Crunch GP3000

mike49504

Member
2006-09-22 8:32 am
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?
 

mike49504

Member
2006-09-22 8:32 am
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??
 
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.
 
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.