MTH Premiere (ps2/ps3 upgraded by previous owner) wont chuff, poor speed control

You have the PS/3 upgrade, though the wiring looks pretty sloppy.  The symptoms certainly suggest lack of tach function.  Start by taking readings of ALL the wires to the PCB to the frame.  Only the black wires on the 7-pin connector should have continuity to the frame.  If anything else shows up, fix it before you proceed.  Next, make sure all the tach wires make it all the way back to the board through the tether.  Check that the spacing from the flywheel is 1mm +/- .1mm.  If all of that checks out, replace the tach reader.

Looking closely at the image below, it appears the black stripes are worn through to the white substrate along a narrow band where something has been rubbing against the flywheel, maybe the sensor.

@gunrunnerjohn Do you think the issue could be caused by the tack sensor trying to read along this path on the flywheel where the stripes are essentially worn through?

If the shell is pressing the tach reader against the tape, that could certainly cause an issue!   I suspect the sloppy wiring is likely a primary cause of the issues here.

looks like that black wire rubbed against the flywheel and the tach. (in between)

Thanks for the thoughts everyone! 

This morning I ran through all the pins on the PCB in the tender as you suggested John.  As you noted, only the two black wires on the 7pin connector showed continuity to frame.

I traced all connections through the tether and to the pcb in the tender.  Everything shows continuity, however one thing that stood out to me was that dark blue (tach wire #3) on the engine side is leading to light blue on the tender pcb.  Is this correct.

Light blue on the engine is leading to purple on the tender pcb.  Is this correct?

I dont see a dark blue wire coming out the tether on the tender side.

Regarding the sticker on the flywheel, I'll get some sticker paper, and reprint the sticker, however I don't suspect this is the issue because it was even cleaner before I started tinkering.  Part of the damage to the sticker is my fault.  Ive open and closed it to test so many times, and one of those times I assembled it in such a way that scratched the sticker when the engine ran.  It had the same issue before the marks on the sticker.

I've been using a small ziptie to gap the tach/flywheel.  Thickness of these small zipties I have are 1.04mm, and work perfectly to get the right gap.

The black wire that Joe called out was entirely exposed on the other side not pictured.  I cleaned that up and protected the exposed portion of the wire.

I see something that could be stuck between the sensor and the flywheel tape….maybe???….looks like something white??….maybe a piece of foam tape used to space out the tach sensor that wasn’t removed??…… maybe just me, but take a look,….I’ve circled on your pic what I’m seeing,…

Pat

Sharp eyes there Pat!

Thanks guys but alas no, that's not related.  The area between the sensor and tape is clean.

I'm thinking with the shell on the tach reader is being pressed down onto the flywheel.  I wonder if this would run properly with the shell off?

Also, it's hard to say from this angle, but it looks like some of the contacts are being pushed up in the connector shell, the light pink wire on the bottom seems seated, but the four in the middle seem to be coming out of the connector shell.

I’m seeing that too John,…I know it’s not the OP’s doing but man this thing is a hack job going to a place to fry,……it just looks so dang sloppy,……sorry Loochy88, …I know this ain’t your doing,….but me,…I’d uproot everything and start over,….but that’s just me,…😉

Pat

These MTH J1's were originally designed before PS2 came out, and it's a pretty tight fit.  If you can't get your PS3 to work, the tach-less ERR Cruise Commander might be a better solution for this loco.

Well I worked on it all dang day and couldn't figure it out quite yet.

I did run it with the shell off but it behaved the same as with it on.

I'll have a look at those pins in the tender.

I may try to track down a replacement tach board just to try it.

If that doesn't work I'll probably just swap it to a tmcc system of some sort.  I have several lcru/rail sounds boards I could use, but I feel like this engine deserves something nicer.

I'm not terribly disappointed since I got the model for well under 200, knowing there were issues with the electronics that still seemed like a good deal for the model itself.

