Caps Or No Caps (dcc 3f)

[Steve Cook]

A quick question for my learned colleagues
My 3F which ran fine on DC exhibits an annoying starting issue on DCC. Dial in a speed, the loco moves very slowly for 0.5 a wheel revolution, then jumps up to the set speed. Before I start playing around with the CV settings for start voltage etc, does anybody know whether there would be any benefit to cutting off the capacitors and resistors the loco is currently fitted with?



The 08 has no caps or resistors, the Black 5 and Hymek have just had chips fitted to the supplied plugs, thus I have a combination of some with caps and some without already. All of the other locos run fine, so I can't narrow it down to 'caps is bad'. Does anybody have any experience one way or the other they are prepared to relate?

Many Thanks
Steve

 

[John D]

For what it's worth....I enquired on an American forum as the running on the first Boxcab I built,using a Bachmann 70 tonner chassis, ran decidedly 'lumpy' and 'would fitting a chip sort it out'. The reply said to get rid of the capacitors before fitting chip and thinking about it WHY do they fit these things in the first place.......anybody suffered the wrath of SWMBO 'cos the telly's gone funny when you're playing trains?

 

[Arty]

I would have thought you would have had a flood of knowledge ?
As far as I understand the general concensus is that it may or may not make a difference depending on the decoder and or loco - which is no answer at all.
Decoders have their own protection to preserve the drivers in the electronics from motor generated interference which should solve the TV interference problem as well.
Having a suppression capacitor directly across the track theoretically would be bad news for the DCC carrier, but leaving suppression across the motor should be ok, but most manufacturers don't make sweeping statements about removing them or leaving them in.
Surfing the net will find you as many conflicting suggestions as you may have had hot dinners.

Rgds

Richard

 

[Steph Dale]

A quick question for my learned colleagues
My 3F which ran fine on DC exhibits an annoying starting issue on DCC. Dial in a speed, the loco moves very slowly for 0.5 a wheel revolution, then jumps up to the set speed. Before I start playing around with the CV settings for start voltage etc, does anybody know whether there would be any benefit to cutting off the capacitors and resistors the loco is currently fitted with?

View attachment 8736

The 08 has no caps or resistors, the Black 5 and Hymek have just had chips fitted to the supplied plugs, thus I have a combination of some with caps and some without already. All of the other locos run fine, so I can't narrow it down to 'caps is bad'. Does anybody have any experience one way or the other they are prepared to relate?

Many Thanks
Steve

Steve,

Yep, get rid of 'em. The running almost always improves and certainly won't get worse. I regularly remove from my (HO) r-t-r stock - some manufacturers have the sense to put the suppression on the blanking plug so it's removed when the decoder is fitted.

Otherwise it's a programming issue - you can improve the running by dialling out the feedback (what decoder is it by the way?), but I'd expect it to be better without half that junk fitted to the motor...

Steph

 

[Steve Cook]

Thanks for all of the replies, the concensous seems to be 'get rid of the buggers', so on that basis, I shall I'll report back.....

Otherwise it's a programming issue - you can improve the running by dialling out the feedback (what decoder is it by the way?), but I'd expect it to be better without half that junk fitted to the motor...

Hi Steph
Its a TCS EU621 decoder, currently reading the instructions on how to turn off the BEMF before getting the snippers out.

...anybody suffered the wrath of SWMBO 'cos the telly's gone funny when you're playing trains?

No No tv or SWMBO though

I would have thought you would have had a flood of knowledge ?

There is another department which deals with all of that, thankfully. I don't need to understand that bit to do my job, there's enough to learn about the mechanics and the logic system which controls it, supression etc is well outside my knowledge sphere (and interest )

Surfing the net will find you as many conflicting suggestions as you may have had hot dinners.

It did indeed, in fact, I'd be rather larger if I'd that many hot meals

 

[Steph Dale]

Hi Steph
Its a TCS EU621 decoder, currently reading the instructions on how to turn off the BEMF before getting the snippers out.

Yee-euch.

Steph

 

[Steve Cook]

Yee-euch.

Steph

Can I take it you don't approve then My only defence is it was the only 21 pin decoder I had in stock Haven't checked to see what is available from Lenz yet...

 

[Steph Dale]

I've had a couple (of different generations I might add) the programming was so variable in terms of ability to programme and the effects the programming had that I couldn't really give them a firm recommendation. Minimum speed was never acceptable and I couldn't guarantee that I'd ever really nailled the pulsing problem you describe. I've had and heard of volatility problems, so guess that's not a unique issue either. They also look 'orrible in terms of output if you stick 'em on an oscilloscope although I acknowledge that an oscilloscope is far from ideal in terms of load.

With agressive programming they can work well, but ESU and Zimo work better (and more repeatably) under the same conditions. Lenz Gold or Silver probably can do, but the manual doesn't cover the motor CV values.

As ever YMMV!

Steph

 

[Steve Cook]

Interesting Steph I've only ever fitted Lenz Gold to loco's and they have been 'fit and leave alone' in my experience, giving good slow speed running and decent progression.
As I've not tried either ESU or Zimo, perhaps now is a good time to do so. I shall have a surf for something suitable.
Ta
Steve

 

[Steph Dale]

ESU LokPilot v4 DCC 21MTC (item 54615) would be my recommendation, for what it's worth. It's a complete generation ahead of the Lenz Gold/Silver (yes, I know there have been several firmware updates) and it'd be interesting to see/hear what you think if you decide to try one.

Steph

 

[Steve Cook]

Cheers Steph, I'm easily persuaded
Having had a quick search, everything seems to be from Germany, any UK suppliers that you would use?
Steve

 

[Steph Dale]

DCC Supplies, Howes or Digitrains tend to be pretty helpful. You could always get it from SouthWest Digital though...

Steph

 

[Simon Dunkley]

I think it is supposed to be written as "3F" and not "3f", so caps for that.
(I am reaching for my coat.)

Otherwise, as has been written, my understanding is that suppression capacitors are not required for DCC, and may cause a problem, so no caps for that.

 

[Steve Cook]

You could always get it from SouthWest Digital though...

A good idea Steph - they didn't appear on the first couple of pages and I didn't even think to put them in - move over Jordan, I'm coming through

Response is significantly improved without all the gubbins. I intially tried just removing the capacitors but the pull away was still a bit ropey, so the resistors have been removed and the leads soldered directly to the motor. Another step change in performance for the better - its now officially borderline! Performance isn't helped by being able to watch the motor turn the centre wheels before the others move, a result of slop in the connecting rods and a generous clearance between the drive gears and motor worm. However, I'm getting picky here given the cost of the model, and its seems now to be running reasonably well in each direction.

A phonecall tomorrow to South West Digital to order Stephs recommended decoder is in order, I'll be able to compare performance between the two at that point. Might as well leave the the loco and tender bodies off for a while longer then

Thanks for all the help and advice, I'll keep this thread updated.

Steve