Well, Yesterday I received the following parts from Conrad.nl:
Today I've got the new parts soldered in place (Yes, got the backsides of the FET's pre-soldered 😉) but not yet soldered to the MEHSA thermal management system.
I wanted to see if the beast would power up.. So I hooked it up to my trusty Delta Elekronika Power Supply E 030-3 (30V 3A both adjustable) without the remote connected. The amp doesn't draw any current so that's a good thing. But when I connect the Remote to B+ it shorts out (Amp draws the full 3A).
Here's a picture of the amp's board in current state:
Green arrow: Parts newly installed
Red arrow: Parts removed
What could be the problem? Is it because there are parts missing?
- IRF3205 (International Rectifier)
- IRF9640 (International Rectifier)
- IRF640 (STMicroelectronics)
Today I've got the new parts soldered in place (Yes, got the backsides of the FET's pre-soldered 😉) but not yet soldered to the MEHSA thermal management system.
I wanted to see if the beast would power up.. So I hooked it up to my trusty Delta Elekronika Power Supply E 030-3 (30V 3A both adjustable) without the remote connected. The amp doesn't draw any current so that's a good thing. But when I connect the Remote to B+ it shorts out (Amp draws the full 3A).
Here's a picture of the amp's board in current state:
Green arrow: Parts newly installed
Red arrow: Parts removed
What could be the problem? Is it because there are parts missing?
Thanks for the reply Perry. Just out of curiosity, how could this component got blown in the first place?
When the power supply FETs fail, they generally short 12v to the gate. Q2 and Q3 in this power supply try to pull the 12v on the gate back down but they often can't handle the current passing from the gates and often fail, especially if the gate resistors don't open.
Parts from Farnell arrived
Alright, thanks for explaining
.
Well, the parts from Farnell finally arrived.
The first thing I did was soldering new MMBTA56's and 06's. I also replaced all other SMD resistors and some other parts (see picture below).
After that I tried powering it up. When connected to B+ and GND the amp doesn't draw anything, so far so good.
But when I connect the remote to B+ it draws the full 3 Amps (just like before). On the bright side, the power LED shows sign of life 😀
Here's a picture of the amplifier in current state:
Green arrow: Parts newly installed
Red arrow: Parts not installed
I measure 3.89V on the right and 1.50V on the left speaker output. When the power supply draws the full 3 Amps, the supplied voltage goes from 13V to 9V.
What could be the problem? Does it need more components installed to see if the power supply of the amp is functional? I want to make sure that it is and its safe to install the other parts.
Perry Babin said:
Alright, thanks for explaining
.Well, the parts from Farnell finally arrived.
The first thing I did was soldering new MMBTA56's and 06's. I also replaced all other SMD resistors and some other parts (see picture below).
After that I tried powering it up. When connected to B+ and GND the amp doesn't draw anything, so far so good.
But when I connect the remote to B+ it draws the full 3 Amps (just like before). On the bright side, the power LED shows sign of life 😀
Here's a picture of the amplifier in current state:
Green arrow: Parts newly installed
Red arrow: Parts not installed
I measure 3.89V on the right and 1.50V on the left speaker output. When the power supply draws the full 3 Amps, the supplied voltage goes from 13V to 9V.
What could be the problem? Does it need more components installed to see if the power supply of the amp is functional? I want to make sure that it is and its safe to install the other parts.
Connect only remote and ground. Measure the DC voltage on the gate leg of all 8 of the power supply transistors.
I don't see where the current could be going with the source resistors out of the circuit.
Does one group of 4 FETs get hot and the others remain cool?
How long have you allowed it to draw 3 amps? It may take more than a few seconds to charge the rail caps.
Does one group of 4 FETs get hot and the others remain cool?
How long have you allowed it to draw 3 amps? It may take more than a few seconds to charge the rail caps.
Hmm, I didn't notice that any of the FETs got hot.
I only applied power to the amp like 5 seconds.
I'll see to it when I get home. I'm at school atm.
I only applied power to the amp like 5 seconds.
I'll see to it when I get home. I'm at school atm.
I had the amp on for about 15 to 20 seconds and Q15, 16, 18 and 35 are getting hot at the touch. Within this time, the amp still draws 3A.
Any Ideas?
Any Ideas?
An externally hosted image should be here but it was not working when we last tested it.
The one on top
Pull the center leg for the rectifiers (U5-U8). Do you still have heating and a constant 3 amp draw?
Whoops, I was referring to the markings on the MEHSA board.
MEHSA / PCB
Q15 = Q6
Q16 = Q7
Q18 = Q5
Q35 = Q13
Sorry about that.
I can't find U5 or U8 🙁
MEHSA / PCB
Q15 = Q6
Q16 = Q7
Q18 = Q5
Q35 = Q13
Sorry about that.
I can't find U5 or U8 🙁
It helps if I look at the correct schematic. 🙁
Do you have a D18, D19, D20 and D21 adjacent to the power supply FETs? If so, pull one leg for each one.
Does anything heat up or do you have a constant 3 amp draw with those out of the circuit?
Do you have a D18, D19, D20 and D21 adjacent to the power supply FETs? If so, pull one leg for each one.
Does anything heat up or do you have a constant 3 amp draw with those out of the circuit?
Yes 🙂 those 4 rectifiers are on this board. I'll unsolder them.
Give me a moment 😉
//EDIT
Pulled one leg of each rectifier.. It now draws 0.5A and the power LED doesn't go on.
Give me a moment 😉
//EDIT
Pulled one leg of each rectifier.. It now draws 0.5A and the power LED doesn't go on.
^^
So, are the rectifiers the problem?
The original rectifiers are STPR1520D
They aren't shorted and they measure (A +, K -):
D18 = .375
D19 = .374
D20 = .382
D21 = .380
Please let me know
So, are the rectifiers the problem?
The original rectifiers are STPR1520D
They aren't shorted and they measure (A +, K -):
D18 = .375
D19 = .374
D20 = .382
D21 = .380
Please let me know
The rectifiers are OK. There's something beyond the rectifiers that is causing it to draw current.
Measure the voltage across the large filter capacitors (no voltage applied to the amp). If it's near 0v, measure the resistance across the capacitors. You should read a low resistance initially and it will increase slowly. If you read 0 ohms and it doesn't increase, one capacitor may be shorted (rare but it happens).
Are you sure that there are no solder bridges anywhere on the board? Sometimes solder drops off of the soldering iron or is bridged between two adjacent solder pads.
Measure the voltage across the large filter capacitors (no voltage applied to the amp). If it's near 0v, measure the resistance across the capacitors. You should read a low resistance initially and it will increase slowly. If you read 0 ohms and it doesn't increase, one capacitor may be shorted (rare but it happens).
Are you sure that there are no solder bridges anywhere on the board? Sometimes solder drops off of the soldering iron or is bridged between two adjacent solder pads.
Allright, I measured the large capacitors and they hold about ~0.3V on each of them. When I set the multimeter to resistance, the resistance increases.
I don't find any solder bridges where I've been soldering.
// EDIT
Wait a sec. I found a, what seems to be a burnt lead below the High-level input connector. I haven't seen it before (maybe overlooked it).
Here's a picture of it:
It appears to be only underneath the High-level input connector. I measured it, and it isn't broken.
Maybe its got something to do with the current drawing issue?
I don't find any solder bridges where I've been soldering.
// EDIT
Wait a sec. I found a, what seems to be a burnt lead below the High-level input connector. I haven't seen it before (maybe overlooked it).
Here's a picture of it:
It appears to be only underneath the High-level input connector. I measured it, and it isn't broken.
Maybe its got something to do with the current drawing issue?
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