@Ted S posted:

These MTH J1's were originally designed before PS2 came out, and it's a pretty tight fit.  If you can't get your PS3 to work, the tach-less ERR Cruise Commander might be a better solution for this loco.

Ted,…it’s great to see you replying again!…been a minute that’s for sure!….I’ve built herds of PS1 & PS2 MTH Hudsons,…there’s no significant tooling changes except for the changes made for wireless ( or wireful) drawbar, ……and that’s just a clearance hole in the bottom of the frame in the back,….as far as boiler shells and other adornments,…no changes,…

Pat

@Loochy88 posted:

Well I worked on it all dang day and couldn't figure it out quite yet.

I did run it with the shell off but it behaved the same as with it on.

I'll have a look at those pins in the tender.

I may try to track down a replacement tach board just to try it.

If that doesn't work I'll probably just swap it to a tmcc system of some sort.  I have several lcru/rail sounds boards I could use, but I feel like this engine deserves something nicer.

I'm not terribly disappointed since I got the model for well under 200, knowing there were issues with the electronics that still seemed like a good deal for the model itself.

You certainly got a descent deal,..so tinkering with it won’t be such a drain on the wallet,….😉

Pat

I'm pretty sure this can be made to run with the existing boards, that's the cheapest option.

@gunrunnerjohn posted:

I'm pretty sure this can be made to run with the existing boards, that's the cheapest option.

Hopefully!  Not giving up quite yet.  MTH stuff always gives me more trouble for some reason.  I always have more luck with Lionel repairs.  Probably just a coincidence...

Do you have enough "hands" and dexterity to position the two sharp-tipped probes of a meter against two exposed metal crimp contacts of a harness connector...while slowly rotating the flywheel?  The 3-wires to the tach assembly form a fairly simple circuit.  There should be a fixed voltage between two of the wires...and a voltage that alternates a few Volts depending on a white or black stripe under the sensor.  There have been previous OGR threads on this.

IF you want to get down into the nuts-and-volts of the matter I think you can isolate where the problem lies.

@stan2004 posted:

Do you have enough "hands" and dexterity to position the two sharp-tipped probes of a meter against two exposed metal crimp contacts of a harness connector...while slowly rotating the flywheel?  The 3-wires to the tach assembly form a fairly simple circuit.  There should be a fixed voltage between two of the wires...and a voltage that alternates a few Volts depending on a white or black stripe under the sensor.  There have been previous OGR threads on this.

IF you want to get down into the nuts-and-volts of the matter I think you can isolate where the problem lies.

Thank you for this info!!!  I will get searching for the other posts.

Ill try to find more details on conducting this test and I'll try to see if I can figure out if it's still good.

I know that with the tach, the outer two wires can be wired up interchangeably, so I assume I'd test it with the center wire and one of the outer?  Not sure about that... I'll try to find more info and get to the bottom of weather the tach is dead.

As far as a replacement tach goes ... Maybe I'm missing it, but it doesn't look like PS3 tachs are readily available anywhere.  Based on a little searching....  The component looks like it might be a QRE1113 optical line sensor. Seems like it's be possible to solder a new one to the board.

https://www.amazon.com/Quickbu...470954011&sr=8-9

I just tried an an OGR search using the must-include-terms "tach blue gray orange" and these will narrow it to the PS tach wiring.  There are several posts by GGG who always has something useful to say...I see some from myself that might apply...such as this one with specific voltages to look for albeit a PS2...but I believe should be relevant to PS3.

Wow.  So if QRE1113 is indeed the replacement part #, it's another one of those shipping costing way more than the part!  But I guess that's life.  I just bought a gasket/seal to repair a leaking toilet; the part was $1 -  shipping was $6.

Maybe obvious, or maybe helpful: When checking small connectors and I need free hands, I often insert a short length of small gauge solid wire into the connector housing, ensuring snug contact with the pin under test.  Then attach an alligator clip lead between the each piece of solid wire and each meter test probe.  This method will add a little more resistance, but this can be accounted for when relevant.  Just checking continuity, the additional resistance wouldn't matter.

