Hi everybody, after a good experience with an SA98E (single TDA7498E) from SMSL, i bought two boards identical to the ones shown in the first page to use in PBTL mode. My power supply is 300VA 35V with 13200uF. (temporary, but voltage doesnt fluctuate much, 1-2v full load). I soldered the jumpers and connected audio to the BTL marked RCA the audio was ok but i noticed only one of fans on the modules turns on. So i let the modules cool down and disconnect the fans then turn on another time with some load: the module wich the fan was turning on heat effectively more, there is something i can check? I would thank everybody in advance for any help
TDA7498E issue
Good evening everyone,
I am having an urgent issue with a TDA7498E amp. I am not familiar with all the terminology used here, so would appreciate "noob terminology" and hope my explanation is good enough.
I bought this amp to build a friend a custom speaker for his birthday. It is powered by a 7S battery pack (21-29.4V), which is also supplying a 2 step down converters for some LEDs and some USB chargers.
Connected to the amp are 2 JBL Club 6520 speakers, I think they are 3 Ohm, one on each amp output channel.
Initially it worked great, I was able to play some music, sounded good even when loud. Then I didn't touch the project for 2 days and literally without touching or changing anything I suddenly had some relatively quiet, but audible white noise coming from the speakers this morning.
I didn't think much off it, but the noise was even there with no RCA cable connected. Constantly at the same volume, regardless of volume knob position.
I connected a second TDA7498E I had lying around, same noise, so I just accepted it and kept going with the project.
Tonight I switched it on again and now the amp still lights up the red LED, but there is no more sound coming out of it and no more white noise. Also after turning if off for an hour.
Did I somehow break it? Can I salvage it? Should I use the other spare amp? bridge those 4 ports on the bottom? connect the 2 speakers in serial and only to one output instead?
What do I do? I am desperate to get this working again for the birthday in 3 days, so would love your help!
Thank you
Good evening everyone,
I am having an urgent issue with a TDA7498E amp. I am not familiar with all the terminology used here, so would appreciate "noob terminology" and hope my explanation is good enough.
I bought this amp to build a friend a custom speaker for his birthday. It is powered by a 7S battery pack (21-29.4V), which is also supplying a 2 step down converters for some LEDs and some USB chargers.
Connected to the amp are 2 JBL Club 6520 speakers, I think they are 3 Ohm, one on each amp output channel.
Initially it worked great, I was able to play some music, sounded good even when loud. Then I didn't touch the project for 2 days and literally without touching or changing anything I suddenly had some relatively quiet, but audible white noise coming from the speakers this morning.
I didn't think much off it, but the noise was even there with no RCA cable connected. Constantly at the same volume, regardless of volume knob position.
I connected a second TDA7498E I had lying around, same noise, so I just accepted it and kept going with the project.
Tonight I switched it on again and now the amp still lights up the red LED, but there is no more sound coming out of it and no more white noise. Also after turning if off for an hour.
Did I somehow break it? Can I salvage it? Should I use the other spare amp? bridge those 4 ports on the bottom? connect the 2 speakers in serial and only to one output instead?
What do I do? I am desperate to get this working again for the birthday in 3 days, so would love your help!
Thank you
I understand your frustration.
I have two TDA7498E boards, probably of the same type as yours, and one of the boards may randomly stop playing for a while, but without white noise.
A further complication is that the TDA7498E chip is extremely small and almost impossible to replace without damaging the circuit board tracks.
The red lamp being lit and no reaction of the amplifier indicates that a fault prevents it from starting up.
Very first test is when the board is disconnected from everything (also no power). Use an Ohm-meter only. Measure the impedance from the supply “-” terminal and to each of the four output terminals (4 measurements). Following, measure the impedance from the supply “+” terminal and to each of the four output terminals (4 more measurements). Anything below 100Ohm indicates that the chip is defect.
I have two TDA7498E boards, probably of the same type as yours, and one of the boards may randomly stop playing for a while, but without white noise.
A further complication is that the TDA7498E chip is extremely small and almost impossible to replace without damaging the circuit board tracks.
The red lamp being lit and no reaction of the amplifier indicates that a fault prevents it from starting up.
