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fuzzface
Bronze Member
United Kingdom
121 Posts |
 Posted - 10/23/2006 : 21:41:42
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Hi all,
I'm after a bit of advice with a poorly MT-2.
Basically, it's dead - there's no sound or LED light. The strange thing is if I connect a battery to it, after a few minutes, the battery gets incredibly hot. I'm sure I've read about this happening somewhere else and what the problem was but I can't seem to find it again now.
My guess was probably a bad Zener Diode but I'm not sure. Anyone have any clues?!
Thanks in advance!  |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 10/24/2006 : 17:03:45
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Hi Fuzzface
The battery most likely, gets really hot cos you have a dead short across the positive to negative ( + and - ) rails in your MT-2
In most situations the protection diode that is across the + & - inside the pedal gets shorted out.
This can happen if you plugged in a plug pack with the polarity the wrong way around & left in in for a while.'
I have repaired a few pedals with exactly this fault
The diode can be replaced with a typical 1 to 2 amp rectifier diode like the:
1N4001 ... 1N4002 ... 1N4004 ... 1N4007
I tend to use the 1N4004 or the 1N4007, as I have draws full of these & they are cheap.
I don't have a schematic circuit for the MT-2, but I do own an MT-2
Maybe one of the other guys who has a schematic can point out the exact diode, you may try to replace.
Do you have & know how to use a multimeter? that will make you life a bit easier, & it would be good if you could solder on small PCB printed circuit boards.
If you get no reply from the other guys, let me know & I will open up my MT-2 & have a bit of a quick look around, for the circuit reference & location of that diode.
Other than that, one of the IC's might be fried & shorted
It can also be the power supply decoupling capacitor, though it's less likely.
Hope this helps,
Check your mail  |
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fuzzface
Bronze Member
United Kingdom
121 Posts |
Posted - 10/24/2006 : 19:57:03
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Thanks very much for the reply and email Dr. Bob - that's very helpful - you're a star 
I actually bought it broken very cheaply and I was going to have a go at 'reanimating' it! I've got a multimeter with a Diode check on it. I've tried them all and they seem to measure nothing one direction and around 666 (quite aptly for this pedal!) the other way around which I think seems normal. Maybe I should just change them all out and see what happens?
Presumably the battery getting hot means it's shorting across the terminals with no load?
I've done a fair bit of soldering so hopefully I can get it going again.
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starr36
Platinum Member
Canada
1172 Posts |
Posted - 10/24/2006 : 23:15:11
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Bossarea:
Maybe we can collect a new subject "standard technical helps", so that we can locate these messages fast. Seems that the HOT battery problem comes up quite a bit, and likely DR. BOB's or one of Stahlharts replies can be "stickied" or something to make easier to find. I dunno, just a suggestion. |
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fuzzface
Bronze Member
United Kingdom
121 Posts |
Posted - 10/24/2006 : 23:47:18
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| Yes, a kind of Technical help FAQ would be cool as a sticky thread. It seems that a lot of issues with dead Boss pedals seem to be due to the same component problems. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 10/26/2006 : 18:14:18
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quote:
Originally posted by starr36
Bossarea:
Maybe we can collect a new subject "standard technical helps", so that we can locate these messages fast. Seems that the HOT battery problem comes up quite a bit, and likely DR. BOB's or one of Stahlharts replies can be "stickied" or something to make easier to find. I dunno, just a suggestion.
starr36
Thanks for the vote of confidence, but I don't want to detract from the excellent support, both Technical & Otherwise, that ALL the Forum members give to each other.
All of us, are at different levels, be it in technical & electronic skills, or music & playing skills.
It's great that this site, has such a great set of members & inherently friendly culture.
Thanks to everyone who has helped me, as much I as am able to help them.
Everyone, please give yourselves a pat on the back for contributing to such a fantastic forum.
I to, would like to see such a compilation of technical information.
But it's all more work for Bossarea.
Regards Dr. Bob
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 10/26/2006 : 18:15:23
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Hey fuzzface
Any luck with your MT-2? 
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Edited by - Dr. Bob on 10/27/2006 15:48:47 |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 10/27/2006 : 15:59:57
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Hi Fuzzface
Just another quick thought, on the plight of your MT-2.
Check the tracks around the DC Power In Jack, on the pedal.
Look for cracked tracks & cracked solder joints.
Recently, I had an Ibanez BC10 Chorus, where one of the tracks on the power jack
had cracked off the board & had twisted, onto one of the other (3) leads on the power jack.
Causing a heavy short...
While I have never seen this, on a Boss pedal,
it would be possible, as some are mounted in a similar way.
Well it's just another thing to look for.
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bossarea
Forum Admin
United Kingdom
3652 Posts |
Posted - 10/27/2006 : 16:10:54
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quote:
Originally posted by starr36
Maybe we can collect a new subject "standard technical helps", so that we can locate these messages fast. Seems that the HOT battery problem comes up quite a bit, and likely DR. BOB's or one of Stahlharts replies can be "stickied" or something to make easier to find. I dunno, just a suggestion.
Good idea. I'll see if I can get that done. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 10/28/2006 : 18:07:42
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quote:
Originally posted by bossarea
quote:
Originally posted by starr36
Maybe we can collect a new subject "standard technical helps", so that we can locate these messages fast. Seems that the HOT battery problem comes up quite a bit, and likely DR. BOB's or one of Stahlharts replies can be "stickied" or something to make easier to find. I dunno, just a suggestion.
Good idea. I'll see if I can get that done.
One Man ------ Champion Of Many |
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stinkfoot
Silver Member
Sweden
181 Posts |
Posted - 10/29/2006 : 13:34:52
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Also, besides the protection diode, there are usually at least one large-ish capacitor across the power rails. I see at least one 100uF capacitor on the schematic - replace that one too. It will usually blow as well, if the pedal gets fed the wrong polarity power.
/Andreas |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 10/29/2006 : 16:09:08
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quote:
Originally posted by stinkfoot
Also, besides the protection diode, there are usually at least one large-ish capacitor across the power rails. I see at least one 100uF capacitor on the schematic - replace that one too. It will usually blow as well, if the pedal gets fed the wrong polarity power.
/Andreas
Hi Stinkfoot/Andreas
I was wondering if you have a pdf of the real schematic, or is it the one on free info?
I would really love to see the real schematic & service notes, maybe you would be kind enough to PM me?
Regards |
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stinkfoot
Silver Member
Sweden
181 Posts |
Posted - 10/29/2006 : 21:14:49
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The one I took a quick peek at when answering the post earlier was the one on FIS, but I do believe I have the original item somewhere on my workshop computer, which is down at the moment. When I get back to the workshop in a few days, I'll have a look if I have a backup copy somewhere. I'll get back to you on that.
/Andreas |
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fuzzface
Bronze Member
United Kingdom
121 Posts |
Posted - 10/30/2006 : 22:51:07
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Hi Dr. Bob,
Sorry I've not updated on this for a while!
Thanks very much for yours and Stinkfoot's help.
At the moment I'm trying to source some of those Diodes you mentioned and If I don't have any joy when changing the protection Diode, I'll try swapping out the capacitor that Stinkfoot mentioned.
I'm going to go to Maplin (a UK electronics shop) tomorrow hopefully and stock up on some components so I'll let you know how I get on!
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MT-2 Problem
