Hi All.
I have a Harman Kardon TS7 Active Subwoofer that has recently developed a fault. It sounds good and Id like to fix it, which seems achievable. The circuits are all accessible and most components are descrete. I have found some schematics. I have some electronics background (trained in it years ago) but its a bit beyond my abilities without assistance. Thats where you can help 🙂
Fault: This sub has a auto-standby functionality. It goes into standby automatically if there is no signal. When a signal is applied (I use LFE port) it comes out of standby and the LED turns from orange to blue. This unit never comes out of standby anymore. The status light stays orange. There is an "auto" or "on" switch that should control this standby functionality. "on" should switch the unit on all the time, this does not work. The unit is always in standby. No input sound is amplified.
Diagnosis: I have the circuit boards out and there is no obvious damage, scorching or blown caps etc. I have tested the voltage rails and all show correct voltages. I have noticed that even though the unit undicates its in standby, the speaker is active. I can hear some hiss/noise. The amplifier heatsink also gets warm given some time. The speaker protection relay seems to click on as well. This lets me believe that the output stage is working and the fault its with the input stage. These stages are seperate circuit boards (see photo) with the top being pre and the bottom being power. As a test I disconnected the 'mute' line from pre to power (removed D101) to ensure it wasnt being sent a mute signal. This made no difference so it doesnt seem like its being muted.
Technical Links:
Photo: Link
Schematic Links: Pre, Power, ICs
Additional: There are other known faults that develop with this unit (researched google) and I have applied these fixes. they did not help and dont seem to apply here. Link. and Link
I need some advice on what to test next. I have highlighted some key components. D209 is the external bi-color LED. Clearly this voltage needs to go high/low to reverse the polarity. I dont know which polarity the standby color is. The switch is highlighted, as is the mute line. I feel the issue is in this area as the switch should force the unit out of standby, change the LED and make the mute line either high or low (not sure which). None of this seems to happen.
I have decent tools and multimeter. I dont have a signal generator or the likes. but im savvy and have time. your advice and pointers are appreciated. Thanks in advance.
I have a Harman Kardon TS7 Active Subwoofer that has recently developed a fault. It sounds good and Id like to fix it, which seems achievable. The circuits are all accessible and most components are descrete. I have found some schematics. I have some electronics background (trained in it years ago) but its a bit beyond my abilities without assistance. Thats where you can help 🙂
Fault: This sub has a auto-standby functionality. It goes into standby automatically if there is no signal. When a signal is applied (I use LFE port) it comes out of standby and the LED turns from orange to blue. This unit never comes out of standby anymore. The status light stays orange. There is an "auto" or "on" switch that should control this standby functionality. "on" should switch the unit on all the time, this does not work. The unit is always in standby. No input sound is amplified.
Diagnosis: I have the circuit boards out and there is no obvious damage, scorching or blown caps etc. I have tested the voltage rails and all show correct voltages. I have noticed that even though the unit undicates its in standby, the speaker is active. I can hear some hiss/noise. The amplifier heatsink also gets warm given some time. The speaker protection relay seems to click on as well. This lets me believe that the output stage is working and the fault its with the input stage. These stages are seperate circuit boards (see photo) with the top being pre and the bottom being power. As a test I disconnected the 'mute' line from pre to power (removed D101) to ensure it wasnt being sent a mute signal. This made no difference so it doesnt seem like its being muted.
Technical Links:
Photo: Link
Schematic Links: Pre, Power, ICs
Additional: There are other known faults that develop with this unit (researched google) and I have applied these fixes. they did not help and dont seem to apply here. Link. and Link
I need some advice on what to test next. I have highlighted some key components. D209 is the external bi-color LED. Clearly this voltage needs to go high/low to reverse the polarity. I dont know which polarity the standby color is. The switch is highlighted, as is the mute line. I feel the issue is in this area as the switch should force the unit out of standby, change the LED and make the mute line either high or low (not sure which). None of this seems to happen.
I have decent tools and multimeter. I dont have a signal generator or the likes. but im savvy and have time. your advice and pointers are appreciated. Thanks in advance.
On the jack panel pcb schematic pin 7 of U203 looks to be the key. With no signal going in monitor pin 7 and switch between "auto on" and "on" does the voltage change? If not the problem is somewhere in the lower right section of the schematic. Check the voltage and we can go from there.
Craig
Craig
I know you said it appears the speaker protect relay is pulling in, but just for completeness, also check the "PTC" signal on the jack panel output connector. It needs to be <0.5 volts.
Pin7 of U203 reads +14.5v at all times
PTC reads + 14.5v at all times
No readings change between Auto or On.
MUTE also stays at +14.5v at all time.
