Crunch GP3000

[mike49504]

I put all new outputs in this amp and a brand new driver board.

Amp powers up and produces + - Rail voltage (115 volts)

Amp also produces + - 15 volts on all op-amps

Relays kick on but amp had no output


Could it possibly be a bad solder joint somewhere Do i need to trace it back to where i lose signal ??

Or any ideas where to check?

 

[Perry Babin]

I think there's a transistor used for muting between the output inductors and the driver board. It may be defective.

Where did you buy a new driver board?

 

[mike49504]

I bought 1 from Sundown audio The SAZ3000 amp uses the same driver board as the crunch gp3000 . Its a 3640 driver board.

I heard cadence also will sell them And i may have another source for them as well but still checking into that

 

[mike49504]

The voltages i get from the D1302 transistor are

Leg1:-114.8

Leg2:-52.4 and climbs up and down

Leg3:-114.5

Does this appear to be defective?

 

[Perry Babin]

I think you need to remove it and test it out of the circuit.

 

[mike49504]

If i set the meter to ohm this is what i get

1-2:OL

1-3:35.94 and then climbs up and down wont lock on a number

2-3: 35.98 then climbs up and down wont lock on a number either

Probes reversed OL in all posistions


If i power up the amp without it and test for output will i damage the amp??

 

[Perry Babin]

35.9 or 34.9K?

This is used to shut down the amp if there is a problem. If the amp is otherwise in good working order, removing the transistor would be safe. If there is a problem causing the amp to pass excessive current through the outputs and the amp is being shut down for a good reason, removing the transistor could cause extensive damage.

 

[mike49504]

35.9 ohms

With it removed still have no output

 

[Perry Babin]

Is the amp producing rail-rail oscillation on the output transistors?

39.5 doesn't seem right because you read OL with the leads reversed. It's also rare for a handheld multimeter to read ohms to 2 decimal places. This probably isn't an issue here but could have you chasing problems that don't exist. If the meter didn't read k ohms, turn it off then back on to make sure the k character on the display is working.

 

[mike49504]

how do i test to see if it has rail to rail oscillation?

 

[Perry Babin]

Probe the input terminal of the output filter inductor.

 

[mike49504]

what would i set me scope at to see if its oscillating rail to rail and what kind of wave should i see?

 

[Perry Babin]

Set the scope to the highest vertical amp setting. Center the trace. Set the timebase to 2ms initially. Touch the various terminals of the output transistors. Find the ones with the positive and negative rail voltage and note where the trace is deflected to. Probe the drains until you find one that fills the area between the points where the trace was deflected to with the rail voltage. When you find it, set the timebase to 5us and confirm that you have a clean square wave.

 

[mike49504]

2ms .5 volts div or what?

I set it to 2 ms and .5 volts div turned the vertical amp all the way up i get no square wave on any drain let of the outputs and when i probe the other legs the trace disappears

 

[Perry Babin]

I don't know what the highest vertical amp setting you have but it's more likely to be 5v than 0.5v.

 

[mike49504]

The highest setting is 20 volts on the volts/div - variable then it goes

20 10 5 2 1

 

[Perry Babin]

Use 20. I forgot you purchased a different scope.