Well, congrats, that’s marvelous.
Maybe you should let the amp idle for the next 24 hrs.
If all still O.K., then let’s hope that this is the end of your journey through Amp-land.
Succes,
Hans
What exactly do I see ? Did you offer an input signal to the Amp, or is this signal with input shorted.
Please measure the same but now with WH.1 and WH.5 shorted.
Hans
First of all: What is in detail the left and resp. the right image ?
1) Now disconnect the four connections of the OL-2 board and make the same recording again with WH.1 and WH.5 still shorted.
2) and with the above situation, connect the shorted WH.1/WH.5 connection to the speaker output to completely disable the output stage.
Now do the measurement again.
Hans
You see sinus on the left channel because by my mistake I made the measurement to left channel also even if I did not do the short in the WHs, so that is why left channel have been all the time same.
Do you need same measurements from the left channel also or is it enough to concentrate to right channel?
Another question; do I need to use 8ohm resistor between the speaker terminals when doing these measurements?
In all these measurements 200mV/div and 5us/div
Do you need same measurements from the left channel also or is it enough to concentrate to right channel?
Another question; do I need to use 8ohm resistor between the speaker terminals when doing these measurements?
In all these measurements 200mV/div and 5us/div
I have sent you a PM where I suggest to shorten the line and communicate per email.
I still don't understand what you are saying, why do I see a sinus from the left channel when no signal is applied ??
This channel should show noise at a very low level, in the uV range.
Hans
I am happy to inform that after countless hours hard work and email exchange, Mark Levinson No.23 is back in life again.
Without help from Hans I could never ever have done it. Thank you diyAudio and Hans Polak. Attached a few photos from the amplifier in action.
Without help from Hans I could never ever have done it. Thank you diyAudio and Hans Polak. Attached a few photos from the amplifier in action.
Attachments
I am happy to inform that after countless hours hard work and email exchange, Mark Levinson No.23 is back in life again.
Without help from Hans I could never ever have done it. Thank you diyAudio and Hans Polak. Attached a few photos from the amplifier in action.
Hannu,
In fact I must thank you.
Because of our conversation in this thread several people contacted me and I could succesfully repair for them 2 further ML23.5 amps and one ML No.380 pre amp.
I had no idea there where so many (broken) ML amps around in Holland.
Hans
I have a No.23,5 acting strangely. The left channel would go much louder (higher gain) after a few hours playing. The lead time would get shorter and shorter if I play music through the 23.5 more often. When this happens if I touch the negative post of the loudspeaker terminal the loudspeaker produces a loud noise like feedback. From the scope I can see some kind of oscillation. Can I ask Hans to help me fixing this issue?
Hi Mat0633,
I found it a great experience to do a remote repair once, but it is way more time consuming than to do the repair myself.
The problem you describe is not a matter of giving a simple advise, but will probably take hours and hours in communication with no guarantee in result.
Don't know where you live, but I'm always willing to do the repair for you.
Hans
Hi Hans,
Thank you so much for your quick reply. I am living in Canada. I am a electronic engineer and will do my best from your advice. I have screen shot of the image of the oscillation from the scope but don't know how to attach to here. I am checking all the small caps in the driver board to see if any one broken causing the oscillation. but these increase in gain happens only continuous on for several days (i.e.3 days) after I switch off the No.23.5 for few weeks, if I switch on it again in the next days it could happens in hours; if I switch it on again the next day it would happen in 30 min. Thanks Hans, I will do my best to save your time.
Thank you so much for your quick reply. I am living in Canada. I am a electronic engineer and will do my best from your advice. I have screen shot of the image of the oscillation from the scope but don't know how to attach to here. I am checking all the small caps in the driver board to see if any one broken causing the oscillation. but these increase in gain happens only continuous on for several days (i.e.3 days) after I switch off the No.23.5 for few weeks, if I switch on it again in the next days it could happens in hours; if I switch it on again the next day it would happen in 30 min. Thanks Hans, I will do my best to save your time.