A tele of two decoders

One of my long standing customers part-exchanged an fairly uncommon loco yesterday. The model in question was a Tech-Cad Design BTH class 15 Bo-Bo diesel, and it came fitted with a Digitrax DH140 decoder. Well the thing was virtually uncontrollable with a 0-60 which would have made a Golf GTI envious, braking would have impressed a Formula 1 car and the noise wouldn't have been out of place in the Isle of Man during TT week.

I did all of the usual tweaks to starting voltage, acceleration and deceleration delay and was able to improve matters, but in the end I unplugged the Digitrax decoder and fitted my favourite Lenz Gold and immediately (without any fiddling to settings) the loco was transformed, and is now sweet as a nut!

So what? Well if all of the pundits are to be believed the major consideration when fitting a decoder is the number of function you'll need, but to me the most improtant factor is how well the loco runs when chipped, and experience of late suggests that the extra price of the top of the range Lenz decoders (Gold and Silver) is well worth paying even if you don't want all of the functions and facilities they offer.

John.

Reply to
John Turner
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Is the model now on sale?

Reply to
mingusbass

"mingusbass" wrote

I had planned to keep it, but if you want to make me an offer?

John.

Reply to
John Turner

Which does rather beg the question of why bother making a decoder that doesn't work very well ?

Cheers, Martyn

Reply to
M Roberts

"M Roberts" wrote

Who knows? Maybe the Digitrax decoder works fine with some mechanisms but just doesn't like the bog standard Mashima which is fitted to the class 15.

I'm told the Lenz LE1000 (allegedly the best selling Lenz decoder in the UK) is fine with British steam locos, but I can't do with the 'buzzing' which it generates. I can't say that I've sold that many, but that could be my influence on my customers.

John.

Reply to
John Turner

I'm interested also John, is it in green? Please email me direct with your asking price. Badger.

Reply to
Badger

I had almost exactly the same issue with a Digitrax DZ143 in a Bachmann Collet goods. Poor control, with very sudden starts, very non-linear across the speed range and noisy operation. I tried playing with the CVs but could not get satisfactory operation. I now use it to drive the lights in non-powered end of a Bachmann 158!

ROB

Reply to
Robert Flint

Or maybe it was faulty decoder, or maybe some part of it failed or simply aged. It's possible for what seems a minor flaw in the chips and associated bits to cause all kinds of wierd and (not so) wonderful problems. In The Olden Days with vacuum tubes (valves) and resistors you could use as a perch for your budgie (to warm it feet in winter :-)), changes in the components as they aged had little effect in the early stages. Not so any longer: micro-electronics just isn't as forgiving.

But as my mythical grampa used to say: It's cheaper to pay for quality once than to pay for trash three times.

HTH

Reply to
Wolf Kirchmeir

I have a Lenz 1024 in a DJH class 02 Shunter. Apart from the poor pick ups that I must attend to, it also does not have much control over the little motor. Maybe I should take out a second mortgage and buy a Lenz Silver !

Andy

I had almost exactly the same issue with a Digitrax DZ143 in a Bachmann Collet goods. Poor control, with very sudden starts, very non-linear across the speed range and noisy operation. I tried playing with the CVs but could not get satisfactory operation. I now use it to drive the lights in non-powered end of a Bachmann 158!

ROB

Reply to
Andy Sollis- Churnet Valley model Railway Dept.

This happens sometimes when mixing a decoder from one different manufacturer and a booster from another. Either your booster is on the borderline of the RPs for DCC signal or the decoder is or even both, both in opposite directions. One would hope that current DC decoders boosters are more compliant.

I have had no problem with a Digitrax DH140 and Digitrax DB150 booster. But when I tried a ZTC decoder with the DB150 I got the behaviour you have described. When the DH140 was released it was a premium decoder not budget/economy decoder. I have had no problems with TCS and Lenz decoders with the DB150, apart from a software bug in early versions of the LE103XF decoder.

