I'm working on Ml 336. Already done the recap (power supply filter capacitors) and the replacement /U1, OP Amp on the VG Board with LT1097CN8. The left
channel is OK, but in the right channel sound is distorted with very low power drive to bass and midrange. Is there a chance that the incorrect BIAS settings are responsible for that?
channel is OK, but in the right channel sound is distorted with very low power drive to bass and midrange. Is there a chance that the incorrect BIAS settings are responsible for that?
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Some additional info:
The regulator capacitors : Cornell-Dubilier-CDE DCMC192T250AJ2B 1900uF/250V AND DCMC513M160DP2D 51000uF/160V IN THE POWER SUPPLY. are brand new from MOUSER.COM, also the U1 IC ( OP AMPS ON VG BOARDS) were replaced WITH LT1097CN8 FROM MOUSER.com.
The regulator capacitors : Cornell-Dubilier-CDE DCMC192T250AJ2B 1900uF/250V AND DCMC513M160DP2D 51000uF/160V IN THE POWER SUPPLY. are brand new from MOUSER.COM, also the U1 IC ( OP AMPS ON VG BOARDS) were replaced WITH LT1097CN8 FROM MOUSER.com.
Hello, was the error already present before the "conversion"? It sounds somehow as if an operating voltage is missing.
It is also possible that a pin in the VG bar was bent during assembly. Please check that first. I had this error before (someone else had tried it before me)
It is also possible that a pin in the VG bar was bent during assembly. Please check that first. I had this error before (someone else had tried it before me)
The error exist before conversion. I was thinking that the power capacitors are old and install a new ones.
Did you buy the device with this error?
If you can solder, then you can take the VG board from the right good channel and re-solder the connector here to test whether it is on the VG board or the CG board.
If you can solder, then you can take the VG board from the right good channel and re-solder the connector here to test whether it is on the VG board or the CG board.
I'm planning to swap the CG's boards from Left to Right , to check if it is the VG or the CG that is failing.
Thank you for the reminder, I'll use 100W /220V bulb Resistance: 484 Ohms for the discharge. The manual recommend 25W resistor with minimum value 10 Ohms
For now the problem is located into the VG power board. I just switch the Right VG board to the Left channel and the problem migrate from Right to Left.
Is there a chance that the incorrect BIAS settings are responsible for that?... or may be faulty capacitor on the board ,there are four caps ( 22uf 100v )on the VG board
Is there a chance that the incorrect BIAS settings are responsible for that?... or may be faulty capacitor on the board ,there are four caps ( 22uf 100v )on the VG board
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This is a complicated amp that needs a relatively experienced know how to repair.
But to answer your question, even with the wrong bias setting you don’t get low drive.
I agree with Staykov that some transistor may have given up, or some cap has gone into short circuit, lots of possible causes.
When you want to go on trying to perform a self repair, start measuring voltages between the good and the bad channel, write those voltage in the circuit diagram and post it on this thread.
Start with supply voltages, output voltage and other obvious places.
Hans
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