AD,
On 23 Aug 2019, at 1:22 AM, AD <bklyns_baseball_club@...> wrote:
If the output of the decoder is producing 15 v dc power (i can measure it with dc meter) as the dc engine is running at full speed does that tell us anything about the decoder. If i did short the output and damaged it would it still produce the dc power.?
As Alan has already said, shorting the output of a decoder often causes a partial short circuit failure of the decoder.
The technical explanation is that there are four electronic switches for a decoder's motor output (known as an H-bridge because of the arrangement). For the loco to move in one direction, two diagonally-opposite legs are pulsed on. For the loco to move in the opposite direction, the other two diagonally-opposite legs are pulsed on instead.
When i place the dc engine on the test track being feed by the tcs m1 decoder output wires and feed by the track outputs from a dcs100 command station and turn on power with a throttle the engine runs at full speed. When i turn the speed knob whose address is set to any arbitrary address nothing changes.
That is a fairly good indicator that a short occurred while moving and resulted in one diagonal set failing in the On position, a relatively common occurrence.
When i set the knob to address 10 and turn the speed up the command station power to the track goes off and its beeping. If i turn the knob speed back to zero the track power comes back on.
That is a fairly good indicator that the command station is telling the loco to pulse on the remaining good pair as, causing a double short circuit and booster overload.
Does this tell us anything about whats wrong with the decoder and what its damage is.
Almost definitely motor output driver failure.
I am sure i must of done something to short the output but what or Howe is not clear
Your arrangement of connecting the decoder output wires to a length of track and placing a DC loco on that track is a high-risk technique. It is highly likely to result in decoder damage due to the high risk of an accidental short/glitch at the loco. Even the sparking that normally occurs with a rolling wheel on track will have its high-voltage spikes amplified by the length of track and connecting wires.
I have little doubt your decoder motor output stage is damaged.
You need to use a spare motor connected directly to the output wires when testing/programming a decoder outside a loco (or better still, buy a proper decoder tester with motor, speaker and lights).
Your Heath-Robinson arrangement of a DC loco on track wired to a decoder output will most likely lead to further expensive failures.
Dave in Australia
