I know this answer was for someone else in the group that was having an issue, but this actually has helped me a lot. My SDS-9 was having issues similar to what was described, and I went for component replacements on the main board first. I had checked the values of the PSU, but had not tested it for a great amount of time. This leads me to believe that I need to re-test it and check for changes in voltages over a longer period of test time. As of right now, after replacing the ICs in the CPU circuit (and in the mux/demux circuits), the unit powers up but will not "start". So....I will have to recheck the PSU values, see if they change, and replace if needed.
Keep you posted.
--- In Simmons_Drums@yahoogroups.com, "Richard" <warlandr63@...> wrote:
>
> Sorry, cat jumped up and hit the keyboard before I could finish..lol
>
> IF the +10 is reducing in voltage;
>
> 1) the transformer internal insulation may be failing - transformer need replacing (same if any other outputs drift down)
> 2) Check (replace) the 4700uF and the 1uF electrolytic capacitors connected to the input of the LM323 (7905) regulator and recheck the fault conditions. If no change, replace the LM323 and check again.
> (same process for the other regulators - though the -6.5v can be adjusted via a 4.7K trimmer)
>
> If you don't have much test equipment, simply desolder one wire off the capacitor you are checking and lift it clear of the board, then power up and check the fault. If no change, the component is ok so resolder it and move to the next to check and repeat the process.
>
> Do this with the supply disconnected from the mainboard!! AND use correct safety procedures when carrying out this sort of work - DO NOT FIDDLE AROUND WITH THE TRANSFORMER OR PSU WHILST IT IS PLUGGED INTO THE AC SOCKET - unplug it, do the work, plug it back in then check. If not - crispy critter can result.
>
> Once the PSU is repaired and working correctly, plug it back into the mainboard and test the unit. If all went well, you are back in business. IT is possible with PSU failure that damage may have been done to the mainboard components - on lower than required voltage faults this is unlikely. IF the +12, +5 or -6.5 went too hi, it is likely the logic devices may have suffered.
>
> Hope this gives a bit of direction
>
> --- In Simmons_Drums@yahoogroups.com, "Richard" <warlandr63@> wrote:
> >
> > The PSU voltages available should be;
> >
> > 1) +12v regulated
> > 2) +10v unregulated - this could range from around 8 - 12v normally
> > 3) +5v regulated
> > 4) -6.5v regulated
> >
> > I dont have an SDS9 open at the moment so can't confirm what colour wire is attached to what output on the PSU. The regulated voltages should be close to those above - within approx .25 - .5 of a volt.
> >
> > The +10v comes from before the LM323 voltage reg ( 5 volt reg) and from my knowledge is used (via a simple delay circuit) to provide a slight delay at start-up before the CPU can access the RAM memory.
> >
> > The +5 is for the logic components (cpu etc) and the +12, -6.5 to supply the required voltage of 18v for the analog components.
> >
> > If the +12 is low, this could cause a problem (including false triggering)
> >
> > If the + 10 drops to low (to 5 -7v);
> >
> > 1) the output of the ram enable delay will be too low to provide the correct TTL signal requirement to enable RAM access reliably thus causing problems
> > 2) This +10 also provides the input for the +5v regulator. The 78xx series regulators (as used in this supply) require between 7 - 9v input to operate correctly. If the voltage is too hi, the regulator will get hot and shut down. If the voltage is too low, the regulator will become unstable and not provide the specified output voltage.
> >
> > Loss of +5v (for the logic devices) will cause all kinds of issues, most notably causing the CPU to restart randomly
> >
> >
> >
> > --- In Simmons_Drums@yahoogroups.com, "sarsipri" <alfco@> wrote:
> > >
> > > The voltage is 12.5 volt not connected. Should be about 9 volt (8.8), and drops to 6.8 volt. I changed it on another sds9, and the problem is in the power supply. I am not sure were 9 volt is coming from for the Brown wire.
> > >
> > > --- In Simmons_Drums@yahoogroups.com, "philmurr" <philmurr@> wrote:
> > > >
> > > > If you unplug the multi-way connector from the main board and measure the voltage at the power supply end, what do you get (on initial power-up and then after a few minutes) ?
> > > >
> > > > --- In Simmons_Drums@yahoogroups.com, "sarsipri" <alfco@> wrote:
> > > > >
> > > > > I have one SDS 9 with a power problem. The wire cable that goes to the mainboard, there is one brown wire with about 9 volt. After a few minutes drops to about 6 volt and all triggers go on. Can anybody check how much the output should be?
> > > > >
> > > >
> > >
> >
>