Speed Control Issues - R-12 Subway

does it have a good batter when doing factory reset? G

Subway,

   GGG is giving great advise, make real sure you have a good battery, then reset again to make sure. 

PCRR/Dave

Bill,

After looking at the video, it appears to be a tach reader problem to me as it takes off at full speed after giving the coupler slack sound, not when it's stopping. But do as G and Dave says first.

I like the tach reader call.  The subway "advances" to the next station or stage when the engine moves some distance as indicated by the tach reader; so if the tach reader failed the electronics never advances to the next station. 

A failed tach reader will certainly cause loss of speed control causing it to take off rather than slowly accelerating.  Hard to hear as wheel noise obscures it, but does the engine ever "rev up" past the idle/stopped engine sound?  That would also be a by-product of a failed tach reader. 

The silver lining if it is a tach-reader issue it's often user-repairable with a mechanical adjustment or re-attachment of a broken wire.

Thank you all for the feedback, tried a new battery, factory reset after battery replaced. Checked for pinched wires and anything loose by tach reader.

Stan2004: What repair would have to be done to the tach reader. I provided an image of the engine, if it helps you describe what can be done.

Any other thoughts. Thanks again

Thanks

Follow the tach reader wires all the way back to the MB connection and make sure they're intact.  They look fine at the tach reader.

Nice pictures Stan.

Stan:
Thanks for the detail images and description. Tach Reader was thoroughly
inspected, appears functional. We swapped parts with another R-12 unit
isolating issue to the part pictured.

Can any elaborate which part this is? Is this easily replaceable or hard
to find? Idea of cost?

Worth mentioning tach reader sits opposite on R-12 having issue compared
to similar engine which functions (pictured on the right-side). Does
this have any relevance to the problem?

The 3V power board lists for $80 and the uP board lists for $120.

Many times, speed control runaway issues are a chip on the power board, these can be repaired for half the price of the new board.

You can send me the board set by itself and I can repair the speed control chip.   G

Assuming it is the so-called speed sensor chip, I found this thread with photo showing the chip in question on the bottom (inside of the sandwich) of the power supply board.

ogrforum.ogaugerr.com/topic/upgrade-audio-amp

If you are curious, or are thinking of simply replacing the power supply board yourself, the two boards separate by pulling them straight vertically apart. Be careful not to bend any of the gold pins.  And when re-mating the boards, be sure each gold pin finds its mating socket contact.  The part in question is on the bottom of the board.  Since not much power flows through this chip, you probably won't see any visual indication that it has failed.

Obviously you could swap in the power supply board from the "good" engine and further confirm you have isolated the problem but