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Runaway Engines


OldSutt

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Started to chip some locos and fitted a Gaugemaster DCC29 into a Bachmann 66xx DCC ready as it is small enough to fit the the small aperture in the body. Everything worked fine, so proceeded to chip a Hornby County 10xx  with a DCC29. This ran off at as soon as the power was applied to the programming track.

So I removed the chip and replaced it in a Bachmann 87xx, which previously had worked fine with a Hattons chip. It again ran away as soon as power was applied. The engine worked fine when the Hattons chip was reinstalled.

Does this mean that the DCC29 is kaput or am I missing something?

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Started to chip some locos and fitted a Gaugemaster DCC29 into a Bachmann 66xx DCC ready as it is small enough to fit the the small aperture in the body. Everything worked fine, so proceeded to chip a Hornby County 10xx  with a DCC29. This ran off at as soon as the power was applied to the programming track.

So I removed the chip and replaced it in a Bachmann 87xx, which previously had worked fine with a Hattons chip. It again ran away as soon as power was applied. The engine worked fine when the Hattons chip was reinstalled.

Does this mean that the DCC29 is kaput or am I missing something?

 

 

I'm not personally very familiar with GaugeMaster decoders, but a runaway like this is sometimes caused by the DC function of the decoder playing up.

 

Suggest you reset the decoder to factory condition and try it again. If the problem persists, turn off the DC function. If this does not cure the problem, send it back . . .

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Power is only applied to a 'Programming track' during the actual programming  - so you appear to have a fault in which the decoder/motor is NOT CORRECTLY ISOLATED - and this may now have resulted in damage.

 

My perenial queston: Do you have a multimeter? - IF SO check for continuity and isolation:

off the track, without a decoder/blanking plug...Remove the decoder, so the socket is empty....

 

Measure from track to socket/pins using the Orange and Grey decoder wires, - this should be near about 20 ohms, and to ALL OTHER socket positions should be infinite.  

(Pin 1 Orange, used for the motor should be marked eg 1 or *  but is sometimes wrong on Hornby locos especially perhaps when assembled with all black wires, or no lamps, just motor.  The diagonally opposite corner  is for 'grey' - the other motor connection.  There should be NO connection (ie infinite) to the chassis / motor casing.

 

0      [w]    0    Motor on orange and grey = expect about 20 ohms and to nowhere else with no decoder/plug

 

0     0    0     0    TRACK on RED and BLACK no where else!     Middle four may have NO WIRES

*

1

 

The other corner pins (if an 8 pin socket) are to and from the track - these should show about 0 ohms - between socket and one rail ( black to left rail, red to right rail usually)  and should be infinite to all other sockets.....The decoder wiring colours to these are Red and Black.

IF your loco has NO lighting or other functions, then there should be NO WIRING to the middle 4 pins - and no damage results from turning the decoder's plug 180 degrees (this can correct incorrect running direction in dc)

 

DAMAGE can occur if, by accident or careless assembly, the loco pickups have been wired to any of the middle 4 socket positions  - one of which is given +12V by the blue wire, and the others are swtiched between that and 0v by the first 3 functions [WHITE], Yellow  [directional lighting] and Green Wires from the decoder.

 

Following recent faults on Hornby locos- place the loco on a separate piece of track -  and again measure; to check that they connect to the same 2 connectors  .... and have not been wired to other positions in error !!!

THIS has been found on some recent locos - they run okay in analogue, but destroy decoders !

 

ALSO CHECK that when the decoder is inserted, that the pins are not so far down in the socket that they are touching metal on the other side - it is best to place a piece of insulation beneath the socket to prevent this.

 

You shopuld also be able to test the loco with a 9V battery held across a pair of wheels with pickup in each, or if only on diagonal wheelsets (like old Lima and Hornby) - do this by placing on a piece of track to connect all wheeels at once.

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Thanks, shall get out the old multimeter and check the wiring.

 

The only question comes to mind is:  the chip concerned causes the same problem in different engines Hornby and Bachmann and the Bachmann works with a different chip, isn't the problem the chip?

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Thanks, shall get out the old multimeter and check the wiring.

 

The only question comes to mind is:  the chip concerned causes the same problem in different engines Hornby and Bachmann and the Bachmann works with a different chip, isn't the problem the chip?

Yes, the fault is in the chip, but you need to establish if there is a wiring fault in the loco that blew the chip

 

Andi

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An update : checked the wiring in the Hornby County 10xx and could not find any wiring problem.

I then Inserted an old noisy Bachmann chip to check if that ranaway and it didn't.

A Hattons chip was inserted and the County moves as required in both directions quietly.

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Power is only applied to a 'Programming track' during the actual programming

 

 

 

Be aware that this is not the case with an ECoS 50200, where the Programming Track output is live at full DCC track voltage by default. You can change this setting in Setup Menu > Setup 2 to remove the DCC track voltage.

 

John

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I was given a tip from a well respected DCC Decoder manufacturer who said this.

Always do a reset to default a new decoder even his own, somehow bugs are the problem even he had no idea how they get there.

Bearing this in mind, and having had problems. A reset invariably cured the problem.

Other causes of runaways are the capacitors. And I believe with older decoders, could pick up taxi radio waves, but we are going back a number of years for this to happen now.

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