B
BillHeronemus
Guest
The reason is that on IC601(uPC1237HA) pin 2 (DCDET) there is some DC voltage,
however with pin 8 of the dual op-amp IC505 lifted, the voltage goes to zero
and the protection relay is allowed to close. The service literature from JBL
does not show any voltage readings on the schematic on what we are supposed to
be seeing. So the voltages we have on IC505 with the set in shutdown mode (and
with an audio signal present up to pin 7 of this op amp) are as follows:
Pin1 14 Vdc
Pin2 7.4 Vdc
Pin3 14.5 Vdc
Pin4 -14.5 Vdc
Pin5 0V
Pin6 -.03V
Pin7 0V with audio
Pin8 15Vdc
With pin 8 lifted the voltages on pin 3 goes down to 9.8Vdc, Pin 6 goes to
-7.4Vdc, and Pin 7 swings to -14Vdc. The rest of the voltages stays nearly the
same. Since we are finding ourselves running in circles, I was hoping someone
out there had been down this road before and give us some insight on what we
are missing here. A subwoofer should not be this difficult to troubleshoot
IMO. Thanks for any information. You can also email me at N3EVG@aol.com.
Bill
Don't give up.
Moses was once a basket case.
however with pin 8 of the dual op-amp IC505 lifted, the voltage goes to zero
and the protection relay is allowed to close. The service literature from JBL
does not show any voltage readings on the schematic on what we are supposed to
be seeing. So the voltages we have on IC505 with the set in shutdown mode (and
with an audio signal present up to pin 7 of this op amp) are as follows:
Pin1 14 Vdc
Pin2 7.4 Vdc
Pin3 14.5 Vdc
Pin4 -14.5 Vdc
Pin5 0V
Pin6 -.03V
Pin7 0V with audio
Pin8 15Vdc
With pin 8 lifted the voltages on pin 3 goes down to 9.8Vdc, Pin 6 goes to
-7.4Vdc, and Pin 7 swings to -14Vdc. The rest of the voltages stays nearly the
same. Since we are finding ourselves running in circles, I was hoping someone
out there had been down this road before and give us some insight on what we
are missing here. A subwoofer should not be this difficult to troubleshoot
IMO. Thanks for any information. You can also email me at N3EVG@aol.com.
Bill
Don't give up.
Moses was once a basket case.