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Class D Switching Power Amplifiers and Power D/A conversion

HK HS500 - power and other measurements
HK HS500 - power and other measurements
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Old 5th February 2018, 07:20 PM   #1
chermann is offline chermann  Austria
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Default HK HS500 - power and other measurements

Hi to all

i try to measure my HArman Kardon HS500 class D amp (DDX 2160 chip). first try

my envoirment:
dummy load about 4ohms load each channel (mounted on an old cdp chassis-fan will be updated)
input is over rigol with 1kHz and 0,775 Vpp to aux in of the HS500 amp
right channel is with an ampere meter to check the current.
scope: yellow channel 1 is input (auxin),blue is right channel, and purple is left channel
on the very right side you will see the probes af a 2nd DMM, but this just check the volts at the amp board (is really stable at 34,55- 34,65Vdc!!!)

pic 1 (left to right) shows the scope probes : auxin yellow, blue and purple R + L channel
pic 2 the DUT right and the dummy load (4ohms 100WATT each channel ) on the left, scope probes are connected on the housing of the AMP (GND) the HS500 has no earth connection.
pic 3 is half volume all channels
pic 4 is full power at 1khz just switch the channel R off to see more
pic 5 is the check of ocp - with the ampere meter on channel R


as you can see i try to see some output (and first time power measurments). So why i get so strange output signals? the form looks distroyed.

did i something wrong?

thx for your inputs...
Attached Images
File Type: jpg 1_HS500 auxin 1khz 0775V.jpg (346.0 KB, 219 views)
File Type: jpg 2_HS500_dummy load and probes.jpg (406.4 KB, 218 views)
File Type: jpg 3_HS500_half volume 1khz 0775V.jpg (332.5 KB, 213 views)
File Type: jpg 4_HS500 at 1khz max power.jpg (374.6 KB, 203 views)
File Type: jpg 5_HS500 one channel Ac current.jpg (254.5 KB, 196 views)

Last edited by chermann; 6th February 2018 at 01:33 PM.
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Old 7th February 2018, 07:37 AM   #2
chermann is offline chermann  Austria
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hi

is there a problem with the appr. 4 ohms load? but the signal is at low volume still "distroyed". (first pic = pic 1 )

beacuse of my last days illness a did no furhter tests. i try to push the amp with different frequ to see the ocp.....yes you can hear a "queeeek" and the current goes down ....but its another thing...


datasheets : DDX 2160 and DDX 8001 are uploaded...

any ideas?
Attached Files
File Type: pdf ddx2160.pdf (541.7 KB, 13 views)
File Type: pdf DDX-8001.pdf (753.0 KB, 9 views)
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Old 7th February 2018, 08:01 AM   #3
chermann is offline chermann  Austria
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...here is th schematic of the service manual HK HS500 - DDX2160


thank you for your time ...
Attached Files
File Type: pdf schematic_ DDX2160 Stereo Mode.pdf (226.4 KB, 33 views)
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Old 7th February 2018, 06:43 PM   #4
chermann is offline chermann  Austria
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Good evening

I changed the frequencies but same scope result.
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Old 7th February 2018, 10:05 PM   #5
Eva is offline Eva  Spain
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The modulator IC and output stage ICs are fully digital, with digital inputs only. The signal does not adopt an analog representation at any point in the modulator or output stage, until after the LC output filters.

The output signal shows a defect (bottom half missing, still switching) that does not match with a digital problem.

In my opinion the problem is analog (negative low voltage rail missing, or broken IC), and it is located in the circuits that condition analog input signal and turn it to digital. A digital sound source, if supported, skipping analog input, could help to diagnose this.
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Old 8th February 2018, 04:56 AM   #6
chermann is offline chermann  Austria
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Quote:
Originally Posted by Eva View Post
The modulator IC and output stage ICs are fully digital, with digital inputs only. The signal does not adopt an analog representation at any point in the modulator or output stage, until after the LC output filters.

The output signal shows a defect (bottom half missing, still switching) that does not match with a digital problem.

In my opinion the problem is analog (negative low voltage rail missing, or broken IC), and it is located in the circuits that condition analog input signal and turn it to digital. A digital sound source, if supported, skipping analog input, could help to diagnose this.
Thank you Eva, thanks that you take time to go through that.....thanks a lot.
yesterday i checked additionally the load with 8Ohms but as expected -- same result.
according to the pcb lines the stereo is not done by 1 chip only...so that means 2 chip broken?....i guess no....... it must be something before.. i will try with digital in

Last edited by chermann; 8th February 2018 at 04:58 AM.
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Old 8th February 2018, 07:49 PM   #7
chermann is offline chermann  Austria
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good evening

i go ahead with measruments. digital in. i did this with an DVD player and a test CD with 1khz test tone. via digital wyde eye cable to the amps coax input.

pic 1 shows the result ..the same result...so i guess the chip is gone..

pic 2 i put the heatsinks off - to have better way for measuremnts. the chip is over 8 ohm resitor load getting hot 60C. after 5 mins.

pic 3 +4 i measure directly on the Resistors which are connected to the outputs of the chip before the L
...... directly on the ddx2160 pins is not possible....i am afraid to make shorts....its too small
pic 3 and 4 looks like a PWM (before the L ...then to the LS outputs)

Q1 is it possible that i shoot the chip after to heavy load tests? i did several time the ocp tests.
Attached Images
File Type: jpg 21_HS500_Coaxin_output strange.jpg (312.2 KB, 25 views)
File Type: jpg 22_DDX2160 without cooling.jpg (467.7 KB, 31 views)
File Type: jpg 23_measurment before L.jpg (316.4 KB, 33 views)
File Type: jpg 24_measurement both before L.jpg (371.3 KB, 24 views)
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Old 9th February 2018, 04:57 AM   #8
chermann is offline chermann  Austria
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add to Pic 4
here is the pic with the yellow circle where a take the probe

for its strange that both signals are positive and exactly the same

thanks for your time
Attached Images
File Type: jpg PWM Point.JPG (59.3 KB, 27 views)
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Old 9th February 2018, 10:11 PM   #9
Eva is offline Eva  Spain
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I forgot to mention this in previous post: Remember this is class BD full bridge, always bridged, one output lead does the positive half of the wave, the other does the negative half. In order to measure output signal, some system for sensing speaker +OUT and -OUT differentially is needed. The proper signal won't be obtained by grounding a single ended oscilloscope probe to GND and connecting tip to +OUT. At least 2 probes are required, one for +OUT and one for -OUT, and the waves have to be displayed in sync (-OUT with inverted phase) to observe the effect. I do not recommend grounding the oscilloscope to an active class-D speaker output, at least not without a CM choke and lifting the ground of oscilloscope power cord, also no data cable allowed to oscilloscope, if any.
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Last edited by Eva; 9th February 2018 at 10:24 PM.
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Old 10th February 2018, 05:37 PM   #10
chermann is offline chermann  Austria
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Thanks Eva.
I will try tomorrow .
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