Actually Stan, I believe the Omron EE-SY124 is the sensor used on the MTH tach reader.  The QRE1113 is the sensor I use on the Chuff-Generator.  I was actually going to use the Omron part, but it was obsolete, so I changed horses.

The QRE1113 has similar specifications, but a different pinout.  If MTH ever stops making tach readers, I figured I could just lay out that little board for the QRE1113 and it would probably work fine.

@SteveH posted:

Maybe obvious, or maybe helpful: When checking small connectors and I need free hands, I often insert a short length of small gauge solid wire into the connector housing, making contact with the pin under test.  Then attach an alligator clip lead between the each piece of solid wire and each meter test probe.  This method will add a little more resistance, but this can be accounted for when relevant.  Just checking continuity, the additional resistance wouldn't matter.

Being super lazy, and also having been bit by wires coming loose and touching places they shouldn't touch, I frequently just tack the wire onto the connection with a dab of solder.

@Loochy88 posted:

I know that with the tach, the outer two wires can be wired up interchangeably, so I assume I'd test it with the center wire and one of the outer?  Not sure about that... I'll try to find more info and get to the bottom of weather the tach is dead.

Not sure where you get your information, but that is certainly NOT true!

Omron EE-SY124 Reflective Sensor Datasheet

@Loochy88 posted:

As far as a replacement tach goes ... Maybe I'm missing it, but it doesn't look like PS3 tachs are readily available anywhere.  Based on a little searching....  The component looks like it might be a QRE1113 optical line sensor. Seems like it's be possible to solder a new one to the board.

As I mentioned to Stan, that is not the QRE1113, but rather the Omron EE-SY124, which is an obsolete part that you can no longer get, at least I can't.  The QRE1113 could be made to work with a new PCB I believe.  Also, that's a PS/2 tach sensor, the PS/3 tach reader is used only for the diesel upgrade or the factory installations.  The steam upgrade kit mimics a PS/2 board and uses the same wiring as the previous PS/2 upgrade kit.

Are we having fun yet?!

I must have gone to the wrong college, but one thing they NEVER taught me in engineering school was the concept of obsolete parts and what to do about it!

So akin to the MacGyver concept of testing a 9V battery by placing it on your tongue, I'm pretty sure no one on OGR has tried this.  If you're messing with the PS tach, take your TV remote control and aim it at the sensor (obviously the sensor harness loose from the motor).  Press the Channel or Volume up/down button or any button that causes a repetitive action when button is held.  This generates an IR burst of energy several times a second.  Depending on the MTH engine, it can take several dozen IR pulses (reflections from a spinning flywheel) to generate a chuff but this will generate an occasional chuff sound or puff of smoke!  Again, this is in the spirit of the OGR being a discussion forum!

I'm pretty sure you're right Stan, I never even thought about it!

And, as wacky at it sounded, it works like a champ!   You never do cease to amaze Stan, that thought never occurred to me!  However, you can no longer say nobody on OGR has ever tried this, and I have proof.

@gunrunnerjohn posted:

Actually Stan, I believe the Omron EE-SY124 is the sensor used on the MTH tach reader.  The QRE1113 is the sensor I use on the Chuff-Generator.  I was actually going to use the Omron part, but it was obsolete, so I changed horses.

The QRE1113 has similar specifications, but a different pinout.  If MTH ever stops making tach readers, I figured I could just lay out that little board for the QRE1113 and it would probably work fine.

If PS2 tach sensors might be NLA, I guess I’m pretty well prepared for the apocalypse,….😉

Pat

Well now we may be getting somewhere.  I just ran the voltage test on the tach using the directions Stan linked.

I'm getting 1.2v on gray/blue for the led.  Ok, that makes sense.

On to orange and gray for the sensor voltage.  No fluctuations!  Stays at 5v regardless of white or black.

I even put a remote control up to it and read the volts.  Same 5v, remote signal or not.

