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Relocating/replacing capacitors and filing edge of board on Titan-SD


benmartinrr@...
 

I have two HO Atlas Dash 8-40CWs with factory installed QSI Titan-SD (Small Diesel type board) decoders. A while back one of them stopped making sounds, and for a while I thought the decoder was at fault. Recently, though, I did some more troubleshooting and it turns out the factory 0.25W speakers were busted somehow. The decoder survived this event and still is functional with different speakers. This is what the factory configuration looks like in my units:



I decided to install Scale Sound Systems speakers in the units to increase sound quality and prevent this factory speaker issue from happening to the other locomotive. The system I want to use is dual speaker, with one going in the A-frame where the existing speakers are, and one at the rear behind the decoder. The rear speaker is designed for a smaller circuit board, though (and this picture does not show the front speaker installed):



Installing this in my units will require removing that plastic mounting plate at the rear of the decoder and either shifting the whole board forward by a couple millimeters, securing it with tape to the top of the motor instead of being screwed into the A-frame up front, or filing the rear edge of the board back a couple millimeters. Of course I will also need to do something with the two huge capacitors soldered to the rear. I am thinking I will need to solder wires to the spots in the board where the current capacitors are mounted, and move the capacitors further forward on top of the decoder near where the large flash chip is.

And this is where my questions come in: first, would it be possible to replace these capacitors with smaller ones of the same specifications, or replace them altogether with a single keep alive? Second, is there any reason I shouldn't file the edge of the circuit board back about 1.5mm as long as I don't remove the through holes for the capacitor? I know some boards have internal circuitry, but I'm not sure about this one. And last, what is the purpose of this metal piece that is screwed in on top of the decoder, as it does not appear to be contacting anything electrically:



If it is necessary, I could snip off the mounting lug it screws into from the plastic bracket, but it would be a lot easier if it didn't need to be there.

Hopefully this photo essay illustrated my questions well enough. My main question is the one referring to filing back the board, if anyone has any info about that.

Thanks!


kjlovesya
 

Hi Ben,

  I don't own any of the OEM equipment, so this is purely guess work.   It's my understanding that all QSI sound decoders are multi-laminate boards.   In other words, like a sheet of plywood, there are multiple levels of circuitry laminated with multiple levels of some type of resin.   As such, we don't know where the inner layer circuitry is located.    That being said, before filing a portion off the end, you might want to, at very least, use an ohm meter and trace the capacitor connections to elsewhere on the board.   If you decide to file the end, be aware that there may be other circuitry between the existing end of the board and the through hole capacitor connections.   There is just no way of telling without QSI's internal engineering documentation.   You could nicely ask Kelly if he could check the engineering drawings to see if there is any other circuitry present in that location.

  Is there a reason that you cannot modify the new speaker housing?   This is probably a much easier and potentially less damaging choice.

  As for removing the capacitors, a substitute of equal value should be no problem.   Perhaps you can reuse the existing with added jumper wires to enable a better location.   Still, I always add a high value capacitor (keep alive type device) to my Titan - U's, even with the presence of existing caps.   As you suggested, you could try using a high value capacitor without the smaller OEMs.   Off hand, I cannot imagine why that would not work.   Experiment.

Good luck!

KJ


benmartinrr@...
 

Hi KJ,

I asked JT Burke at Scale Sound Systems if modifying the speaker enclosure would be detrimental to sound quality, and he said that there is no room for filing or sanding as the enclosure walls are only 1mm thick to begin with and contribute significantly to the system’s resonance. I could just use a smaller speaker, but that would defy the point of this whole project as I want to try and get the best sound quality I can out of those Titans.

As for the high value capacitors you add to your Titan-U's, do you just wire them in raw somewhere or are they in a keep alive circuit? And the OEM ones are only there to provide continuity to the sound portion of the decoder after interruption, right?

Thanks,
Ben


kjlovesya
 

Hi Ben,

  When I mention high value capacitors I'm referring to the aftermarket super cap package available under different brand names.  e.g. Keep Alive, etc.     The Titan - U provides the rectified (+) blue wire and the ( - ) black wire with white stripe so connection is quite easy.

  The Titan - U, like the Revolution - U, Titan - A and Revolution - A, is delivered with a small tethered capacitor.   It's my understanding the tethered capacitor supplies backup power to the micro-controller, lights, sound amplifier; everything but the motor circuit.  It's worth noting that the black wire of the capacitor is shared with ground ( - ) of the bridge rectifier.   i.e. the common ground of the entire board.      This suggests to me that the two capacitors on your OEM may share the same common ground ( - ).  verify with an ohm meter.


