AMT Electronics - S1 Legend series  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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mensur
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Post by mensur »

IvIark wrote:Thanks for the info. :thumbsup
I'm doing it through-hole so I'll check the specs of the 2SK208 and try to choose a similar alternative
The only two replacements that I could find are 2SK212-C and J201, both with similar vgs and idss values.

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Post by Ice-9 »

I hve some 2SK208 (JR) versions on the way, I bought some JY versions on ebay and i asked the seller if he could source some JR's for me, he kindy stuck them in the post free of charge. Just got to wait till they arrive now.
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

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Post by mensur »

Guys, I just found the cheap replacement for 2SK208, it's the 2SK30A-R, it has the same characteristics as 208, but in the TO-92 package, perfect for DIY.

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Post by Ice-9 »

mensur wrote:Here's AMT P1
I am just going through the AMT P1 schematic here and checking it off against mr P1 pedal. I notice that the fet marked Q1 in the schematic is not a 2SK208 (JR) it has markings 6AS but there difficult to make out, and there is no D1 Bat 54 on it's gate either. The first fet seems to be just a buffer like on the S1 pedal.

@Mensur could you please check your PCB revision . Mine is marked as V.3A, i'm just wondering if there has been some changes to the circuits in different PCB revisions ?
Good find on th ereplacement JR's
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Post by mensur »

I made a mistake, the diode isn't there, but the FET is 6AS.Mine is V.2A.The first fet doesn't need to be hi gain, 2N5458 is used in other versions, cause of the high VGS,so it doesn't clip the signal.Do you have more of these pedals?

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Post by Ice-9 »

mensur wrote:I made a mistake, the diode isn't there, but the FET is 6AS.Mine is V.2A.The first fet doesn't need to be hi gain, 2N5458 is used in other versions, cause of the high VGS,so it doesn't clip the signal.Do you have more of these pedals?
Thanks for clearing that up, I thought that would be the case. I had breadboarded some of the S1 using j201 and 2n5457 for the first buffer stage and it is a clean stage.
I had the S1 and then I got the P1. I'm not getting any others because the new range of legend 2 pedals should be available soon and I might get one of those instead.
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Post by Ice-9 »

mensur wrote:Here's AMT P1
I noticed you have 1 missing value for C5 in the schematic, as it's a small ceremic SMD component I have just removed it from my P1 and measured it with a capactance meter, its value on the meter is 244n so allowing for inacuracies I would think it is a 220n cap.
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Post by mensur »

Here's updated P1 schematic:
P1.png
Also a perfect replacement for BAT54 smd diode is BAT85 - DO-35 case, again perfect for us DIY'ers

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Post by sugab »

2SK208 = J201 ???

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Post by mensur »

sugab wrote:2SK208 = J201 ???
It could be used in a replacement but, 2SK30A-R is identical device with characteristics, only a different package.

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Post by Stephanovitch »

Please Can you verify ref on Q9 and Q10?
On my R1 version I read M6 or MG on SOT23 package.
Other package are SOT323(JR)

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Post by mensur »

Ice-9 wrote:
mensur wrote:Here's AMT P1
I noticed you have 1 missing value for C5 in the schematic, as it's a small ceremic SMD component I have just removed it from my P1 and measured it with a capactance meter, its value on the meter is 244n so allowing for inacuracies I would think it is a 220n cap.
Ice, can you desolder VD6, and clarify which diode is it?

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Post by Ice-9 »

mensur wrote:
Ice-9 wrote:
mensur wrote:Here's AMT P1
I noticed you have 1 missing value for C5 in the schematic, as it's a small ceremic SMD component I have just removed it from my P1 and measured it with a capactance meter, its value on the meter is 244n so allowing for inacuracies I would think it is a 220n cap.
Ice, can you desolder VD6, and clarify which diode is it?
Is it VD6 from the S1 or P1 pedal you need to know.
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Post by Ice-9 »

VD6 on the S1 pedal is a 1N5822 schottky diode on the P1 the same diode is VD8. Polarity protection
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Post by lugburz2000 »

Hi
Noting schemes recently added, I'm realizing that the schematic
I draw about B1 pedal there are some missing components.
I am preparing a new updated schematic and soon I'll be adding to
the forum.
Thank you all for your contributions.
Greetings and see you soon

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Post by mensur »

Ice-9 wrote:VD6 on the S1 pedal is a 1N5822 schottky diode on the P1 the same diode is VD8. Polarity protection
1N5822 is in a bit large case DO-27A?

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Post by Ice-9 »

mensur wrote:
Ice-9 wrote:VD6 on the S1 pedal is a 1N5822 schottky diode on the P1 the same diode is VD8. Polarity protection
1N5822 is in a bit large case DO-27A?
yeah ! it's a beast of a size diode.
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Post by mensur »

Ice-9 wrote:
mensur wrote:
Ice-9 wrote:VD6 on the S1 pedal is a 1N5822 schottky diode on the P1 the same diode is VD8. Polarity protection
1N5822 is in a bit large case DO-27A?
yeah ! it's a beast of a size diode.
We could use any other schottky diode, like BAT47.

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Post by Ice-9 »

mensur wrote:
Ice-9 wrote:
mensur wrote:
Ice-9 wrote:VD6 on the S1 pedal is a 1N5822 schottky diode on the P1 the same diode is VD8. Polarity protection
1N5822 is in a bit large case DO-27A?
yeah ! it's a beast of a size diode.
We could use any other schottky diode, like BAT47.
For polarity protection in all my builds i now only use Mosfets these days, I never use the standard diode protection.
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Post by Liquids »

Ice-9 wrote:
mensur wrote:
Ice-9 wrote:
mensur wrote:
Ice-9 wrote:VD6 on the S1 pedal is a 1N5822 schottky diode on the P1 the same diode is VD8. Polarity protection
1N5822 is in a bit large case DO-27A?
yeah ! it's a beast of a size diode.
We could use any other schottky diode, like BAT47.
For polarity protection in all my builds i now only use Mosfets these days, I never use the standard diode protection.
Can you draw a simple picture of how you do that?

I don't build polarity protection into anything I build - and I build only for myself. Invariably, it will catch up with me but...
However, and ironically, I REGULARLY fry components of all kind in my breadboarding, due to 'oops' power hookups, backwards chips, AC power, dead shorts to ground with a regulator supplying power, etc...annoying, but at least it didn't fry a finished pedal...? I guess I'm Q&D when breadboarding and 'wear kid gloves' when assembling and powering my pedals. I did have a rack unit that was powered with an AC wall wort...the rest all powered by a one-spot...so I color coded the two with red (danger - AC power) and grey (nothing special, just 9v DC) ribbons via a knot at the plug end, so as to differentiate the two clearly even under cable tangles.

Anyhow, I've digressed - the mosfet seems wise since it can really functiona like a zener in one direction and a regular diode in the other. I'm also curious the percieved (or actual) benefit of using a mosfet instead of the standard diode with anode to ground approach for a positive DC voltage pedal.

By the way, will that diode with anode to ground at the DC power supply connection do anything to spare a pedal that gets an AC adaptor plugged into it? Or only save it from a negative DC voltage adaptor?

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