Fitting Decoders to the Bachmann class 66

A word of warning ! Clipping these capacitors off is all well and good for DCC, but do make sure it runs OK under DCC before you clip it.

I have had the mis-fortune of having a duff motor in a class 24, and because it is still under warranty, Bachmann wish me to send it back.... I'm not so sure as I have removed the capacitor, which I guess will either invalidate the warranty, or mean at the least if it is faulty, be charged for any repair or replacements!

Andy

"Ian Birchenough" wrote in message news: snipped-for-privacy@birchenough.demon.co.uk... Anyone had problems with the Bachmann 66 once chipped? Are there any capacitors that have to come off?

"Ian Birchenough" wrote

It's just plug & play (at least with a Gold decoder) but I snipped the capacitors to be on the same side.

Finest running large diesel model I've come across once Gold chipped.

John

I would advise the removal of any capacitor and inductor where fitted, when fitting a DCC module. The capacitor is a 'spark quench' for the old DC system and all DCC mobile modules have one incorporated in the circuit so it would be duplication. Capacitors in parallel, which it would be if left in situ, their values are additive. The greater capacitance could affect the DCC signal to the encoder.

At Wed, 08 Jun 2005 16:19:33 GMT, message was posted by "Chris" , including some, all or none of the following:

I forgot to do that (or rather, didn't know not to - RTFM!) the first time. The first decoder was somewhat - ahem - degraded as a result.

Guy

--

"To every complex problem there is a solution which is simple, neat and wrong" - HL Mencken

Encoder?

Any capacitors across a motor are isolated from the DCC signal on the track by the decoder circuitry and have no effect on the DCC signal. It has nothing to do with adding to any suppression built into the decoder.

The motor output of the decoder is pulse width modulated (PWM) effectively an AC signal (but not the same as the DCC signal) and this is why suppression components (capacitors and inductors) affect the running of locos. They present a varying impedance to the decoder depending upon the PWM frequency (which can be varied in some decoders) and the capacitance or inductance value.

Suppression components designed for DC use are exactly the opposite to what we want for DCC, which uses an AC drive to the motor. Inductors block AC and an inductor in series with the motor (in DC designed to prevent interference getting back to the track) will attenuate the motor drive. Capacitors block DC but conduct AC and a capacitor across the motor (in DC designed to suppress interference as noted by Chris) will shunt some of the motor drive away from the motor. The characteristics of the motor also come into play due to the series and parallel combination of the motor and suppression components.

Unless you analyse the circuitry of each individual decoder (accounting for all possible PWM frewuencies), suppression and motor combination it is very difficult to predict what the results will be. This is why some people report good results leaving suppression components in place. The best policy is to always remove the suppression components.

Andrew

wrote

I may be misunderstanding what you're trying to say, but surely with DCC although the track voltage is AC the drive to the motor is rectified by the decoder and as a consequence is DC not AC.

John.

You are correct John. Andrews comment about Pulse Width Modulation being AC is wrong. An AC voltage or current has a positive and negative component hence the name alternating whereas PWM is pulsed DC i.e short pulses width give a slow motor speed and long pulse width give a faster motor speed till eventually the motor could - note could - be fully turned on. I am using Lenz, Digitrax, NCE decoders and you know what they say "if all else fails read the instructions" and without fail they all say make sure the motor brushes are totally isolated and any capacitors are removed. I'm a bit long in the tooth and the only system I can remember that insisted that a spark quench condenser oops! capacitor be installed and they provided one if one wasn't fitted was Hornby's Zero 1. their rational behind this was a spark contains all the odd harmonics to infinity and hence RFI would cause problems but you all know that anyway :-).

Sorry, I must have had a brainstorm. The motor drive is pulsed DC and not AC.

I'll get my coat...

Andrew

Yes, but apart from the misuse of the term AC the rest of your argument is sound, the inductance and capacitance effects you describe are equally valid for DC pulses as its the rate of change of current that matters. Keith

Make friends in the hobby. Visit Garratt photos for the big steam lovers.

This could go on and on so this is my final gripe. A Capacitor is a DC block pulsed DC or not. A discharged capacitor will allow current to flow whilst charging and will be deemed fully charged when 5xCxR (5CR's) has elapsed when it blocks DC till it is discharged when the cycle repeats itself. I believe SCR's (Silicon Control Rectumfriers oops Rectifiers) rectify the AC from the track and the control part of the SCR is pulsed to apply pulsed DC to the motor. I also understand that Hornby are developing a DCC system. Has anyone any idea if it is NMRA compatible?

