Memphis 16-MCD1500 repair help

[Lerch256]

First post.. thanks in advance for any help.

I have a Memphis mcd1500 that had blown up or at least had some bad Ird3205.. I sourced them Nos from out of country .. and replaced all of them and all the ird 640 also the irf 9640 .. the amplifier will power on now no protection light comes on but it isnt receiving a drive signal from the board... I believe it to be the chips are blown but Memphis has sanded off the part numbers .. or if any of y'all could think up something different it may be let me know .. I'd appreciate it ..

I removed all the amp section MOSFETs and rechecked but I have no drive signal ..

Any idea what the part numbers are in the ic chips??

 

[Perry Babin]

MC14060 and LM361.

What signal do you have on pin 5 of the MC14060?

The attached diagram is similar to what you have here.

 

[Lerch256]

I'm getting a -24 mv at 22.08khz

I'm just learning or trying to learn to repair this amp thanks .. amateur hour over here.. I took a pic of the oscilloscope on pin 5

 

[Perry Babin]

That's a low frequency but shouldn't stop the drive from being produced.

What's the input signal on pin 4 of the LM361?

Set the scope to DC coupling2v/div and 5us/div.

 

[Lerch256]

That's what I'm seeing on pin 4 of the lm361.. thanks

 

[Perry Babin]

Are you sure that you were on pin 5 of the MC14060 previously?

Is your scope grounded to the negative terminal of the 12v power supply supplying power to the amp?

 

[Lerch256]

Yes sir.. I believe so .. I was on the pin I have a red arrow pointing at .. is that correct??

I do have the scope grounded at The negative on the power supply

 

[Perry Babin]

No. Pin 5 is directly below that in the photo. Look up the datasheets for the ICs for the pin numbering scheme.

What's the DC voltage on pins 4 and 3 of the LM361?

 

[Lerch256]

Ok thanks I will get that information in the morning and report back .. thanks

 

[Lerch256]

First picture is pin 5 on the mc14060

Lm361.. pin 3 voltage is -5.44v

Lm361.. pin4 voltage is -7.80v

Thanks

 

[Perry Babin]

What are the signals on pins 9 and 11 of the LM361?

Are the output FETs in the amp or out of the amp?

 

[Lerch256]

Those are the signals on pin 9 and 11 on the lm361..

I have the output fets uninstalled from the amp at this time.. thanks for the help

 

[Perry Babin]

DC voltage on pins 10 and 14?

 

[Lerch256]

Pin# 10 .. -2.12v

Pin#14 .. +2.72v

 

[Perry Babin]

Solder a bridge between pins 13 and 14 of the TL074 on the driver board. Does the DC voltage on pins 3 and 4 go to about 0v DC?

 

[Lerch256]

Pins 3 and 4 stay in a negative dc voltage .. I'll solder a bridge on pins 13 and 14 shortly and report back .. thanks

 

[Lerch256]

That's the signal I get on pin 3 and 4 of the MC14060

 

[Lerch256]

Both are at 6 volts.. I soldered the bridge but still no drive signal to where the fets go in the board .. thanks

 

[Perry Babin]

MC14060?

Bridge on the TL074?

 

[Lerch256]

Yes on the TL074