TTS decoder Class 37 Bachmann 8 pin Issue

[Peter-351502]

TTS decoder Class 37 Bachmann 8 pin, with Hornby e-link

Voltage being pulled down when the motor is running - okay when using the sound only

All other locos work fine

Bad comms when the motor is active

Fine when using sound only

Do I need to change the CV settings?

[96RAF]

Are you using 1-amp or 4-amp power supply unit with your eLink.

Voltage drop doesn’t look much but obviously affects the loco.

Try setting CV150 to value 1 (default is zero).

Edit - if you use a link file you can translate the binary code the controller is sending into text. You can either make your own in Excel or I have a basic file that works that could be improved upon.

e.g.

[rpjallan]

How do you have your layout wired?

Have you removed the capacitor/s from the motor?

[Peter-351502]

Does the internal regulator of the elink support 4 amps - if yes, I’ll try a 4amp supply. Good tip!

Yes, I could decoder the commands, but as you can see I’m getting corruption, which I don’t get from any of my other locos. Basically the loco is very slow to respond to commands when the motor is running, which is understandable looking at the waveforms.

I was thinking of trying something else, but I like using the elink with my tablet pc.

The capacitors, where are they located? On the pcb or on the motor? I’m happy to remove to remove them.

many thanks

[96RAF]

@peter

The 4-amp power supply is the Hornby recommended and approved replacement for the 1-amp unit. It has been known to cure several operating problems when using eLink in RM and may be the reason for your odd readings on this one loco.

The eLink along with the other Hornby DCC controllers has an internal polyfuse set to protect at 4-amps. The 1-amp power supply unit obviously never reaches this value so it protects itself against overload by dropping its output voltage and this can be seen on a Select screen by the display fading and looping as the unit continually reboots. eLink doesn’t have a screen so there is no direct observable clue as to this voltage drop happening.

The 4-amp unit passes self protection back to the eLink.

You could try measuring the DC stall current of the motor in this model as it may just be tipping the balance. This must be done in DC rig, i.e. with the decoder unplugged and the blanking plate refitted for the test.

The capacitor we are talking about is attached between the motor brushes and may be underneath out of direct view. I do not have this particular model so cannot confirm that.

The other place to look for rogue capacitors is in the power track or slide in track power connector, which can also be found in the connectors supplied with link cables (if you are not using a power bus wire system in lieu).

Picoscope Link File - it is handy for me to be able to see the DCC commands in readable text form. Its use is not mandatory.

[Peter-351502]

below is a list of my cv settings for the motor

[Peter-351502]

Is this the capacitor that needs removing?

[RDS]

@Peter

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[Fishmanoz]

Sure looks like it Peter. Just double-check by tracing the PCB tracks do in fact connect to the motor.

Then also check those two copper-wound inductors next to the capacitor. Are they in series with the motor connections? If so, they can come out too.

[96RAF]

If you remove those inductors you need to fit a link wire in lieu of each as they are in series, else you will have a gap in your motor circuit.

Here is a typical full house on the motor pins.

[ColinB]

Are you sure you need to remove the capacitor? I remove them when it is easy and Hornby seem to use very bad ones that go short circuit but generally on Bachmann locos I leave well alone. Assuming all the components aren't damaged, all the capacitor and inductors is going to do, is round off the pulse width modulated signal going to the motor. I remove them on Hornby locos if I am doing a DCC conversion but otherwise I leave well alone. I did have one go short circuit on a Hornby class 66 but I knew about that as it took out the decoder. I must do some tests with my Bachmann class 66s and see if I get the same effect.

[Flashbang]

You don't need to remove the Inductors (Chokes), but if they are removed then wire links need to be soldered in their place. The capacitor(s) across the motor.... My rule is only remove them if they cause problems with poor running. Some models have one capacitor others can have three or more, often you will find them soldered to the motor wiring tabs and the motors metal case, but some are fitted onto the PCB, There is no hard and fast rule!

The removal of motor capacitors can allow far better Bemf regulation between the decoder and the motor. If the decoder allows, try turning Off Bemf to see what happens (Not all decoders allow this!)

TBH Im not sure what the problem is? Your track readings seem to show slightly above 12 volts on the rails all the time, but it's fairly hard to read the trace. The volts dipping and rising a little as the motor turns and loading is placed on the decoder/motor. I would expect the 'Sound only' trace to show a fairly constant reading, as the load is constant. Does the loco not run correctly? As there seems no mention of how it is actually running?

To answer your question re "is this the capacitor"? Yes, it's the light brown item marked C1. The Inductors are the two copper coloured coils seen to the left of the capacitor and somewhat hidden by the yellow circle line drawn.

Up grading to the 4.0Amp power supply will always improve a layouts general operation, as you have effectively quadrupled the power available. But a loco will only consume whatever it needs, so if it only needs say 350ma then a 1.0Amp or 4.0Amp Power supply will still provide that 350ma. But of course, if you go over 1.0Amp (1000ma) loading then the 1,0Amp Power supply will soon trip as its on overload!

Edit to correct typos!