Converting R392 County of Bedford to DCC

[Johnbw]

I have been attempting to convert the old Hornby County of Bedford to dcc without success.  It runs very well on DC but is a non runner on DCC so I wonder whether I have made some mistake in the conversion along the way.

I have isolated the brush contacts using plastic kadee screws (just in case) and connected the orange wire to the left hand tab and grey wire to the right tab, and the feed from the loco pickup to the red decoder wire,  and the black decoder wire to the tab on the front of the block which I assume picks up the power from the tender wheels.   Is that corrrect? it is the last one that I am uncertain whether I am correct or not.  

I have checked the new Hornby decoder and it working fine on my ESU tester.

I have looked for similar conversions on line without success.  Any help would be appreciated.

[ColinB]

I converted this loco to dcc. I cheated on this, the ringfield motor on this is the same as the Henry drive unit that Peters Spares sells. The big advantage is with this one it is a 5 pole motor and slots straight in, plus it has pickups on both sets of wheels on the tender.

It sounds like you are doing the right thing, the wiring sounds correct. What you should do is wire a socket in so you can change from dc to dcc by just changing the header, that is the way I do it, it saves a lot of time. What it may be, when you replaced the screws you disturbed the brush retainers, so the brushes may no longer be touching the armature, so with a multimeter check you have a resistance reading between the two brush clips. It happened to me when I was converting one of my ringfields. What might be good idea is to remove the orange and grey wires ( to prevent damage to the decoder) and check that the motor still runs with just dc.

Did you know on these, you can rewire the loco so it picks up on both wheels. If it is the same as mine there is no connection to the chassis of the loco, the loco power comes off wipers. So if you make a connection to the chassis and replace the pin connection with a plug and socket, you have pickups from both loco wheels. It will run a lot better.

[Fishmanoz]

Service sheets for this loco are No 136 and HR1982 T5&6.  The loco appears to be T6 (Type 6) which you can confirm by checking the lugs on the brush holders.  T6 lugs are horizontal with no connection the LH (almost certainly indicates the need to isolate this one, it's always the LH) while T5 they are angled up at 45 degrees and the LH has a wire attached going to chassis.

 

I believe you are correct on the wire to the front of the block.  It notes the need to push the tender draw bar pin down firmly to make contact.  I'd also agree with Colin on improvement by including pickups on both sides of loco and tender.

 

On the motor itself, Margate-Richmond will tell you the motor should be fine with proper maintenance with little improvement by going to 5-pole or replacing as Colin has done.

[Johnbw]

Thank youColinB and Fishmanoz for your very prompt response.  I will look into this as you suggest and post later.