Yes, the yellow terminal is connected to pin 9 of the LM324.
No, there is 12.65v on the yellow terminal, but -0.00 on the orange terminal.
No, there is 12.65v on the yellow terminal, but -0.00 on the orange terminal.
That's a 6.8v zener (or whatever the numbers are in your amp). If it has 12v on it, it's blown open.
I believe there is a short circuit across this diode. I replaced it with another 6.8v zener diode and there was a puff of smoke. On diode check, the yellow terminal (LM324 PIN 9) is showing 006 to B+ while the orange terminal (LM324 PIN 11) is reading 000 to GND. Do I have a shorted component somewhere or is the LM324 damaged? What to check next?
The readings above were taken with the 6.8v zener diode removed, and the probe on the pads on the board...
Did you install the replacement diode with the striped end on pin 9?
If you read very low resistance between B+ and pin 9, the 324 is likely shorted internally (pin 4 to pin 9).
If you read very low resistance between B+ and pin 9, the 324 is likely shorted internally (pin 4 to pin 9).
I only have 1 spare LM324 from my Digikey parts order for this amp. I want to be very cautious with it.
So the yellow/PIN 9 terminal of the 6.8v zener diode should not have a low reading when checked to B+?
Should the orange terminal be connected to GND?
When I remove the LM324, the low reading on the yellow terminal of the 6.8v zener diode should change to a much higher or open circuit reading?
So the yellow/PIN 9 terminal of the 6.8v zener diode should not have a low reading when checked to B+?
Should the orange terminal be connected to GND?
When I remove the LM324, the low reading on the yellow terminal of the 6.8v zener diode should change to a much higher or open circuit reading?
If I recall correctly, it was a short between the B+ and GND input terminals that caused this issue...
With the 324 off of the board, you should read about 10k ohms to B+
Check the pin 4-9 resistance when the IC is off of the board.
Orange should go to ground (pin 11 of the 324).
Check the pin 4-9 resistance when the IC is off of the board.
Orange should go to ground (pin 11 of the 324).
Ok, found the problem. There was a solder bridge at the 10k resistor next to the 6.8v zener diode. Removed the solder bridge, replaced the 6.8v zener diode and now the amp powers up and plays clean audio on all four channels. The thermal light issue is now my only remaining problem with this amp. It should not be a solder bridge or mistakenly connected to the green led as upon applying remote power, the red led lights first, then the green led lights up a second later with the red led remaining illuminated. I will resume tracing the red/thermal led circuit but a lot more carefully this time. Hopefully someone can interject with some useful, helpful information. I will update with my progress as it is made. Thanks
Found that the thermal led signal is being triggered by the rear channel. I have found a transistor with 3B on it that has 11.1 on it, going to a 2.2k resistor, then through a transistor/diode marked F3 then to the red led. The front channel has no voltage coming from 3B and is not illuminating the led so that circuit is intact. I lifted F3 to interrupt the signal to the red led and everything looks normal.
What is the 3B? Is it a BC856B?(according to another thread on here)
I don't have any of those, are there other substitutes I can use? I have BC850 and other more common smd components...
What is the 3B? Is it a BC856B?(according to another thread on here)
I don't have any of those, are there other substitutes I can use? I have BC850 and other more common smd components...
Where is it in the amp (circuit board designation if it has one). I want to look at the markings on the photos that I have.
Have to try to get a photo soon. The emitter of the 3B transistor is connected to pin 8 of the LM358M which is close to the 74VHC132 and 74VHC112. Pin 8 of the LM358M has 11.3v on it for both front and rear channels which is present on the emitters of both 3B transistors. I currently have the collectors of both 3Bs lifted to monitor the difference in output/voltage. The base of the 3B in the front channel has 11.1v with 0.01v on the collector tab. The base of the 3B in the rear channel has 10.4v with 11.1v on the collector tab. If i reconnect the front channel, the thermal led stays off as there is no voltage proceeding forth, but if I reconnect the rear channel, the thermal led illuminates as there is voltage going forth through the circuit.
Obviously, the transistor in the rear channel is shorted so I need to know whether I can substitute another PNP transistor in place of the 3B?
Working on getting a pic up if necessary...
Obviously, the transistor in the rear channel is shorted so I need to know whether I can substitute another PNP transistor in place of the 3B?
Working on getting a pic up if necessary...
