Gilligan8

Repairing a JoeMeek VC3
« on: April 17, 2006, 06:51:31 PM »
I picked up a VC3 v2 from a pawn shop for a decent price... well couple weeks later I plugged it in and it sounds sick... it needs quite a bit of gain for my RE20 and has a pretty nasty hum (like a bad Power Supply or something).  Obviously these things are pretty simple in design and I see test points with recommended voltages but I am unsure if I am supposed to be running a test tone through it during testing or what?  Anyone know what I could maybe look at doing to fix this sucker up and maybe even hotrod it a little with some replacement chips?

Thanks for your time,
Gilligan
"Can't take it any longer getting weaker not stronger, switch to self-destruct cause that don't take any guts!"


compactaudio

Repairing a JoeMeek VC3
« Reply #1 on: April 17, 2006, 07:16:06 PM »
Quote: "Obviously these things are pretty simple in design"

Have you got the schematic for the design you're workin with?

Gilligan8

Repairing a JoeMeek VC3
« Reply #2 on: April 17, 2006, 07:45:47 PM »
No, no schematic, but the circuit isn't too hard to follow and is spaciously laid out and well marked.  I know that a schematic helps tons but if you can read all the part numbers and clearly see where the traces are it makes it straight forward enough to get your hands dirty in there and start trying things.  I have a VERY high res pic http://gilligan.kicks-ass.org:1023/JoeMeek.jpg If anyone cares to see the inside of this guy.

Warning the image is huge (2mb).
"Can't take it any longer getting weaker not stronger, switch to self-destruct cause that don't take any guts!"

Brent Casey

Repairing a JoeMeek VC3
« Reply #3 on: April 18, 2006, 12:51:31 AM »
I have the VC3 schematics. They are hand drawn by Ted Fletcher and a bit hard to discern. Email me at [email protected] and I will send them over.

The circuit drawings I have are in a pdf called "JoeMeek Service Handbook". Not all models are represented, but perhaps it would be good to find a permanent spot for this at The Lab. I don't think Alan would object, but I'll have to run it by him just the same since it's his property. My feeling is that circuits should be freely shared. Of course there are plenty of exceptions to this, but in the case of the old Meeks - all for the better if it keeps some "sick" units from darkening my door.  

Brent Casey
Brent Casey
PMI Audio Group
877-563-6335

Mbira

Repairing a JoeMeek VC3
« Reply #4 on: April 18, 2006, 01:49:07 AM »
Quote
has a pretty nasty hum (like a bad Power Supply or something)

Is this just a random guess, or do you have anything telling you this?  A hum could mean a million things.  To me, usually not a PS problem.  Poke around there gently with a sharpie (NONCONDUCTIVE!) while you are sending signal thru.  Could be something as simple as a bad solder joint...

Joel
Joel Laviolette

Rattletree   |  https://www.rattletree.com
The Rattletree School of Marimba | https://www.learnmarimba.com

Repairing a JoeMeek VC3
« Reply #5 on: April 18, 2006, 05:00:50 AM »
Ted is a member of this forum
If you ask him very nicely - he may want to come out to play

Gilligan8

Repairing a JoeMeek VC3
« Reply #6 on: April 18, 2006, 11:27:42 PM »
Well, aren't I the jackass... I decided to double check to make sure I had the "good" brand powersupply... well upon closer inspection, the power supply not only isn't the "good" brand but is also wasn't even the right output!  It's 12v DC!  I can't believe I made such a stupid mistake... I just assumed they had the right PS, it was labeled as the one that came in the store.

Too bad I didn't notice this in the Pawn Shop, I could have hooked it up and showed them it was "messed up" and got a incredible discount!

Anyway, I dug up a 12v AC PS and fired it up again and it sounded perfect!

But, at least my diagnosis was correct, it was a powersupply problem ;)
"Can't take it any longer getting weaker not stronger, switch to self-destruct cause that don't take any guts!"

Gilligan8

Repairing a JoeMeek VC3
« Reply #7 on: April 19, 2006, 01:12:18 AM »
Quote from: "mediatechnology"
OK, so you got the power supply sorted out.

As to your original question about improvement I can't tell what op amps they use underneath(?) the board from the photo. But, I do see an ADI/SSM2017 mic preamp. You might consider replacing it with an SSM2019 or a THAT1510. They should just drop in once you remove the 2017 and replace it with a good socket.


When I said it was simple, I meant simple... that is ALL there is... what you see in the photo is it... there is no underside (except traces)... it's a single sided PC board.

So what do I gain with the 2019 or THAT1510?
"Can't take it any longer getting weaker not stronger, switch to self-destruct cause that don't take any guts!"

Kev

Repairing a JoeMeek VC3
« Reply #8 on: April 19, 2006, 05:14:53 PM »
I still prefer the 2017
and
yes they all are ordinary at the high gains ... perhaps the 1510 did fair better but if I need that sort of gain I head to a better unit anyway

perhaps I'm just very used to the sound of the old 2017 and 2016
Kev
DIY Factory

 

Related Topics

  Subject / Started by Replies Last post
16 Replies
6826 Views
Last post July 17, 2004, 12:51:13 PM
by HiString
7 Replies
3839 Views
Last post February 13, 2005, 05:23:34 PM
by Scenaria
2 Replies
1601 Views
Last post May 06, 2006, 04:32:41 AM
by fatboy135
2 Replies
2238 Views
Last post March 13, 2013, 03:36:08 AM
by duantro