Can someone help with Mark Levinson JC-2?

Is there someone out there who either is a qualified technician or knows
one in Atlanta? I came to the forum because of a problem with my
JC-2 preamplifier. I see from the discussion there that a posted schematic
is either correct or not correct. Sorry, I am confused. Then again, I'm
not a technician. The phono preamp in the thing is apparently blown-
can someone help me get this thing back on its little rubber feet again?

Thanking you all in advance.

AAP
 
Member
Joined 2001
Paid Member
You might try Shlomo at The Circuit Board in Chamblee (770.457.5391). He is an electronics service generalist, but has done plenty of hi-fi over the years, and is very "old world" in his business dealings.

If you'd prefer a high-end audio guy, you could try Otha at Audio Alternative in Lilburn (770.931.0606). I don't know his work personally, but he's their service tech, and they seem to have a good local reputation.
 
heh

i had one with the same problem if you can get it open. you will
see that the phone stage is a Module that is sealed and unplugs
from the main board. just replacing it works. if it powers up

the module is not servicable

i got mine on e-bay cheap plus parts
or you can order it from mark levinson

its old:)

but worth it:D

http://www.marklev.com/JC2/jc2schematics.jpg

http://www.marklev.com/JC2/review2/_jc2_us_2.html

http://www.marklev.com/JC2/img/index.html

http://www.zenn.com.sg/mark_levinson_parts.htm
 
phono stage

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thank you all for your help!

thank you both for your rapid responses!

I will check out The Circuit Board and I have already contacted
the place in Singapore regarding a replacement module.

As for opening up the box, I did take a deep breath and do that -
those little screws were TIGHT. But I did see the modules and
I am assuming that the only module I need to replace is the
Phono preamp, not the Remote Phono preamp.

(Just a tip I discovered - I had to put a tiny bit of oil on the screws
before putting them back in.)

BTW, is anyone interested in Dynaco equipment? I have a PAT-4,
FM-5 and Stereo 70 - and somewhere I have the schematics (not that
I can understand these things) for the amp and preamp.

AAP
 
John Curl (the JC in JC-2) is a member here. You could do worse than to enlist his help if he's willing.
Those modules aren't as difficult to mess with as you might think. My experience has been that you can sometimes slide a knife between the side of the plastic housing and the epoxy filler. Run it around the edge and pop the circuit loose. Once you've got the insides out, it depends on how thorough they were in potting the parts. If they're completely encased, think acetone or lacquer thinner (aka epoxy thinner). If they're free or nearly so, you can sometimes free things up by fiddling with the filler with a knife.
Are you sure the gain block(s) is/are dead? You could simply have a cold solder joint. Much cheaper, faster, and easier to fix. It might be worth your time and trouble to do a little trouble shooting before dropping bucks.
Or you could send the poor waif over to me. I'll give it a good home.
Promise.

Grey
 
Help for JC-2 preamp

Hello AAP, Yes a certain someone has made replacement modules.
But first you have to establish if the fault is in the phono module or in the powersupply filter module. (the most right in the picture).
Are both phono modules dead or only one?. Do you have +/- 13 V supply for the modules? The latter can be measured in the open area on the motherboard for the moving coil cartridge module. The chassis is ground for your meter.
In my experience the phono mododules seldom fail but the line modules far more often. Do you have two channels from tuner or CD?
Forget about opening the modules. I tried with boiling glycerol, that's antifreeze for cars, but only very partially succeeded.:cool:
 
Hello Elso, are you making replacement modules? If so, have you tried the AD-797 yet? That would be my first choice for an IC replacement. Someone should make replacement modules. The chassis of the Levinson JC-2 should last virtually forever, but unfortunately some of the plastic parts that we originally used had an active ingredient that slowly ate through the glass passivation layer over time.
This design is over 30 years old, so it deserves to be upgraded.
PS The power supply module is only a pair of complementary cap multipliers in order to lower the power supply noise. It suffered from potential xtalk, because of its relatively high output impedance, (a few ohms) and parallel connection to both channels. It took me years to discover this problem:xeye:
 
I had an Advent 300 Reciever and Norman's Electonics had a Service manual. I would try them. they have been in business fo ever. At least since the 60's . If you are selling a Stereo 70 E-mail me I am Interested depending on condition. I worked at a stereo place
(High fidelity SSS). We sold that preamp. If they sold it then Normans wound up fixing it. Normans is on Clairmont rd. Hi Fi SSS
was on East paces ferry.
 
