punch 100 dsm question

[ben04srt]

I replaced the outputs on this amp and I am still getting about 7 volts dc on the left channel output.

My question is would anything on the driver board cause this?
If so where on driver boards should I test?

 

[Perry Babin]

Do your driver boards have all of the resistors on one side and the transistors on the other side or are they mixed?

Is it drawing excessive current?

 

[ben04srt]

resistors on one side transistors on other.

it draws a good bit of current .

 

[Perry Babin]

Turn the bias pots fully counter-clockwise to see if the current draw decreases.

Check the parts highlighted on the following images.
http://www.bcae1.com/temp/db1.jpg
http://www.bcae1.com/temp/db2.jpg

 

[ben04srt]

Replaced the transistors on the driver board along with the resistors.
Pots are turned all the way down.
The dc voltage in not 7 volts anymore it is less than 1 volt.
The amp still draws excessive current.

 

[Perry Babin]

Clamp the transistors and power up the amp for just long enough to measure the DC voltage across the large 0.1 ohm source resistors. Which ones have more than 0.000v across them?

Do this with no audio. If you have a 2 ohm current limiting resistor, insert it in the B+ line.

 

[ben04srt]

Dc voltage is gone on left channel.
None of the source resistors have more than 0.000 on them.

amp still draws lots of current when remote voltage is applied

 

[Perry Babin]

How much current?

 

[ben04srt]

My multimeter is not letting me check amperage.

If I turn the power supply of and on a few times it turns the amp on, If I turn it off then back on only a few seconds after it was working it turns right on.

When I wait a few minutes to turn it back on is when I have to toggle it of and on.

 

[Perry Babin]

What are you using for a power supply?

If it's an AC-DC converter, what's it's amp rating?

How do you know it's pulling excessive current?

 

[ben04srt]

I am using a 500 watt computer power supply, when I hook up the the remote it shuts the supply down and I have to keep turning it off and on to get the amp to stay on.

The supply is rated at 15 amps.

 

[Perry Babin]

It could be that the supply is sensitive the the instantaneous current draw of the amp when it switches on. After you pulse it a few times, the current draw is significantly less because most of the capacitors have charged.

Does it power up with a current limiting resistor in series with the B+ line?

 

[ben04srt]

Don't have current limiting resistor , but if i use a car driving light in series it powers up fine.
I have fosgate and ppi amps that are 500 watts and above and they never shut it down thats why I was concerned.

 

[Perry Babin]

If it powers up and produces audio when powered through a driving/head light, it's not drawing excessive current.

 

[ben04srt]

fixed this amp awhile ago(atleast thought I did) ,I am now getting distortion on the left channel and with no load my dc offset is up and down constantly.

Do the smd caps on the preamp board go bad like the rest of the ones in the amp?

 

[Perry Babin]

The ones on the preamp board are typically the first ones to cause problems. You can generally see corrosion around the capacitor and on the ICs and resistors.

 

[ben04srt]

would that be what is causing the distorsion ?

 

[Perry Babin]

It could be. Do you have an oscilloscope?

 

[ben04srt]

I don't have a scope, I replaced the caps on the preamp board and no luck.

When I touch the board it makes all kinds of wierd noises.
I have another of the same amp I may switch boards and see what happens.

 

[Perry Babin]

Was there any corrosion of leakage from the original caps?