Help with Juno 106 Dead VCA

Any music gear discussions that don't fit into one of the other forums.

Moderators: Joe., lisa, luketeaford, Kent

Post Reply
TijuanaKez
Learning to Wiggle
Posts: 4
Joined: Wed Mar 18, 2020 11:27 pm

Help with Juno 106 Dead VCA

Post by TijuanaKez » Wed Mar 18, 2020 11:40 pm

Firstly hello Muff Wigglers! long time voyeur, but I'm stumped so I've decided to bite the bullet and make a post.

So I've acetoned all the voice chips on my 106, and they were all working fine till late last year when one went crackle crackle dead.
I'd already purchased a couple of analog renaissance chips so I lifted the dead one and put the fresh new AR voice chip in.

Now the crackle has gone, but the voice is completely silent.

I've run all the test and calibration procedures I could find, and the other voices are all %100 goodness, but voice 3 I can't figure out.

Cycling through voices, voice 3 is silent.

VCA Gain Test
TP8-1-6Vpp
TP9-2-6Vpp
TP10-3-0v
TP11-4-6Vpp
TP12-5-6Vpp
TP13-6-6Vpp

Unfortunately, this is where the inter webs dries up on info.
Can someone please help me revive voice 3???

User avatar
Power Mic 3K
Learning to Wiggle
Posts: 18
Joined: Sat Apr 01, 2017 8:07 am

Re: Help with Juno 106 Dead VCA

Post by Power Mic 3K » Thu Mar 19, 2020 12:49 pm

I have a torn down 106 ATM and I sympathize. I’ll offer what ideas I can...

Is voice 3 the one you replaced? Referring to the Roland service notes, did you start from start as in from power supply adjustment? Were you able to get through the VCA offset and bias adjustment procedures?

Have you found and attempted the procedures at the following link?
http://www.analoguerenaissance.com/

User avatar
Overand
Common Wiggler
Posts: 162
Joined: Mon Jul 02, 2012 6:29 pm
Location: Maine, United States

Re: Help with Juno 106 Dead VCA

Post by Overand » Thu Mar 19, 2020 12:55 pm

Look really closely at the PCB traces (the 'wiring') around that chip you changed out - the traces on the 106 are notoriously delicate and easy to lift. I'm lucky, in that I did this with a desoldering iron, but even with one of those, it's very easy to damage the traces.

If the voice is dead-dead-dead, you probably lifted or otherwise damaged a trace. Even if you think they all look fine, go ahead and check it electrically. Use your multimeter in "continuity tester" mode and track those traces - put one end on the leg of the chip, and the other where the connection is supposed to be.

Here's hoping you have a multimeter!
Sites: overand.com | SoundCloud | YouTube ModularGrid: MOTM | Euro
WTB: MOTM Case, Euro VCAs, Sequencers, Env Followers & Interfaces.
Building the modular since ~2003

TijuanaKez
Learning to Wiggle
Posts: 4
Joined: Wed Mar 18, 2020 11:27 pm

Re: Help with Juno 106 Dead VCA

Post by TijuanaKez » Thu Mar 19, 2020 7:13 pm

Hey guys, thanks for the replies.

Yeah I have a meter and a scope (as of 2 days ago yay!)

As noted in the first post I did all testing procedures including Analogue Renaissance one and service manual calibration and that's where I got my reading that I posted. There is 0Vpp on the scope when running VCA Gain calibration for voice 3 (yes the one I changed)

I did do this with a desolating iron, but I did have trouble with a couple of holes where the solder was dry and wasn't responding to flux so I did work it a fair bit and I also suspected I may have damaged a trace. Problem is I can't see any visible damage to the traces.

My level of expertise (crap level) is not able to glean any more helpful information from the schematic, I was hoping someone more familiar with Junos might point me in the right direction e.g what I might expect to see on the pins of the voice chips with the meter/scope.

Thanks in advance!

User avatar
Blairio
Super Deluxe Wiggler
Posts: 1723
Joined: Mon Oct 07, 2013 9:50 pm
Location: Glasgow, Scotland

Re: Help with Juno 106 Dead VCA

Post by Blairio » Thu Mar 19, 2020 10:01 pm

It would be worth checking whether there is a decent Tech in your area. I have a lot of older kit, and I can do the basics (like reflow dry joints), but after that I rely on my local Tech to help me keep my gear working. It is great when you find a Tech who specialises in e.g. Roland synths, but most good Techs can fix stuff with a circuit schematic and an oscilloscope.

TijuanaKez
Learning to Wiggle
Posts: 4
Joined: Wed Mar 18, 2020 11:27 pm

Re: Help with Juno 106 Dead VCA

Post by TijuanaKez » Fri Mar 20, 2020 12:01 am

Ha yeah I'd love a tech close by, but there's no one near me that can do that stuff that I know of. And if I ever do end up finding people online, the price with postage is always close to a new second hand synth, or at least I could buy a whole workshop of equipment for the same price.
But...... on closer inspection of the board, I've gone and completey melted Q13 which is VCA Gain for channel 3 (or something like that :)

I can't see a part number in the service manual though (tr13), can anyone identify it? (img is from a working voice)
You do not have the required permissions to view the files attached to this post.

cs1729
Common Wiggler
Posts: 167
Joined: Fri Oct 07, 2011 5:39 pm

Re: Help with Juno 106 Dead VCA

Post by cs1729 » Sun Mar 22, 2020 8:11 am

2sa1115

You can buy it on eBay

User avatar
Power Mic 3K
Learning to Wiggle
Posts: 18
Joined: Sat Apr 01, 2017 8:07 am

Re: Help with Juno 106 Dead VCA

Post by Power Mic 3K » Mon Mar 23, 2020 8:50 am

I agree with cs1729. The transistor in the image you provided is a 2SA115. Q13 is the same. The 41F marking identifies a manufacturer lot number.

There are A LOT of counterfeit parts out there, so shop with caution. You might want to contact some synth repair shops to see if they have any NOS parts on hand. Another potential course of action is to find a donor board.

cs1729
Common Wiggler
Posts: 167
Joined: Fri Oct 07, 2011 5:39 pm

Re: Help with Juno 106 Dead VCA

Post by cs1729 » Mon Mar 23, 2020 9:28 am

https://www.ebay.com/itm/2SA1115-2SC260 ... SwevdaEMvY

I bought some from this seller and they are fine. I've used them on nava and other roland repairs.

TijuanaKez
Learning to Wiggle
Posts: 4
Joined: Wed Mar 18, 2020 11:27 pm

Re: Help with Juno 106 Dead VCA

Post by TijuanaKez » Tue Mar 24, 2020 12:16 am

Thanks everyone for the help. Unfortunately that seller doesnt ship to Australia, but I went a head and grabbed a 5 pack from here https://www.ebay.com.au/itm/273089920021.
Chances of counterfeit probably high, but I have 5 working voices to compare it to.
I'll do some tests with ears and scope when they arrive and post results.

Post Reply

Return to “General Gear”