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Hi All

Having read a few posts regarding capacitor removal to improve running when converted to DCC I decided to look inside my Bachmann 108 DMU but failed to find any capacitors.

Should there be any? and am I missing something?

Any info would be welcome.

Cheers Mike

PS I was led to beleive that all loco's should be fitted with capacitors from new.
 

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QUOTE (mikebiggles @ 30 Sep 2008, 19:02) <{POST_SNAPBACK}>Hi All

Having read a few posts regarding capacitor removal to improve running when converted to DCC I decided to look inside my Bachmann 108 DMU but failed to find any capacitors.

Should there be any? and am I missing something?

Any info would be welcome.

Cheers Mike

PS I was led to beleive that all loco's should be fitted with capacitors from new.

*** All locomotives produced for sale specifically within the UK will have some form of suppression, and this will always include capacitors. Some US prototypes may not - it depends on the source of the importation.

On some of the newer production models the usual easy to see ceramic disc capacitors have been replaced by chip (Surface mounted) components on the printed circuit boards. These are a little harder to locate, as are the small disc types Bachmann also place under the motor on occasion.

regards

Richard
 

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Discussion Starter · #3 ·
QUOTE (Richard Johnson @ 30 Sep 2008, 14:41) <{POST_SNAPBACK}>*** All locomotives produced for sale specifically within the UK will have some form of suppression, and this will always include capacitors. Some US prototypes may not - it depends on the source of the importation.

On some of the newer production models the usual easy to see ceramic disc capacitors have been replaced by chip (Surface mounted) components on the printed circuit boards. These are a little harder to locate, as are the small disc types Bachmann also place under the motor on occasion.

regards

Richard
Thanks for the info Richard

Cheers Mike
 

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Any product placed on the market in the EU, wherever it was actually produced, will have to meet all relevant EU standards. Some of these standards cover permitted levels of radio frequency interference from model railways.

It is up to the manufacturer to deal with this problem, and most choose to provide capacitors in parallel with the motor. However this isn't universal - the more recent Bachmann Farish locos use inductors in series, and older Bachmann Farish diesels (including many still in the current range) don't have any suppression at all.

Personal imports from non-EU countries need not comply with EU standards. I believe it is legal to bring in and use these products in most cases, with some exceptions including radio transmitters using frequencies that are not available in the country of use.
 

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QUOTE (Edwin @ 6 Oct 2008, 15:54) <{POST_SNAPBACK}>the more recent Bachmann Farish locos use inductors in series,

***DC motor suppression circuits always use both capacitor in parallel with motor leads and inductors in series - they form a useful suppressor only when working together and without both it simply won't work.

Newer loco's have chip capacitors which are harder to spot, but they wil be there.... and should be ditched.

the inductors really do no harm though, and can be left in place if desired.

Richard
 

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QUOTE (Edwin @ 6 Oct 2008, 08:54) <{POST_SNAPBACK}>Any product placed on the market in the EU, wherever it was actually produced, will have to meet all relevant EU standards. Some of these standards cover permitted levels of radio frequency interference from model railways.

It is up to the manufacturer to deal with this problem, and most choose to provide capacitors in parallel with the motor. However this isn't universal - the more recent Bachmann Farish locos use inductors in series, and older Bachmann Farish diesels (including many still in the current range) don't have any suppression at all.
I think you have to be careful which specific locos you refer to. The BachFar 04 has only caps, on a small circuit board on the end of the motor. I left these in place with no problems with a Zimo MX620. The Jubilee, I'm not sure about, again I left them in place with no problems. ALL of my older BachFar and Farish have (or had) at least a ceramic disc across the motor. Indeed, in the steam outline ones, the leg of the cap is crimped to the chassis and is a convenient way to get a connection to the chassis block.
QUOTE Personal imports from non-EU countries need not comply with EU standards. I believe it is legal to bring in and use these products in most cases, with some exceptions including radio transmitters using frequencies that are not available in the country of use.
Correct. There's also no problem in removing capacitors from your own locos.

Andrew
 

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QUOTE (SPROGman @ 6 Oct 2008, 15:44) <{POST_SNAPBACK}>I think you have to be careful which specific locos you refer to. The BachFar 04 has only caps, on a small circuit board on the end of the motor. I left these in place with no problems with a Zimo MX620. The Jubilee, I'm not sure about, again I left them in place with no problems. ALL of my older BachFar and Farish have (or had) at least a ceramic disc across the motor. Indeed, in the steam outline ones, the leg of the cap is crimped to the chassis and is a convenient way to get a connection to the chassis block.

I was referring to older Bachfar diesels, I've personally dismantled a 47, 158 and 170 and from what I see on the web the others are pretty similar. No capacitors in any of them.
 

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QUOTE (Edwin @ 6 Oct 2008, 18:46) <{POST_SNAPBACK}>I was referring to older Bachfar diesels, I've personally dismantled a 47, 158 and 170 and from what I see on the web the others are pretty similar. No capacitors in any of them.
Well, so was I, as well as steam. The class 20 and 101 certainly had capacitors. I say had, as I did remove those when chipping them.