Very first test is when the board is disconnected from everything (also no power). Use an Ohm-meter only. Measure the impedance from the supply “-” terminal and to each of the four output terminals (4 measurements). Following, measure the impedance from the supply “+” terminal and to each of the four output terminals (4 more measurements). Anything below 100Ohm indicates that the chip is defect.
Dear FauxFrench,
thank you for your fast reply. Here is what my multimeter reads (rounded off):
VCC (+) to ports: 0.480MΩ 0.520MΩ 0.500MΩ 0.530MΩ
GND (-) to ports: 0.570kΩ 0.570kΩ 0.550kΩ 1.960kΩ
Does that help? the multimeter keeps changing quite a bit though, especially when turning red and black wire around. Very weird as direction should not matter...
The spare board I have reads between 19-24kΩ to GND and 25-28kΩ to VCC.
Whats next? Should I try the spare board? If so, how should I connect it? Jumpers? Speakers to one port in series?
Thank you!
thank you for your fast reply. Here is what my multimeter reads (rounded off):
VCC (+) to ports: 0.480MΩ 0.520MΩ 0.500MΩ 0.530MΩ
GND (-) to ports: 0.570kΩ 0.570kΩ 0.550kΩ 1.960kΩ
Does that help? the multimeter keeps changing quite a bit though, especially when turning red and black wire around. Very weird as direction should not matter...
The spare board I have reads between 19-24kΩ to GND and 25-28kΩ to VCC.
Whats next? Should I try the spare board? If so, how should I connect it? Jumpers? Speakers to one port in series?
Thank you!
The values you have measured do not seem as proof that the IC is defect. It is strange that you have such differences with your spare board. Could you have turned the Ohm-meter test pins oppositely for the two measurements (red-black)? That can make a difference. Would you have a constant voltage source around 19Vdc to use as supply for test only?
Yes if I turn the multimeter the values change but also sometimes not at all and the values fluctuate.
I just used the spare board with the 2 speakers looked to one output in series and ran it 4-5h at normal volume.
All fine. Paused the music on my phone, went outside, returned 5 mins later and now it is also dead. No more music, no more nothing, also not on the other channel.
Can it be that the board muted itself or something? Or what am I missing here?
I just used the spare board with the 2 speakers looked to one output in series and ran it 4-5h at normal volume.
All fine. Paused the music on my phone, went outside, returned 5 mins later and now it is also dead. No more music, no more nothing, also not on the other channel.
Can it be that the board muted itself or something? Or what am I missing here?
As you have not shorted any pins or so in the time in-between, it should work as before.
Do have a 19Vdc power supply or so? Like a charger for a lap-top. The first test should be with as little as possible that may cause problems. Batteries do not always behave ideally.
A first test should be with a minimum of elements: the headphone-output from a a SmartPhone, two simple speakers and a fixed voltage supply with a voltage in the middle of the supply range.
If that does not work with any of the amplifier boards, it is going to be difficult.
Do have a 19Vdc power supply or so? Like a charger for a lap-top. The first test should be with as little as possible that may cause problems. Batteries do not always behave ideally.
A first test should be with a minimum of elements: the headphone-output from a a SmartPhone, two simple speakers and a fixed voltage supply with a voltage in the middle of the supply range.
If that does not work with any of the amplifier boards, it is going to be difficult.
I certainly hope that your boards are not dead.
As I described before, it is generally clever to test a new board for if it functions using simple and not demanding operational circumstances.
If it suddenly does not work anymore, you go back to the same little demanding working conditions. If it still does not work then, you have to look for the flaw on the board itself and that is far more demanding.
Please let the boards cool off for some 15 minutes and try each board in such a simple test setup.
It is absolutely not normal that two boards work for a couple of hours and then stop working when the supply voltage is well within limits and the sound level was not excessive.
Is it a red or green board with a golden heatsink having a small fan in the middle?
As I described before, it is generally clever to test a new board for if it functions using simple and not demanding operational circumstances.
If it suddenly does not work anymore, you go back to the same little demanding working conditions. If it still does not work then, you have to look for the flaw on the board itself and that is far more demanding.
Please let the boards cool off for some 15 minutes and try each board in such a simple test setup.
It is absolutely not normal that two boards work for a couple of hours and then stop working when the supply voltage is well within limits and the sound level was not excessive.
Is it a red or green board with a golden heatsink having a small fan in the middle?
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Good hint.
