Colin's Work Bench

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The small one-off jobs behind the scenes

Introducing Colin's Work Bench

Before starting out in earnest to build my new Project, I decided that, like Jeff (SR Man), it would be good to separate the things I will be doing into layout related and work bench related. The latter starts here……..

(PS July 2022) addition of an index listing of my various ramblings which will follow. (Page and Post no #, but these are not hyperlinks!)

DCC Installs

Hornby Peckett p1(#1,#2)
SR 2662 p1 (#6, #7); sound p3(#42,#45,#46)

Small Prairie 4539; p1(#9), p2(#31, #36)

Track and control

British Finescale "Finetrax" Single Turnout Kits  p2(#22, #27, #29, #30)
"Finetrax" Single Slip Kit p4 (#61, 62)
"Finetrax" Freelance single rail Trap Point p4 (#64)

A kit built Capacitor Discharge Unit (CDU) p1(#10), p2(#21), p3 (#60, #68)

Misc.
NCE PCP spare interface p3(#55)
Bullhead Rail joiner tool p3(#56)

The above lists only my primary posts on each topic, in some cases there is follow on discussion
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As good a place to start as any is with my DCC installs.

I have had a backlog of DCC related purchases held up when the UK Royal Mail managed to lose a warranty return I'd entrusted them to get back to Youchoos several months ago. This failed Sound Chip of course continuing my long run of being able to find any dud out there in search of a customer! After the inevitable delays I finally just got my insurance payout and a big order has been placed.

My plans included various upgrades to existing stay alives and tidying up wiring on the less than satisfactory jobs.

First job onto the bench was my Hornby Peckett W4 Port of London Authority (R3679) which I DCC fitted with a small ZIMO Processor and SACC 16 stay alive in June 2020:

Peckett DCC Install
 
While it might look like a neat and tidy job, the one thing I was unhappy about was the long spool of very fine wires from the DCC which I ended up having to bundle up and tuck into a small space between the Capacitors and motor end with risks of fouling or applying pressure to the motor shaft, shown here.




BTW this shows the versatility of the SACC16 as you can snap off the tiny and thin control section (here sitting on top of the gear housing) and have your capacitors elsewhere.

The wires on the MX617 are incredibly fine and inevitably I damaged one when trying to better locate them. Hence a partial rebuild was in order……. TBC
 



This Post to here is full of formatted text so I'll just pop new additions below the line

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Opening a Dapol Cattle Wagon Link to Dapol Cattle Wagon surgery

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Peckett #74 Continued

This photo shows my original attempt to access the Ground pad for the Stay alive wire at the bottom of the chip, also the spaghetti of fine wiring is better seen when the Chip is pulled out.



The thick protective sheath on the chip is hard to cut selectively when you have no other option. I've since moved to the Youchoos method of fully removing the outer cover and replacing it with Polyimide (Kapton) tape to seal and insulate when done. This is best done with a new long scalpel blade run along the edge of the chip which will make the cut without risking damage any SMDs.

The six solder tabs on the top side sit very close and I found it just needed iron heat on the wire near to the tab to remove / add back a new wire.




The replacement wires are all DCC Concepts Gauge 32 Decoder wire (DCW-32BK  etc.). The blue and black at the LHS come from the two solder tabs on the rear lower of the chip, now all safely encased in polyimide and much thinner for it! I've gained about 1- 1.5mm extra gap with this easy slimming aid!

  I need my SACC 16 for another install so will be fitting a Youchoos Lifelink with some thin Tantalum Caps this time, when they arrive.

PS Useful Tip: Don't throw away the old chip sheath, it's very useful to protect the chip when soldering etc. where you need to hold it in a crocodile jaw on your soldering station.

 

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As you'll probably realise Colin, I'm following this closely - very closely !  ;-)

'Petermac
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Very nice. I always get worried inside a loco. I don’t have much confidence once the top is off. I’m usually worried if I can get the screws back in by that point as well!…
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Thx Peter, Chris.

There will delays to further posts I had lined up as our NBN Internet supply has gone down JIT for the weekend. 'Twas on the Monday morning……" etc.

Colin

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SR A1X TERRIER #2662 - DCC and Stay alive

This lovely loco made a fleeting guest appearance on Westown back in January and promptly stole the limelight:



Now it finds itself with the prospect of a proper home at Upper Hembury running services on the shared GWR / SR branch to Sidmouth Junction. Initially I'd just popped in a simple DCC with no stay alive and my troublesome insulfrogs were a bit much for it to handle.

 Due to recent changes I have a spare SA on hand so I've reworked and tidied up the DCC configuration and created enought space should I choose to add sound in future.

First step was to strip out the mounting where the 6 pin socket was held (I'd removed the socket and direct wired the 6 pin chip first time around). This is shown below (before cutting the mounting bracket and after). Removing the mount as per the Youchoos method frees up quite a bit of wasted space, there not being that much available in total!



