Progress report number two, one night later: I'm closer than I was last evening with getting my SDS9 fixed. Thought I had it tonight after replacing all 17 TL084N chips (a tedious job I might ad). Started off like it was fixed and then after a bit....the random triggering started again. On the plus side of things the constant "dooming" from the low tom channel has stopped. It now triggers normally with the pad input as well as randomly when it starts acting up, so its not non-functioning, its just randomly functioning like the others. So, now that I've eliminated the 4051 chips, the tl084 chips and IC61, it has to be IC58 causing this. I have that on order and should see it Tuesday after the Memorial Day holiday (here in the USA). This is the next step. If that doesn't cure it, I suspect that IC50 in the input mux side of things may possibly have an issue as everything seems to run through that first, then on to the rest of the mux/demux circuits.
So close, yet so far.
And Gordon, I do understand what you are saying about test first, then replace. However, I do NOT own an oscilloscope, and the factory service manual is only schematics, no test procedures for the various ICs. I've been using the schematics supplied by Michael Buchner to me that are far superior to the factory ones and this has been a major asset. I am NOT a professional electronics repair tech by any means, but I do have a basic understanding of what the various electronic components are supposed to do and have limited schematics reading ability. Fortunately my soldering skills are much better than my "diagnosing" skills. This is why I've been asking advice here to help point me in the right direction. It may seem to some that I'm just randomly replacing parts, but I am going on the theory that these components are nearly 30 years old and are near the end, if not already at, the end of their life and should be replaced anyway in order to make it function correctly again. I have been going in stages as suggested by others here, and as it is, I'm having progress. Limited as it may be, but it is still progress. I am closer to it being fixed more tonight, than any time in the past. Recapping it helped the sound AFTER I replaced the mux/demux 4051 ICs and IC61. The sound quality is even better after replacing the mux/demux tl084 ICs, and it has resolved a couple of the issues I was having, but not all.
Again, thanks to those who have helped here by steering me in the right direction, especially Michael for the great schematics and advice.
--- In Simmons_Drums@yahoogroups.com, "simmonssds7fan" <ptmetcalf@...> wrote:
>
> Progress report: replaced IC61 and the six 4051 demux chips, no real change other than the sound generation is a bit stronger. The original random triggering issue is still there. The TL084 chips arrive tomorrow. I'll see what transpires after the replacement of those. Starting to lean towards IC58 being the problem, but I guess it won't hurt to replace those TL084s either.....
>
> --- In Simmons_Drums@yahoogroups.com, "simmonssds7fan" <ptmetcalf@> wrote:
> >
> > I should have the replacement 4051s here today, so this may be a nice starting point on this project for the weekend. I ordered some tl84s as a precaution (they were cheap) just in case the 4051s aren't the entire problem. I also ordered a replacement IC for IC61 and am planning on changing that one out as well as the six 4051s. I didn't think of changing IC58, but if replacing these seven IC's doesn't change much, I may get one of those and change that one out before changing all the tl84's. I'm jumping the gun a bit I suppose, but I need to have some kind of game-plan right?
> >
> > Thanks to everyone with helpful insight to the workings and faults to these SDS-9 units, it is much appreciated. I'll keep everyone up to speed with what happens after the 4051 replacement.
> >
> > --- In Simmons_Drums@yahoogroups.com, "Richard" <warlandr63@> wrote:
> > >
> > > I like Michael have repaired quite a few SDS9's in my time and fully agree with what he is saying. 95% of the random triggering issues I have dealt with were the result of a faulty 4051's the others were due to faulty address decoders (IC's 58 and 61) or dud bypass caps associated with the demux circuit (creating noise spikes)
> > >
> > > Here is my take... Replace (ic socket fitted at same time) IC19,IC64,65,66,67 and 68. Replace ALL 100nf decoupling caps for these IC's also (you have already done this I see) The parts are cheap and once this has been done you will know for certain that the demux section can be ruled out. We can then go from that point to narrow down the fault.
> > >
> > > As to recapping...well that is a subject that stirs up a hornets nest every time it is mentioned. To state that capacitors "wear out" is a bit of a false statement. They simply don't. BUT there are types that can and will deteriorate over time to a point that they no longer function as a capacitor (acting more like a resistor or going dead short) or there rated value at time of manufacture is way out.
> > >
> > > Ceramics, mylars and the like are generally quite robust and don't need replacing (unless they have been stressed beyond ratings due to PSU fault or similar)
> > > Tantalum caps usually fail dramatically releasing magic smoke in the process. They are notorious for failing and in any "vintage" gear I replace them...THEY WILL FAIL< IT"S JUST A MATTER OF TIME.
> > > Electrolytics also fail on a regular basis. The electrolyte dries out over time causing drift of value and voltage piercing through between the plates (dead short)
> > >
> > > I speak from experience, 35 yrs as an electronics engineer and technician working with gear from the simplest up to highly accurate and sensitive lab gear in universities. I can say without exception any equipment I have recapped has benefited greatly from the work carried out. Gear that once was way out of spec would become usable once again. Yes the process of electronic repair can insert new faults, but in due care is taken during the process this is minimized. It's not rocket science but a bit of knowledge and understanding certainly goes a long way.
> > >
> > > Richard
> > >
> > >
> > > In Simmons_Drums@yahoogroups.com, "Michael Buchner" <buchnerelectronics@> wrote:
> > > >
> > > > Start with the 4051s. In most cases...
> > > >
> > > > Best
> > > >
> > > > Michael
> > > >
> > >
> >
>