Mark Levinson 380s PreAmp Schematic needed

Mark Levinson 380

First thank you so much for helped me out. I changed all the electrolytes capacitors. After I replaced the capacitors, on both channels, left channel VR1401 is very hot. I didn’t know because I changed out all 4 big capacitors.
I didn’t know what I did wrong, before that is not hot.
I did not have time to check it out the D/A converter chip yet.
Thanks,
Bruce
 
Hi Samchen,

this is a link you can download the ML38, thanks to Lbud4

MARK LEVINSON NO380 Service Manual download, schematics, eeprom, repair info for electronics experts





To Lbud4,

just said thank you very much for helping me out. I tried to locate the D/A 74HC4094 in the ML380, but did not see it, can you please help me. ML380 may be had a different chip.



Thanks



The DAC chip is an AD DAC8222. It is physically in the middle of the board in the analog section — one for each channel. The 4094 is a logic chip that digitally controls the DAC in order to adjust the resistor ladder within the DAC. I would see if you have input signal on the input of the dac and on the output.
 
Mark Levinson 380 NO audio on the left channel

Hi Samchen,
this is a link you can download the ML38, thanks to Lbud4
MARK LEVINSON NO380 Service Manual download, schematics, eeprom, repair info for electronics experts


To Lbud4,
just said thank you very much for helping me out. I tried to locate the D/A 74HC4094 in the ML380, but did not see it, can you please help me. ML380 may be had a different chip.

Thanks

Hi Samchen,
Did you received my link for ML38. If not look under Elektrotanya.
 
The DAC chip is an AD DAC8222. It is physically in the middle of the board in the analog section — one for each channel. The 4094 is a logic chip that digitally controls the DAC in order to adjust the resistor ladder within the DAC. I would see if you have input signal on the input of the dac and on the output.

Hi Lbud4,

I found the Register chips, in ML380 had different chips (Register) and Obsolete (MC14094BCP). I tried to compare the register ID you gave me. The different is the DC Supply Volatge, (ML380 register IC=MC14094BCP is -0.5 to +18V), ( CD74HC4094E voltage from 2 to 6.
Thank You
 
Hi Lbud4,



I found the Register chips, in ML380 had different chips (Register) and Obsolete (MC14094BCP). I tried to compare the register ID you gave me. The different is the DC Supply Volatge, (ML380 register IC=MC14094BCP is -0.5 to +18V), ( CD74HC4094E voltage from 2 to 6.

Thank You



Yes the voltage matters as the logic chip is power by the analog rail. The CD4094 should be pin compatible and still available. I gave you the chip off of the schematic which is incorrect.
 
Thanks for sending the photo. I own a 380s and there are a couple of differences. The main differences I see are the following on the 380s:

- input opamps are opa627
- output bjts are mat02 and mat03
- there are different resistors / more precision around the input stage
- there are different film capacitors again around the input stage
 
IMG_0142.jpg

IMG_0143.jpg

IMG_0160.jpg

Someone asked me for 380s board pictures via PM. See them attached here.
 
There is a thread on the forum that talks about most of the changes - link below. In general, the changes are the following:

  • Better resistors / higher tolerances
  • Better film decoupling caps for the opamps
  • Upgraded opamps - check the thread for details - OPA627 in front-end, AD823 in the middle
  • I believe the output BJTs are changed as well
  • Rectifier bridges I think are changed to fast recovery
  • LDO regulators for +-15V rails - LM2937 and LM2990
  • Different PCB material - they are fragile and won't give you any audio benefits

Thread:

Building Mark Levinson 38 preamp chassis from scratch​

https://www.diyaudio.com/community/...evinson-38-preamp-chassis-from-scratch.33409/
 
Hi guys,

I use a ML 380 preamp since several years without any problems, and I keep it on power 7/24 except when I go for longer holidays; but recently it seems that sometimes when I turn the volume knob the volume and the dB on the display does not change - a bit later it does when I try again. All other functions work flawlessly - what could be the reason for that?