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Hornby TTS sound decoder not working well on Bachmann 2-6-4 BR tank


Virgil
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Once more i will prevail on the good and knowledgeable members of this forum, your opinions and suggestions will be gratefully received.

I am attempting to fit a Hornby TTS sound decoder to a Bachmann DCC ready BR 2-6-4 tank and am at the stage of body off and test running on rollers.

I had to tweak the wheel pickups on the driving wheels due to poor and intermittent connection.

Fine I thought, that's sorted but no, leaving aside the sound functions, the motor runs beautifully at up to 16 out of 28 speed steps, then as speed is increased especially between 16 and 22 runs very jerkily and erratically.

Has anyone else come across this problem with a Hornby TTS decoder please?

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It’s pretty standard for a TTS decoder in a Bachmann loco,  the motor control isn’t anywhere near as good as some of the higher end decoders. 
 

you could try changing cv150 to 1 which should be an improvement, it changed the way the decoder controls the motor, if it makes it worse the default is 0

 

Richard

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As well as changing CV150 to 1, if it's still not quite smooth it's also worth adjusting CV 3 (try around 35) and CV4 (try around 20). By fine tuning these three CVs I have been able to obtain smooth performance at all speeds with TTS decoders. Also make sure DC running is switched off in CV29.  If it's still very slightly jerky sometimes adjusting the BEMF (CV10) will do the trick.

 

It seems like hassle, but time spent experimenting is usually rewarded with very good results. I have all of my diesels running excellently. 

 

Once you do get it right it's worth keeping a note of the values for each individual loco - I use an old fashioned notebook! I have four Bachmann TTS fitted Class 47's each one needed slightly different settings!

 

Let us know how you get on.

Edited by cravensdmufan
Change of wording for clarification
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To get the TTS sound sequence right at start off and throughout the speed range you need CVs 3 and 4 set to 15. You also need your controller speed steps set to 128. Once you have those set then CV150  is next follwed by tweaks to CVs 15x depending upon which value is set in CV150 all per the instructions.

 

Edit: 

TTS Steam needs BEMF working to control the chuff/coast sequence and checks this versus throttle applied to go up or down the chuff sound brackets.

Edited by RAF96
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A big thank you to all respondents to my post, my thoughts so far.

Changing CV150 was indeed very beneficial and improved the erratic running in the medium to fast speed range to a more acceptable level. The other CV's mentioned made little difference.

On the sound side the chuff rate however is all over the shop, erratic and variable, and not at all acceptable.

I'm wondering if it is the Bachmann 3 pole motor that is upsetting the decoder settings, as I have tested it on another loco fitted with the Hornby skewed 5 pole motor (rebuilt Merchant Navy etc) and it is more acceptable.

Are there any more suggestions please?

 

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3 hours ago, RAF96 said:

....... to go up or down the chuff sound brackets.

 

What does this mean? What's a chuff sound bracket, please? I've been creating steam sound projects on a range of sound decoders for a dozen years or more and I've never heard the term before.

 

Best regards,

 

Paul

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15 hours ago, pauliebanger said:

 

What does this mean? What's a chuff sound bracket, please? I've been creating steam sound projects on a range of sound decoders for a dozen years or more and I've never heard the term before.

Best regards,

Paul

 

My own terminology Paul. I apologise for teaching granny to suck eggs here, but for others...

 

TTS chuffs are recorded in many lumps of sound each at constant speed, similar to diesel notches. Each of these ‘chuff brackets’ as I call them has a repeating sound.  There are up to 18 of these lumps of sound strung together to fool the ear as they are played in sequence. There is no continuous play progression from zero speed to max although each ‘bracket’ plays at a speed to match the throttle and as the speed increases then the brackets jump from one to the next. Ditto when slowing down.

 

The whole thing is the equivalent of a movie film with frames of sound flickering past the ears and appearing to be continuous.

 

On a TTS diesel the sound notches can be adjusted to control at which speed they kick in and out at. Hornby lists this as TTW - Trigger Transition Window. The steam decoders do not have this facility which is why the chuffs get out of synch with the wheels.

 

That is how I understand it.

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45 minutes ago, RAF96 said:

 

My own terminology Paul. I apologise for teaching granny to suck eggs here, but for others...

