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Old 16th September 2020, 08:22 PM   #3541
MEPER is offline MEPER  Denmark
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I had a strange experience when making the final DC offset adjustments on M2X mono blocks. The L-channel was easy to adjust and was very stable. The R-channel fluctuated and jumped suddenly 20-30 mV and never got really stable. I had scope on power supply and output to see if voltage was ok and if I had an oscillation at output. Then I worked the spade connectors to the M2X PCB and after that R-channel was as stable as L-channel. Strange......maybe this also was the reason why I had more 50 Hz noise on R-channel than L-channel in above measurements. Maybe I check later but first I think I will see if the amps can play some music.......but as I use high quality connectors I don't like this.......
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Old 16th September 2020, 09:00 PM   #3542
WKCox is offline WKCox  United States
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Did you crimp or solder the female spade connectors?
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Old 16th September 2020, 10:11 PM   #3543
MEPER is offline MEPER  Denmark
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They were crimped on using a prof. Knipex crimper tool.
I think the bad connection was not in the crimping but in the connection.
I pulled connectors half off and on again which seems to work. I don't know which was bad. I think very little contact resistance can cause unstable DC offset. The resistance will probably not be stable but change a bit all the time. I will keep an eye on it and measure DC offset regularly.
I heard some music and they played extremely well. It was hard to switch off for the night....... :-) .....very crisp and detailed with good bas control....and no noise.....
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Old 16th September 2020, 10:16 PM   #3544
MEPER is offline MEPER  Denmark
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A stable DC offset after warm-up seems to be a good way to check if there are any bad connections.....and PSU is stable.
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Old 17th September 2020, 12:22 AM   #3545
grataku is offline grataku  United States
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Quote:
Originally Posted by MEPER View Post
I also have a couple of those which are good if you need more DMMs for e.g. combined bias/offset adjust. I got my in Lidl. 0.1 mV resolution is quite normal if you pay around 100 - 150 USD :-)
I have considered a bench model which goes lower......but they are more expensive.
I used to have HP with 5 zeros precision, alas that's no more.
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Old 17th September 2020, 08:04 AM   #3546
MEPER is offline MEPER  Denmark
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Locally there is one who want to sell his 6.5 digits Tektronix DMM. Reason is that he has now got the 7.5 digits model :-)
0.1 mV in AC mode and 0.01 mV in DC mode in my current DMM is probably all I need but always fun with more "toy" :-)
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Old 17th September 2020, 01:10 PM   #3547
Mark Johnson is offline Mark Johnson  United States
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Ask him how many minutes it takes to warm up after power-on. Short the probes, turn on the meter, set the display to microvolts, and wait until the reading settles out to zero. How long?
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Old 17th September 2020, 09:08 PM   #3548
MEPER is offline MEPER  Denmark
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I would guess it never settles to zero and to be able to measure uV you need to be in a special environment with no electrical/magnetic fields around?
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Old 17th September 2020, 09:26 PM   #3549
thompsontechs is offline thompsontechs  United States
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I have an 8808A and it always reads something leads, lights whatever.
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Old 23rd September 2020, 02:33 AM   #3550
flamethrower1 is offline flamethrower1  United States
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The diyAudio First Watt M2x
The route I have chosen to go.
If it saves me one dropped nut, it will be worth it.
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