Class 37TTS trouble

[Spireblade]

My Class 37 has thrown a major wobbly. It just stopped dead  although both sound and lights still worked. I took it apart and all looked ok. On trying it again a few days later it suddenly burst into life, did half a lap and stopped dead again. Trying it again today and the whole thing is as dead as a Dodo.

I have tried to reset the decoder but RM will no longer recognise it. Is it a deceased decoder?

Having looked around for a replacement, Hornby dont seem to be making them anymore. Is this right?

 

Cheers

[Howbi]

Might be worth plugging the decoder into a different loco to test...........HB

[96RAF]

It would be unusual for the decoder to work lights and sound but not the motor.

 

Unplug the decoder and apply DC direct to the motor terminals - does it run in both directions. That will prove the motor is OK or not.

 

Warning - do NOT apply voltage direct to the motor with the decoder plugged in or its toast.

[Phil_Spiegel.]

Did any of the Class 37's suffer from the 'which physical way round they wer on the track problem?? - if so, what controller was being used when it didn't appear to work ??

It is behaving more like a motor-short causing protection to cut in...

Protection circuitry in the decoder - due to motor overloading - could shut down the motor drive ... does this leave the LEDs unaffected ??? (On Lenz decoders, and many electronic devices like TVs, the LEDS are given a diagnostic flash-pattern to identify the cause of the shutdown )

Continued use might cause permanent failure,if the cause is not identified.

If it had been a modern DMU bogie, I would have suggested checking for metal objects across the motor terminals attracted by the adjacent motor magnets - the motor terminals are next to each other and totally unprotected - and would short the decoder.  [ Another similar fault I know of in an anlogue loco caused the internal wiring harness to melt - the analogue controller presumably allowed an Amp or more of current to flow, whereas the decoder limited it locally ] - these terminals should have a piece of insulating tape added over them !!!

[Spireblade]

Well, I have tried the TTS decoder in another loco and it works perfectly., so that is illiminated. I tried a replacement decoder in the 37....nothing. It buzzed a little, moved about a millimeter.

Had it to bits and all seems to be wired correctly. Off to the repair shop with it then  :-(

 

 

Yes Phil, the LED's are unaffected.

 

Just to add, the traction tyres look like they could do with replacing. Would this have an adverse effect?

 

[Phil_Spiegel.]

'motor buzzing'  ( when loco supposedly stationary) usually means that the ac track dcc signal is reaching the motor.

There have been mis-wired hornby 'dcc ready' locos where they run on dc okay, but blow decoders because some of the track pickup wires have been wired to adjacent pins (which are commoned by the blanking plate - thus running 'okay' on dc   ... and apparently okay when tested on an axle by axle basis, off the track ... until you realise which socket postion they are connected to, as opposed to non-connected to 8-(

If tje 'wiring' is okay, another possible cause is the long pins passing through the socket and touching metal beneath - thus shorting the connections ... avoided by the manufactirer havinf a sheet of plastic or rubber benath, or sockets which are not 'pass through', but blind.

The buzzing of this 2nd decoder may have been 'masked' or avoided with the TTS by its protective circuitry.

A multimeter check that, with no decoder plugged in to the socket, the motor is totally isolated from all the other 6 sockets is needed ... the motor will show as about 20-30 ohms between the 2 sockets (orange and grey wires)

 

[Spireblade]

I took the motor from another class 37, soldered it in and I still have the same proble. I then wired the original "faulty" motor into the other 37 and it ran sweetly. So, not the decoder or the motor! I then did a total rewire which produced positive results, although not at all fantastic. There is life but needs encouragement. The only thing left to try is the non powered bogie but somehow it wont "split". I dont want to damage it so it looks like a trip to the repair shop afterall. At least I know what ISN'T the problem.

[96RAF]

You should be able to continuity check the bogie from wheels to wire ends, Also check there is no continuity side to side on the dummy bogie.  The other thing is has the dummy bogie got a wheel set in reversed, which would show as a short wheel to wheel diagonally across the bogie.