KJ


benmartinrr@...
 

OK, good to know. I'll do some testing on my SD boards to see. Any idea what the factory capacitors' other legs are connected to on the board?


kjlovesya
 

Sorry Ben!   I haven't a clue about those circuits.   You could ask Kelly.


benmartinrr@...
 

No problem. I've sent him email but he hasn't been responding, which I understand with everything going on.


kelly dorf
 

HI Ben,
I posed your question to one of our engineers, and I got this lengthy answer:

And this is where my questions come in: first, would it be possible to replace these capacitors with smaller ones of the same specifications, or replace them altogether with a single keep alive? Second, is there any reason I shouldn't file the edge of the circuit board back about 1.5mm as long as I don't remove the through holes for the capacitor? It is always risky to file on ECB's. The filing itself can create static charge (especially with a Dremel tool), that can damage components and there is a risk of shorting or damaging buried wiring runs in the ECB. I did review the check-plots for the 050-0172-01 circuit board and there are no ECB runs from the capacitor's through-holes to the end of the board except for the ground plane and the 5 volt supply plane; there is always a chance that these two place will short together from the filing but a visual inspection of the board edge after filing should revile any problems. Replacing the capacitors with equivalent one's is acceptable but when this system was designed, we used the smallest ones we could get for the total capacitance necessary. Of course, technology keeps improving so it might be possible to find physically smaller ones at the same capacitance and voltage rating. I'm not sure about the keep alive working on the SD boards but in principle it should work. I know some boards have internal circuitry, but I'm not sure about this one. And last, what is the purpose of this metal piece that is screwed in on top of the decoder, as it does not appear to be contacting anything electrically: The Titan FX SD board runs hot because the ECB design used a linear voltage regulator to reduce sound system cost for the locomotive manufacturer. The metal plate acts as a heat sink that transfers the heat from the linear regulator mounted on the ECB to the ECB mounting screw to the metal support and down to the chassis. 


kjlovesya
 

Kudos Kelly!   

Regarding the static discharge from using a motor tool, could one use tin snips instead?


benmartinrr@...
 

Wow, thank you so much! I really appreciate the help.

Going off of your advice I decided not to try and file the board. I ended up filing a small notch into the weight ahead of the decoder, allowing it to shift forward by about 1mm. It no longer lines up with the factory screw holes, but some double sided foam tape still secures it to the top of the motor just fine. After relocating the factory capacitors and re-attaching (what I now know is) the heatsink via a small square of plastic tapped for the 2-56 screw, it is all back together. The locomotive sounds really good, I am very impressed at how well the QSI Titan handles the better speakers! I am going to do the second unit soon and I will post pictures of the finished work before putting the shell back on.

I do have one more question - is it possible to load new sound files onto one of these Titan-SD boards using a Quantum Programmer, or is that just for the normal Titan-U version?

Thanks again!


kjlovesya
 

Ben, the heat sink must be anchored through metal to metal contact (plastic will not transfer the heat).    If you cannot use the metal frame for heat dissipation perhaps you can purchase an aftermarket heatsink.


benmartinrr@...
 

It is mounted exactly the same way as it was from
the factory. The underside of the heat sink is still
firmly covering the linear voltage regulator. The plastic piece is on the underside of the board and is essentially a nut/washer for the mounting screw, in place of the original plastic bracket. When I do the second install the pictures should show this a little clearer.


benmartinrr@...
 

Still haven't gotten around to the second locomotive, but I thought I would share a couple videos of the completed first one. It really is amazing how much better these Titans sound with good speakers.

https://drive.google.com/file/d/1ftuY8FSJSVGHc6IyggAlDnjAm3bd2gG9/view?usp=sharing
https://drive.google.com/file/d/1y-LKT7n9EjtujeRP4zvIjJFAMWNXJMAE/view?usp=sharing


Jon Heller
 

Without schematics and or a part number identifying the components values it is dangerous to substitute a different value or capacitance. 

Jon Heller 


On Thu, Jun 11, 2020 at 2:44 PM, benmartinrr@...
<benmartinrr@...> wrote:
Still haven't gotten around to the second locomotive, but I thought I would share a couple videos of the completed first one. It really is amazing how much better these Titans sound with good speakers.

https://drive.google.com/file/d/1ftuY8FSJSVGHc6IyggAlDnjAm3bd2gG9/view?usp=sharing
https://drive.google.com/file/d/1y-LKT7n9EjtujeRP4zvIjJFAMWNXJMAE/view?usp=sharing


kjlovesya
 

Ben,

  I couldn't get the videos to play.   Is the problem just with my system?

KJ