Need help with Boss HM-2 pedal please

Started by Mat88, January 25, 2020, 09:01:34 PM

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Mat88

Hi everyone, i hope this is the correct sub forum to post this in.
I have a problem with my Boss HM-2
It sounds like if not enough power was getting in there, the sound is kinda gated and not constant when i strum the strings soft. If i play hard on the strings then it sounds closer to what it's suposed to but still weird and it gets very weird when the sustain of the strings stops vibrating.
Also the LED is almost not visible when it's activated, i can barely see the led on or off but it definetely turns on and off just very dimmed.
It was just fine before this happened, i'm pretty sure i didnt use the wrong power supply but not 100% sure.
It happened by itself one time i tried to use it the day before it was fine.
So i opened it and i noticed the 2 cables going to the battery clip were cut by the previous owner.
Other than that i don't see any component burnt or desoldered.
I probed using multimeter on the DC mode, pins of the DC socket and they show aprox 4.6v DC but the power adapter i use is 9v dc.
Some background: I did a big schematic from scratch for a tube distortion, from breadboard to pcb layout smd 0805 and tssop ic's but finding the issue here is kinda hard since it's not my design i don't know how it works and i'm not used to pedals, more used to eurorack synths.
Anyway if anyone can help at least what to check first..
Here's some pictures i hope it can help..
Thanks a lot !







DIY Bass

My first thought would be to check whether it needs ACA or PSA power supply.  It will be on the bottom plate.  If it requires ACA then from memory you need to feed it about 12V, not 9.  There are various web sites that have a lot more details about the different Boss supplies.

Mat88

And that must be the quickest solved thread ever. Thanks a lot, feeding it 12v works like a charm.
For some reason i assumed it was 9v like the MT2. I read about the boss different psu's, now it all makes sense.