Boss HM-2 Problems

[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

[duck_arse]

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?

[whomeno]

pots are wired in. using a pedal test box to test it. will check the 82K

[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

[whomeno]

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?

[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]

pots are wired in. .....

yes, yes. and?

[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

[whomeno]

here is a schematic from freestomp. hope it helps

[whomeno]

these are the only ones I can find. I think he used the 1st one i posted

[ElectricDruid]

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]

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

[ElectricDruid]

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