Strong indication that it's the sensor!  Now I just need to figure out where the heck to find one of these.... Or a suitable replacement...???

Btw, fun fact... I'm sure some of you know, but did ya know you can "see" the ir led using your camera phone (see attached)

YES have used that trick for many many many years a great way for a quick test to see is sensor is functioning !

Alan

I use my camera to check the Lionel IR link between locomotives and tenders all the time.  Also useful for checking the LCS IR transmitter on newer Legacy locomotives.

If you can get a tach sensor from MTH that should solve the issue. Usually (not 100% fail safe) a short in the tach sensor wiring just kills the sensor without damage to the board. Go back and trace all the tach sensor wiring and check for any pinched wires or damage. To be honest trace all the wiring to check for damage. You're locomotive had quite a hack job done on the wiring. No wiring was shortened or routed with any thought. You want the wiring to be more akin to the below images.

@Loochy88 posted:

...

Strong indication that it's the sensor!  Now I just need to figure out where the heck to find one of these.... Or a suitable replacement...???

Per GRJ's earlier post you apparently have the PS2 tach board with an obsolete sensor IC chip.  Seems options are:

1) find a PS2 tach board assembly,

2) replace just the obsolete chip - there's a listing on eBay right now for used chips but must buy 8 for ~$30,

3) replace just the obsolete chip with an equivalent part...possibly requiring delicate wiring if the chip pinout is different (e.g., QRE1113 vs. EE-SY124).

Curious which path you're taking?

Given the simplicity of the PS/2 tach sensor board, it probably makes sense to lay one out for the QRE1113.  Of course, then MTH will start selling them again for peanuts and I'd have wasted my time.

And this is where the announcer says, "Let the games begin!"

Considering this is likely a one-off from the OP's perspective, here's one approach...

From the datasheet, the 4 holes to mount the sensor chip are essentially on the same "grid."  That is, 4mm x 1.8mm vs. 4mm x 1.75mm.  It appears that the parts are NOT mounted flush to the board but are extended off the board by some critical distance.  Once we accept that this is a "hack job" I'd mount the incorrect component at the right height off the board and then cut/re-route traces on the circuit board.  I suggest it's much easier to modify the connections on a circuit board this simple rather than re-routing wires in mid-air to the sensor chip.  I don't know if I'm making any sense.

I realize that 99% of the OGR readership would send the engine in, or scrounge a genuine working PS2 tach board at whatever the going price (plus shipping!)

Last night I bought 5 QRE1113 chips from digikey to mess around with.  I've got a bunch of perf board and a 3d printer.  Between those two things I should be able to come up with a wiring/mounting solution.  We shall see ..

Draw a schematic of the wiring and maybe I can make a PCB that will use them.

@Loochy88 posted:

Last night I bought 5 QRE1113 chips from digikey to mess around with.  I've got a bunch of perf board and a 3d printer.  Between those two things I should be able to come up with a wiring/mounting solution.  We shall see ..

Right.  Please share any DIY findings/insights! 

For the cheapskates (like me!), I found this on Aliexpress.com.  If you are a new customer you can get 10 pieces of the QRE1113 for a net price of <10 cents each after $2 new user coupon.  Yes, you'll have to cool your heels for a month or so as the proverbial slow-boat-from-China meanders across the Pacific but it's hard to resist the price!  Maybe I'm just lucky, but I've had no problems with aliexpress.com to date; OTOH I have had issues with eBay-Asia for inexpensive components like this.  In other words, one of those Your-Mileage-May-Vary.

"We" (the OGR gang) may want to take GRJ up on his offer to design a DIY board for the QRE1113.  I don't know what the MSRP is for an official MTH tach board...but for the DIY'er who knows which end of a soldering iron to hold, I'd think you could make PS2/PS3 tach boards for less than 50 cents each!

Probably should do one of the prototypes and make sure the schematic is right and the QRE1113 works in this application.  A casual look at the spec sheets seemed to suggest it should, but I like to see stuff like this actually working.   Making the board is no big deal, not exactly a lot of components on it.

