4 Pin Decode Stay / Keep Alive

[Dave Liptrot]

Evening,

I am looking to install a stay / keep alive capacitor into the 0-6-0 Class 08 that comes as a part of the mixed rail set. Has anyone got any experience fitting a capacitor to the 4 pin R7274 decoder included if it is even possible?

TIA,

Dave

[Chrissaf]

The number of pins is somewhat immaterial. The principle of connecting a 'stay alive' is the same  for most decoders. One thing that is common for all decoders, they have a bridge rectifier on them to convert the Bi-polar DCC track voltage to DC to power the decoder circuitry. To fit a 'stay alive you just have to identify the positive and negative DC side of the bridge rectifier and connect your 'stay alive' to those two locations.

.

Note that 'stay alives' are polarity sensitive and must be fitted the correct way round. The positive of the 'stay alive' connects to the positive output of the bridge rectifier and the negative side of the 'stay alive' connects to the negative side of the bridge rectifier.

.

I suppose your next question is going to be, how do I identify the positive and negative output of the bridge rectifier on the decoder?

.

Well identifying the connection points is the relatively easy bit - see image below. The hard bit is having the skill and the right soldering tools to solder the 'stay alive' wires to the bridge connection locations without making a 'pigs ear' of it.

.

/media/tinymce_upload/e2175a55da294d2706f5c27413395f78.jpg

.

If you don't feel confident on your ability to perform this soldering task. Then I suggest that the easier option is to purchase a non Hornby decoder that already has the 'stay alive' fitted as an option and if necessary convert whatever the included plug provided on the decoder (6 or 8 pin for example) to a 4 pin plug. The 4 pin plug parts are standard Du-Pont 2.54" pitch female connectors available online.

.

/media/tinymce_upload/7c702f0c4e95a726710e73ee7d222025.gif

TIP: As a newbie poster on the forum, just be aware that the 'Blue Button with the White Arrow' is not a 'Reply to this post' button. If you want to reply to any of the posts, scroll down and write your reply in the reply text box at the bottom of the page and click the Green 'Reply' button.

.

Particularly as my reply includes an image, using the 'Blue Button' may result in your reply being held back for image approval, even though it is an existing image.

.

See also – further TIPs on how to get the best user experience from this forum.

https://www.hornby.com/uk-en/forum/tips-on-using-the-forum/

.

[ColinB]

When I did this to my Hornby TTS decoder, instead of adding just a capacitor I added a YouChoos "stay alive" circuit. It adds some extra components to the "Stay alive" circuit, it also makes reading CV easier, which you cannot do if you just add a capacitor.