Mark Levinson JC-2

john curl said:
Hello Elso, are you making replacement modules? If so, have you tried the AD-797 yet? That would be my first choice for an IC replacement. Someone should make replacement modules. The chassis of the Levinson JC-2 should last virtually forever, but unfortunately some of the plastic parts that we originally used had an active ingredient that slowly ate through the glass passivation layer over time.
This design is over 30 years old, so it deserves to be upgraded.
PS The power supply module is only a pair of complementary cap multipliers in order to lower the power supply noise. It suffered from potential xtalk, because of its relatively high output impedance, (a few ohms) and parallel connection to both channels. It took me years to discover this problem:xeye:

Hello John,
Back in time I had no access to the AD797. I built a circuit with AD817 and the AD711 for servo and a Darlington output buffer after the opamp. My main source of inspiration was Walt Jung’s book Audio Opamp Applications. With an opamp like the AD817 the output buffer stage was not really necessary, I discovered. Also I did not like the sound of the servo so I left that out too. I am almost sure the AD797 will work fine.

The power supply filter module often fails as it bursts literally open, probably due to gassing electrolytes. I made a new filter module with a Darlington cap multiplier and a lot of bypassing at the base and the output. That worked quite well. I figured the base of the Darlington must be at 13.3V plus two diode drops. So the base must be at about 14.5 V. I simply connected a conducting 1N4148 diode from the base to the 15V supply.
Separation of the left and right supplies for the phono modules does not seem to be easy as the supply lines are shared between right and left channels on the motherboard.

The JC-2 has given me many years of musical enjoyment but eventually I sold the unit, as the Elma 23 position volume switch got rotten. Unfortunately nothing larger fits. I did not like the Penny & Giles the Levinson Company later built in.

I now have my own preamp with a hefty Shallco 47 position volume switch as a shunt attenuator and a FET input folded cascode circuit and Jung like regulator power supply.

;)
 
Disabled Account
Joined 2004
Hi, guys

Concerning JC2 problem, I am of the very same advice Elso Kwak has (he is now a friend). Of course, John Curl is right too. DRF filters did have 4 electrolytic capacitors along each side, and as you may know electrolytics 25 years ago weren't made for lasting eternity. So, electrolyt gave attempts to gaz out, and because of epoxy arousing, gazes couldn't really go out. As a net result, typically, DRF filter all burst at module angles.

Elso used boiling antifreeze at a mere 400 °C (that hot ! I am afraid of !) to wipe out epoxy and have a look inside the module. I smetimes used at room temperature methylene chloryde to do so (used in printing press to clean inks), but is is very volatile, carcinogenic and ultra inflamable. So, I prefered to use this time mechanical means to see what was inside the DRF module, but doing so, I salvaged parts. Not many parts really : 4 electrolytics, 4 resistors, two ceramics, and MPSU transistors. It's all, folks ! It would have been simpler not to pot them.

John Curl said on another forum that he used capacitor mutipliers. So I went this way. I will not put salvaged module pics on forum (you would abe frightened I am sure). But built replacement module is here. Drop me a line if schematics and PCB foil patterns are needed and/or could be of interest. Of course, Elso and John advices would be appreciated !
 
JC-2 Problem (broken line driver module)

Dear Hifi fans

I am new in Diyaudio and look for help of my JC-2 and find this wonderful website.

I have an old Mark Levinson JC-2 from my dad almost 25 years ago. BUt the one of the line driver module is not working now. Really want to replace if not too expensive. But no more stock avlaible in authorised dealer of Mark Levinson in Hong Kong. Any one can help? Any advise is thankful and appreicated.

Ken1967
 
I also need help with JC-2

I have a JC-2 that is missing the power supply and has one channel not working. The preamp came with a Radio Shack adjustable power supply but I would like to build a more permanent supply for it and repair the non working channel and perhaps prevent the other channel from failing.
 
Re: I also need help with JC-2

rwwear said:
I have a JC-2 that is missing the power supply and has one channel not working. The preamp came with a Radio Shack adjustable power supply but I would like to build a more permanent supply for it and repair the non working channel and perhaps prevent the other channel from failing.


heh i did the same thing when i had mine. i had no power supply
so i made my own. dead on the money and it still killed the modules. u will find if you do get another module the one thats working will go to. down the road. forget about the module get the right power supply. than the module, save yourself the trouble



;)

peters happy he got all the parts;)