BTW Stan, I buy my QRE1113 sensors on AliExpress, best prices I've found.  I look for larger lots, I like to buy a couple hundred at a shot.

Yup.  I just looked at the OshPark site and it says the minimum board size is 1/4 sq. inch for their $5/sq. inch pricing which gets you 3 boards.  I measured a couple of different MTH PS tach boards and they were all less than 1/4 sq. inch.

So if I have this right, one could buy qty 3 OshPark PCB's for $5/sq. inch x 0.25" = $1.25 or ~40 cents per board.

Then add a ~10 cent QRE1113 and that's 50 cents per board for the patient DIY'er! 

Yep, that's about right.  Actually, the tach sensor board is about 1/4 wide, and I could just put two of them on one design to make the size.  Add a cut line in the middle and you just hack it in half.  Six of the PCB's that way would probably cost you around $1.75 total, and they ship free.  For that price, I normally order several orders.

One bonus of doing your own board and soldering the sensor is you can get it the right height.  Many times I have to unsolder the sensor and reposition it.

@stan2004 posted:

Right.  Please share any DIY findings/insights!

For the cheapskates (like me!), I found this on Aliexpress.com.  If you are a new customer you can get 10 pieces of the QRE1113 for a net price of <10 cents each after $2 new user coupon.  Yes, you'll have to cool your heels for a month or so as the proverbial slow-boat-from-China meanders across the Pacific but it's hard to resist the price!  Maybe I'm just lucky, but I've had no problems with aliexpress.com to date; OTOH I have had issues with eBay-Asia for inexpensive components like this.  In other words, one of those Your-Mileage-May-Vary.

"We" (the OGR gang) may want to take GRJ up on his offer to design a DIY board for the QRE1113.  I don't know what the MSRP is for an official MTH tach board...but for the DIY'er who knows which end of a soldering iron to hold, I'd think you could make PS2/PS3 tach boards for less than 50 cents each!

Well, time will tell.  This may end up a total flop but there's only one way to find out.  I'll share whatever I happen to learn...

@gunrunnerjohn posted:

...

One bonus of doing your own board and soldering the sensor is you can get it the right height.  Many times I have to unsolder the sensor and reposition it.

I was looking at a PS2 tach board on an open engine and it has the sensor chip flush on the board (photo above right).  Yet, on the OP's photo the sensor chip is clearly off-the-board quite a bit with some kind of "foam" spacer:

Since the old sensor chip needs to be replaced anyway, here's a one-off idea that may allow the existing board to be used AS-IS with only a modest amount of wire/lead bending...and still account for the change in pin-out between the EE-SY124 and the QRE1113.

The Idea is to notice that the PS2 board connects the A and C pins of the sensor chip together (and this then goes to the Gray wire).  This A=C connection can be used to advantage as it then makes the 4 sensor holes in the correct orientation for the QRE1113.  Yes, the 4mm x 1.75mm is now 1.75mm x 4mm but I think that can be worked-with since the chip is above the board (would be more difficult if chip is flush to board as in my photo).  The 4 terminal leads could be clipped close to the sensor chip leaving 4 wires sticking up; the QRE1113 chip would then be soldered to the 4 stand-up wires.  Not sure this makes any sense!

But if it does work out, I'd think there would be future application for guys who need to repair one (1) PS2 tach board.

MTH sells a few tach sensor boards.

• Tach Reader board (no spacer)  AG-0000033  for Mabuchi motor w/ 30mm flywheel
  Tach Reader board (1.5 mm spacer)  AG-0000047  for Mabuchi motor w/ 27mm flywheel
  Tach Reader board (2.2 mm spacer)  AG-0000041  for Pr Steam with 30 mm flywheel
  Tach Reader board (no spacer w/ resistor)  AG-0000048  for LocoSound board in tender 30mm
  Tach Reader board (1.5 mm spacer w/ resistor)  AG-0000054  for LocoSound board in tender 27mm
  Tach Reader board (no spacer) with hole in pcb  AG-0000058  for RK L-3 Mabuchi w/ 30mm flywheel

And also the sensor, though I suspect they are out of them.

