Can someone help with Mark Levinson JC-2? - diyAudio
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Old 31st March 2004, 07:17 PM   #1
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Cool 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
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Old 1st April 2004, 12:57 AM   #2
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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.
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Old 1st April 2004, 02:15 AM   #3
karma is offline karma  Canada
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Default 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

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
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Old 1st April 2004, 02:20 AM   #4
karma is offline karma  Canada
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Default phono stage

.
Attached Images
File Type: jpg jc2l3.jpg (32.5 KB, 2324 views)
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Old 1st April 2004, 02:33 PM   #5
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Thumbs up 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
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Old 2nd April 2004, 11:15 PM   #6
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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
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Old 3rd April 2004, 12:06 AM   #7
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This is a tough problem. If your phono module is out, then it has to be replaced. I have never made replacements, but someone, somewhere, may have.
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Old 3rd April 2004, 07:08 AM   #8
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Lightbulb 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.
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Old 3rd April 2004, 11:04 PM   #9
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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
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Old 4th April 2004, 12:03 AM   #10
Barfey is offline Barfey  United States
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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.
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