Hornby R378 - 4-4-0 DCC install

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aleopardstail
Posts: 314
Joined: Thu Apr 29, 2021 9:48 pm

Re: Hornby R378 - 4-4-0 DCC install

Post by aleopardstail »

I made a thing

Image http://www.aleopardstail.com/IMG_3075.JPG

Was looking at stay alives, wondered "whats in one of these anyway?" turns out its one or more capacitors a diode and a resistor, well the shelf above me has no shortage of any of them.. so I had a go, and while 440uF (a pair of 220uF) isn't much it showed two things, well three

1. soldering the ground wire to the MX600 is a royal PitA
2. it works
3. 440uF isn't enough, runs for maybe quarter of a second to half a second

still a bit stop/start and obviously doesn't help with start from zero if there is rubbish contact, however once moving its generally better - a lot better forwards than reverse for some reason.

these are cheap capacitors, more a case of wanting to test if this actually helped, it does, quite a lot, before getting a proper one or hard wiring the loco and tender and stuffing the loco body with a few 2,200uF capacitors. space was a bit limited hence these (I wanted to shove in a pair of 470uF, but the ones I have are 50V rated and thus larger than they could be. such is life.

but nothing blew up
Bigmet
Posts: 10333
Joined: Tue Aug 14, 2007 2:19 pm

Re: Hornby R378 - 4-4-0 DCC install

Post by Bigmet »

aleopardstail wrote: Tue Jun 11, 2024 10:19 pm I made a thing... nothing blew up.
That's a thing alright!

A quarter second should be ample to overcome intermittent poor contact, I feel your proposal to make soldered connections from loco to tender is likely to deliver considerable improvement. My general contempt for Margate Hornby's electrical arrangements can be found in older posts on this site. Reliance on a series of face contacts to make the circuit, with soldered connections restricted to inside the motor, is doubleplus ungood. Unreliable on DC, distinctly DCC unfriendly.

Some improvement may be possible by setting the decoder 'time out' on loss of supply to zero. I resorted to this on a couple of Lenz decoders fitted in a couple of the first Chinese Hornby loco drive steam productions when starting out in DCC, until the penny dropped that Hornby's continued use of the chassis block in the pick up path led to momentary shorts between the coupling rods (which were live to chassis) and the tyres of the insulated side driven wheels.

Isolating the chassis block by nothing more complex than a soldered on wire to what had previously been a loose wiper with a cast projection on the chassis block to make that 'live' completely fixed this problem. Applicable to such as 8F, Q1, Duchess, A3, A4, (and probably several more not sampled) until Hornby got with the programme on their 2006 introduction of the Britannia, which was properly RTR for DCC out of the box, (among other desireable features) which arrangement thereafter slowly replaced the bad old Margateness...
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