• Optical sensor component  AG-0000078  Omron part EE-SY124

Such a wealth of knowledge!

So I looked at a few, and from what I can tell the MTH tach board have an MSRP of about $7.  It's fascinating that they sold "just" the tiny sensor chip for $5.  I wonder how many of those they sold.

I also saw some LocoSound tach boards which apparently have a resistor added.  Do you have any "Service Bulletin" type info given to Authorized MTH Techs that explains the need for this resistor?  Hard to imagine why they would have a different design for the Locosound sensor vs. PS2/3??

Also, as for an OSHPark version that supports the QRE1113, I'd be amazed if MTH or whatever MTH becomes would have interest in frying such a small fish...they surely have bigger fish to fry.  That is, if I understand it, the only difference between some of the tach boards is the spacer distance.  Hence a raw PCB for anyone to order from OSHPark for $2 (shipping included) would be (IMO) a contribution to the hobby.   

And while:

Nothing is so easy as the job you imagine someone else doing!

Perhaps there's someone else on OGR who sees this DIY PCB design and wants a real "project" to experiment with.  I mean this is what the OGR discussion forum is all about....right?!

Got it working!

So I had those QRE1113s on the way from digikey but I'm not particularly patient.

Amazon had some breakout boards available via prime next day that included a QRE1113 on them.  I ordered a set of 3 for 5 bucks and it showed up this afternoon.  I removed the QRE1113 from the board and based on the schematic for the QRE1113 and the EE-sy124  determined that the boards are just a mirror layout of each other.  So with that I soldered the QRE1113 to a small piece of PCB, laid out my connections in reverse, and bam, we have a running Hudson.

Thanks everyone for your help.  Figuring these little projects out is my favorite part of this hobby.

Stan - as for the resistor on that version of the board... i think thats needed in both circuits.... the newer locos look to have it on the large board in the tender.  probably the resistor working as the other half of the voltage divider circuit opposite the phototransistor...?

Either way, its not on my tach board (the old broken one or the new one i made)

*Edit: Actually looking at that picture of the resistor closer, that resistor is on the ir led cathode, limiting current through the led.  still something that's probably being accomplished on the tender board in ps3 version.

Great stuff here!

@stan2004 posted:

I was looking at a PS2 tach board on an open engine and it has the sensor chip flush on the board (photo above right).  Yet, on the OP's photo the sensor chip is clearly off-the-board quite a bit with some kind of "foam" spacer:

Since the old sensor chip needs to be replaced anyway, here's a one-off idea that may allow the existing board to be used AS-IS with only a modest amount of wire/lead bending...and still account for the change in pin-out between the EE-SY124 and the QRE1113.

The Idea is to notice that the PS2 board connects the A and C pins of the sensor chip together (and this then goes to the Gray wire).  This A=C connection can be used to advantage as it then makes the 4 sensor holes in the correct orientation for the QRE1113.  Yes, the 4mm x 1.75mm is now 1.75mm x 4mm but I think that can be worked-with since the chip is above the board (would be more difficult if chip is flush to board as in my photo).  The 4 terminal leads could be clipped close to the sensor chip leaving 4 wires sticking up; the QRE1113 chip would then be soldered to the 4 stand-up wires.  Not sure this makes any sense!

But if it does work out, I'd think there would be future application for guys who need to repair one (1) PS2 tach board.

Just saw this!  This would probably have been easier, but somehow I got the wire bending to work.  Either way I'm thrilled its up and running!  Sorry if I seem like I'm not following but I'm sort of learning as I go.  I dont really have any background in this stuff... just a youtube education of how electronics work.

So, a universal board would have a spot for a resistor and perhaps a trace that jumpers it out for PS/2 use.  Sounds like a pretty easy thing to do.

