I wired 3x 4733 diodes in series. The voltage across D102 and D103 are now the same: 15vDC. R93 still gets hot but not as quickly. I think C57 has a problem as its not measuring up to snuff like C67 is while on the board. I'm going to check them both off the board.
Still no sound out of the amp.
Still no sound out of the amp.
Assuming that you've run all controls through their entire range (signal source and speakers connected and there was no signal)...
Check the output pins of all of the op-amps to confirm that all are at 0v ±0.01v DC (no signal). Place the black probe on one of the non-bridging speaker terminals. Also confirm that you have ±15v on the power supply pins of ALL of the op-amps. If those check out...
Drive a signal into the amp and start following the signal at the back of the RCA jacks through the various op-amps to see if you can find where it stops.
Check the output pins of all of the op-amps to confirm that all are at 0v ±0.01v DC (no signal). Place the black probe on one of the non-bridging speaker terminals. Also confirm that you have ±15v on the power supply pins of ALL of the op-amps. If those check out...
Drive a signal into the amp and start following the signal at the back of the RCA jacks through the various op-amps to see if you can find where it stops.
Amp controls dont change output of the amp at all.
The opamps dual, 8 ping in-line ICs; JRC 2068LD. Here is datasheet:
http://semicon.njr.co.jp/njr/hp/fileDownloadMedia.do?_mediaId=117
I have +15vDC on the power supply pin 8 of all the opamps which is good. Also measured -15vDC on supply pin 4 of the opAmps.
The opamp outputs seem to be having a problem however. 5 out of the 6 opamps are outputting +15vDC. You say this should be 0v so theres a problem here.
Measuring the opAmps directly from V- to V+ pins comes up with 30vDC.
I'm starting to trace out both the RCA signal and potentially where this 15v output is coming from.
The opamps dual, 8 ping in-line ICs; JRC 2068LD. Here is datasheet:
http://semicon.njr.co.jp/njr/hp/fileDownloadMedia.do?_mediaId=117
I have +15vDC on the power supply pin 8 of all the opamps which is good. Also measured -15vDC on supply pin 4 of the opAmps.
The opamp outputs seem to be having a problem however. 5 out of the 6 opamps are outputting +15vDC. You say this should be 0v so theres a problem here.
Measuring the opAmps directly from V- to V+ pins comes up with 30vDC.
I'm starting to trace out both the RCA signal and potentially where this 15v output is coming from.
Thats correct. No U107. This amp was never opened before me, and it looks like U107 was never installed on this PCB from the factory.
What's the resistance between the RCA shield and the non-bridging speaker terminals?
U107 is used to drive the 'output' RCAs.
U107 is used to drive the 'output' RCAs.
I didnt see your post until now. I'll have to check on that later today.
R93 still gets *hot* D102/D103 are still measuring up alright (3 x 4733 diodes in series on D102).
R93 still gets *hot* D102/D103 are still measuring up alright (3 x 4733 diodes in series on D102).
Referencing amp ground, the opAmp behind U107 (Empty) is U101 and measures the vollowing DC voltages:
2068LD Pin / vDC
1. 15
2. 15
3. 0
4. 0.018
5. -14.8
6. 0.2
7. 2.4
8. 14.4
Isnt Pin 4 supposed to be -15vDC? Some of the opamps are measuring about +/- 14vDC on pin 4, but U106, U101, and U103 are measuring less than 0.1vDC on Pin4
2068LD Pin / vDC
1. 15
2. 15
3. 0
4. 0.018
5. -14.8
6. 0.2
7. 2.4
8. 14.4
Isnt Pin 4 supposed to be -15vDC? Some of the opamps are measuring about +/- 14vDC on pin 4, but U106, U101, and U103 are measuring less than 0.1vDC on Pin4
Last edited:
They are definately 8 pin. The thing is theres an extra hole in the PCB where a '9th' pin could have been. They are all installed like this. Do they look installed upside down or what?
Perry; Im sorry but I was measuring the pins backwords from Pin 8 to 1 instead of Pin 1 to 8 in my previous post. U101's pins are comming up like this:
2068LD Pin / vDC
1. 14.4
2. 2.4
3. 0.2
4. -14.8
5. 0.018
6. 0
7. 15
8. 15
That makes things a little better... All opAmps have ~-15vDC on Pin4, and ~+15vDC on Pin 8. Sorry again about that. Working upside down sometimes.
That also means at least U101 outputs are pushing 15v...
2068LD Pin / vDC
1. 14.4
2. 2.4
3. 0.2
4. -14.8
5. 0.018
6. 0
7. 15
8. 15
That makes things a little better... All opAmps have ~-15vDC on Pin4, and ~+15vDC on Pin 8. Sorry again about that. Working upside down sometimes.
That also means at least U101 outputs are pushing 15v...
If the op-amps are DC coupled, one could cause the others to have DC. Remove this op-amp and connect pins 1 and 7 to the RCA shield ground. Does that eliminate the DC on the other op-amps?
U101 or U106?
I removed U101 and soldered a wire from Pin 7 through Pin 1 and then to RCA shields. Seems the other opAmp outputs were not affected and still measuring +/- 14vDC, Except U106.
I removed U101 and soldered a wire from Pin 7 through Pin 1 and then to RCA shields. Seems the other opAmp outputs were not affected and still measuring +/- 14vDC, Except U106.
Last edited:
Do you think something might be wrong with the opAmps? I'm measuring U101 on the bench and cant get the internal 'transistor' to check out right. Maybe I'm just doing this wrong; there are no shorts between pins but I cant get the diode check to beep on pins 1 through 3. Pins 5 thru 7 diode check with Com on pin 6 and 7.
At any time, did you power the amp up with the Zener out of the circuit?
Did the original Zener open or short?
Did the original Zener open or short?
The original zener in D103 shorted out - 0 Ohms in both directions. I know something else must have also shorted enough to pop a trace leading from the RCA shields twards the center of the PCB. You think the shorted zener may have also taken out some opAmps? Something similar to this happened to my two Fosgate 60dsm amps but those opAmps survived.
The shorted diode in the Rockfords served a different purpose and generally only cause engine noise. The trace likely burned because 12v contacted the RCA shields.
This amp is entirely different. The shorted diode would not have damaged any op-amps. An open Zener would been likely to cause the op-amps to fail. In this type of amp, it's likely that a speaker wire (one connected to one of the bridging speaker terminals) contacted chassis ground in the vehicle.
I don't know what caused the op-amp(s) to fail. To determine how many have failed, you could bridge the output and the inverting input pins (1-2 and 6-7) with solder. If the voltage on the output pin (1, 7) matches the voltage on the non-inverting inputs (3, 5), the op-amp is likely OK. If it doesn't, the op-amp is likely defective.
This amp is entirely different. The shorted diode would not have damaged any op-amps. An open Zener would been likely to cause the op-amps to fail. In this type of amp, it's likely that a speaker wire (one connected to one of the bridging speaker terminals) contacted chassis ground in the vehicle.
I don't know what caused the op-amp(s) to fail. To determine how many have failed, you could bridge the output and the inverting input pins (1-2 and 6-7) with solder. If the voltage on the output pin (1, 7) matches the voltage on the non-inverting inputs (3, 5), the op-amp is likely OK. If it doesn't, the op-amp is likely defective.
- Status
- Not open for further replies.