Testing the ON legs of the switch (203), when switched it jumps to 15v. This is expected. When switched back to auto, the voltage stays high and drops only very slowly like a cap discharging. This seems strange to me as I would have thought the voltage would drop when disconnected from +15v rail. Also, testing the base leg of Q206, it reads 0v at all time. This also seems strange to me, but all just guesses at this point.
Thanks.
PTC reads + 14.5v at all times
No readings change between Auto or On.
MUTE also stays at +14.5v at all time.
Testing the ON legs of the switch (203), when switched it jumps to 15v. This is expected. When switched back to auto, the voltage stays high and drops only very slowly like a cap discharging. This seems strange to me as I would have thought the voltage would drop when disconnected from +15v rail. Also, testing the base leg of Q206, it reads 0v at all time. This also seems strange to me, but all just guesses at this point.
Thanks.
I looked closer at this, and I see your point. You would expect the PTC rail to go to ground to energise the relay. keep in mind that VCC in this case is +47v (there are two voltages supplied from the trasnformer). Even with PTC at 15v, the difference between 47v and 15v (minus drop on R132) might be enough to energise the relay. it clicks and I can feel it with my finger.
+/- 15VDC good at the ICs? Pins 4 and 8? With pin 7 HIGH Q201 is on causing the audio mute and turning on the MUTE LED but that should have nothing to with PTC. The voltage on pin 6 should tell you if it's PTC is causing the problem, low should be PTC and high,+9-10VDC, should be normal.
Craig
Craig
Ok. I slowly rechecked PTC by following through from R263. it seems Im made a mistake by relying consistent pin numbering between boards. Nope. PTC is indeed low so i think we can rule that out. Sorry about that.
U203:
Pin 4 has -15v
Pin 8 has +15v
Pin 7 is high at +14.5v
Pin 6 is exactly 10v.
for consitency, I checked all the ICs. All have correct supply voltage.
One note is that D209 is not connected during testing. its attached to the casing with an very short lead so connectivity isnt easy. Would this be an issue around testing?
Not sure what else to suggest at this point. But thanks so far.
U203:
Pin 4 has -15v
Pin 8 has +15v
Pin 7 is high at +14.5v
Pin 6 is exactly 10v.
for consitency, I checked all the ICs. All have correct supply voltage.
One note is that D209 is not connected during testing. its attached to the casing with an very short lead so connectivity isnt easy. Would this be an issue around testing?
Not sure what else to suggest at this point. But thanks so far.
With the bypass switch set to "ON", you should see:
Q206 - base about +0.6 volts
Q206 - collector, <1 volt
Q207 - base, <3 volts
Q207 - emitter, <2 volts
U203 - pin 5, <3 volts
Whether D209 is connected or not is immaterial.
Anytime U203 pin 5 is > U203 pin 6, then the output (pin 7) should be high (near +15 volts). Anytime U203 pin 5 is < U203 pin 6, the output should be low (<1 volt).
Q206 - base about +0.6 volts
Q206 - collector, <1 volt
Q207 - base, <3 volts
Q207 - emitter, <2 volts
U203 - pin 5, <3 volts
Whether D209 is connected or not is immaterial.
Anytime U203 pin 5 is > U203 pin 6, then the output (pin 7) should be high (near +15 volts). Anytime U203 pin 5 is < U203 pin 6, the output should be low (<1 volt).
The only thing left is what is on pin 5? Pins 4,8, and 6 all look normal. Pin 7 may be correct depending what's on pin 5. Pin 7 should normally be low if pin 5 is lower than pin 6. U203 is being used as a comparator, comparing inputs 5 and 6.
Craig
Craig
Hi. Sorry for the delay, I have been away.
U302 Pin 5 is 14.89v volts.
Q206 - base about +0.6 volts - FAILED - This is at 0v.
Q206 - collector, <1 volt - FAILED - This is at 14.75v
Q207 - base, <3 volts - FAILED - This is at 15.3v
Q207 - emitter, <2 volts - FAILED - This is at 14.89v
For reference, Voltage rail reads 15.55v
So, I would think the 0v on base of Q206 is a concern? Could it be blown? This measurement would also clarify why there is 0v drop across R255 and C232.
Thanks
U302 Pin 5 is 14.89v volts.
Q206 - base about +0.6 volts - FAILED - This is at 0v.
Q206 - collector, <1 volt - FAILED - This is at 14.75v
Q207 - base, <3 volts - FAILED - This is at 15.3v
Q207 - emitter, <2 volts - FAILED - This is at 14.89v
For reference, Voltage rail reads 15.55v
So, I would think the 0v on base of Q206 is a concern? Could it be blown? This measurement would also clarify why there is 0v drop across R255 and C232.
Thanks
If Q206 isn't cooperating nothing after it will be correct. Start testing transistors and diodes in the circuit. Check the voltage on SW203.
