DCC chip?

[Kettering Junction]

I know nothing about DCC (although I plan to upgrade in the future) and upon stripping my City of Bristol loco for servicing, I discovered this. No idea if it’s a sound chip or something else, but could someone identify it? Theres also 2 small wires under the pony truck, which attach to the tender connection. I broke one of these off but it doesn’t seem to affect the running.

[96RAF]

That is a blanking plate that allows the loco to run on DC. To convert it to DCC you replace that plate with a decoder with a matching pin configuration (in this case 8-pin). A sound decoder will come with a suitable speaker, but some locos require modelling skills to get a sound decoder and speaker installed.

The broken wire at the loco-tender interface is to connect the tender wheel pickups to the loco for more reliable running and should be re-connected even if just to prevent a short circuit.

[P-Henny]

Just to expand on what 96RAF has written.

A DCC decoder is wired in series between the wheel pickups and the motor. Thus the decoder socket is installed in series with that wiring route. If no decoder is fitted and the socket is empty, then the circuit between the pickups and motor would be broken and open circuit and the loco wouldn't run.

So a DCC Ready loco that has the socket factory fitted includes the 'blanking plate' that 96RAF mentions. This substitutes the basic connectivity of the decoder to provide a connection between the pickups and motor to allow the loco to run on DC.

All the different types of decoder have their own versions of 'blanking plate', whether that be 4pin, 6pin, 8 pin, 18pin, 21pin etc.

Thus the conversion to full DCC requires the 'blanking plate' to be removed and replaced by the decoder. The 'blanking plate' should be kept and stored safely as it is useful when needed to test the loco back on DC if a decoder fault is suspected.

[LesXRN]

Hi KJ.

On a seperate note, take a look at the bottom most centre motion rod in your picture, it looks as though it is bent towards the wheels slightly, it should be straight. A gentle pull should fix it.

Cheers. Les.

[Kettering Junction]

Thanks all. Appreciate the detailed replies. Much more in the ‘loop’ now.

Les - I hadn’t noticed that, however she is quite noisy going forward but silent in reverse. Could that be the issue. Like a clunking/tapping sound?

[Kettering Junction]

Unfortunately I’ve had a few issues with City of Bristol. Took her apart for a service, put back together and its running terribly. Judders, won’t do one smooth lap of the layout, and the cylinder box just wobbles regardless of how tight I screw it back in. Also, the engine used to run on its own, now it won’t even power up without the tender connected up. I am a novice, but have taken things apart before, this has stumped me though. One of the wires from the engine has come adrift but it was working fine previously, even with it disconnected. I’m stumped, and annoyed with myself!

[Fishmanoz]

If it won’t run without the tender, that’s a strong indication the pickups to the loco wheels are disconnected. That’s probably the result of your broken wire and the cause of your poor running given only tender pickups working.

[Kettering Junction]

Thanks for your help. Decided to strip and start again. Running as good as new so guess I missed something! Only issue is the screw for the conrod box (not sure of the real name!) will not hold it in place fully. Same screw as previous but the box is a bit wobbly. Any suggestions?

[96RAF]

A drop of PVA glue under the cylinder block flat plate may help retain it against movement.

This diagram may help with the broken wire on the live drawbar.

[Kettering Junction]

Excellent thanks, I’ll give that a try. I just find it strange that it fitted lovely before but now it’s loose!