PPI PC21400.2

[Perry Babin]

I didn't see many of these but in the ones I saw, I remember having to replace the 4081s in them.

 

[caraudioguy2100]

I replaced the 4081’s in the amp and same issue .

Wondering if they have a high failure rate like the 4080’s ?

Wondering if they get easily damaged when installing them

 

[Perry Babin]

I don't think that they are likely to get damaged. The 4080s are generally always in sockets.

Do you have drive signals on all 4 inputs (2, 5, 6, 7) to the IC?

 

[caraudioguy2100]

Here are the drive signals on pins2,5,6,7

Scope settings are 5us 5volts/div

 

[Perry Babin]

Are all of the PS FETs in the circuit?

 

[caraudioguy2100]

No

 

[Perry Babin]

Are any FETs in the circuit?

 

[caraudioguy2100]

No fets are in the 2 banks causing issues .

I will put a fet in the bank and take pics of the drive

 

[caraudioguy2100]

With 1 fet in the bank this is what I get on pins 2,5,6,7 on both 4081’s

 

[Perry Babin]

The 12 FETs that you listed are in 4 different banks.

 

[caraudioguy2100]

If I put a fet in any of the locations that are not populated the amp loses drive signal

 

[Perry Babin]

What's changing (voltage on the terminals) at the 3525 when those FETs are in the circuit?

 

[caraudioguy2100]

Pin 1:1.31
Pin 2:4.06
Pin 3:0.03
Pin 4:0.75
Pin 5:2.90
Pin 6:6.65
Pin 7:2.85
Pin 8:7.72
Pin 9:6.04
Pin 10:0.00
Pin 11:0.05
Pin 12:0.00
Pin 13:13.57
Pin 14:0.18
Pin 15:13.57
Pin 16:8.25

 

[Perry Babin]

The IC appears to be defective. Pin 16 should be 5v.

 

[caraudioguy2100]

Ok I replaced the 3525 and it blew the fet I had in 1 bank instantly.

So should I use a cap and look at the drive signals and post them ?

And should I use a 0.1 if cap or something different to load the the drive circuit ?

 

[Perry Babin]

You should always check the drive circuit before installing the FETs. A 0.1uF would work.

 

[caraudioguy2100]

With the cap in place this is what I get

Scope set to 5us 5 volts/div

 

[Perry Babin]

Do you get the same drive for all FETs?

 

[caraudioguy2100]

No

Here is what I get on all 4 banks of fets

 

[Perry Babin]

Did any have FETs installed?

Which FET locations were each of these taken from?

2 and 4 look OK. The first doesn't look like it has any load.

The 3rd may be due to having no reference.