@gunrunnerjohn posted:

So, a universal board would have a spot for a resistor and perhaps a trace that jumpers it out for PS/2 use.  Sounds like a pretty easy thing to do.

So are you volunteering?  If so, I'll make some caliper measurement of a PS2 tach board and "we" can average the measurements to come up with the dimensions.  Like you say, it probably makes sense to design a 2-up board that can be easily cut-sawed-broken in half so you get 6 boards in an OshPark design.  Obviously anyone going thru the effort to deal with OshPark is a card-carrying DIY'er (!) and knows how to solder, etc.  I figure with Aliexpress pricing for the QRE1113, OshPark, and such you could make MTH tach boards for 50 cents or at most a buck.

You measure and show me a schematic for the QRE1113 version, I'll do the board design and post it.  I'll make it a share on OSHPark so anyone can find it.  I figure we'll add the resistor and a trace around it, for LocoSound you add the resistor and cut the trace.  It'll be useful for me, I have lots of the QRE1113 sensors, and I won't have to look for tach boards any more.

When finished, is it OK to add it to the projects list here on the forum?  It would link back to the devices original thread as all the other projects now do.  Definitely a useful project and maybe it will get a bit of extra exposure there and help a few extra forum members... that is if anyone ever reads that list?

@rtr12 posted:

When finished, is it OK to add it to the projects list here on the forum?

Sure, it's going to be a one-for-all project.

@Loochy88, what happened to the post you just posted?

Hey John, It was incorrect.  I noticed after posting.  The correct layout is below.

Here is how I designed mine.  I added caliper measurements of the MTH board, but trace design would be correct for QRE1113 version.  Viewed from flywheel facing side of board (side with QRE1113)

Thanks, I'll watch out for it and add it when finished.

Looking at my own illustrations and the board here in my hand.... I just came to the realization that both boards are the same (if you have the non resistor version).  If you remove the phototransistor components you could essentially solder either the QRE1113 or the EE-sy124 to opposite sides of the board, and have the same thing.....  Probably would have been a lot easier than the pcb hack job I came up with. 

@Loochy88 posted:

Looking at my own illustrations and the board here in my hand.... I just came to the realization that both boards are the same (if you have the non resistor version).  If you remove the phototransistor components you could essentially solder either the QRE1113 or the EE-sy124 to opposite sides of the board, and have the same thing.....  Probably would have been a lot easier than the pcb hack job I came up with. 

That's interesting, never considered that the sensor change would be a mirror image.

I found a tach board that has a reference corner etched on the board suggesting pad placement might be relative to the corner:

That's an interesting observation about the mirrored pinouts.  I suppose the new board could be used for either version with the silk-screen on each side showing version.  OTOH, the EE-SY124 is obsolete so why bother...but then again I'd think there are equivalent parts that use the same pinout.

If the board can be reversible, why not?   The only wild card is where to position the optional resistor for LocoSound applications.  The other consideration is the wiring would be backwards, so that would have to be made clear.

The other oddity is some of the tach boards have a hole in the tang, I'm sure there's a reason for some application.  Maybe my universal board would also have the hole, it doesn't appear to affect it's use to replace ones without the hole.

Silkscreened on both sides, the proper sensor and also the corner cut orientation should be added as well.

@gunrunnerjohn posted:

If the board can be reversible, why not?   The only wild card is where to position the optional resistor for LocoSound applications.  The other consideration is the wiring would be backwards, so that would have to be made clear...

I think the pads for the resistor might need to go on both sides.  Especially for the case of a spacer under the sensor, the resistor must go on the other side of the board.  I don't have a LocoSound tach but it looks like an 0805 might fit (as shown below).  It appears they violated some design rules placing the resistor pad overlapping the sensor pad depicted in red below.

I'd think a thin trace between the 2 pads might be simplest.  Cut the trace (thin blue line) if installing the resistor. Of course you'd have to cut the trace on both sides of the board; or run vias thru the two SMT pads so the shorting trace is only on one side.

