Massive D8000

[caraudioguy2100]

Power supply fets are blown along with the drivers .

They are using MMBT4401,4403 as the drivers for the power supply .

Can I use the A06,56 for replacements ?

 

[Perry Babin]

Yes but if you're going to repair these amps, you should order the right transistors. The 2x/2t are critical in the output stage so you should have them in stock.

 

[caraudioguy2100]

Replaced the drivers with original part numbers .

I get no drive signal even at the 494 .

Amp is not powering up for some reason here is what I get on the 494

Pin 1:0.00
Pin 2:0.84
Pin 3:0.03
Pin 4:0.00
Pin 5:0.00
Pin 6:0.00
Pin 7:0.00
Pin 8:1.46
Pin 9:0.00
Pin 10:0.00
Pin 11:1.41
Pin 12:1.45
Pin 13:0.60
Pin 14:0.60
Pin 15:0.24
Pin 16:0.00

 

[Perry Babin]

There is no 12v on 8, 11 and 12. See if there is a large SMD transistor somewhere near the 494. It may be defective.

 

[caraudioguy2100]

Ok I traded pin’s 8,11,12 back to a smd transistor marked AGQ that’s shorted .

I don’t have one on hand wondering if you know of a transistor I can put in for testing only ?

 

[Perry Babin]

Do you have an A1661?

 

[Bertje]

Check remote circuit, transistors are located near the remote terminal.

 

[caraudioguy2100]

Yes I have one it’s marked DY

 

[caraudioguy2100]

I replaced the transistor I still don’t get any drive signal .

Here is what I get on the 494 now

Pin 1:0.00
Pin 2:4.96
Pin 3:4.44
Pin 4:0.00
Pin 5:1.44
Pin 6:3.88
Pin 7:0.00
Pin 8:13.88
Pin 9:0.00
Pin 10:0.00
Pin 11:13.88
Pin 12:13.88
Pin 13:4.96
Pin 14:4.96
Pin 15:2.03
Pin 16:3.90

 

[Perry Babin]

Do you have any FETs in it?

 

[caraudioguy2100]

No

Thought I could check this amp like others check drive before installing the fets

 

[Perry Babin]

Some amps have protection circuits that shut down the driver if they don't see rail voltage after the drive pulses start.

It's easy enough to install one FET per bank for one transformer. That should allow the pulses.

There are 3 transistors that are in the drive protection, Q85, 86 and 87. Removing Q87 will defeat it. I don't know if the numbers match this circuit.

 

[caraudioguy2100]

I will install 1 fet per bank and see what I come up with .

Wondering do you still offer the tutorial ?

If so I will email you for all the details I’d like to learn a lot more about amps so o can limit the number of questions I have

 

[Perry Babin]

It's still available. Email me directly so I can provide that you need before deciding to buy it.

babin_perry@yahoo.com

I won't be near the computer for a few hours so any reply will be delayed.