Boss - HM-2 Heavy Metal  [schematic]

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

Re: Boss - HM-2 ( Heavy Metal )

Postby Greenmachine » 29 Nov 2012, 20:40

:popcorn:
"[Y]ou want sketchy, dude? I breadboard on a door." -- RnFR, 2011
"This amp is freakin loud, like crazy, I'm going to kill pets loud." -- mich, 2011
User avatar
Greenmachine
Cap Cooler
 
Posts: 621
Joined: 31 Aug 2008, 18:59
Location: Jersey City, NJ
Has thanked: 102 times
Have thanks: 19 times

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 06 Dec 2012, 21:35

Well, i think this circuit is not true-bypassed, right ?
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby Pruttelherrie » 07 Dec 2012, 22:47

slammer88 wrote:Well, i think this circuit is not true-bypassed, right ?

That's correct. Take a look at the schematic attached to the top post of page 9.
Q4, Q5, Q10 determine the signal path, they are switched by the flipflop around Q8/Q9.

To make it true-bypass you'd only use the part between Q4 and Q10 (actually C32), but it might end up sounding slightly different because of the extra filtering that's always in the path in the original.
User avatar
Pruttelherrie
Solder Soldier
 
Posts: 240
Joined: 18 Feb 2011, 20:35
Location: The low lands
Has thanked: 48 times
Have thanks: 112 times

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 08 Dec 2012, 10:32

Pruttelherrie wrote:
slammer88 wrote:Well, i think this circuit is not true-bypassed, right ?

That's correct. Take a look at the schematic attached to the top post of page 9.
Q4, Q5, Q10 determine the signal path, they are switched by the flipflop around Q8/Q9.

To make it true-bypass you'd only use the part between Q4 and Q10 (actually C32), but it might end up sounding slightly different because of the extra filtering that's always in the path in the original.


or use an external millenium by-pass circuit?
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby Pruttelherrie » 08 Dec 2012, 17:30

slammer88 wrote:
Pruttelherrie wrote:
slammer88 wrote:Well, i think this circuit is not true-bypassed, right ?

That's correct. Take a look at the schematic attached to the top post of page 9.
Q4, Q5, Q10 determine the signal path, they are switched by the flipflop around Q8/Q9.

To make it true-bypass you'd only use the part between Q4 and Q10 (actually C32), but it might end up sounding slightly different because of the extra filtering that's always in the path in the original.


or use an external millenium by-pass circuit?

Sure, I don't see why that wouldn't work.
User avatar
Pruttelherrie
Solder Soldier
 
Posts: 240
Joined: 18 Feb 2011, 20:35
Location: The low lands
Has thanked: 48 times
Have thanks: 112 times

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 08 Dec 2012, 18:07

Pruttelherrie wrote:
slammer88 wrote:
Pruttelherrie wrote:
slammer88 wrote:Well, i think this circuit is not true-bypassed, right ?

That's correct. Take a look at the schematic attached to the top post of page 9.
Q4, Q5, Q10 determine the signal path, they are switched by the flipflop around Q8/Q9.

To make it true-bypass you'd only use the part between Q4 and Q10 (actually C32), but it might end up sounding slightly different because of the extra filtering that's always in the path in the original.


or use an external millenium by-pass circuit?

Sure, I don't see why that wouldn't work.


Actually i dont want to make any changes on the default circuit, as i will only follow the PCB version of it. After finishing and working it properly, i will make an external by-pass circuit :wink:
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby Pruttelherrie » 08 Dec 2012, 22:22

slammer88 wrote:Actually i dont want to make any changes on the default circuit, as i will only follow the PCB version of it. After finishing and working it properly, i will make an external by-pass circuit :wink:

In that case, leave out the parts not needed (such as the flipflop) and tie R33 (that drives the diodes to the FETs) to +9V. Or just solder in everything except for R35. (Which is a waste of components)
Personally, I don't see the need to make these things true-bypass but if it makes you happy :D
User avatar
Pruttelherrie
Solder Soldier
 
Posts: 240
Joined: 18 Feb 2011, 20:35
Location: The low lands
Has thanked: 48 times
Have thanks: 112 times

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 08 Dec 2012, 23:44

Pruttelherrie wrote:
slammer88 wrote:Actually i dont want to make any changes on the default circuit, as i will only follow the PCB version of it. After finishing and working it properly, i will make an external by-pass circuit :wink:

In that case, leave out the parts not needed (such as the flipflop) and tie R33 (that drives the diodes to the FETs) to +9V. Or just solder in everything except for R35. (Which is a waste of components)
Personally, I don't see the need to make these things true-bypass but if it makes you happy :D


Actually i did not know that this pedal was not true-bypassed until my friend saw the circuit and said so. Actually i'd like to use it only with 9V Battery, as i don't have an adapter besides this will be my first and last pedal. I'm making this, because there is not any VST version of HM-2 around, only one is the one in Amplitube 3, which is however not so good at all..In this case, i'll solder everything as it has been done in the pictures, eh? And connect 9V Battery Cap instead of DC Output
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 10 Dec 2012, 17:26

I've got some questions..

1- The only type of pot's i could find in my city are B (linear) ones. They said it's really hard to find A (Log) ones..Does it differ that much?
2- I could not find 250K, instead i had to buy 220k. Is it ok ?
3- I will connect a 9V Battery Cap in the place of DC Output, as i want to use the pedal only with 9V..Is that ok?
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby Pruttelherrie » 10 Dec 2012, 19:15

slammer88 wrote:1- The only type of pot's i could find in my city are B (linear) ones. They said it's really hard to find A (Log) ones..Does it differ that much?