Craig
Craig
test the output of the amplifier. It should be 0v relative to ground, both power rails 47v. pins 4 and 8 on the op amp should be -+ 15 volts
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I would suspect Q206 shorted B-E. Pull it out of circuit and test it with an ohmeter. Then with it out of circuit measure the voltage where the base would be connected and SW203 set to On. Should see about 7.5 volts.
Now short where the collector was connected to ground. The amp should come on.
Now short where the collector was connected to ground. The amp should come on.
Some positive news.
After a bit of mucking around I ended up removing Q206 and shorting C-E. I then tested the U203 outputs and everything looked good. I have reassembled and the unit indeed turns on and functions normally as if "On" were selected. "Auto" of course does nothing.
I have multimeter tested Q206 using some transistor testing instructions found on google, and it seems to test ok. I have not put it back in as yet.
I then moved to look at the R256/R255 voltage divider. This is expected to give 7.5v. it doesnt. I removed D214 and C232 to completely isolate this area of the circuit and remove any other factors. Still, its confusing, as it seems to be 0v. This would explain why Q206 does not turn on. Both resistors have been checked and read correct ohms. Im still really scratching my head on this on and will take another look tomorrow.
The one factor I know is that this schematic is not 100% complete. my unit has another mini-jack input, related to when 'auto' is switch on, which allows the unit to be turned on using an external <30vac source. I assume from some other audio component equipment. This is not shown on this schematic. I fear that this part of the circuit, that I cant see, is the cause.
Big thanks to all the inputs so far. its been invaluable.
After a bit of mucking around I ended up removing Q206 and shorting C-E. I then tested the U203 outputs and everything looked good. I have reassembled and the unit indeed turns on and functions normally as if "On" were selected. "Auto" of course does nothing.
I have multimeter tested Q206 using some transistor testing instructions found on google, and it seems to test ok. I have not put it back in as yet.
I then moved to look at the R256/R255 voltage divider. This is expected to give 7.5v. it doesnt. I removed D214 and C232 to completely isolate this area of the circuit and remove any other factors. Still, its confusing, as it seems to be 0v. This would explain why Q206 does not turn on. Both resistors have been checked and read correct ohms. Im still really scratching my head on this on and will take another look tomorrow.
The one factor I know is that this schematic is not 100% complete. my unit has another mini-jack input, related to when 'auto' is switch on, which allows the unit to be turned on using an external <30vac source. I assume from some other audio component equipment. This is not shown on this schematic. I fear that this part of the circuit, that I cant see, is the cause.
Big thanks to all the inputs so far. its been invaluable.
Success! I believe I have entirely fixed the issue. Its been running for a few hours and seems to be working normally.
I was able to find a snippet of a more up to date schematic. note the extra circuitry and relocated ON/AUTO switch. This explains the logic issues earlier.
From there was able to determine that D302 showed 15v on the anode, but 0v on the cathode. So the rest of the circuit, including Q206 base, was not powered. I had a spare 1N4004 laying around so used that. Functionality seems normal.
Many thanks for all comments and assistance.
I was able to find a snippet of a more up to date schematic. note the extra circuitry and relocated ON/AUTO switch. This explains the logic issues earlier.
From there was able to determine that D302 showed 15v on the anode, but 0v on the cathode. So the rest of the circuit, including Q206 base, was not powered. I had a spare 1N4004 laying around so used that. Functionality seems normal.
Many thanks for all comments and assistance.
Using only filter Board From H/K-TS11
Hi, I received a H/K-TS11 sub which did not have only the amp board in. The Filter board is quite similar to the TS-7 Filter board with the High Level input and RCA etc.. I would like to Use the same filter board to power a standard AMP board. Can anyone tell me if it is possible?
From what i see in the SUB-TS7 Filter image above, there are 7 connections of M201(My board has same labeling) DGND, Mute, -15V, AGND, +15V, PTC, OUT. I followed the Diagram and all seem same.
If i supply the +/-15V to power the board, will i be able to get the preamp output from this board?
Hi, I received a H/K-TS11 sub which did not have only the amp board in. The Filter board is quite similar to the TS-7 Filter board with the High Level input and RCA etc.. I would like to Use the same filter board to power a standard AMP board. Can anyone tell me if it is possible?
From what i see in the SUB-TS7 Filter image above, there are 7 connections of M201(My board has same labeling) DGND, Mute, -15V, AGND, +15V, PTC, OUT. I followed the Diagram and all seem same.
If i supply the +/-15V to power the board, will i be able to get the preamp output from this board?
@jdvuyk, could you share the updated schematic? I've got one of these subs which the auto on is always on.. I suspect C228 but found this as while realising I'm not looking at the full picture.
Best,
Josh
Best,
Josh