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Start voltage adjustment TTS decoder (rebuilt MN)

Posted: Sat Sep 14, 2019 7:41 am
by markS&D
This question may or may not have been asked before, but given the limited number of running adjustments that can be made via CV to a TTS decoder, what effect if any would lowering the start voltage have on the top speed of the loco? I would like my model to run slower, to try and make the chuff sound appear a bit more in sync with the loco wheels.

Re: Start voltage adjustment TTS decoder (rebuilt MN)

Posted: Sat Sep 14, 2019 7:56 am
by Roger (RJ)
TTS decoders do not have a start voltage adjustment CV so you are stuck with it. See the decoder manual for available CVs.

Re: Start voltage adjustment TTS decoder (rebuilt MN)

Posted: Sat Sep 14, 2019 8:05 am
by mjb1961
Hi,,,running tts equipped LOCOS in 128 speed steps is best ,,mjb :roll:

Re: Start voltage adjustment TTS decoder (rebuilt MN)

Posted: Sat Sep 14, 2019 9:54 am
by Bigmet
markS&D wrote:... what effect if any would lowering the start voltage have on the top speed of the loco?...

None at all, if available from the decoder. (Characteristic of pulse width modulation for the speed control.)

markS&D wrote:...I would like my model to run slower, to try and make the chuff sound appear a bit more in sync with the loco wheels.

Now we come to the awkward question: is the TTS decoder sound output intended to synch with the driving wheel rotation? Run it at speed step 1 and count, should be six exhausts for a Bulleid pacific.

Re: Start voltage adjustment TTS decoder (rebuilt MN)

Posted: Sat Sep 14, 2019 11:08 am
by RAF96
If using software to run your trains then most allow you to set limited speeds for shunt and cruise, regardless of if a decoder can have its start voltage or speed table adjusted or not.

Re: Start voltage adjustment TTS decoder (rebuilt MN)

Posted: Sat Sep 14, 2019 11:25 am
by markS&D
I am using the Hornby Elite, and I refer to the instructions that come with the Hornby elite controller, page 33:

IMG_0078.jpg


I apologise for the image quality, I did this in a hurry. Not 6 beats per wheel revolution, as you quite rightly mentioned for a 3 cylinder steam loco, it is more like 3, which I know is totally wrong.

I may have to bite the bullet and go for a loksound decoder, which at £110, is not really an option, when I have got 7 bulleid pacifics!

Re: Start voltage adjustment TTS decoder (rebuilt MN)

Posted: Sat Sep 14, 2019 9:38 pm
by Paul-H
To adjust top speed you need to adjust the value of CV5 for top speed and then CV6 to set medium speed

CV2 is for adjusting start value so your loco just starts to move on Speed Step 1.

The trouble with TTS decoders is that they don't support changing CV2, 5 or 6, they only support CV3 & 4 which is for brake and acceleration delay.

IIRC there is a setting to help with chuff syncing, which is something like CV151, check the instructions for more info

Paul