Atlas HO SD35 with QSI decoder

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tootnkumin

Well-Known Member
Staff member
I have just opened 1 of the 2, QSI equipped SD35's I have in preparation for a decoder change. A couple of pics to show the current setup and questions.


IMG_0185.JPG

Quite a large, what appears to be a CPU and some heavy for it's size, metal brackets of indeterminate purpose
IMG_0187.JPG


But, of most interest, is what seems to be the capacitors for a current keeper, mounted on the same board as the SMD for the rear light. Anyone know if that is indeed their purpose? And if the circuitry for it is also on that board or is in the main decoder. Reason for questions: Whether it can be used with a replacement decoder.
IMG_0189.JPG
 

tootnkumin

Well-Known Member
Staff member
You've got to admit, these are very neatly wired, with all the miniature plugs and sockets. The headlights mini board has a mini resistor, so no need to insert another one . The positive, marked + is the Green wire, so therefore the common. And the Red marked - the negative and function.
Somewhat answering my own question about the Caps on the rear light's board, which as seen, has the usual type resistor, there are 4 wires soldered to contacts on the back of the board. Red, Black, Brown and Blue. Only the brown one had a plug, oddly a 4 pin. The other 3 were directly soldered to the decoder not far away from the brown's socket.

The red wire is soldered to one end of the resistor and by the trace on that board to one side of the large Cap. The other end of the resistor, come back through the board as shown and connects to the rear SMD's extension. The brown wire with it's plug, connects to the other side of the SMD.
The other side of the large cap connects via a trace to both one side of the small cap and the black wire. The blue wire connects to the board and via a trace to the other side of the small Cap.

So...we have a circuit connecting both caps between red and blue wires and the SMD using also the red wire, but the brown to complete it's. What is obvious, is that if those caps are part of a CK circuit, the rest of it is part of the decoder and to be used with what I've got to replace it with (Tsunami TSU-1000), additional circuitry would be required. I'll leave them where they are for now and tie their wires out of the way. All I have to do is find out which of the red or brown wires is + or - for the SMD.. Trial and error I guess. 50-50, one or the other. I always get 6 of one or half a dozen of the other wrong on the first attempt.

At least having the speakers fitted and wired and an easy decoder mounting plate to make, the job should come out OK.

Oh yes. The connections on the motor has small radio interference caps fitted. I believe these should be removed?
 

tootnkumin

Well-Known Member
Staff member
I tried using the capacitors with a replacment decoder, and it turned into more trouble than it was worth.
I thought that might be so. With running at a club with the possibility of collisions because of derailments, misaligned turnouts causing stoppages etc, I've had doubts as to whether something that will keep your train moving uncontrolled, when all others are stopped is a good idea anyway.
 

Espeefan

Well-Known Member
I thought that might be so. With running at a club with the possibility of collisions because of derailments, misaligned turnouts causing stoppages etc, I've had doubts as to whether something that will keep your train moving uncontrolled, when all others are stopped is a good idea anyway.
Those caps are only good for keeping the decoder powered through switches with unpowered frogs and like that. They aren’t beefy enough to keep the model running unpowered for any length of time. What are you replacing with?
 

kjd

Go make something!
My experience with keep-alives has been with the TCS motherboard. The KA capacitors are mounted on the motherboard and the decoder has a 21 pin connector with two of the pins designated keep-alive. You can see the decoder on top of the motherboard and the two rows of the 21 pin connector toward the front of the engine. I don't know anything about QSI except they are located about 11 miles down the road from me. If the motherboard and decoder are proprietary, the TCS system shown here was just over $100 in 2018.
DSC_6152.jpg
 

tootnkumin

Well-Known Member
Staff member
Those caps are only good for keeping the decoder powered through switches with unpowered frogs and like that. They aren’t beefy enough to keep the model running unpowered for any length of time. What are you replacing with?
I'm replacing with a Tsunami TSU-1000, which is the 1st edition version, I bought some time ago. I have already put one of the same into a DCC ready, Silver series Atlas and the sound file is quite good compared to the QSI Quantum used by Atlas when these locos were made. The difference will be in that I used an iP6splus loudspeaker/ringer in that one and I'll keep the twin 30mm ones that Atlas used in their sound (Gold) versions, if they are OK with it. I won't bother with a current keeper.
 

