From this topic is this a snapshot of PS2 wiring.

https://ogrforum.com/...20#38596415944659820

Note, there is a huge difference- there is P5V- 5V positive voltage rail, and then there is PV- positive voltage- direct unregulated DC +.

The tach uses P5V.

Also note, that on suspected runaway that is not a faulty tach- there is the OP Amp IC.

LMV358M/NOPB

https://www.digikey.com/en/pro.../LMV358M-NOPB/270692

https://ogrforum.com/...58#83790477343103458

You may have a board failure.

@Vernon Barry posted:

From this topic is this a snapshot of PS2 wiring.

https://ogrforum.com/...20#38596415944659820

Note, there is a huge difference- there is P5V- 5V positive voltage rail, and then there is PV- positive voltage- direct unregulated DC +.

The tach uses P5V.

Also note, that on suspected runaway that is not a faulty tach- there is the OP Amp IC.

LMV358M/NOPB

https://www.digikey.com/en/pro.../LMV358M-NOPB/270692

https://ogrforum.com/...58#83790477343103458

You may have a board failure.

Thank you so much for the information! I was just reading about the U12 speed control chips ironically.

Thanks again i will keep digging!

Are you visually seeing the tach reader smoke and burn up?  Wires should be gray, blue and orange and fed from the 7 pin per diagram.  Wires in right position?  If so, there is a 180 ohm current limiting resistor on the PS-2 board.  If that is shorted, that might cause a physical burning of the tach reader.  G

@GGG posted:

Are you visually seeing the tach reader smoke and burn up?  Wires should be gray, blue and orange and fed from the 7 pin per diagram.  Wires in right position?  If so, there is a 180 ohm current limiting resistor on the PS-2 board.  If that is shorted, that might cause a physical burning of the tach reader.  G

Yes the moment power was applied, it visually burnt up and smelled instantly. (No smoke, faint glow for a moment) Powering slowly from Z4000 throttle too.

**when i got this subway, a traction tire was mangled in the gears. Wonder if it caused an amp spike and shorted something?

The three wires are all correct, the first tach sensor came with pre-soldered colored leads

I was maybe thinking the U12 OP amp Vernon mentioned.

I'll dig up a diagram and check the resistor out. Thank you for taking the time to reply! Worse case I'll probably send this to you too lol. I just really enjoy learning how to work on these boards and beyond satisfying once working again. An audio amp being my biggest replacement lol.

Thanks again!

@p8ntballer789 posted:

Ordered ANOTHER tach sensor, installed tonight, and watched it burn up when power applied...ugh!!

Is there something im missing or something else blown out?

There is, most definitely.  (This is another of the many variants of Murphy's law.)

Never, ever, assume that electronics are the sole source of a problem, and the first thing needing to be changed out, when something doesn't work.  Very often they fail as a result of some other underlying cause, like a pinched wire, or a bad switch, or load.

Looking for the actual root cause is always step one in diagnosis.

Many thanks to the folks here, like @Vernon Barry, @GGG, @gunrunnerjohn, and so many others, for understanding and following these words of wisdom, and most importantly for teaching the rest of us about their importance..

Mike

I have literally changed several hundred opamps or tested boards with bad op amps that never smoked the tach reader.  The only time I smoked a tach reader (once) was testing a harness and I used a none mux engine harness with a mux tender assembly.  The tach reader smoked because the MUX tender does not use the current limiting resistor of the PS-2 board, but has it on the engine MUX side.  This is why swapping tenders in PS-2 can get you in trouble.

This is a diesel, so no mux.  But swap a new power supply board in and new tach reader and it should work.  AS LONG as NO tach wires pinched to chassis as mentioned above.  G

The problem you can run into is when you get a track short momentarily any time it can blow the tach board or the op amp And I've even seen it blow both chips audio amp and op amp, the op amp is easy to change the audio amp is much more difficult depending on your soldering skills!

Alan

@GGG posted:

I have literally changed several hundred opamps or tested boards with bad op amps that never smoked the tach reader.  The only time I smoked a tach reader (once) was testing a harness and I used a none mux engine harness with a mux tender assembly.  The tach reader smoked because the MUX tender does not use the current limiting resistor of the PS-2 board, but has it on the engine MUX side.  This is why swapping tenders in PS-2 can get you in trouble.

This is a diesel, so no mux.  But swap a new power supply board in and new tach reader and it should work.  AS LONG as NO tach wires pinched to chassis as mentioned above.  G

Very good to know and interesting! I'll buy a power board and tach to install after the holidays. The subway sets an xmas gift for my fiancé as she really enjoys them lol. I'll report back with an update!

Thank you tremendously for all the help over the years, from info here to mailing things to you for repair. You're the man! 🍻

@p8ntballer789 posted:

Very good to know and interesting! I'll buy a power board and tach to install after the holidays. The subway sets an xmas gift for my fiancé as she really enjoys them lol. I'll report back with an update!

Thank you tremendously for all the help over the years, from info here to mailing things to you for repair. You're the man! 🍻

Good luck buying a power board for the PS/2 board stack.  Those are long out of stock.

@gunrunnerjohn posted:

Good luck buying a power board for the PS/2 board stack.  Those are long out of stock.

Hey John! Is the power board part number AE0000011 ?

They have them in stock if so thankfully 🙂

@p8ntballer789 posted:

Hey John! Is the power board part number AE0000011 ?

They have them in stock if so thankfully 🙂

Color me surprised, I thought they had long abandoned those!

PS are available, no processor boards though.  I have them available also, and they can be repaired.  G

@GGG posted:

PS are available, no processor boards though.  I have them available also, and they can be repaired.  G

Yep, I have a few P/S boards, what I need are processor boards.

Just a follow up, George got our PS board repaired! I have a happy fiancé running her subway! Thank you all for the help and George for the super fast repair!

Yes....I second p8ntballer789 sentiment......George is one of the best when it comes to repairing "troubled" Protosound boards.

Sent him two "troubled" PS3 steam boards, and a board that runs the flashing beacon on top of the MTH RailKing double track girder bridge. All tested, and all repaired where required. I am one happy camper!!!

Thank you GGG!!!!

Peter....Buco Australia.

As I guessed the current resistor was shorted.  First time I saw a short.  A few times I have seen them go open.   G