Next; the Polyimide tape has been removed prior to adding the Stay Alive wires to the chip.

TBC . I've been summonsed to go for a walk!

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SR 2662 Continued

The chip I'm using is the Bachmann 36-358A which is a re-badged ZIMO MX622 6 pin, bought because I had an order into Rails at the time for my Loco purchase.

This shows the chip after I've cut away unwanted pins and shortened the other four. The Stay Alive +ve and Ground tabs were identified from the ZIMO manual and the blue and lower black leads attached before taping up securely.



With the Mount removed, the DCC chip sits snugly flat on the base in front of the motor,



The Stay Alive in two parts, Capacitors below ("L" shaped combination) and the tiny control module on top, together sit snugly on top of the DCC. If I were adding Sound, the the speaker would take the place of the SA components, a tight fit though.





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Very neatly done, Colin. I have a few of those Bachmann / Zimo decoders in use and they are very good.

I don't have any of the new Terriers, either from Hornby or Rails, but I have done four of the older Dapol / Hornby versions. Space is just as limited in those!  :roll:

Jeff Lynn,
Amateur layabout, Professional Lurker, Thread hijacker extraordinaire
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Small Prairie 4539 Revisited

This Bachmann is one of my favourite locos, a real workhorse of smaller GWR lines and one which had served me well until the sound chip developed a glitch back in May. Four months on and I finally have a replacement, thanks to its being lost somewhere in the UK by the postal service followed by inevitable delays while recouping the insurance.

I planned a proper reworking of the wiring as it is a very tight fit, as will be seen.

First up, I replaced the existing stay-alive with a newer smaller set of kit from Youchoos. This shows before and after:



The main difference is the space gained by moving to 470uF Tantalum Capacitors and replacing older electrostatics which are bulky and hard to place because of their shape. Here I just have two as the loco ran very well with that storage before but there is easily room for more.

The new Youchoos Stay alive pack is tiny and I'm looking forward to having them for my fleet of small locos




The beauty of using tantalums is the ease which they can be soldered in parallel, just using spare resistor wire off cuts.

The big challenge in wiring up this loco back thru to the cab / bunker is the very tight fit (width) between the chassis and the lower metal bodywork, barely 0.5mm total, a very snug fit. Hence any wire not securely held back will get pinched as the chassis is offered up to the bodywork. A nightmare I'd not resolved satisfactorily in the Mark I install.

A total of 5 wires are needed aft, two speaker wires plus common (+) and lines to the light on F2 for firebox, and Stay-alive circuit. In addition the two motor wires need to get to the rear of the motor area but these do have small channels just below the motor that can be used if the wires are secured forward.

The next photo shows part of the solution, the three wires other than the two ultramarine speaker wires will all sit very snugly in the channel between the metal and plastic parts of the bodywork if you carefully align them.



In this first effort I still had the speaker wires on the same side (from the original job); next I moved them over to the other side so they could also fit in its channel



With everything tidied up somewhat I repurposed the old mounting for the DCC socket into a cable clip to hold the power and motor lines tidy and forward away from the worm gear. The orange and grey wires to the motor can be seen to sit very neatly heading back alongside the gears once secured under the clip. Previously these two wires were loose and constantly getting trapped and squeezed during assembly.

 The new slimmer chip with Kapton tape and minimum excess wires now easily feed into the boiler space.
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When a Silver Lining emerged from the Dark Clouds of Incompetence in Action

Being comfortable with what has worked for me regarding Turnout motors over many years, I decided to stick with trusty solenoids but not before I'd asked opinions from a variety of users, several who operate large layouts. One consideration they raised was that of frog switching, of which more later.

Now I do know that there are many lovers of complex and more pricey devices named variously after the tortoise and cobalt and they do have their place. With no need myself for complexity of control with just 11 or 12 devices to switch, I went with the old trusty PL10.

On Westown-Heathfield I had a CDU driven system whose main limitation was my inability to install motors accurately aligned! Mostly it worked very well. Hence I went looking for the latest locally available CDU devices and came up with something rather interesting.

The local supplier has a very clever device that is in effect a bank of mini CDUs that offer direction indication. At a unit cost of A$8 or under 4 GBP (per turnout) all up including the switching and direction indication, it sounded almost too good to be true!

The concept is different. In a standard CDU setup, a momentary switch triggers the fully charged Capacitor to discharge through the solenoid coil in the selected direction. It then recharges quickly for any next action. In the device I'm using, the circuit remains closed, allowing for direction indication from the Module.

The CDU module (blue) is fed by a central capacitor which acts as a charge reservoir. The CDU switching is DPDT ON-ON so there is always one closed circuit in this design.

