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amagic
Copper Member
New Zealand
7 Posts |
 Posted - 02/19/2009 : 00:27:01
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Hi there,
I wanted to share something and I was also just wondering if any of you guys (Dr.Bob /Laurie �), when you have time, can help me/ point me in the right direction for troubleshooting MIJ Boss OC-2 Octave pedal.
Pedal was working fine until recently when I�ve placed it in the effect chain right after digitech Whammy. (Usually I use a compressor before the OC-2 �)
At one point signal sent from whammy was also �octaved� (base tone with one octave up preset) and that obviously did some damage to OC-2. I suspect that a combination of hotter signal coming out of whammy combined with the already �effected� signal caused the damage to the OC-2 and the way it creates the effect.
Now when the OC-2 is engaged, it does not produce any effect...it lets trough the �base� signal but no octaves. What is interesting, if I play trough the pedal that is on (red led is on) for couple of minutes the effects come back � both OCT1 and OCT2(). Pedal then works fine (I can switch it on off and it holds the effect) until I unplug the jack from the input (cut DC supply coming from the battery), after which it needs a few minutes of warming up again to get it going.
Any help would be greatly appreciated: Should I be concentrating on IC�s or some other bits�I have the schematics for it (thanks ssanyee) but I still need some help understandig what bit does what�
Thanks!!!
Andria
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 02/19/2009 : 00:33:27
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quote:
Originally posted by amagic
Hi there,
I wanted to share something and I was also just wondering if any of you guys (Dr.Bob /Laurie �), when you have time, can help me/ point me in the right direction for troubleshooting MIJ Boss OC-2 Octave pedal.
Pedal was working fine until recently when I�ve placed it in the effect chain right after digitech Whammy. (Usually I use a compressor before the OC-2 �)
At one point signal sent from whammy was also �octaved� (base tone with one octave up preset) and that obviously did some damage to OC-2. I suspect that a combination of hotter signal coming out of whammy combined with the already �effected� signal caused the damage to the OC-2 and the way it creates the effect.
Now when the OC-2 is engaged, it does not produce any effect...it lets trough the �base� signal but no octaves. What is interesting, if I play trough the pedal that is on (red led is on) for couple of minutes the effects come back � both OCT1 and OCT2(). Pedal then works fine (I can switch it on off and it holds the effect) until I unplug the jack from the input (cut DC supply coming from the battery), after which it needs a few minutes of warming up again to get it going.
Any help would be greatly appreciated: Should I be concentrating on IC�s or some other bits�I have the schematics for it (thanks ssanyee) but I still need some help understandig what bit does what�
Thanks!!!
Andria
Hi amagic! And welcome!
I have a fair bit of experience with the OC-2 and the situation you describe is not something that can damage the electronics... unless there is an additional external factor.
Did you change power supplies at that time? Did anything else in the rig change?
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amagic
Copper Member
New Zealand
7 Posts |
Posted - 02/19/2009 : 00:55:23
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Hi Laurie,
Thanks for the welcome �I was hoping to hear from you as I've seen your post on OC-2...great job :))))
OC-2 was running off a battery - so no PS at all�no other changes either�there was no nasty peaks coming from the guitar (ones associated with loose input jack plugs) or anything of that sort�
I agree it is a bit unusual that a complexity of the signal do some damage to the electrics but it is the only thing that I can think of that could to do some damage to the one of the components: the fact that whammy can produce hotter output and the fact that the input signal coming form whammy was one of a �complex nature� and that that somehow confused the OC2 and damaged one of the components that decode the signal and send it to the bits that do the octave 1 & 2 parts.
When there is no effect coming out of the OC-2, original tone level pot works fine, bypass works fine as well. OCT1 and OCT2 come in only after 3-4 minutes of signal passing trough the engaged circuitry�very strange. Usually chain goes like this whammy -> compressor -> oc2 � all that was changed was whammy->oc2->compressor
A.
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 02/19/2009 : 02:14:09
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Hi amagic!
Well... been doing this a long time and never seen an instance of the complexity of the signal killing off a pedal. Same for hot input level - it will just clip. I'm not on the same page about the signal doing the damage (at all  ).
Sooo... let's think about other things. The pedal was physically moved I'm presuming? Perhaps something was "on the edge" mechanically, and the move broke it? And if it wasn't that, then it must surely be concidental.
To summarise what we know about the fault:
1) it happens with a known good battery
2) the pedal works as expected, but only after a couple of minutes
3) when it is not working as expected, the on/off function works, and the dry signal passes
So, we can conclude:
a) The power inside the pedal is working. The dry signal would not pass, and the LED would not switch without that.
b) We may be looking at something heat related - when it warms up it works? This is actually completely in alignment with a dry solder joint on the circuit board, which is the first thing I'd look for.
C24 is the capacitor that couples the direct signal into the octave stages. I would check C24 and see if it looks OK and that its solder joints look nice and silver and complete. If it looks OK, bridge across the pads of C24 with another capacitor - I'd use a 1�F polyester if it was on my workbench, but almost anything between 0.l�F and 10�F will do. Do you get the octave signal with the other capacitor bridged across C24?
