Boss HM-2 Problems

Started by whomeno, October 02, 2020, 10:06:15 AM

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whomeno

Hi All got a problem with a boss HM-2. no go when engaged. built from here http://tagboardeffects.blogspot.com/2014/05/boss-hm-2-heavy-metal.html
I have looked over every thing can't seem to find the problem. .Not sure if is the right schematic they went off of. Thanks















Voltage 9V
Ic1 Top TL072
1-4.3
2-4.3
3-4.3
4-0
5-3.7
6-3.7
7-3.7
8-8.76

IC2 LM358 Middle
1-4.3
2-4.3
3-4.3
4-0
5-4.3
6-4.3
7-4.3
8-8.76
IC3 Lm358 Bottom
1-4.3
2-4.3
3-4.2
4-0
5-4.2
6-4.3
7-4.3
8-8.76

Q1 called for BF 245 I used a 2n5457 Had to rotate 180
D-8.76
S-4.45
G-3.97

Q2 2SC2240
E-0
C-4.1
B-.59

Q3 2SA970
E-7.97
C-3.7
B-7.34









Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

duck_arse

#1
check the value of your 82k resistor.

oh, also, why no showing of the pots and off board wirings? you are assuring us they are 100% absolutely no fail garanteed not the problem and wired correct?
I feel sick.

whomeno

pots are wired in. using a pedal test box to test it. will check the 82K
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

ElectricDruid

Does the 10K by the LM358 go all the way up to the bottom of the 1M resistor? It looks like it stops one hole short on the photo, but it might be hidden by the 47u cap.


whomeno

yes it dose go up to the 1m
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

whomeno

#5
ok doing some probing. I got sound at the bottom of the 10k beside d4 but nothing at the top of 10k. i checked it is a 10k.  looked for shorts on that row nothing
I think it heads through the 10k to the 1uf to pin 3 of the top tl072. I'm I correct?
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

ElectricDruid

Dunno. The schematic only has a few references on it, and I'm not convinced the ones there are match the strip board layout. Someone needs to tell TagboardEffects to link to the schematic they used to lay the board out and to label stuff properly. Just a layout is great if it works first time, but when is that ever true?

duck_arse

I feel sick.

whomeno

I agree 100%. I have had some builds with no problems. but lately I have not.
I will try too find the schematic they used. I do know they use a lot from free stompboxes
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

whomeno

here is a schematic from freestomp. hope it helps



Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

whomeno

these are the only ones I can find. I think he used the 1st one i posted
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

ElectricDruid

Quote from: whomeno on October 03, 2020, 12:44:56 PM
here is a schematic from freestomp. hope it helps


That looks like a Boss original service manual schematic. Certainly it's much better than the other one, and includes reference designators for all the components.

Ok, so you said you'd found signal by D4, so that'd be the output of that op-amp IC 1b. Pin 7 would be a better place to check. Then check you've got signal at pin 3 of IC1a, so the same chip, other side. If you have, the gain and clipping is working, and we've just got the tone control left to wonder about.

Of course, all this is predicated on TagboardEffects using the same op-amps for the same jobs as the original. If they moved stuff around to make the layout easier, all bets are off. *Unless they give us a damn schematic there's no way to know without having to trace their whole damn board*. Grrrrr...

whomeno

#12
yes I have signal at pin 7 on IC1B traced it to the Bottom of the10K resister beside D4. no signal coming through top of 10 K which I I think goes to 1uf cap then to pin 3 of IC1A. I have re soldered all joints. recut all traces. replaced the TL072 for IC1. I'm lost why it is not going through the 10K resistor on the last schematic it would go from IC1 b to R23 10K -D6-D7 -R30 10K
at the R30 10K is where I lose signal
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

ElectricDruid

Quote from: whomeno on October 03, 2020, 03:28:14 PM
at the R30 10K is where I lose signal

A short across one of the two diodes D8 D9 or C16 is most likely. That would ground the far end of the 10K, and you'd hear nothing.

HTH,
Tom

whomeno

going to put this one on the back burner for now. I have to before I go insane over it
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals