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schematic/layout help
Posted: Wed 04/14/21 7:36 am
by geoff 1965
i'm struggling to trace which IC module is for the reverb section in my boss me50,i've replaced the potentiometer but there is a squeal/oscilation on the spring reverb section and the unit works perfectly apart from that.
i contacted roland/boss UK but they no longer service or sell spares! so i will have to source the module if i can identify it on the layout and it's part number.
appreciate any help, here is the service manual
boss ME50.pdf
Re: schematic/layout help
Posted: Wed 04/14/21 10:45 am
by Bieworm
Hey Geoff..
I think you need to look into this part of the circuit
Screenshot_20210414-174258_Adobe Acrobat.jpg
Re: schematic/layout help
Posted: Wed 04/14/21 10:50 am
by JMPGuitars
geoff 1965 wrote: ↑Wed 04/14/21 7:36 am
i'm struggling to trace which IC module is for the reverb section in my boss me50,i've replaced the potentiometer but there is a squeal/oscilation on the spring reverb section and the unit works perfectly apart from that.
i contacted roland/boss UK but they no longer service or sell spares! so i will have to source the module if i can identify it on the layout and it's part number.
appreciate any help, here is the service manual
boss ME50.pdf
What makes you think there's an isolated IC for the reverb? I don't believe there is. There's parts specified as DSP, and other chips (that I assume require programming) in other spots.
I would consider if you power source is an issue (is it filtered?), and I would also check for bad filter caps.
You can also take a look at the attached service manual and see if there's anything useful there.
Boss_ME-50_Multi-Effects_Service_Manual.pdf
Re: schematic/layout help
Posted: Wed 04/14/21 1:53 pm
by geoff 1965
not sure Josh about IC but there has to be a module,the reverb has room,hall,spring and mod sections that sweep on a potentiometer.the room,hall and mod reverb all work perfectly as do the rest of the effects in the unit.
it could be an associated capacitor but would'nt that affect all the reverbs?
i'll have to study the schematic/layout again and see if i can trace the reverb circuit,this is driving me nuts!
Re: schematic/layout help
Posted: Wed 04/14/21 5:35 pm
by JMPGuitars
geoff 1965 wrote: ↑Wed 04/14/21 1:53 pm
not sure Josh about IC but there has to be a module,the reverb has room,hall,spring and mod sections that sweep on a potentiometer.the room,hall and mod reverb all work perfectly as do the rest of the effects in the unit.
it could be an associated capacitor but would'nt that affect all the reverbs?
i'll have to study the schematic/layout again and see if i can trace the reverb circuit,this is driving me nuts!
It's DSP (digital signal processor), and I don't think they separate much. The diagrams in the service manual show roughly what's going on.
My guess to check filter caps is that 1. the unit is very old, and 2. certain effects might require more filtering than others, so it might not be obvious on all effects. This is just a guess, since it doesn't make much sense otherwise.
Re: schematic/layout help
Posted: Wed 04/14/21 6:20 pm
by geoff 1965
if you look at the block diagram it has 3 analog multiplexers,i was hoping one of them was a dedicated reverb like this one
s-l1600 (5).jpg
Re: schematic/layout help
Posted: Wed 04/14/21 6:37 pm
by JMPGuitars
geoff 1965 wrote: ↑Wed 04/14/21 6:20 pm
if you look at the block diagram it has 3 analog multiplexers,i was hoping one of them was a dedicated reverb like this one
s-l1600 (5).jpg
What's a multiplexer?
Re: schematic/layout help
Posted: Wed 04/14/21 7:52 pm
by geoff 1965
a multiplexer selects between several analog or digital input signals and forwards the selected input to a single output.
seeing as there is 4 reverbs available one might be used for that?
not sure though,there’s codec,dsp,cpu modules as well all with IC numbers.
the multiplexers have 4 inputs each with its own capacitor so you might be right there Josh,but if I go to the trouble of removing the pcb I might as well replace all of them.
Re: schematic/layout help
Posted: Wed 04/14/21 8:14 pm
by JMPGuitars
geoff 1965 wrote: ↑Wed 04/14/21 7:52 pm
a multiplexer selects between several analog or digital input signals and forwards the selected input to a single output.
seeing as there is 4 reverbs available one might be used for that?
not sure though,there’s codec,dsp,cpu modules as well all with IC numbers.
the multiplexers have 4 inputs each with its own capacitor so you might be right there Josh,but if I go to the trouble of removing the pcb I might as well replace all of them.
I'm all for random chip replacement if for nothing else than the soldering fun.
Re: schematic/layout help
Posted: Wed 04/14/21 8:41 pm
by geoff 1965
hopefully just capacitor replacement, want to keep away from the chips if i can!
Re: schematic/layout help
Posted: Fri 04/16/21 6:38 pm
by zaphod_phil
Multi-FX pedals, like this one, generally have everything done in one big VLSI chip, and it's just firmware creating the various different effects. So nothing you can separate out physically
