PPI A1200

[Perry Babin]

The only one that may be close is the IX402. Email me if you want the schematic diagram.

babin_perry@yahoo.com

 

[mike49504]

Ok back to this amp.

I replaced all of the power supply fets I put in IRFZ48N's.

I replaced outputs On 1 side of the amp and replaced the regulators on the same side. Also replaced a few emitter resistors.

If i hook up a speaker to the amp on 1 side it plays great.

Hook the speaker to the other side of the plug it will start drawing 20 amps of current and makes the transformer squeal. But will play audio perfect

If no speakers are connected amp idles perfect.

Any Ideas?

 

[Perry Babin]

If you look at the speaker output for the defective channel (speaker connected), do you see clean audio?

Does it start oscillation when you connect the speaker?

Is there any DC on that channel?

 

[mike49504]

I first checked for DC voltage on the channel And got 1.95 volts Didnt get any further yet,

Do i need to test for clean audio or what do i check at this point?

 

[Perry Babin]

Yes.

 

[mike49504]

Amp has 1.92 volts of dc on 1 channel Also when i test to see if if has clean audio on that channel I get something that looks like a square wave on the outputs.

Any ideas?

 

[Perry Babin]

It appears that it's oscillating. Does it do this if the crossover is set to low pass?

 

[mike49504]

Theres no crossover in this amp. When i recieved the amp no external crossover was provided either like the one you plug into the din plug of the amp.

The 2n6487's and 2n6490's get hot within secs also.

 

[Perry Babin]

Do any of the ceramic or film capacitors appear to be physically damaged?

The 6487/90s used as regulators will get hot very quickly. It's important that you not let them overheat and fail. If they fail shorted, it can do significant damage to the amp.

 

[mike49504]

On a couple of the disk caps in that channel where the leg enters the body of the cap they are craked.

Also on the regulators on the bad channel channel i get the following

2N6487
1:14.6
2:95.4
3:14.3

2N6490
1:-15.7
2:-95.7
3:-15.3

working channel
2N6487
1:65.2
2:95.2
3:65.5

2n6490

1:-64.2
2:-94.8
3:-64.8

Dont know if that hanything to do with the problems

 

[Perry Babin]

That's fairly common on ceramic capacitors. If the leads are still firmly attached, they're probably OK but if you have replacements, I'd suggest replacing them.

With no load, are the signal levels for both sides of the amp about the same?

 

[mike49504]

Also on the regulators on the bad channel channel i get the following

2N6487
1:14.6
2:95.4
3:14.3

2N6490
1:-15.7
2:-95.7
3:-15.3

working channel
2N6487
1:65.2
2:95.2
3:65.5

2n6490

1:-64.2
2:-94.8
3:-64.8

Dont know if that hanything to do with the problems

--------------------------------------------------------------------------------

 

[Perry Babin]

Those are OK.

 

[mike49504]

when you say are the signal levels the same for both sides . What do you mean by that?

The rca's are comming out of my head unit right now to test So how do i tell if they are the same?

 

[Perry Babin]

Correct me if I'm wrong. Isn't this a mono amp that has half of the outputs (on one side of the heatsink) driving the positive speaker terminals and the other half (on the other side of the heatsink) driving the negative speaker terminals?

 

[mike49504]

On both sides of the amp the outputs are A1303's and C3284's

On 1 side of the board the A1303's are closest to the power supply fets.
On the other side the C3284's are closest to the fets

 

[Perry Babin]

Do the outputs drive the speaker terminals as I described?

 

[mike49504]

Yes

 

[Perry Babin]

Is the signal level on the positive speaker terminal the same as on the negative speaker terminal?

 

[mike49504]

How do i find that out?