mb quart ONX4.60

[hifonics hugh]

Does anyone have schematics for this amp. Nothing stands out visually but I dont have a power or protection light so I assume their is a PS issue?

Tia

 

[Perry Babin]

Post the DC voltage on all pins of the TL494 driver IC. Copy and paste the following and fill in the blanks.


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:

 

[hifonics hugh]

Hi Perry
I removed the insulators try to get in there better. Then used a small battery versus a set supply like an idiot shorted two pins on the 494 and got the smoke from the power supply. Where do I go from here. i think what was minor I just made major.

 

[Perry Babin]

What smoked?

When testing, you should have a low-rated fuse (10 amp or so) in the B+ line or have an inline B+ limiter. It won't save the amp from all mistakes but it reduces the risk in case of one.

After the amp is powered up, you have to either monitor the temperature of all of the heatsink mounted components closely or have them clamped tightly to the heatsink.

 

[hifonics hugh]

I have the Z44N here so let me replace these and start over Q3 was fractured but I did this before there had been no sign or essence of tghe smoke anywhere the board was immaculate.Amplifier was certainly not abused. Just started acting intermittent then finally no power. But the fuses never blew and even on the bench no power

 

[Perry Babin]

Check the drive signal and the gate resistors before installing the FETs. The driver transistors and the gate resistors could have been damaged.

 

[hifonics hugh]

Perry
I have 44's not 44N I do have IRF3205. Can I go with these?

 

[Perry Babin]

The 44s will be OK. The 3205s aren't likely to work with the 100 ohm gate resistors.

 

[hifonics hugh]

I think from your guide they should be safe. I've installed them already. LOL okay.

 

[Perry Babin]

3205s are rarely OK to use with 100 ohm gate resistors unless deadtime is programmed into the drive circuit.

 

[hifonics hugh]

Ok Perry were in business with the 44's now.

 

[hifonics hugh]

From ground to pins

Pin 1: 0 vdc
Pin 2: 0 vcd
Pin 3: 0 vcd
Pin 4: 0 vcd
Pin 5: 0 vcd
Pin 6: 0 vcd
Pin 7: 0 vcd
Pin 8: 13 vdc
Pin 9: 0 vcd
Pin 10:0 vcd
Pin 11: 0 vcd
Pin 12: 0 vcd
Pin 13:13 vdc
Pin 14: 0 vcd
Pin 15: 0 vcd
Pin 16: 0 vcd

 

[Perry Babin]

Pin 12 needs to have 12v. Follow the circuit back to see where it's lost. There is likely a transistor between the remote terminal and pin 12 that's at fault, assuming that the transistor is being driven on by the remote.

 

[hifonics hugh]

Looks like Q60 is where it leads.

 

[Perry Babin]

Is it defective?

What was the voltage on it's terminals in the board?

It's odd to have an NPN transistor in that type of circuit but not impossible. Confirm that there is no PNP instead in that circuit. The NPN generally drives the PNP which drives voltage to the IC.

 

[hifonics hugh]

How about the a1015 almost 100 percent thats where it goes. I never checked the npn in board because there isnt alot of room to even seen what is written on the transistors.

 

[Perry Babin]

It could be the 1015. At least that's a PNP transistor.

Check from the bottom.

 

[hifonics hugh]

I checked it with the multi meter and saw no OL across the base to emitter or collector and no voltage drop from the emitter or collector to the base

 

[hifonics hugh]

Can I run a jumper to see if i get power? Should the base pad be at 12 volt or so?

 

[hifonics hugh]

Since i had an a56 on hand i tried it in the 1015's place and get .5 vdc on pin 12