I don't think that the thermal protection circuit has anything to do with the individual channels. The connection to the LM358 is simply a power supply connection.
If the 3B is a PNP transistors, the MMBTA56 should be a good sub for this circuit.
If the 3B is a PNP transistors, the MMBTA56 should be a good sub for this circuit.
I don't think the 3B is the problem as I swapped them from front to rear channels and the rear channel is still doing the same thing. The transistor is still passing 11.1v through its collector even though it worked properly in the front channels, and the one from the rear channels is working properly in the front channel. I don't understand how this is taking place...
I do have another problem though. After probing around some more I have discovered that whatever components that regulate the rail voltage for the rear channels is not working properly. Previously, the rail voltage would stabilize and settle at +- 28v, but right now, the voltage goes all the way up to +-41v and stops there. I turn it off quickly after that as I know the circuit was not designed for voltage that high. The front channel rail voltage still settles at +-38V as it did before.
I am not sure exactly what I did to create this new development but this amp is giving me grey hair...
I do have another problem though. After probing around some more I have discovered that whatever components that regulate the rail voltage for the rear channels is not working properly. Previously, the rail voltage would stabilize and settle at +- 28v, but right now, the voltage goes all the way up to +-41v and stops there. I turn it off quickly after that as I know the circuit was not designed for voltage that high. The front channel rail voltage still settles at +-38V as it did before.
I am not sure exactly what I did to create this new development but this amp is giving me grey hair...
Have you measured the resistance of the thermistor? What is it?
Have you read about the various features of the amp regarding thermal rollback and rail voltages that vary with load?
Have you read about the various features of the amp regarding thermal rollback and rail voltages that vary with load?
Resistance across the thermistor (U500) is 21.7k ohms.
I know that JL Audio has those features incorporated into this slash series amplifier, but from an electrical engineering standpoint, I am not familiar enough with the circuitry to understand and manipulate their methods of achieving this. The more that I do on this amplifier, the more that I understand how it works.
I no longer have +-41v at the rails for the rear channels after teching through some more. It is currently peaking at around +-20v. The drive signal for the PS FETs is 3.1v for the front channels and 1.8V for the rear channels. I assume that the lower drive voltage for the rear PS drivers is why full power is not being produced.
The voltages at the IP3525AD on the PS driver boards:
REAR FRONT
1) 0.0 / 0.0
2) 4.9 / 5.0
3) 0.02 / 0.02
4) 0.1 / 0.1
5) 1.7 / 1.6
6) 3.8 / 3.8
7) 1.6 / 1.6
8) 1.7 / 2.9
9) 5.2 / 5.2
10) 0.1 / 0.0
11) 1.7 / 3.1
12) 0.0 / 0.0
13) 11.2 / 11.2
14) 1.7 / 3.1
15) 11.1 / 11.1
16) 5.0 / 5.0
QUESTIONS:
The voltages are almost identical with the exception of 8, 11 and 14. Since 11 and 14 are the output PS FET drive signal, am I correct in assuming that the input voltage on PIN 8 is responsible for the output voltage on PINS 11 and 14 and that I should continue to work my way backwards from PIN 8?
Are the extremely slight differences on PINS 2, 5 and 10 anything to investigate concerning my issue?
Thanks.
I know that JL Audio has those features incorporated into this slash series amplifier, but from an electrical engineering standpoint, I am not familiar enough with the circuitry to understand and manipulate their methods of achieving this. The more that I do on this amplifier, the more that I understand how it works.
I no longer have +-41v at the rails for the rear channels after teching through some more. It is currently peaking at around +-20v. The drive signal for the PS FETs is 3.1v for the front channels and 1.8V for the rear channels. I assume that the lower drive voltage for the rear PS drivers is why full power is not being produced.
The voltages at the IP3525AD on the PS driver boards:
REAR FRONT
1) 0.0 / 0.0
2) 4.9 / 5.0
3) 0.02 / 0.02
4) 0.1 / 0.1
5) 1.7 / 1.6
6) 3.8 / 3.8
7) 1.6 / 1.6
8) 1.7 / 2.9
9) 5.2 / 5.2
10) 0.1 / 0.0
11) 1.7 / 3.1
12) 0.0 / 0.0
13) 11.2 / 11.2
14) 1.7 / 3.1
15) 11.1 / 11.1
16) 5.0 / 5.0
QUESTIONS:
The voltages are almost identical with the exception of 8, 11 and 14. Since 11 and 14 are the output PS FET drive signal, am I correct in assuming that the input voltage on PIN 8 is responsible for the output voltage on PINS 11 and 14 and that I should continue to work my way backwards from PIN 8?
