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ScottC
Copper Member
USA
20 Posts |
 Posted - 01/17/2009 : 01:15:38
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Hi all, I'm a new guy here.
My son and I play guitar and we've built a couple effects pedals on our own (using a Tonepad PCB and perf board), so my DIY skills are OK.
I bought an "as is" Boss Metal Zone pedal off E-Bay for cheap ($25 including shipping). It was advertised as "fully functional level and EQ, distortion does not work". So, I figured worst case I'd have an EQ pedal, best case I could solder a loose wire or replace a blown component and have a great pedal for a great price.
Well.. got the pedal and the Level works mostly (it works up to about 3:00, then the sound gets quieter past there. The Distortion doesn't work, which I expected. But the EQ also has no effect on the sound.
So, this is what works: LED, Level up to about 3:00 position.
This is what doesn't work: any of the EQ and Distortion.
I disassembled the pedal and there is nothing obvious - no loose wires, exploded components, obvious shorts.
So, any troubleshooting experts out here that have any ideas?
Or, should I just take my losses and build a DIY distortion and EQ and put it into this enclosure???
Thanks for reading this long post and for any advise.
NEW info (also posted below): turn switch on, LED goes on and volume works mostly. Turn switch off and LED goes off but Volume (Level) still works the same). Hope this helps. |
Edited by - ScottC on 01/18/2009 01:50:16 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/17/2009 : 02:19:40
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G'day and welcome! The MT-2 is a really simple pedal... (then, so is the ODB-3 and my record on remote fixes for that isn't good!). ANYWAY, we can probably help. Don't cut your losses just yet 
To confirm:
1) the LED changes from off to on with a pedal press as expected?
2) when the LED is off, does the bypass signal come through as expected?
3) when the LED is on, the signal passes through, but the level, EQ and distortion work as described? |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 01/17/2009 : 03:32:00
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Hi ScottC
Welcome to the forum from Australia.
I see Laurie has already picked up on the thread, Thanks Laurie.
You're in good hands. 
He has modded quite a few MT-2's in his time,
And he has even engineered, his own custom Stormchaser Mod for them.
Regards Dr. Bob. |
Edited by - Dr. Bob on 01/17/2009 03:33:19 |
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ScottC
Copper Member
USA
20 Posts |
Posted - 01/17/2009 : 04:31:11
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quote:
Originally posted by Laurie
G'day and welcome! The MT-2 is a really simple pedal... (then, so is the ODB-3 and my record on remote fixes for that isn't good!). ANYWAY, we can probably help. Don't cut your losses just yet
To confirm:
1) the LED changes from off to on with a pedal press as expected?
2) when the LED is off, does the bypass signal come through as expected?
3) when the LED is on, the signal passes through, but the level, EQ and distortion work as described?
Thanks for the offers of help.
1) is correct
2) Yes, bypass works fine
3) LED on, signal passes thru, level works until about 80%, then it seems to get a little quieter. The other 3 knobs don't seem to work at all.
I'll try to post pics soon.
Thanks again. |
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ScottC
Copper Member
USA
20 Posts |
Posted - 01/17/2009 : 04:39:19
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Here it is. |
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ScottC
Copper Member
USA
20 Posts |
Posted - 01/17/2009 : 04:40:49
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Another view. Let me know if any other view would help.
Thanks again.
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/17/2009 : 05:03:59
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Thanks! Wont get to look at this until tomorrow (helping another member with a very stubborn ODB-3).
I can tell you that I've sometimes found the cores in the ribbon cable connecting to the pot board to be broken where they enter on of the boards. For the EQ problem, there must be something common to all controls - so it's worth checking that the ground actually goes to the pot board - test from the pedal case to the ground track on the pot PCB (you'll have to find it, but it's obvious).
There is nothing common with the EQ and drive - so the drive problem will probably be something else.
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/17/2009 : 19:08:59
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Just checked the schematic and I still think it's likely that the "ground" connection to the pot PCB has failed - let us know what you find. If it isn't that wire, please check the continuity of all the wires in the ribbon cable.
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DeFrag
Moderator
USA
3409 Posts |
Posted - 01/17/2009 : 23:50:56
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Whoa.. I never realized or expected the MT-2 to be that simple inside!  |
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zerksies
Double Platinum Member
USA
3406 Posts |
Posted - 01/18/2009 : 00:22:27
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| You can always power the pedal up and probe around with a wood dowel and see if anything is loose |
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ScottC
Copper Member
USA
20 Posts |
Posted - 01/18/2009 : 00:56:22
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Thanks all. I need to clarify what works and what doesn't (I'll edit the first post too).
Plug in the battery, plug in the cables, hit the switch and the only things that happen are:
1) the LED goes on
2) The volume sort of works. Turned down all the way, I get about 25% volume, turned up to about 8 (on a 1 to 10 scale) and I get about 80% volume, turn it up to 10 and I get about 25% volume again.
EQ and Distortion have no effect on sound at all.
And, what I just found out is, when I hit the switch to turn it off, the LED goes out, but the volume still works as described above.
Hope this helps Laurie or any other experts out there.
By the way, I checked the continuity of the ribbon cable best I could and all wires seem OK.
Thaanks again all. |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 01/18/2009 : 04:06:50
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The Level/Volume knob should not have any effect on the sound when the effect is off. The Level pot is in the signal path between Q9 and Q2. When the pedal is off they should switch-off.
With this in mind, I would check/replace the JFET transistors Q9, Q2 and Q3 to see if the problem is there. A cheap substitute is the 2N5457.
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Edited by - cctsim on 01/18/2009 04:07:30 |
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ScottC
Copper Member
USA
20 Posts |
Posted - 01/18/2009 : 04:20:11
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Thanks, sounds like a cheap fix. Is there a way I can check those components with a simple multimeter? I guess they are cheap enough that I could just replace them.
Thanks again, please keep other educated suggestions coming, because I appreciate the education. |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 01/18/2009 : 04:36:12
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If you have any other Boss pedal you could take out a JFET to quickly test if it is working. On DS1 for example the equivalent transistors are Q6 and Q8.
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ScottC
Copper Member
USA
20 Posts |
Posted - 01/18/2009 : 05:09:14
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Since the EQ and distortion also don't work, do you know which other transistors I should replace? Should I just replace them all for a few dollars and see what happens?
Thanks again for the help. |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 01/18/2009 : 05:28:34
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The opamp used for the distortion is IC3, while IC1 and IC2 are used in the equalizer. The opamp type is 2M5218L the SIP version.
Good replacements are also NJM2904L or NJM3404A (the SIP versions)
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MT-2 Metalzone Problems - Help Please