When the switch is moved to Position #2, current flows from the Reservoir through one Solenoid coil to charge up the Capacitor on the CDU module. Once the two Capacitor Voltages are matched, current flow through the solenoid is greatly reduced. There is however a minor path via an indicator LED to ground so a very low current continues to flow.

When the switch is reversed to Position #1, the circuit from the CDU Capacitor thru the other Solenoid Coil to ground is closed and the CDU Capacitor discharges. The design allows for A minor residual current flows via the other LED (circuit details not shown).

In essence, the CDU Capacitor is charged up from 0V via one solenoid coil then discharged down to 0V via the other solenoid coil when the switching is reversed.


The benefit of this is that using a DPDT switch, frog polarity can be switched at the same time as the turnout.
 

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Sol
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I use a similar circuit for my solenoids - the switch shown is normally a DPDT with the other pole switching the frog.
  the capacitor is 2200uf for one solenoid - & for two in parallel, I use a 4700UF.
I have the panels set up so in the normal direction of the turnout, the capacitors are discharged otherwise when power is switched on, all may attempt to charge up & overload the power supply. ( The same problem I had with the early DCC Concepts Masterswitches)

Ron
NCE DCC ; 00 scale UK outline.
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Thanks Sol,

One difference in the "Talking Electronics" circuit to your diagram, is the presence of the reservoir Capacitor.

I'll email you his circuit as it is posted on his website so I'm not free to put it up on here #

As I read his design, if the switch is set to "Siding" at power-up, there is no path to charge the Module Capacitor, current flows to charge the reservoir and just thru the "siding" LED to ground.

If the point is set to "main" then the Module Capacitor will charge up, along with the reservoir and the "main" LED is lit. With his 5 module setup there is no mention of overloading the PS but I might check back with him. It makes sense to have separate power bricks for each 5 CDU module I guess.

Colin


# anyone interested can find it on their website but beware as it is a bit of a rabbit warren!
Talking Electronics

Look for CDU -1,000uF slim NEW in the main sidebar
While it's not exactly the device I bought, the electronics are broadly the same





 
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Colin, thanks.
I have also used this
http://www3.sympatico.ca/kstapleton3/751D.HTM

Ron
NCE DCC ; 00 scale UK outline.
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[user=606]Sol[/user] wrote:
Colin, thanks.
I have also used this
Sol,

Have you any thoughts on the rating I'll need to power one of my banks of 5 modules? My points are lightweight so don't need a massive force and the travel is modest as well.

Colin

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Colin, I use a 19v laptop supply of  4.7 Amps & costs under $20 from E-Bay so the overload problem is reduced but I guess looking at that circuit you provided, a 2 amp supply would be adequate.

Ron
NCE DCC ; 00 scale UK outline.
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[user=606]Sol[/user] wrote:
Colin, I use a 19v laptop supply of  4.7 Amps & costs under $20 from E-Bay so the overload problem is reduced but I guess looking at that circuit you provided, a 2 amp supply would be adequate.
I've a 15VDC 4A supply that's going spare and checking back with the supplier that'll be more than enough for my needs. Thanks for your help,

Colin

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I'm in total awe of your chip wiring Colin - you must have very steady hands, a good eye and tiny fingers ………….. :shock:

I would really like to add some decoders and stay-alives to some of my non-DCC locos but thus far, I've been thwarted by the scale of the things - just too small for my fat fingers and wobbly hands ……… :cry:

Practice may improve my ability but decoders are rather too expensive to practice on unless you get it right !!  I've already had to bin a couple of MX617's just trying to solder the ground to that silly little pad ………….iron too hot ?  held there too long ? - whatever, it hasn't worked for me yet.  :sad:

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Hi Peter,

I know what you mean. Assuming you have a suitable small iron, try practicing on an old piece of circuit board from something redundant.

Typically I pull anything electronic apart once it fails for potential "opportunities in search of a need", odd diodes etc.

Try this technique:
Find a board with some very fine electronics, snip off a small component topside and excess wire if any beneath and practice soldering a spare DCC chip wire to the residual solder spot on the reverse.

Tin the trimmed wire first, then with iron not too hot, apply heat to the wire, not the solder point. Offer the wire still being heated to the spot and it should mate directly. This way you avoid direct heat on the DCC chip. You can have a short piece of fine heat shrink on the wire to pull up, if the bare section gives you concern.

Even if your test join is larger than your DCC, this way you'll get the idea and feel for the technique. 
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Thanks for those tips Colin - I'll certainly give it a go.  I have more than my fair share of circuit board with "bits connected" !!

'Petermac
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[user=6]Petermac[/user] wrote:
Thanks for those tips Colin - I'll certainly give it a go.  I have more than my fair share of circuit board with "bits connected" !!
small LEDs would be ideal as they are lightly soldered in (usually) being heat sensitive themselves
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