pre-amp was plugged in, only time it didnt.

Also the motorboating is NOT consistent. only happens on first hit of power. after it runs for a few seconds, the motorboating and hiss goes away. amp becomes dead silent with valid rail supplies. However, no audio either. only time i can get audio with the jumpers in place, is when its hissing/motorboating. once the hissing and motorboating stops, so does the audio.
 
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This amp has balanced signal lines so there are two lines from the RCA op-amp and two lines to the class D driver section.

MP3 players have caused more problems than you could imagine. The response is always... 'it worked for every other amp'. Some amps are finicky and need a grounded signal source. You may have another problem but this is one possible problem that needs to be eliminated before you do anything else.
 
Well the MP3 player is grounded to the amp via the RCA grounds?

also the motorboating is a higher pitch, around 80 to 100hz, and begins to fall down to nothing. then motorboat sound is gone... But it still hisses, the hiss has the audio mixed in with it, but the hiss + audio begins to fade away after a few seconds, then the amp is dead silent with both the service LED lit, and the led near the A3312 or A3122 or whatever the MOSFET drivers are....

Also it makes NO difference if the player is connected to the jacks or not... it happens on powerup no matter what condition...


P.S. I am wondering if it could have taken out my class-D mosfet driver ICs again.... As when i first got the amp and seen the 15V regulator circuit blown, i swapped out all those parts, including both NE5532s and both A3122s digikey only had 3, so i bought them. means i only got 1 left....
 
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Beginning to wonder if the failure of the regulators had taken out the TL072 near the RCA jacks. Reason i mention, is because if i had the preamp connected, it does NOT his, and does NOT motorboat. so that means its gotta be comming from an analog source, rather than the PWM system for that amp. Since the preamp is dead, it blocks the signal between A and B. Wouldnt you think?
 
The RCA shields are not grounded on this amp. The input circuit is much like the ones in the JL amps which rarely work properly with an ipod.

If it does it without the RCAs being plugged in, you need to look at the signal on those two pins. Set the scope to ~1v/div to look for the noise.

Any op-amp that was in the circuit when the regulator failed is likely to be damaged.

Do you mean 3120s?

The 3120s are powered by dedicated supplies, if I'm not mistaken. Measure the DC voltage from pin5 to pin 8 with a multimeter to determine if their supplies are intact. They should have ~18-20v across those pins.
 
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