Measuring DC Offset on a HiFi Amplifier, DC offset & Mains Voltage Adjustment How To, HiFi
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- เผยแพร่เมื่อ 20 ส.ค. 2024
- How to check an Amplifier/Receiver Health by testing Speaker Outputs DC offset
and adjust mains voltage selector if needed for your country.
"For Capacitor Coupled output Amps and Receivers you may need a load across the speaker terminals connected for correct measuring, otherwise they could read very high to start (10-30 volts).
I use a 10k resistor ( volume on zero ) and you see the voltage start coming down straight away and to normal within a few mins.
Or you can use a 8 ohm 20 watt Resistor for a dummy load or even an old pair of speakers."
( DISCLAIMER ) If in doubt get a qualified electronic engineer. I accept NO responsibility on any errors you make.
good info for the beginners
you will be surprised how many times they have the dc offset pots wrong in the manual books
Thanks, always worth double checking with a quick search with Google to see if there is any other information on the amp that may help.
Thanks for that as I have ordered a meter to check the fifty ish years old Sony str 6055.
I have no idea of how to adjust the levels though.
Hopefully the figures will be within normal range.
Thanks again.
Hi James. There is infomation on HiFiengine if you download the service manual for the 6055. But if you do go ahead be very careful as it looks quite tight where you have to get the readings from and one slip could kill the outputs. If I was you I would just check the DC offset across the speakers with the multimeter set to DC millivolts. Have the volume on zero and tone controls to normal and on AUX input, but be careful not to short anything out.
Thanks for this helpful video, btw I can hear you no problem,
A nice video.
Thanks!
Nice video! Just wondering how I do this test with jack outputs on the amplifier?
One way would be to open the unit up and take the readings from the jack connections inside the amp or buy a jack plug that you can unscrew to get to the connections then plug that into the amps jack outputs and take the readings that plug.
What setting is your multimeter set at? Every meter has different settings.
Between 100 millivolts and 1 volt DC should be availible on most meters for this test
Slow down and get your mic closer or something. One bloke advised speaking louder. I think you're speaking loud enoughl, but your mic is not close OR your record level is set low. Thanks just the same.
what do you set the multimeter to? I know it is an elecmentary question but I dont know
Set the meter to volts DC and a low setteing on the range of the meter around 200 milli volts as mine is set in video, usally the lowest setting on most multi meters, some might have as low as 100 milli volts, even some might have 2 volts as the lowest but this is still ok as you will get a reading.
Best voltage output saftey?
What that black tube on the back of the Marantz? I see these on older receivers. Is it an antenna?
Yes this is the external ferrite rod antenna for MW & LW depending on receiver, though an extra wire can be attached to a terminal to improve reception. Some receivers have this antenna inside the unit
@@MichaelYates cheers!
Is an input meant to be selected, like cd, tuner? If left in standby its a few mv down.
Yes an Input should be selected, in this case AUX , but Tape or CD is fine, with volume on zero and tone controls flat
@@MichaelYates I did the Bias. Using those clips, very useful tip.
Realised the offset on left speaker terminals was around 12v!. Got them both to 23-25mv. But as I moved the amp, it was stuck to the table, so it jolted. Just re checked the terminals with hood on. Right was around 30mv which is OK as this is the recommended amp requirement but the right was 40ish. It recommends to do both bias and offset twice anyway, But it made me realise how these slight knocks can turn the trimming pots. Very annoying. I will say though, I've noticed a louder 'pop' to when I turn the amp off through the speakers. Hopefully nothing to be concerned with?
I did notice the left speaker terminal overloaded the multimeter so I had to change the range. Can't remember which setting it was but it didn't move the first three numbers being 273. With the number after the decimal fluctuating. I gathered 27 represented mv so I thought this was still OK...
The bias readings were around 6mv, which was 1mv more than recommend. I took them down to 3.2ish. Was I too heavy on getting them down? (Service manual states between 3-5)
@@CM-dw3gh That 12 volt reading was dangerously high, 23-25 is pretty much the norm and quite expectable so I would be pleased with that. Some pots can be very touchy, though you can of course replace the pots, but only if it kept on moving about to much
@@CM-dw3gh The bias reading looks good, think its a job well done
Speak louder... or get closer to the microphone..
Thanks for letting me know David, I am getting a new camera and microphone soon
@@MichaelYates Right... just trying to help, not being mean. I know it's hard to tell sometimes. *smile*
@@davidhigginbotham5451 Thanks David, no offence taken at all, always good to know where I am going wrong, helps me get the channel right.
Wish I could understand him speaking. 🤷🏻♂️
Sorry Ray for my deep cockney accent and fast speaking, your not the only on to comment on this