Locobox - Mysto-Dysto Distortion Unit  [schematic]

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Locobox - Mysto-Dysto Distortion Unit

Postby mirosol » 01 May 2014, 14:08

Got one of these in for repairs. To begin with, original pots were fastened with hot glue, stomp switch had turned into momentary, DC jack was shattered and the battery snap was dead. Swapped the broken parts and tested it. Sounded really nice. I figured that there has to be a schematic available on the web as it quite old and very nice sounding OD/Dist. So i packed it up with a ton of packaking tape, ready to be sent back to the owner.

In the evening i started to watch some Voyager episodes on the couch, armed with a mug of cola and a laptop. Started looking for a Mysto-Dysto schematic as i figured i might want to clone one for myself at some point. Damn. No schematic anywhere. Only some random mentions about the circuit being OD250/Dist+ with BMP-style tone control. Just a few hours back i had the unit wide open on my desk and a camera about one meter away from it. Didn't occur to snap some photos at the time. Asked around for the schem, and no-one had a copy. Or even seen one.

The next day i opened the parcel i had taped shut last night and opened the Mysto-Dysto up again. Snapped couple of photos and wrote the component values down.
Haven't have time to trace it to a schematic yet (nor will have in the next week or so). But i thought i'd share the values and photos anyway.

Opamp is 6552, there are two 2SK30As and four 2SC1815 transistors in there. All three diodes seem to be Si signal diodes. Should be pretty close to modern 1N4148s.
Pots are: Distortion C500K, Tone A100K, Volume A100K (I'd suggest trying linear for tone and volume...)
"Bypass" switch is latching SPST. LED-, SW2, Dist lug 3 and DC jack tip connect to ground with in/out jack sleeves I have no idea what colour the original LED was. Swapped the hot glue blob for a 5mm diffused red. Works fine...
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Re: Locobox Mysto-Dysto Distortion Unit

Postby Dirk_Hendrik » 01 May 2014, 20:51

Give me a few days/some hours of undisturbed time and this should be enough to make a full circuit diagram.

Cool! :thumbsup
Sorry. Plain out of planes.

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Re: Locobox Mysto-Dysto Distortion Unit

Postby mirosol » 01 May 2014, 21:02

Would love to see your schematic of this Dirk!
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby Manfred » 15 Aug 2016, 09:24

I recently traced the Panther Distortion, it gots the same PCB.
The schematic is very much alike but still different in some componets.

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Re: Locobox - Mysto-Dysto Distortion Unit

Postby Manfred » 15 Aug 2016, 17:38

[quote="Manfred"]I recently traced the Panther Distortion, it gots the same PCB.
The schematic is very much alike but still different in some componets.

I don't mention it, the schematic shows the Locobox distrotion, with the proper values form the Locobox PCB shots.
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby Manfred » 16 Aug 2016, 09:23

The Schematic was faulty, the IC pin lables were wrong and the capacitor to the level pot is 47nF not 47uf.
Here the corrected schematic.
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby tube-exorcist » 16 Aug 2016, 11:05

Schematic is still wrong. there is no cap in parallel to the diodes, this cap is after the 27k-resistor near the tone-pot
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby Manfred » 16 Aug 2016, 17:54

tube-exorcist wrote:Schematic is still wrong. there is no cap in parallel to the diodes, this cap is after the 27k-resistor near the tone-pot


Thanks for the hint, you are right.
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby Manfred » 17 Aug 2016, 23:44

In accordance with the Panther Distrotion corrections,
here the corrected schematic.
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby Manfred » 18 Aug 2016, 11:21

Missed 1N914 reverse polarity protection diode added.
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby TWAlex » 22 Aug 2016, 14:37

1981:
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Re: Locobox - Mysto-Dysto Distortion Unit  [schematic]

Postby Manfred » 03 Sep 2016, 18:45

Drawing error in the switching control part fixed.

LocobocDistortionSchematic.JPG
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby Renegadrian » 15 May 2017, 23:32

I got one for dirt cheap (10€) but it sucks big time...tone is useless, so the gain, and the feeling you get is that you have a blanket on your (possibly true bypass) distortion pedal...not an heavy overdrive, not a good distortion, not a good pedal at all...think I'm gonna rip it up on the fly and have something better to fill the box!!!
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby mirosol » 16 May 2017, 06:43

Could there be something wrong with yours? After all, it is a 250/Dist+ with BMP tone control. Upping the cap at gain control would be a nice mod to get slightly better balance and possibly even tweak the tone stack more usability. For me this circuit isn't bad sounding thing at all.
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby Renegadrian » 16 May 2017, 12:17

It seems to be in good working order, it's just a not so good sounding pedal IMO. Gonna try to skip the switching part and make it TB, Else I could try to skip the tone part too, and have a regular 250 alike...
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby Renegadrian » 16 May 2017, 13:15

Right, just desoldered the output wire (it's purple if anyone cares) and soldered to the output diodes, so now it's a 250 with input buffer. now it's more usable IMO, yeah you haven't got tone but that BM tone was cutting too much and it was usable only at its middle point...otherwise it was too shrill or too muffled...now you can get 80s riffs and sound good, not bad...gonna try to use the other IC side and get a more usable tone, else I'll leave it this way.
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Re: Locobox - Mysto-Dysto Distortion Unit

Postby Renegadrian » 16 May 2017, 13:30

...or take the second part of the OCD schematic, so invert the pins at the op amp making it non inverting and have the tone control at the end.
damn, I wish this forum had the EDIT button!!!
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