If Hornby try to push a non-nmra system they will be wasting a lot of effort and money! Fleischmann and others have tried this and have had to give in and change to nmra standard. Only Maerklin have been able to do their own thing, and that only because their 3-rail AC system gives them a huge captive customer base. Keith

Make friends in the hobby. Visit Garratt photos for the big steam lovers.

"Keith Norgrove" wrote

I think they'll be wasting time and effort anyway, but I can understand why they will want to go along this route. Equally so I think Hornby believe they can do no wrong, so whatever system they come up with, NMRA compliant or not, they'll just go their own sweet way.

I think there's already enough choice in the DCC field, and unless someone is able to produce a high quality, high specification, NMRA compliant system at a significantly lower price than is currently available then I see little point.

John.

The DCC signal is rectified with a bridge rectifier to provide DC traction power. This is regulated to a lower voltage to power the microcontroller that generates the PWM signals based on the incoming commands. The motor drive is a MOSFET H bridge. I'd be confident to assert that this is true for at least 99% of all commercially available decoders.

What you describe sounds more like a DIY system once produced by Maplin, 20 years ago, and maybe Zero-1 but I don't know about that.

Andrew

"John Turner" wrote I think they'll be wasting time and effort anyway, but I can understand why they will want to go along this route. Equally so I think Hornby believe they can do no wrong, so whatever system they come up with, NMRA compliant or not, they'll just go their own sweet way.

John.

I would be suprised if Hornby were going to all this trouble to now backdate all their old locos with 8 pin sockets only to go alone with their own system? They really would be shooting themselves in both feet if it was not NMRA complient etc or even on a par with the Bachmann Eee Zee system... Hopefully it will be better - although the recent live steam may serve as an example and support your theory John... :-(

Andy

"Andy Sollis- Churnet Valley model Railway Dept." wrote

I'd say that the Bachmann system is probably NMRA compliant, but not necessarily NMRA compatible. Gulp, now explain what you mean.

Basically the Bachmann system is produced by Lenz, but because Bachmann are going along this route in a fairly half-hearted manner (they seem unwilling, for instance to produce DCC equipped locos without capacitors) that they are trying to modify their system to cope.

The latest 36-550 decoders (Lenz LE1014 in a bigger box) are no longer default configured in the same way as the standard Lenz chips. Consequently you can't just bang one in a conventional Bachmann DCC-ready loco and expect it to work properly with any other DCC command centre (including those made by Lenz). I believe they've disabled the silent drive, changed some performance curves, and certainly adjusted starting voltage and acceleration and deceleration delay. A big mistake in my opinion.

What's betting that Hornby won't so something similar?

John.

"John Turner" wrote

The latest 36-550 decoders (Lenz LE1014 in a bigger box)

A big mistake in my opinion.

What's betting that Hornby won't so something similar?

John.

Apologies for how I have snipped the post, I'm not trying to twist what you wrote, I can assure you !

Frankly, I don't see why either firm needs to bugger about with a third parties decoder when they are good enough off the shelf in the first place... To be honest, I was thinking along the lines of a Controller only anyway, still using the excellent range of chips like Lenz or TCS... So why should they need to deviate away and make something up? But , like you say, I bet they will...

I think (not discounting a controller) that their time and money would be better spent on R & D for sound or lights (in the locos not currently fitted, that can be done at an acceptable mass produced product (maybe with the ability to change\add further sounds?) to keep the cost down for the people who may not want it....

Andy

In message , John Turner writes

Ah could this be why my 66's are not happy? Is there a method of resetting them so they work as any normal compatible decoder?

"Ian Birchenough" wrote

Not that I've found. Previous batches could be reset by writing '33' to CV8, but it appears that they have different default settings to previous batches.

My recommendation would be to try a Lenz Gold decoder in your 66 - that way you'll see just how well your loco is capable of running, and then having proved the point get the Bachmann decoder back to your supplier and ask for a refund.

Bachmann have not made any announcement about the apparant changes in default settings, but if you compare the instruction sheet which accompanied the decoder and compare it with those of a standard Lenz LE1014 you'll see the differences. In my opinion these changes make the 36-550 not fit for general DCC use, although they *may be satisfactory* for use with Bachmann's E-Z Command system/

John.

And I believe that Bachmann are also looking at fitting sound chips to the

66's............ £38 is the minimum price I've heard, but Bachmann say that this would push the RRP of the 66 over the "magical" £100 mark, which they're not prepared to do. Even though this would obviously be discounted down by *some* retailers to below £100.

Cheers, Mick