 

TTS chuffs are recorded in many lumps of sound each at constant speed, similar to diesel notches. Each of these ‘chuff brackets’ as I call them has a repeating sound.  There are up to 18 of these lumps of sound strung together to fool the ear as they are played in sequence. There is no continuous play progression from zero speed to max although each ‘bracket’ plays at a speed to match the throttle and as the speed increases then the brackets jump from one to the next. Ditto when slowing down.

 

The whole thing is the equivalent of a movie film with frames of sound flickering past the ears and appearing to be continuous.

 

On a TTS diesel the sound notches can be adjusted to control at which speed they kick in and out at. Hornby lists this as TTW - Trigger Transition Window. The steam decoders do not have this facility which is why the chuffs get out of synch with the wheels.

 

That is how I understand it.

 

This is exactly what we found when examining the TTS sounds.
Lots of 4-chuff sequences that are played one after the other while accelerating.

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1 hour ago, Locoman58 said:

 

This is exactly what we found when examining the TTS sounds.
Lots of 4-chuff sequences that are played one after the other while accelerating.

It appears that the chuff sequences switch in and out of playing order when running with the Bachmann 3 pole motor, changing CV150 improved the motor speed control but not the chuff sequencing.

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37 minutes ago, Virgil said:

It appears that the chuff sequences switch in and out of playing order when running with the Bachmann 3 pole motor, changing CV150 improved the motor speed control but not the chuff sequencing.

You'll never really improve that on TTS, its been criticised for it since they brought TTS decoders out, I guess it cant be easy for Hornby to resolve or they would have done it by now

 

Richard

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Thank you to everyone, at least I now have an understanding of the problem which seems unresolvable and should perhaps stand as a warning to those wishing to fit TTS decoders to Bachmann steam, I for one don't consider the money saved over a higher end decoder to be worth it.

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3 hours ago, RAF96 said:

 

My own terminology Paul. I apologise for teaching granny to suck eggs here, but for others...

 

TTS chuffs are recorded in many lumps of sound each at constant speed, similar to diesel notches. Each of these ‘chuff brackets’ as I call them has a repeating sound.  There are up to 18 of these lumps of sound strung together to fool the ear as they are played in sequence. There is no continuous play progression from zero speed to max although each ‘bracket’ plays at a speed to match the throttle and as the speed increases then the brackets jump from one to the next. Ditto when slowing down.

 

The whole thing is the equivalent of a movie film with frames of sound flickering past the ears and appearing to be continuous.

 

On a TTS diesel the sound notches can be adjusted to control at which speed they kick in and out at. Hornby lists this as TTW - Trigger Transition Window. The steam decoders do not have this facility which is why the chuffs get out of synch with the wheels.

 

That is how I understand it.

 

Thank you for that comprehensive and illustrative explanation.

 

I believe that what you describe as a Chuff Bracket is what I would call a Sample, so that's the answer I was looking for, thank you.

 

Best regards,

 

Paul

 

 

 

 

 

 

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A final post to clear up any hint of uncertainty as to whether Bachmann steam 3 pole motors will work satisfactorily with Hornby TTS steam decoders.

I have disconnected the motor wires from the Bachmann motor and substituted (off chassis) a Mitsumi motor of the type obtainable cheaply off EBay from China.

The sound obtained with the Mitsumi has none of the glitches suffered using the Bachmann motor, the chuff sequences following each other correctly and not jumping erratically.

The Bachmann motor is not fault and runs well on a LAIS DCC silent decoder with no glitching.

Lesson now learnt and I shall have to find a replacement motor to use the TTS decoder.

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It's just a thought, and might not be relevant, but have you found and removed any capacitors that may be attached to the Bachmann motor? I know the loco is DCC ready but they are fitted whatever and might just be making the difference. I always remove them and have read that some can be hidden and not obvious on brief inspection.

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Thanks for the thought Izzy, there are no capacitors on the motor, I also removed the two wire wound chokes on either side of the Bachmann 8 pin socket and rewired it accordingly.

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  • 1 month later...

Well the Bachmann 4MT tank sound project was concluded satisfactorily and worked out quite well considering the drawbacks associated with fitting a Hornby TTS steam sound decoder to a Bachnann steam loco.

 

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