kjd

Go make something!
I'm replacing with a Tsunami TSU-1000, .....keep the twin 30mm ones that Atlas used in their sound (Gold) versions, if they are OK with it. I won't bother with a current keeper.
As long as the resistance on the speakers is the same. I think some are 100ohm, some 32, some 8 and some are 4 ohm. I don't think you can measure speaker impedance with an ohm meter but a quick spec check might help keep the magic smoke inside.

As far as current keepers, they definately will power the locomotive and sound for several seconds. I find it makes derailments much more interesting.
 

tootnkumin

Well-Known Member
Staff member
I installed a Tsunami TSU-1000 in a Bachmann 4-8-4 (http://www.modelrailroadforums.com/...rting-a-bachmann-dc-4-8-4-to-dcc-sound.31558/ ). I really like the sound it produces.
I've been mostly happy with the 1st edition Tsunami, on some, that have the turbo sound, that has been a tad overwhelming of other sounds, but you can adjust it down from default. The new TS2 and Econami decoders that I have installed have to my audio assisted ears may be a bit better refined. All of the other functions they have enabled mean that some "F' keys don't match and require re-mapping, something I haven't got into yet. When Athearn began installing the TS2's into their new SD60e models, they did offer a list of changes that could be made to it's CV's to make it more compatible with the early version. Haven't as yet done anything about that either to see what that does.
 

Espeefan

Well-Known Member
I'm replacing with a Tsunami TSU-1000, which is the 1st edition version, I bought some time ago. I have already put one of the same into a DCC ready, Silver series Atlas and the sound file is quite good compared to the QSI Quantum used by Atlas when these locos were made. The difference will be in that I used an iP6splus loudspeaker/ringer in that one and I'll keep the twin 30mm ones that Atlas used in their sound (Gold) versions, if they are OK with it. I won't bother with a current keeper.
I've got plenty of Tsunamis installed in the fleet. Good sound, easy installs, and the ones I put in my Athearn Genesis models had caps on the board. Only two QSI's on the roster, one in a Sunset 2-6-0, and the other was detailed in my posts over in the coffee shop where I was talking about the wayward Atlas H-660. I put the QSI board back in that one, and the steamer sounds just fine as is. I find myself gradually transitioning to Los Sound because I like their capability. I also like the 21 pin connection more manufacturers are using. Just plug it in and go. Maybe solder up the speaker wires, and that's it. Will you be exploring programming with Decoder Pro?
 

tootnkumin

Well-Known Member
Staff member
I prefer the board replacement PNP decoders too over the wrapped type such as the TSU-1000. I have a couple of the Loksound Selects to install yet. Not 21 pin ones though. A problem with the TSU-1000 is finding somewhere to put that capacitor, a difficulty I'm trying to solve on this engine. Think I might have stuck it inside the empty speaker housing on the Silver one. Decoder Pro, I'm all set up for it, even got the downloads installed, just need the motivation.

As I found out that the capacitors attached to the rear light circuit board are non functional with out the QSI decoder, I noticed that the smaller one, is the same physical size as the one attached to the Tsunami, and both being the same uf value but the Atlas' being 35V and the Tsunami 25V, whether the higher Voltage would make it unsuitable as an alternative, for the Tsunami, don't know what their function is on the early Tsunamis. They're not there on the Tsunami2's or the Econami. If you want current keepers on them, they are an extra. From what I recall my Father telling me about capacitors (He was a keen Ham Radio operator way back in the 1930's) they hold current for later release, on demand, or smooth out fluctuations in it's flow.

After I've done this engine I've got another similar "Gold" to do with the same decoder. Hopefully that one will be a breeze.
 




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