Chris

Reply to
Chris

Which control station do you use as it might be a problem with the interaction between that and the control station.

Chris

Reply to
Chris

Another question is what speed steps are you sending to the decoder? And what is the decoder expecting?

Chris

Reply to
Chris

"Chris" wrote

It doesn't seem to matter with the Lenz Gold - set at any of the four settings it runs superbly. In my opinion this is how DCC should be - you shouldn't need to mess - after all there's no need with conventional analogue control.

John.

Reply to
John Turner

"Chris" wrote Another question is what speed steps are you sending to the decoder? And what is the decoder expecting?

Chris

Sorry, been away playing with a new SWD sound decoder in a class 24. I'm using a ZTC 511 and SPROG. All should(!) be set at 128 steps as I feel this is best (Maybe not always the case?)

Andy

Reply to
Andy Sollis- Churnet Valley model Railway Dept.

Phil: Communications speed-wise, 128 is not the best, as the controller has to send the full information. Most decoders, if sent only 14 or 28, use 128bits internally to ramp to the new speed, at a rate determined by one of the other CVs (one for accelerate, one for decelerate). On the ZTC hanheld 622, it cannot do 14 speed steps (although the main controller can) - which caused me a problem at a show when I had to suddenly use it for an LGB MTS system (decoders can do 14 or 28 or 128, but are set for 14 speed steps to be compatible with LGB MTS) - I could control a loco from the main controller, but not then hand it over to the handheld! (14 steps makes directional light control easier??)

Yes, on the MTS, I can see the speed changes with 14 steps (WHEN little or NO inertia has been set with the CVs mentioned above), but on 28 steps its harder to see, and for realism, perhaps we should be using FEWER to match the limited number of driving notches available on the diesel or electric locomotive??? 8-)

Reply to
Phil

On class 86s and 87s, the tap-changers had about 40 steps but any change in speed would be much more dependent on the weight being pulled and the gradient of the track, sometimes you would need to add another 10 steps to get any noticeable acceleration.

The class 90s were effectively continuously variable (the 91s were the same I think) in that there was a speed controller which was a variable resistor and this translated to speed control but I'm guessing in the electrics somewhere there is a finite number of steps that are actually handled and it would almost certainly be a binary weight number of 64. 128. 256 etc...

Luke

Reply to
Luke Briner

You mean more information, sending only partial information would not work with any scheme;-) The extra byte per packet is not going to make any practical difference.

A command station sending 28 step packets will still control a decoder set for 14 step operation but the lights will be erratic if FL (directional lighting) is used. The bit that controls FL in 14 step mode is the least significant speed bit in 28 step mode so the lights will go on and off as you send different speed commands.

While we're on the subject, which fool coined the term 128 step? By applying the same reasoning as used for 14 and 28 step, it should be referred to as 126 step mode.

MBQ

Reply to
manatbandq

Well you are probably using a Lenz booster/command station etc so it should work great together its when you mix different makes that you can encounter problems. The only decoders you can really be sure that work with all systems are those manufactures that do not make boosters/command stations such as TCS and South West Digital.

As you say it should be install the decoder set the address maybe also set the speed curve and go. Which is what I have found with Digitrax, TCS and Lenz decoders but not ZTC.

Chris

Reply to
Chris

I think you will find that command stations send out at best 28 steps and the decoder interpolates 128, or for newer decoders 256, speed steps for acceleration and de acceleration. As defined in CV29 bit 2 i.e. add

0 to CV29 for 14 speed step or 2 for 28 speed step see
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for a discussion on CVs and there values, Lenz in particular.

Chris

Reply to
Chris

Do you know this for a fact, or just basing it on the bits in CV29? The

14 and 28 speed step commands share the same packet format and need the bit in CV29 for backward compatibility with old decoders that were very limited in functionality.

The 128 speed step command uses a completely different packet format and CV29 is irrelevant. If a decoder support 128 step packets then it will do so, regardless of the value in CV29.

MBQ

Reply to
manatbandq

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