I sat down today with both "dead" boards. Found a 19V charger, used that and some 4 Ohm speakers and my iPod. Nothing. Dead. Just the red LED.
I then took another amp out of an old speaker project I made a while back (I bought that one on Amazon for 24 Euros 3 Years ago, rather than the 15 Euro china boards that both broke which I bought recently for this new project).
Initially they looked identical except for the fan logo and the tops of the capacitors. Multimeter readings (continuity etc) all similar.
Amp - Album on Imgur
Boards labelled 1 and 2 are the new boards that both stopped working. Both had 0 thermal paste.
My old board had thermal paste and a component soldered where my finger is in the picture. And the chip has slightly different writing on it.
That could be due to design changes over the last 3 years? Or its fake and broke because of that? Or it just overheated?
I am now est running my old board with the other speakers. The speakers read 2.5 Ohm.
Can I run them each on an output? Or should I run both in series on one output to give the amp 5 Ohms?
Cheers
I sat down today with both "dead" boards. Found a 19V charger, used that and some 4 Ohm speakers and my iPod. Nothing. Dead. Just the red LED.
I then took another amp out of an old speaker project I made a while back (I bought that one on Amazon for 24 Euros 3 Years ago, rather than the 15 Euro china boards that both broke which I bought recently for this new project).
Initially they looked identical except for the fan logo and the tops of the capacitors. Multimeter readings (continuity etc) all similar.
Amp - Album on Imgur
Boards labelled 1 and 2 are the new boards that both stopped working. Both had 0 thermal paste.
My old board had thermal paste and a component soldered where my finger is in the picture. And the chip has slightly different writing on it.
That could be due to design changes over the last 3 years? Or its fake and broke because of that? Or it just overheated?
I am now est running my old board with the other speakers. The speakers read 2.5 Ohm.
Can I run them each on an output? Or should I run both in series on one output to give the amp 5 Ohms?
Cheers
I get nothing from "Imgur" but a dark screen. It may be due to settings of my PC. I will try another PC tomorrow.
No thermal paste is bad news. Due to the very small size of the IC, thermal coupling to the heatsink is critical. But, too much thermal paste may end up between the IC pins at that is no good either.
No thermal paste quickly leaves the IC to overheat. However, the chip should have thermal protection such that when it cools off it should work again. It should not become defect even from overheating.If the chips overheated to destruction, you should measure low impedance values at the outputs. You tested them and it seems OK.
The marking on the ICs, is that TDA7498E or TDA7498?
I will try to look at "Imgur" again tomorrow from another computer.
I will have to see if there is a small 3.3V voltage regulator on-board and which type that may be. Perhaps that regulator may have failed.
I would not run such amplifiers with 2.5 Ohm load impedance. Use 5 Ohm.
No thermal paste is bad news. Due to the very small size of the IC, thermal coupling to the heatsink is critical. But, too much thermal paste may end up between the IC pins at that is no good either.
No thermal paste quickly leaves the IC to overheat. However, the chip should have thermal protection such that when it cools off it should work again. It should not become defect even from overheating.If the chips overheated to destruction, you should measure low impedance values at the outputs. You tested them and it seems OK.
The marking on the ICs, is that TDA7498E or TDA7498?
I will try to look at "Imgur" again tomorrow from another computer.
I will have to see if there is a small 3.3V voltage regulator on-board and which type that may be. Perhaps that regulator may have failed.
I would not run such amplifiers with 2.5 Ohm load impedance. Use 5 Ohm.
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The second link is a dud (spaces?), your first link does work.
It would be much better if you attach images directly
How to attach images to your posts.
Attachments
Dear Mooly, sorry I did not know - I tried the image icon but that led me nowhere. Tried your instructions just now, but my jpgs don't upload. the site just gets stuck for 10 minutes. Yes I pasted the link with spaces as I thought then maybe it will be forwarded as text.
@FauxFrench do you mean the chap Chinese board 1 and 2 is what you use or the one on the bottom with thermal paste?
Mine have not returned to life in 3 days. 3rd board working fine so far. Fingers crossed until tomorrow
@FauxFrench do you mean the chap Chinese board 1 and 2 is what you use or the one on the bottom with thermal paste?
Mine have not returned to life in 3 days. 3rd board working fine so far. Fingers crossed until tomorrow
