YO! Boss RPS10 heeeeelp!

[lazydog]

hi,
i received a Boss RPS10 yesterday, beautiful condition, but had been badly
packed for post. worked fine as i checked it out, until i plugged in a microphone
to check out the 'pitchshift'(...). wrong mic, of course: just a cheap (stero minijack PC mike,
into a 1/4" adaptor. then it went superquiet. coincidence? and when i engage
the level button, there is hum. overall the sound is distorted, but all the functions
seem to operate, at very low level, poor sound. have i done this? or is something
knackered in transit, or worn out? like the level switch, for example. could it be
shorting? bad contact? what can i test?

(er, at that very moment, i was thinking this thing could be modded, eg: a kind
of triggered AR envelope on the feedback, for example)

[Gordonjcp]

PC microphones need about 5V bias on them otherwise they won't make any sound at all.

Get a proper input sorted out, and then test again.  Lots of hum and a low output are possibly just caused by you having the gain cranked up so you can hear anything at all.

[lazydog]

yeah, i did
i put 202 back into it, that's when i realised something had happened,
because it was working fine immediately before trying to check out...
pitch-shift with a mic(...)

i still have to test the rca i/o instead, but the level button brings on the hum
whether connected or not, and did not before ( i think).
damn, there i was, thinking uh-this-is-a-bit-disappointing, and it goes'well sod off then'
('i vill not verk for you..') my money is on some sort of groundloop, judging by what's
going on. have been sent schemz this morning by a bod who mods them, but couldn't
offer help..

before it packed up -on first test...- i was trying to figure out how i could use it, and
what exactly it is, and already having thoughts about how the feedback param could be
made more interesting...like triggered feedback controlled by an EG. it is fairly out of
control otherwise. better get it working again first, eh.
googled rps-10+found a guy reporting a similar/same problem, who decided not fix, but
to bend instead, and results not that great. up for sensible mods, though>

could it be the level switch packing up? or something shorting in i/o? i read about blown
zener diodes(now i'm lost...). i'll post the schem.

[lazydog]

here is the schematic(for your archive if nothing else)
Boss RPS-10 schematic:
http://www.box.com/s/d03e30a58e4d30bf8c80

kindly offered by RPS-10 modder geezer

[lazydog]

update:

i've opened it all up and removed the board, desoldering the ground case connections x3.
can see no apparent fault, and it is very clean for something this age. ii was hoping something
like the mode selector was loose from board, but is in fact connected via wires, and i'd
loosened the pot retainer nut so it wouldn't sit in place any more.

it occurs to me that i just could have accidentlally plugged boss psa220 into the 'out' power
socket when i tested it the second time...would this blow something? terrible design, if so...
far too easy to do.

other than that, i've taken photos and can upload if helpful.
i am wondering if this is a common fault with rps-10, as i've seen mention of something
similar by another owner (who chose not to fix it). to re-cap', the level is extremely low, unusable,
and hum is introduced when the level button is engaged. i will check audio symptoms again later to
see if problem remains.

as i said, all parameter functions can be heard working (very faintly), so i figure it must be something
on the i:o audio paths, or in the switch or connectors themselves.

re-cap#2: it appeared to be working at first with a line level source; then i tested the other unit(rdd10)
quickly, before trying to check out the pitchshifting with a mic - in this case a stereo minijack PC mic job,
probably completely wrong level etc. >> and at this point the fault was present.

please let me know anything obvious i should test, and how. my feeling is that this could be something
quite simple, as it -???- resembles some kind of short to ground thing.
cheers!

[Gordonjcp]

What a fiendishly complicated machine!  The D-to-A and A-to-D converter has a bunch of sample-and-holds that must be fired at the right time to "grab" the output of the DAC (RA1, a resistor pack, quite common in Roland kit).

I'd have a listen around the low pass filter - try the base of Q8, which is fed from the VCA.  Use a small amplifier of some sort and start with the volume low - and use a DC blocking capacitor.  Or better still, use an oscilloscope!

[lazydog]

ah! well, i managed to get it working the other evening!!! having de-boxed it and
unsoldered the 3 ground wires, i fiddled with the socket a bit, and it came back!!
used it like this for? 45minutes, and it seemed quite normal. maybe not as loud as
the clean line signal.
oh, so then i got smart and resoldered the socket pins and now it sn't working again..
bn: even so, there definitely seemed to be what was like a short 'warm-up' on the
level, even when it was working.
next plan is to take that socket right off, clean up the area and re-attach it with wires.
i still suspect there's a more difficult fault. need to get hands on a scope...measuring
resistance across the socket, it looks like it is shorted.