Memphis 16-mc1000d

[mike49504]

I have this amp in for repair I opened it up and noticed the power supply is blown.

There are 8 power supply fets in this amp 4 of them are IRF3205"s

The other 4 have markings ive never seen.

500 12L4
1R 837D
59 40


Are theese 3205's as well or is there a part number for theese??

 

[Perry Babin]

It should have 8 3205s.

 

[mike49504]

Ok i have yet another one of theese amps so now i have 4 total.

The next one has 13 volts DC on the outputs . All outputs test fine so i took out the driver boards and the board behind the rca jacks still measures that i have 13 volts on outputs.


Maybe a leaking output ?

 

[Perry Babin]

Do you read 0v on the secondary center tap and the RCA shields?

 

[mike49504]

Yes 0 volts on rca shields and 0 volts on secondary center tap

 

[Perry Babin]

A leaking output is a likely suspect. If the voltage is positive, it's likely one of the 9640s.

 

[mike49504]

I fixed the Dc on the outputs. Amp powers up and relay kicks on but no output.

I checked and its producing + - 63 volts on the outputs (rail voltage)

I have 15 volts on pin 4 of 2 op amps but not on pin 8

Other op-amp has no voltage + or - 15 volts

The op-amps i tested are the TLO72's


I swapped the board behind the rca jacks with another one .

Still same thing.

Wondering what controls the 15 volts on pin 8 of the op-amps and why doesnt one of the 3 op-amps have voltage on pin 4 or 8?

 

[Perry Babin]

The 15v regulator next to the 3205s produces the 15v. Confirm that it has supply voltage on pin 1, 0v on pin 2 and 15v on pin 3.

Which op-amp has no DC voltage on it?

 

[mike49504]

Regulator
pin1: -1
Pin2:0
pin3:-.6

Q143 has no voltage on it

 

[Perry Babin]

There is a green inductor in front of the 7815 regulator. Do you have 15-20 volts on one end of the inductor?

 

[mike49504]

The inductor your talking about looks like a resistor?

If so i have -.1 on both sides of it

 

[Perry Babin]

What's the resistance between legs 1 and 2 of the 7815?

If you pull the 7815, do you have 15-20v on pad 1?

 

[mike49504]

5.08 ohms

Black probe on ground terminal red probe on pad 1 of 7815 when removed 0.1 volts

 

[Perry Babin]

5 ohms is defective.

Measure the DC voltage from pad 1 of the 7815 to the middle leg of the 7915. What is the voltage?

 

[mike49504]

It measures 33.2 volts

 

[Perry Babin]

Try replacing the positive regulator.

 

[mike49504]

replaced the regulator . Still have the same problem no voltage on leg 1 of the 7815

 

[Perry Babin]

Do you have 33 volts on pin 2 of the negative regulator?

 

[mike49504]

- 30.1 volts on pin 2 of the negative regulator

 

[Perry Babin]

It seems like there is a short between leg 1 and 2 on the board. It could be a shorted cap. Check the caps in front of the positive regulator. You should also check the diodes behind the power supply driver board.