For dist. no, you'll want to run the pedal full-on distorted anyway :)
But for the tone pots you really need 10k-G (or 20k-W, see [url=http://freestompboxes.org/viewtopic.php?p=146890#p146890] ths post by Crumbchildz and the posts above that one)
2- I could not find 250K, instead i had to buy 220k. Is it ok ?

Should be ok.
3- I will connect a 9V Battery Cap in the place of DC Output, as i want to use the pedal only with 9V..Is that ok?

Of course! The original has both battery clip *and* DC input, the DC plug disconnects the battery.
User avatar
Pruttelherrie
Solder Soldier
 
Posts: 240
Joined: 18 Feb 2011, 20:35
Location: The low lands
Has thanked: 48 times
Have thanks: 112 times

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 11 Dec 2012, 00:42

Pruttelherrie wrote:
slammer88 wrote:1- The only type of pot's i could find in my city are B (linear) ones. They said it's really hard to find A (Log) ones..Does it differ that much?

For dist. no, you'll want to run the pedal full-on distorted anyway :)
But for the tone pots you really need 10k-G (or 20k-W, see [url=http://freestompboxes.org/viewtopic.php?p=146890#p146890] ths post by Crumbchildz and the posts above that one)
2- I could not find 250K, instead i had to buy 220k. Is it ok ?

Should be ok.
3- I will connect a 9V Battery Cap in the place of DC Output, as i want to use the pedal only with 9V..Is that ok?

Of course! The original has both battery clip *and* DC input, the DC plug disconnects the battery.


Well, i guess i won't be able to find G or W Taper pot in Turkey, what happens if i cant find them ?
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby greigoroth » 12 Dec 2012, 13:45

Try musikding.de or banzai - they're shipping is really reasonable - might cost a bit but it's worth it for an HM-2!
User avatar
greigoroth
Breadboard Brother
 
Posts: 97
Joined: 09 Dec 2010, 11:59
Has thanked: 4 times
Have thanks: 12 times

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 12 Dec 2012, 16:09

Ok, i've got all of the parts except 0.1 Ohm Resistors, about which i've been told that i can use just a cable to get that amount of resistance :) I will start tomorrow and take lots of pictures
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 15 Dec 2012, 17:53

I think the new circuit board lacks 4th 330R Resistor, as there are only 3 in the PCB but it says 4 on the part list..
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 16 Dec 2012, 13:36

It's ready, but i cant get any sound when i plug the battery. There are no short circuits on the board, i've checked them maybe 5 times, yet it does not work. What would be the problem? I've used sockes for trannies and IC's in order to not to burn them :hmmm:
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 16 Dec 2012, 15:10

I need some detailed photos GodSaveMetal, for the connections.. can you do that for me ?
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 16 Dec 2012, 22:54

OK, its working now! But it lacks a little gain. I do not know why, i'm on it right now. Probably either trannies didnt sit well, or because of the dist. pot, as i only could find 220k..And i can only get dirty sound, when i switch it off, i dont get any clean bypassed sound..
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 17 Dec 2012, 00:19

ALL FIXED! Only thing is, personally, i found the gain level a little less than the original one. Its maybe because of using 220k Pot for Dist., for which actually had to use 250k..
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

Re: Boss - HM-2 ( Heavy Metal )

Postby GodSaveMetal » 17 Dec 2012, 01:59

slammer88 wrote:ALL FIXED! Only thing is, personally, i found the gain level a little less than the original one. Its maybe because of using 220k Pot for Dist., for which actually had to use 250k..

I Have that problem wen I made mine, cuze I made the conections with a molex conector an use a pin conector 90º from the pots PCB and one of the pins have a "cold" solder; you must pay attention on that, and PHOTOS of yours!!!!!!!
The first time I use a B250K and is aprox the sound, the second time I used a damaged?? A250K (in the multimeter is a C250K!!!) and is exactly the original sound!! great man!!!! from 0 disto to aprox max at 12 o´clock and them max to 5 o´clock; in the original that it´s idem!!!!!!!!
GodSaveMetal
Resistor Ronker
 
Posts: 301
Joined: 19 Sep 2009, 17:11
Has thanked: 141 times
Have thanks: 52 times

Re: Boss - HM-2 ( Heavy Metal )

Postby slammer88 » 17 Dec 2012, 09:04

GodSaveMetal wrote:
slammer88 wrote:ALL FIXED! Only thing is, personally, i found the gain level a little less than the original one. Its maybe because of using 220k Pot for Dist., for which actually had to use 250k..

I Have that problem wen I made mine, cuze I made the conections with a molex conector an use a pin conector 90º from the pots PCB and one of the pins have a "cold" solder; you must pay attention on that, and PHOTOS of yours!!!!!!!
The first time I use a B250K and is aprox the sound, the second time I used a damaged?? A250K (in the multimeter is a C250K!!!) and is exactly the original sound!! great man!!!! from 0 disto to aprox max at 12 o´clock and them max to 5 o´clock; in the original that it´s idem!!!!!!!!


No worries, i will add photos when it's done 8) But first, i have to solve all of the problems..As i said, its impossible to find any A Taper Pot's and also 250K pots in Turkey. Nearest ones are 220k and 500k. I think i will have to use 500k and decrease it into 250k by using an external resistor.
slammer88
Breadboard Brother
 
Posts: 64
Joined: 31 Dec 2011, 13:41
Has thanked: 7 times
Have thanks: 0 time

PreviousNext

Return to Modern Stompbox Effects (1975 - ...)

Who is online

Users browsing this forum: marvilla, resynthesis and 9 guests