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Discussion Starter · #1 ·
I got my crossover servos hooked up, and working, at least for the most part. I have two servos (SG90's) that work a
crossover using a 'Y' cable as per attachment. The controller is a TAM Valley Depot QUAD PIC. The crossover appears to switch properly, but afterwards one of the servos HUMS for a while.

I adjusted the throw of each separately, although the switching speed doesn't see to take when I try to adjust them together. Using a dual facia controller that appears to blink a bit too long before settling on final position. I say too long in that I have a single servo driving a turnout elsewhere on the layout, and it switches quickly and there is no servo hum

Any ideas what might be going on here, and/or how to fix?
 

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Humm is usually caused by A/C current.
Since you are using the Tam Valley controller
can we assume it is not A/C?

Don
It's not. They're DC.

Sounds to me like you have voltage leaking into your servo after it's thrown. Check your wiring connections, and check all your jumper settings. After that, I'd reach out to TVD with the question. They're a little in disarray after their founder / owner was diagnosed with Stage 4 Cancer, but you'll probably still get an answer.
 

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Discussion Starter · #4 ·
Servos are indeed DC, and have their own power supply. Jumpers are in right spots, and again the single servo seems to work correctly. I'm guessing the limiter isn't working properly, in that the controller is supposed to shut down once it detects 'it's done'.

Thanks for your responses. I was reluctant to reach out to TAM Valley due to the news, but I suppose it's worth a try.
 

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Servos are indeed DC, and have their own power supply. Jumpers are in right spots, and again the single servo seems to work correctly. I'm guessing the limiter isn't working properly, in that the controller is supposed to shut down once it detects 'it's done'.

Thanks for your responses. I was reluctant to reach out to TAM Valley due to the news, but I suppose it's worth a try.
You can also try realigning the servo and see if maybe you are over-driving it so that it's trying to move beyond it's physical limit. I just checked -- TVD used to have a product that you installed in the joint between two RC cables that would eliminate buzzing. Shows as out of stock now, but it might be worth asking the question.
 

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Discussion Starter · #7 ·
Thanks to all for your feedback. The TAV crossover facia controller has 2 connections, J1 and J2. Can I drive the 2 servos independently using the 2 jumpers, or do I brute force it and use another port on the QUAD pic controller?
 

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I haven't used the Quad controller, but I'm using 10 of their Octpus III servo controllers.
Are you using 2 of the 4 channels, or are you trying to run the servos on just one channel??? I know with the Octpus, you can only drive one servo per channel. To drive two servos on 2 channels with one button, you need to add a extra wire to fascia controller and plug it in the corresponding channels on the Quad.
 

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Discussion Starter · #9 ·
Yes, I'm only using 2 channels on the QUAD. Specs indicate that a single port can drive 2 servos. They switch ok, except for the excess amount of time the facia controller takes to settle, along with the hum. The crossover facia switch has 2 connections on the back, but it isn't clear whether I can use it to drive another servo.
 

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Discussion Starter · #12 ·
I heard back from TAM Valley:
"If the geometry of each linkage does not match, then you can adjust each independently using two channels. You can configure the Quad so that one servo follows the other so your crossover always aligns with only one command or facia button. "

I had asked about using the J2 connection on XFR Facia controller, but he didn't respond to that question.

I 'think' I've go the servos working now. I isolated them from each other and did an independent alignment on each one. Things seem to switch now, and the HUM is gone.

Unfortunately, when the crossover is switched to CROSS, it shorts out my transformer ! Different problem now. I'd sure like to find a simple wiring diagram for a crossover.
 

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You're creating a polarity mismatch between the two sets of rails. What kind of turnouts are you using? Is this the only crossover between two loops? Do you have a reversing loop?
 

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Discussion Starter · #14 ·
This is a DC layout, using 'old school' track. Attachment shows crossover in question. Top portion has 2 dead-end paths, there is no power directly connected to these rails. The bottom rails are the main path, and connected to main power bus. The second attachment show a closeup of the crossover. Photo is in straight path mode. I suspect that when it is switched to crossover the short occurs along the red line, where the outer rail get connected then shorts to the main inner rail.
 

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