[sdiy] Need help understanding a schematic !

Roman Sowa modular at go2.pl
Mon Dec 13 11:43:06 CET 2021

Check if FPGA gets proper mode change signals, so if it gets proper 
logic levels at pins 18-23 at every mode switch position. It may be just 
dirty switch as well

check if DRAM gets address signals all the time in every mode, you 
should see massive train of pulses on most pins of the RAM.

It wouldn't hurt to see if ADC is working all the time or just in few 
modes. Check the output (pin 7) of LM311, that's possibly IC6. It should 
generate insane loads of semi-random pulses, maybe at 1MHz or so.

connect scope (and then audio amp) directly to DAC's ladder output - 
RA1, even before 5534 buffer, to see if FPGA generates some audio in 
every mode. If not, then check RA1 inputs as well.

check every clocks in the system in every mode - VCO I, VCO II, PLL on 
4046. It may be that one of pitch shifting VCOs is dead no matter what 
mode is selected, and it's simply not needed for plain delay.

One might say it's easy to spit with ideas like machine gun, while 
actually I'd rather look at it myself than try to actually nail the 
fault by email.


W dniu 2021-12-11 o 01:06, Jean Bender via Synth-diy pisze:
> Hi !
> I have to repair a boss sps-10. The unit works when used in delay mod, 
> but nothing when used as pitch shifter.
> But i also discovered that the tuner output is not working when the 
> effect is on, in delay mod or pitch shifter one. The output is only 
> working when the effect is powered but not engaged.
> When i look at the scheme, i don"t get the way it's built, nor i can see 
> where i could find a faulty part. I assume some transistor is not 
> working and i'm looking for a voltage problem, but i'm a bit confused 
> with the way some parts are wired together.
> Would someone here agree with explaining me how the different parts of 
> this effect work together ?
> Actually i know how to troublecheck with my scope and multimeter, but i 
> stuck on how are working the remote effect input and tuner output.
> Thanks for your help !
> Best
> J.
> here is a link to the schematics and service manual !
> http://www.univertron.com/SAS/manuals/Boss%20(Roland)/Boss%20RPS%2010/ 
> <http://www.univertron.com/SAS/manuals/Boss%20(Roland)/Boss%20RPS%2010/>
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