If that doesn't produce results, I would next check carefully around IC5 looking for bad solder joints.
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amagic
Copper Member
New Zealand
7 Posts |
Posted - 02/19/2009 : 02:22:50
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Hi!
Thank you so much for this! I will open the pedal tonight and give it a closer inspection...
At one point I did suspect a cold solder joint, but in the middle of the night(that's when this happened) it looked too easy that could be a reason for failure...and so my mind stated to form all sorts of pedal conspiracy theories :)))
I'll keep you posted !
Thanks
A. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 02/19/2009 : 07:02:36
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Hi amagic
Welcome to the forum from Australia.
Some internal pictures might help us.
Not wanting to jump to conclusions, i'm guessing it's a cold solder joint, or a wire has come off the board.
The time delay issue, is a strange one.
Like Laurie has already explained, signal complexity, is unlikely to be the cause.
You can pump quite a large signal into most Boss pedals, in the order or volts of signal, before any damage occurs.
Try to think of what may have happened to the pedal before it failed.
And have you tried it with A KNOWN GOOD BATTERY.
We have had a few pedal faulty lately, that were just a crappy batch of 9V batteries.
In one case, the owners entire new collection was flat.
have you tested it with a good regulated tip neg. power adapter?
Please take some clear closeup pics.
or spend a bit of time just looking at all the internals on your OC-2.
Use a magnifier if you have one.
Regards Dr. Bob |
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bossarea
Forum Admin
United Kingdom
3652 Posts |
Posted - 02/19/2009 : 09:53:33
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If it's consistently starting to work correctly after a few minutes, the problem could be a termal issue with a semiconductor. This can be troublehsooted using cooling spray. Wait until the pedal works, then spray each diode, transistor or IC until the pedal stops working.
Laurie's and Dr.Bob's suggestions about a cold solder joint sounds more probable so don't invest in any spray before checking that out. |
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amagic
Copper Member
New Zealand
7 Posts |
Posted - 02/19/2009 : 11:57:41
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Hi guys,
Thanks for your suggestions...I did check all the solder joints (and even went over them with the soldering iron just to 'reinforce them a bit') but still no luck... there are definitely no loose wires and I'm sure that after tonight there are no dry joints. Pedal was in more/less mint condition - it was never abused and pretty much kept in the box for the last 10-15 years(I think it was built may '87)
I also checked the diodes and they seem fine...at least when hooked up to a meter...I still think that there is problem with one of the components but I guess I will need to trouble shoot them individually...and see which one faulty. I suspect that the signal is not coming to the circuitry where octaves are produced...
Laurie, when you mentioned C24 capacitor, I was not so sure that I found the right one...is it the black, round one between IC4 and IC5 - sorry I am not the best for tracing components from schematics to PCB's.
Here are some pics of the pedal...
Cheers!!
A. |
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amagic
Copper Member
New Zealand
7 Posts |
Posted - 02/19/2009 : 12:05:08
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...and yes I tried good batteries as well...tried new Duracell and also couple of Varta's that are current used in two other pedals...
I also don't know where did the pic's I've just uploaded disappeared ??? am doing something wrong or they just need to be moderated ?
A.
Image display code added by moderator.
Andria - Click on edit to see the HTML code to display your pics.
Make copy of the string, & next time you need it, just paste it into your post with the new file name/s
Some browsers do this automatically. looks like your doesn't.
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Edited by - Dr. Bob on 02/19/2009 12:26:07 |
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amagic
Copper Member
New Zealand
7 Posts |
Posted - 02/21/2009 : 06:49:00
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Hi guys...
Just a little update...I tried to narrow down what the nature of the problem was and what I did was took Mrs's hair dryer and 'warmed' up the components and surprise, surprise OC-2 started working straight away...so it looks like one of the components has a 'thermal issue'...next thing is to get cooling spray and see if I can find which one it is...
Also, I have managed to find a nice Texas instruments OP amp that is almost identical to the original Sharp ones used for IC's - so if it turns out that one of the IC's is faulty I have a nice replacement :)..
A. |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 02/21/2009 : 11:35:26
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| hi amagic! As both Oct 1 and Oct 2 have failed, it almost has to be either IC5 (my money's on this one) or an outside chance it is IC7... |
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amagic
Copper Member
New Zealand
7 Posts |
Posted - 02/25/2009 : 23:57:09
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Hi Guys,
I have changed all IC's and pedal started working after I've changed IC2 and IC3 ...so I guess that is where the problem was. I am still testing the performance with new OP Amp's but it looks like it is all good...
Thank you all for you help !!!!
Take care
Andria |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 02/26/2009 : 02:51:39
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IC2 and IC3 form the "frequency detector", so that fits. If one of them had failed, one half of the detector drive would fail it would probably stop the octaving.
Great to hear it's working again! |
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Topic |
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Boss OC-2 Octave MIJ Problem
