Boss - HM-3 Hyper Metal  [schematic]

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

I got a Boss Hyper Metal HM-3 for repair. While I was looking for a schematic online, all of them are just mere drawings of HM-2, therefore I decided to trace the unit...
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rs
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Post by rs »

I can provide some gutshots if you like.

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Post by RnFR »

split topic for clarity.


look, no crossover diodes! i guess it's not a HM2 after all. thanks for the trace.
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Post by DimebuGG »

Ooops, I found some error. The 47K biasing resistor in the first opamp should go to V/2 not to ground. Sorry. :slap:
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Post by RnFR »

that's ok, i labeled it as unverified, so we can leave it up until you hash out the final version.
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Post by DimebuGG »

Yeah, I'll redraw it again once and include the pcb part numbers.
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Post by DimebuGG »

This should be the final schematic with PCB part numbers..
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Boss Hyper Metal HM-3.pdf
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Post by DimebuGG »

Modifications I've made with the pedal:

- Lift one leg of or remove D2, D3, and D4.
- Lift one leg of or remove C31.

BTW, I changed the opamps to a TL074. Stock opamps got busted.
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Post by GodSaveMetal »

rs wrote:I can provide some gutshots if you like.
I´m cloning these pedal please some gutshots of it!! the layout and PCB; thanks a lot! :mrgreen:

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Post by mozwell »

axe & you shall receive :mrgreen:
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boss hm3 hypermetal dist.pdf
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Post by GodSaveMetal »

mozwell wrote:axe & you shall receive :mrgreen:
Well I note the tone stack are with ICs; in the HM-3 the tome stack is transistorizer!!! the HM-2 is with ICs!!! is it OK? or I´m wrong???
Her´s a photo o the guts of a HM-3 and a original layout and scheme BOSS HM-3:
Attachments
BossHM3.pdf
here is the original BOSS scheme plus layout
(280.81 KiB) Downloaded 564 times
Hm-3 GUTS
Hm-3 GUTS
20100825164319eab.jpg (99.28 KiB) Viewed 5449 times

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Post by daneelolivaw »

GodSaveMetal wrote:
mozwell wrote:axe & you shall receive :mrgreen:
Well I note the tone stack are with ICs; in the HM-3 the tome stack is transistorizer!!! the HM-2 is with ICs!!! is it OK? or I´m wrong???
Correct.

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Post by GodSaveMetal »

I´m doing a clone of the HM-3, its great, adapting the pads and the pots of 16mm here is the layout I made:
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Her´s my etching and drilling PCB
Her´s my etching and drilling PCB
Pots PCB for pots 16mm
Pots PCB for pots 16mm
HM-3 Main LAYOUT
HM-3 Main LAYOUT

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Post by tommasomatassini »

DimebuGG wrote:Modifications I've made with the pedal:

- Lift one leg of or remove D2, D3, and D4.
- Lift one leg of or remove C31.

BTW, I changed the opamps to a TL074. Stock opamps got busted.
Hi DimebuGG, thanks for the info, and sorry for my poor English.
How do the sound improve modifying these components?

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Post by GodSaveMetal »

Well here again I FINISH THIS ONE!!
Image
Image

I replace the diodes S5500G for a 1N3007, the diodes 1SS133 for the 1N914; the FETS 2SK184 and 2SK118 for the 2SK30A; the 2SC3378 for the 2SC2240; finaly the ICs M5218AL for the NJM4558L; this replaces are recomended by the BOSS team; and really sounds better than HM-2 more mids frecuencies, more EQ control, surprising, the tone stacks is from tranies!! not from a IC like the HM-2!! fantastic!! I´ve to made his BOSS case this days, like my BOSS HM-2 clone!!!

SALUTIS FROM PERÚ!!!

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Post by M0zhe3z »

Hi.. I'm new (for posting) here..

By the way, I thought there's a transistor bypass circuit in every Boss pedals, can I remove it easily by removing all the FETs and also anything between their 'gate' except the Input buffer?
and, is it possible to change the input buffer with BS170 preamp?

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Post by GodSaveMetal »

M0zhe3z wrote:Hi.. I'm new (for posting) here..

By the way, I thought there's a transistor bypass circuit in every Boss pedals, can I remove it easily by removing all the FETs and also anything between their 'gate' except the Input buffer?
and, is it possible to change the input buffer with BS170 preamp?
WhY remove the SEND-RETURN IS amazing; the best of the BEAST!!!!!!!!!!!
Change the switch with a industrial ones and it´s for the ETERNITY!!!!!!!!

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GodSaveMetal
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Post by GodSaveMetal »

Here new photos of the HM-3 I´m clonning yet:
Image
In his BOSS case.
Image
Lateral view.
Image
with his cloned brother HM-2.

In the next year I paint black the HM-3 and made similar brillant finish like the HM-2, stay tuned!!!!

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Post by Greenmachine »

You're hardcore man!
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Post by GodSaveMetal »

Greenmachine wrote:You're hardcore man!

OHHH!!! GOODNESS I don´t know what it means????? :shock:

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