Andrew
 

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QUOTE (mikebiggles @ 30 Sep 2008, 11:02) <{POST_SNAPBACK}>Hi All

Having read a few posts regarding capacitor removal to improve running when converted to DCC I decided to look inside my Bachmann 108 DMU but failed to find any capacitors.

Should there be any? and am I missing something?

Any info would be welcome.

Cheers Mike

PS I was led to beleive that all loco's should be fitted with capacitors from new.

They are surface mount components on the underside of the printed circuit board in the base of the driving unit which you can only see by unscrewing the board and turning it over.

Decided to leave them on this occasion and it seems to run quite well if you fix the inherent pick up problem caused by the brass rubbing strips-I have hard wired round these otherwise you tend to get intermitent pick-up unless your track is laid on marble!!
 

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QUOTE (SPROGman @ 6 Oct 2008, 17:50) <{POST_SNAPBACK}>Well, so was I, as well as steam. The class 20 and 101 certainly had capacitors. I say had, as I did remove those when chipping them.

Andrew

The Bachmann split chassis, which I still maintain has no capacitors, has been fitted to (off the top of my head and as far as I'm aware) classes 25, 31, 33, 37 (not latest 37/0), 40, 44, 45, 46, 47 (not forthcoming version), 50, 52, 55, 56, 158 and 170. All but the 170 were previously produced by Farish using a different mechanism.

The 08 (not the forthcoming one) and the 20 are different. Like the steam locos the Bachmann versions still use essentially the same mechanism as the previous (UK) Farish products. Bachmann have never produced the 101 as far as I'm aware, and certainly not with the new mechanism.
 

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QUOTE (Edwin @ 7 Oct 2008, 05:03) <{POST_SNAPBACK}>The Bachmann split chassis, which I still maintain has no capacitors, has been fitted to (off the top of my head and as far as I'm aware) classes 25, 31, 33, 37 (not latest 37/0), 40, 44, 45, 46, 47 (not forthcoming version), 50, 52, 55, 56, 158 and 170. All but the 170 were previously produced by Farish using a different mechanism.

The 08 (not the forthcoming one) and the 20 are different. Like the steam locos the Bachmann versions still use essentially the same mechanism as the previous (UK) Farish products. Bachmann have never produced the 101 as far as I'm aware, and certainly not with the new mechanism.

***You are quite correct in that suppression parts are rarer on split bachmann chassis loco's in both OO and N... in fact they are rrare in N scale generally. I presume its because with split chassis the motor is completely encapsulated in the much higher mass of the cast metal of the chassis so doesn't radiate like an unshrouded motor.... or that the very much smaller motor doesn't radiate enough to require suppression.

(In OO scale, I've wondered if these two large bits of closely parralel metal insulated from each other but physically close are in fact a capacitor in their own right!)

Richard
 

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QUOTE (Richard Johnson @ 7 Oct 2008, 06:32) <{POST_SNAPBACK}>***You are quite correct in that suppression parts are rarer on split bachmann chassis loco's in both OO and N... in fact they are rrare in N scale generally. I presume its because with split chassis the motor is completely encapsulated in the much higher mass of the cast metal of the chassis so doesn't radiate like an unshrouded motor.... or that the very much smaller motor doesn't radiate enough to require suppression.

I think there are two separate issues here. A split chassis would to some extent block the direct RF emissions from sparking brushes, but then again all modern motors including this one are in metal cans which would do the same thing. The other issue is that the connecting wires and rails act as an aerial to turn current spikes from the motor into RF emissions. These spikes include much higher frequnencies than the normal motor current - the capacitor conducts at high frequencies so shorts them across the motor so they don't get near the wires, and the inductor in series blocks them by presenting a high impedance at these frequencies. Without capacitors or inductors the decoder should prevent these spikes getting back into the rails, though there is still the risk of emissions from the wires between the decoder and the motor.

Anyway Bachmann have got this chassis on the market so they must have tested and decided that they don't need capacitors or inductors to meet required interference levels. As the motor currents are smaller than the spikes may be too. Oddly enough though, the later BachFar diesels (class 66 onwards) are of very similar mechanical contruction but include a PCB with inductors and solder pads for a decoder. There are various other components too, I haven't checked whether any are capacitors and I might also try and work out if the suppression components are still in circuit when a decoder is fitted.
 

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QUOTE (Richard Johnson @ 7 Oct 2008, 06:32) <{POST_SNAPBACK}>(In OO scale, I've wondered if these two large bits of closely parralel metal insulated from each other but physically close are in fact a capacitor in their own right!)

From dimly-remembered A level physics, refreshed by a visit to the internet, the capacitance in farads of an air gap is the cross-sectional area divided by the separation multiplied by epsilon-nought.

So taking optimistic values your split chassis could have 50cm2 cross-section (0.005m2) and 0.5mm air gap (0.0005m). Epsilon-nought is 8.854E-12 so your capacitance would be about 9E-11 farads or 90 picofarads or 0.00009 microfarads. Probably too small to worry about...
 

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QUOTE (Edwin @ 7 Oct 2008, 16:06) <{POST_SNAPBACK}>From dimly-remembered A level physics, refreshed by a visit to the internet, the capacitance in farads of an air gap is the cross-sectional area divided by the separation multiplied by epsilon-nought.