Are the extremely slight differences on PINS 2, 5 and 10 anything to investigate concerning my issue?
Thanks.
Traced pin 8 of the 3525AD on the PS board to a 1k resistor which has 5.0v on the other side on both driver boards and also to pin 7 of the LM311 on the PS driver board. The voltages on both LM311s are identical except for pin 2. Pins 2 appears to be fed by pin 7 of the LM358M on the PS driver board. There is a capacitor in line with it but the other end has 2.8v on both boards. The voltages of both LM358Ms are identical with the exception of pin7.
LM311 Voltages: LM358M Voltages:
REAR/ FRONT/ REAR/ FRONT
1) 0.0 / 0.0 / 0.0 / 0.0
2) 0.8 / 1.1 / 0.0/ 0.0
3) 0.9 / 0.9 / 0.0/ 0.0
4) 0.0 / 0.0/ 0.0/ 0.0
5) 11.0 / 11.0/ 2.8/ 2.8
6) 11.0 / 11.0/ 2.8/ 2.8
7) 1.6 / 2.9/ 0.8/ 1.1
8) 11.1 / 11.1/ 11.1/ 11.1
Do I have a faulty LM358M?
The only other thing I suspect may be the top left transistor on the circuit board just to the left of the base of the PS driver board. All of the incoming voltages to these three components are identical except for the drive signal voltage on the 3B transistor. I did remove and reinstall this transistor during my search for the thermal led issue. Can this one be substituted with an MMBTA56 also?
LM311 Voltages: LM358M Voltages:
REAR/ FRONT/ REAR/ FRONT
1) 0.0 / 0.0 / 0.0 / 0.0
2) 0.8 / 1.1 / 0.0/ 0.0
3) 0.9 / 0.9 / 0.0/ 0.0
4) 0.0 / 0.0/ 0.0/ 0.0
5) 11.0 / 11.0/ 2.8/ 2.8
6) 11.0 / 11.0/ 2.8/ 2.8
7) 1.6 / 2.9/ 0.8/ 1.1
8) 11.1 / 11.1/ 11.1/ 11.1
Do I have a faulty LM358M?
The only other thing I suspect may be the top left transistor on the circuit board just to the left of the base of the PS driver board. All of the incoming voltages to these three components are identical except for the drive signal voltage on the 3B transistor. I did remove and reinstall this transistor during my search for the thermal led issue. Can this one be substituted with an MMBTA56 also?
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OK. Discovered that the same 3B transistor that is responsible for sending the thermal light signal is also responsible for the low rail voltage. I removed the transistor altogether and bridged the base to the emitter with solder for testing purposes to see what would happen. The supply voltage from the LM358M pin 8 is passed through full current and the rear channel rails go straight up to +-28v just like before. The red led is not lit also because there is no transistor to output anything from its collector, but of course I now have no thermal fault.indication.
It would appear that either the MMBTA56 is not a suitable substitute for this location or I still have an existing fault in the protection circuit. With the base and emitter bridged, the amp is idling with both rail voltages steady at +-28v and +-38v.
It would appear that either the MMBTA56 is not a suitable substitute for this location or I still have an existing fault in the protection circuit. With the base and emitter bridged, the amp is idling with both rail voltages steady at +-28v and +-38v.
Was the thermistor at room temperature when you measured it?
I measured 2 (U800 and U801) in a junker 500/5 and they read approximately 150k ohms (actually 170k but it's less than 25C in the shop).
I measured 2 (U800 and U801) in a junker 500/5 and they read approximately 150k ohms (actually 170k but it's less than 25C in the shop).
Yes, room temperature but not with climate control on. I would say about 30°c. I cannot remember if the amplifier was idling before or not.
Should I try changing it?
What would that part # be?
Are they the same in all slash series amps?
It is located between the front channel components, shouldn't it be triggering the thermal circuit for the front channels also?
Should I try changing it?
What would that part # be?
Are they the same in all slash series amps?
It is located between the front channel components, shouldn't it be triggering the thermal circuit for the front channels also?