Ok, here's the update I have on this unit. As of this past week, all the circuits tested ok as far as continuity from the appropriate pin to pin on the IC per the schematics I have (thank you again Michael for those.) So, now I'm starting to question one of my choices of replacement ICs. While I was replacing the other IC in the mux/demux circuits I opted to replace the LM13600N chips. (My theory was I'm this far in and they were cheap enough, why not have everything of the same age now and eliminate them from the equation.) Well.....I was told by the electronics supply house I was using that the LM13600N chip was discontinued and no longer available, but that the NE5517 chip was a suitable replacement for it. Well....after taking their word for it and installing them, I'm not so sure of that. After thoroughly reading the LM13600 datasheet, the LM13700 datasheet (the supposed "twin sister" to the 13600) and the NE5517 datasheet, I think I might have been lead down the wrong path.
I realize there is a slight difference between the 13600 and the 13700 as explained per wikipedia: "The darlington output buffers on the LM13700 are different from those on the LM13600 in that their bias currents (and hence their output DC levels) are independent of IABC pin. This usually results in performance superior to that of the LM13600 in audio applications." General consensus on other electronics forums is that they are interchangeable. Is this true?
The NE5517 is supposed to be a replacement for the LM13700, rather than the 13600 so I'm told by other electronics forums, however, after reading the circuit schematic of the chip, it seems closer to the 13600 with the exception of three added transistors, a diode and a resistor in the circuit leading to the Iabc pin.
Could this be my issue causing an internal short causing the unit to not work, or are these ICs truly interchangeable without changing anything to the board circuitry?
Since making this substitution, I did find a source for new 13600 ICs, (of course!) but they are JRC brand chips labeled NJM13600. The internal schematic appears icentical to the original LM13600N ICs. Before I go and order these and get into replacing the replacement ICs (and hence more desoldering/soldering)I would appreciate some of the more knowledgeable group members to chime in and let me know what they think. Am I on the right track and did I "screw the pooch" on this one?
--- In Simmons_Drums@yahoogroups.com, "simmonssds7fan" <ptmetcalf@...> wrote:
>
> Oh wonderful...I get to be the guinea pig on this one...LOL! Well....I guess I'm spending time with my multi-meter and schematics this weekend testing circuits again....
>
> --- In Simmons_Drums@yahoogroups.com, Jacquot.Patrice@ wrote:
> >
> > Hi, I know that symptom but any tech hasn't see it yet so I can't help you.
> >
> > In Btw the SDS9 has been the most reliable Simmons I had of all till now. Wth the V.
> > & a breakdown appeared when I set a Zero force socket Insertion for the Eproms on both of my units... would you beleive ?
> > I'm sure it's not a really bad one but well it needs investigation.
> > Nothing about PSU nor recapping has been done on them yet (but it will).
> > We seem to be at the same place with a different way to acces to it... :)
> >
> > An old british tech told me to start by removing all the Eproms & unsoldered circuits, & checking if all th contacts are well clean... But I think you already did it.
> >
> > THE AMPLIFIED HISS ON THE SDS9 HEADPHONES is a sort of... "normal" ... Well at least I heard that on all of them I had in my hands... even close to new.
> > So It's not normal at all but it was in the package ^^ ...Magic of Simmons ;)
> >
> > The firts to resolve the Issue tells the other . It might be you actually as mine won't be seen before a few weeks.
> >
> > Good luck !
> > P.
> >
> >
> > ----- Mail d'origine -----
> > De: simmonssds7fan <ptmetcalf@>
> > Ã: Simmons Drums <Simmons_Drums@yahoogroups.com>
> > Envoyé: Wed, 12 Jun 2013 20:07:06 +0200 (CEST)
> > Objet: [Simmons Drums] More issues with my SDS-9
> >
> >
> >
> >
> >
> > First off, I'd like to thank those that have helped me along with repairing this, but I'm currently at a standstill.
> >
> >
> > What's been replaced so far: all the caps and IC's in the input mux and mux/demux circuits. This hlped the issue with the low tom circuit with the constant triggering.
> >
> >
> > The unit also had a random triggering issue with all but the bass channels, almost like the autorun function was stuck, but instead of sequentially triggering, it would randomly trigger channels until all were triggered at the same time constantly, causing basically a constsant buzz noise. Someone mentioned that it may have been an issue with the logic circuit. So, I decided to replace the IC's in the logic/computer circuit as they were pretty reasonably priced. Only the main processor chip: P8031AH, and the PPI chip P8255, were not available as new. I did find New Old Stock chips though, that did appear to be new and unused.
> >
> >
> > Now the issue: when I turn the unit on, the 4 led's for the kit bank (A,B,C,D) BREIFLY come on and go out, but the "mode" led and the 7 segment led never come on. The unit does generate an amplified hiss through the headphone output jack, like normal amp noise waiting for something to happen is the best way I can describe it. When I try to trigger the unit with the pads, I get nothing. Also, the select buttons do not seem to do anything either. I've checked and rechecked the board to make sure no circuits were damaged from the IC replacements and have found no damage. The unit seems to act like it's waiting for data, but not seeing it. I have tried a few different OS EPROMs, including the original one which did work before and there is no change. I also tried the original processor chip (it is in a socket, s no big deal to change) and it does the same thing with either processor chip. I'd like to note that I did NOT replace the 6116 RAM chip for fear
> > of data loss, so that is original.
> >
> >
> > What am I missing here? Is there an initialization sequence I need to do that I am unaware of? Is it possible that the PPI chip (P8255A) that I got is defective? The best way I can describe what the unit is doing is like this: it is like an old DOS based PC, whereas you have the blinking cursor on the screen waiting for you to tell the computer what to do. Does this make sense to anyone?
> >
> >
> >
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> >
> > [Non-text portions of this message have been removed]
> >
>