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Dr. Bob
Moderator
Australia
6593 Posts |
 Posted - 03/04/2008 : 09:28:52
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Hi Laurie2
First of all, I don't own an OC-2, but have similar pedals,
from the same era.
I have heard that some of these might have been a bit ordinary.
especially with low output pickups.
A lot of people use a Compressor in front of the OC-2
and some use a booster or OD set to min gain & turn up the level a bit,
using it as a default booster.
Seeing you have gone this far, I would swap out the 4013 flip flop.
I had a 4066 (Bi-FET switch) from around 1982, go south, on a pedal I repaired last week.
I notice that Boss really redesigned the later OC-2, from the pic that Ssanyee posted above.
I know I have an Pre-Boss era ( yes there were pedals before Boss)
Yamaha Effector Series... Tracks like a POS & it use a similar circuit with a 4013 as the divider.
But I haven't really spent time trying to trace out the Schematics for those old Yamaha Effector Pedals. I have the Distortion, Chorus, Octaver & the Flanger.
The Flanger is highly sought after, in the keyboard & synth communities, it has so many great sound options & a Resonance control, that will self oscillate, as well as a manual sweep.
I heard the compressor commands a good price as well.
Sorry I diverged a bit there.
Regards Dr. Bob
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/04/2008 : 09:40:40
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Dr. Bob, I really appreciate your onging comments and help! Thank you! (never mind the diversion  )
I'm running completely clean into the pedal and don't have fret-buzz or anything else obviously nasty. It holds fine with a single frequency test tone, but as soon as you plug in a guitar, wobble wobble. Best result I can get is with my strat on the bridge pickup and the tone wound down a bit - still wobbles for most notes. Haven't tried a compressor, but I'll do that tomorrow.
Yep. The 4013 is the next to go (tomorrow). I checked the incoming signals and the truth table for the flip-flops and it looks like it's working OK, but there is nothing else left.
Any idea why the NTE458 didn't work? What do you use as a replacement for the 2SK30?
Regards, and thanks!
Laurie.
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/04/2008 : 17:27:08
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Tried it with compressor and line driver. No change on any setting (either or both effects turned on).
In frustration I changed IC2 and IC3... and it is a LOT better! (not great, just better - sounds OK through the DS-1) Maybe the old op amps have drifted a bit?
I'll change the last opamp (IC1) today and the 4013 and see if that improves it further.
It's almost good enough at the moment to say "fixed" 
Thank you all!
Laurie. |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/04/2008 : 21:30:15
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G'day!
IC1 and IC7 were changed with no effect. However, as per my post last night after replacing IC2 and IC3, I'm going to call it fixed.
It's not brilliant (tracking is not perfect) but it's as good as an OC-2 gets from what my research shows. Sounds pretty good to me if I'm careful with the guitar 
At the end of the repair here are some conclusions:
1) Two faults were found - D11 was dry (OCT2 had disappeared), and IC2 and IC3 seemed to be out of spec - although they looked like they were working Ok on the scope, replacing them cleaned up the tracking substantially.
2) The dual op-amps were all replaced successfully with RC4558 opamps. The original opamps were actually Sharp IR9022 (not TI TL022). Anyway, sonically the RC4558 opamps seem OK to me. Current draw for the pedal is 21 mA which is definitely up from the published 4mA - not an issue for me though as I always run from external power.
3) I tried an NTE458 JFET in place of a 2SK30 and it didn't work (but it might have ben bad out of the package).
4) I pulled one of the 1�F coupling capacitors to see what condition it was in after 21 years in the pedal. It measured 1.0004�F.
THANK YOU EVERYONE FOR YOUR HELP!!
I now have more knowledge about the OC-2 than I really wanted 
Regards,
Laurie.
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Edited by - Laurie on 03/04/2008 22:49:28 |
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nasyo
Copper Member
Philippines
5 Posts |
Posted - 03/18/2010 : 15:03:42
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| my OC-2 (MIJ) doesn't work. no octaves. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/18/2010 : 16:02:50
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Hi nasyo
Welcome to the forum from Australia.
To help us - help you, please tell us.
What happened to your OC-2 just before it stopped working?
And what electronics skills & tools, test gear do you have?
Regards Dr. Bob 
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Edited by - Dr. Bob on 03/18/2010 16:03:47 |
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nasyo
Copper Member
Philippines
5 Posts |
Posted - 03/19/2010 : 04:43:42
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I am an Electronics Engineer sir.
I only have a Multimeter.
I bought this OC-2 from a friend. It's defective when I bought it from him. No octaves.
I made a thread regarding with my OC-2. Let's go there. |
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Topic |
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OC-2 repair - "fixed"
