Boss HM-2 manufacturing fault?

[jaytee]

It was working with a battery but not with DC supply. There's a resistor and diode to ground that comes in for the DC supply. The resistor, 330 ohms, was dropping 3.8V so about 11mA (about right for this pedal?). I swapped that resistor for 100 ohm and it's working ok. Thing is, the resistor looks original. Has anyone come across this before? I only have a partial schem so does anyone know what that resistor usually is?

[BubbaKahuna]

If I get some time this weekend I'll pull mine apart and peek inside for you.

Cheers,
- JJ

[Rob Strand]

I've traced this circuit from the PCB but I don't have my files here.  I'll have a look but I won't get back to you for a few days.

I can't remember if the trace matched the boss schem.

[new]

ACA Adaptor (12V) is recommended to use .

[the recluse]

Yeah, the HM-2 is made to use the ACA adapter.  Indyguitarist has a mod to adapt it for PSA 120 use though.

[Monotremata]

Ok now.. The HM-2 is my ultimate distortion pedal, been using one for years and years now..

But I never understood what the deal was with the ACA adapter?
I remember reading that the older ACA's were made to accomdate 12V, but the one I bought at Guitar Center just a few months back was 9V..
Both my HM-2 and my old PH-2 Phaser use the ACA plug..

If any of you guys that have opened and traced it have a layout please post it up!!!
Id love to build a backup or two but there is no way in hell Im gonna open mine hehe.
Its way too important to my tone and if anything ever happened to it Id probably cry and then go mad..

[snufkin]

 form bossarea

the early compact pedals was designed to run on either a 9V DC battery or 12V DC adapter. Because of this the ACA adapter was a 12V adapter. The voltage was reduced to 9V internally by using a 470 Ohm resistor and 1S2473 diode between the minus input on the power jack and ground. The resistor diode pair was later removed and at the same time the ACA adpater was redesigned to output 9V instead.

Powering ACA pedals with a PSA power supply
Powering the older pedals designed for 12V DC input with either a newer ACA or PSA adapter will not work very well. The voltage drop over the resistor and diode will prevent the pedal from getting enough power and its LED will usually only glow faintly. The solution is to use a daisy chain and plug in another pedal designed for the newer ACA or PSA adapter. The lead between the two pedals will short the resistor diode pair and the pedal will receive full power.

Depending on the mains voltage there are 4 were versions of the ACA adapter. ACA-100, ACA-120, ACA-220 and ACA-240. The number denotes the mains voltage that the adpapter should be plugged into. The 9V version of the ACA adapter has a G appended at the end of its name. Pictured is the ACA-120G which is the version sold in the U

[jaytee]

So the 'fault' is my ignorance I'm thinking it's more useful to have it running off 9V so I could probably put a link in for the resistor and leave the diode in. Thanks for the info.

[Monotremata]

Hmmm so Im guessing mine is an ACA-120G since I bought it just over a year ago at Guitar Center..
And I actually HAVE noticed that the LED on it is somewhat dimmer than my PSA powered DS-1 or SD-1.. Never noticed it on my Phase Shifter though which is also an older ACA pedal. Not sure of the year on the phaser but my HM-2 is an early made in japan black label model.. Perhaps the PH-2 is one of the newer ones with the resistor/diode. Never have been confident enough to rip a Boss open to look inside..

Sounds like Line 6's power supply scam.. They force you to buy their overpriced PSU to power the big modeling pedals like my LM-4 delay, which are 18v (maybe 12 but I think 18) and the pedal itself converts the incoming voltage to 9V on the way in.


Now a tech question.. As long as Im using them on a fairly clean amp, my distortion pedals volumes can all stay around 12:00 and match the bypassed volume.
My HM-2 though, still needs to be at around 3:00 or so to really pump it up and match bypass volume..
Could this be the pedal dropping too much voltage because of the underpowerered PSU?
I remember when I first got it almost 10 years ago and had a bunch of Radio Shack PSUs at the time and the only one that would properly power it up was a 12v one I had.
Always thought that was odd and I was always worried I was gonna fry the pedal but maybe that was the only time I was running it properly??

No wonder I put the thing up a few years ago thinking 'god somedays this thing sounds like complete sh*t!'

Guess its time to stock up on 9v's for the HM-2 and PH-2 eh?

[jaytee]

Probably a good idea to stick a battery in it then you can plug/unplug the power supply and see if theres any difference.
For reference if anyone wants it the diode on the board I have is D1. Resistor is R2 330 ohms.

[snufkin]

as it says above all you have to do is put one newer psa pedal in front of it with daisy chain linking them all  to a 9v power

they all run off 9v realy

[Monotremata]

Yeah too bad the catch is you have to have the Boss tuner that has the daisy chainable power output on it..
Not gonna spend $100 Id just assume buy the Voodoo Labs pedal power in that case and take care of the Line 6 delay, DS-1, SD-1, Metal Muff, Rat, Wah, Trem, Phaser and whatever else is on my board too..

Just grabbed a pack of 9v at work jaytee so Ill give that a run tonight and see.. Things eat batteries like theres no tomorrow though hehe.

[snufkin]

um no why not just get a good 9v supply and plug or wire a daisy chain up to it

[arawn]

cause sme f us can get batteries at work for FREE, and since there is always somebody that is po folk, FREE is always good.

[snufkin]

um i think you misunderstood me arawn

i meant that you don't need a boss tuner (or similar) to daisy chain

NOT that they can't get round this problem by using batteries. They could use batteries but it wasn't in question

[arawn]

your prolly right I was still drinking my first cup of Coffee when I posted that

[snufkin]

 

I was just discussing excessive coffee consumption and its negative effects with my flatmate
caused some unusual episodes