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?