So taking optimistic values your split chassis could have 50cm2 cross-section (0.005m2) and 0.5mm air gap (0.0005m). Epsilon-nought is 8.854E-12 so your capacitance would be about 9E-11 farads or 90 picofarads or 0.00009 microfarads. Probably too small to worry about...

It was idle speculation and not much more than that, but thanks for the refresher on calculation - It brings back memories of labouring over such things in pre-calculator days ....its many a year since I've bothered with any of that!

Richard
 

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QUOTE (Richard Johnson @ 7 Oct 2008, 08:12) <{POST_SNAPBACK}>
It was idle speculation and not much more than that, but thanks for the refresher on calculation - It brings back memories of labouring over such things in pre-calculator days ....its many a year since I've bothered with any of that!

Richard

A learning experience for me too!
 

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QUOTE (BVM @ 6 Oct 2008, 17:58) <{POST_SNAPBACK}>They are surface mount components on the underside of the printed circuit board in the base of the driving unit which you can only see by unscrewing the board and turning it over.

Decided to leave them on this occasion and it seems to run quite well if you fix the inherent pick up problem caused by the brass rubbing strips-I have hard wired round these otherwise you tend to get intermitent pick-up unless your track is laid on marble!!
That is interesting. I have a three car set and a twin set of 108's. They both run very well with the inestimable TCS MC2's and FL2's and without the capacitors being removed; They also run well in consist (multiple). With respect to the intermittent pickup, there is evidence that the trailer car of the 3 car set has a problem, i.e. flickering lights, which needs looking into. The latest Class 25/1, with lights runs smoothly with capacitors left in. It would be intriguing to have a matrix indicating which locos run ok with capacitors left in and which don't. I have formerly been of the opinion that capacitors do need removing, as a matter of course. This has led to the need to brush up soldering due to the unfortunate snip here or there!

However, I have got the latest G2A, which needed the capacitors removing so that it would run well. Luckily the chassis and the body separate easily and the capacitors (all three of them) are easily accessed and so easily removed.

I wish there was a protocol within model making which designed in easy access for these capacitors.

Regards,

Hugh Williams
 

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Re the Bachmann G2A - my mate got his DCC fitted one yesterday & not touched a thing & it runs sweetly on Step 1 of NCE Powercab.
I have removed some caps of some locos depending on how they run before I put the body back on.
 

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Hi All

I just wonder if the capacitors interfere with the Decoder's BEMF

A few of my older conversions I ended up switching the BEMF off and utilized the Dither (TCS decoders only)
as the lumpy running of the 3 pole motors , with BEMF on , caused the loco to move forward in little surges at slow speed

But with the Dither adjusted properly they really crawl along nicely and smoothly

Dither is like a "super pulse power" it really did the trick for the older loco's

I'm not knocking the BEMF because in most off the newer loco's it works fantastic.
Just that there are other things that can help with better running -some times it pays to experiment a bit

Regards Zmil
 

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QUOTE (zmil @ 8 Oct 2008, 09:43) <{POST_SNAPBACK}>Hi All

I just wonder if the capacitors interfere with the Decoder's BEMF

A few of my older conversions I ended up switching the BEMF off and utilized the Dither (TCS decoders only)
as the lumpy running of the 3 pole motors , with BEMF on , caused the loco to move forward in little surges at slow speed

But with the Dither adjusted properly they really crawl along nicely and smoothly

Dither is like a "super pulse power" it really did the trick for the older loco's

I'm not knocking the BEMF because in most off the newer loco's it works fantastic.
Just that there are other things that can help with better running -some times it pays to experiment a bit

Regards Zmil

***Capacitors always interfere in some way between loco motor and decoder, the issue is simply that some motor + capacitor combinations have markedly less impact than others.

The difference in effct loco to loco is related to both the tpe of parts AND the layout of those parts between where the wires join to the PCB of the decoder and the motor brushes.

In all analog RF related circuitry the actual component parts are only part of the answer... component layout has also always had a marked effect on performance and this sort of application is no different.... physical layout configuration of the parts and wiring has an effect here in the same way that combinations of inductor and capacitor value do to the degree of suppression.

Removing them is therefore always wise but pragmatically of course, it is a matter of choice as loco/decoder combination will never run better with them in place ....however in some cases the effect may be insignificant to the loco owner.

As a professional I'll always take them out when I install a decoder: Whether an individual does so is his own decision.

To me I suppose the sensible question is, as modellers rarely enjoy the act of disassembling a loco + installing a decoder and always taking them out results in never having to do that job twice, why would you ever leave them in.

Richard
 

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Hi All

I must admit I remove everything that looks like an unnecessary electrical component , diodes , RF chokes , Caps etc
The decoder does the whole job anyway , for directional lighting , suppression etc
Although I have been thinking about putting a 100uf Cap across the Internal Lighting on my DMU's to even out the flicker from the LED's when going across points etc. The LED's react so fast to power outage compared to the 30mA globes of the directional lighting

Regards Zmil
 
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