Since I'm not doing the work I can only make peanut-gallery comments, but it seems like the instructions to support either chip is much more complex than if just supporting the QRE. 

Yep, I might just make a board to support the readily available sensor.  Perhaps we're gilding the lily with all the options.

I figured the resistor would be on the opposite side from the sensor.  FWIW, for my Chuff-Generator, I don't have any spacer, the sensor is just extended on it's leads.  The spacer doesn't do anything that useful unless you're ham-handed.

Huh. This is neat. I've got 6 spare PS2 tach sensors but it's good to know a readily available replacement can be made to work. Nice job figuring this all out .

Speak now or forever hold your peace!   Here's what I have for the QRE1113 replacement. Check it over and see if there are any wiring or dimensional issues that you can see.

I measured my sensor boards, they're all 17mm long, so that's what this one is.  I added the hole that some have as it doesn't seem to affect the usage where they don't have a hole.  Finally, I added the provisions for a 0603 resistor and it's jumpered in the copper.  If you want the resistor, cut the jumper and add the resistor.  The resistor is only for Locosound, they supply 5V to the sensor LED without current limiting, PS/2 supplies the proper current limited drive voltage for the sensor LED.

Top & Bottom Board Layout and Dimensions

Top & Bottom 3D Views

Schematic Diagram

Looks good to me!  I don't suppose that it would make any difference if the QRE was oriented backwards.  (Led to front of engine / sensor to back) ...other than ensuring the installing user is aware.

The corner cut is in the silkscreen as well as the square pin-1.  Hopefully, anyone that's going to "roll their own" is aware enough of pin numbers and designations that they can orient the opto sensor correctly.

As for functionality, it won't make any difference.  We'll see if Stan has any additional comments and I'll get a set of these from OSHPark.

I forgot the Stan Memorial dual-board configuration, so here it is.  This is two of the boards on one design to minimize the PCB costs at OSHPark.  Six PCB blanks will be $1.90.

I admit I only measured the pad diameter, but why are the holes for the harness wires smaller than the holes for the sensor chip?  On my board(s) it's the other way around as indicated in my earlier diagram (1.5mm pad diameter for wires, 1.3mm pad diameter for chip...with holes sizes presumably commensurate).

Any chance you can fit 0805 pads for the resistor?  I realize you can typically/likely fit an 0805 onto 0603 pads but it's all about option.  I think 0805 are generally easier to find than 0603...and working with 0603 is probably pushing it for any of us fixed income retirees.

You should by all means take credit and initial the board design, I suggest you silkscreen the letter B O G (instead of JWA) below the 3 pads where the harness Blu, Org, Gry wires ENTER the board which, in all tach boards I've seen, are on the opposite side of where the sensor chip is mounted.

BTW. For anyone following along who is not familiar with the process of designing a circuit board for market, you are witnessing a so-called "time-to-market" that is unheard of in this industry!

@gunrunnerjohn posted:

I forgot the Stan Memorial dual-board configuration, so here it is.  This is two of the boards on one design to minimize the PCB costs at OSHPark.  Six PCB blanks will be $1.90.

I'm still alive!

I'll bet OshPark complained about the 1-board version as it's less than 1/4 sq. inch.  LOL.

Any chance the OshPark design rules allow you to drill a string of closely spaced holes along the 2-board cut-line so that you can more easily snap the board into 2...perhaps using just diagonal-cutters instead of needing a hobby-saw.

That's pretty cool.  $1.90/6 =  32 cents per board. And that's delivered to your door! 

I can drill holes, that's no problem, good idea.

Here it is with the changes.

To summarize what just happened (in record time I might add), if you are a DIY'er with a soldering iron, you can make your own MTH tach boards for less than $1 each.  And that includes shipping!

The QRE1113 sensor chip is WIDELY available.  In addition to the aliexpress (Asia) site I showed earlier where the chip is ~25 cents a piece, it is available from essentially everywhere - eBay, Amazon, and of course DigiKey and other mainstream parts distributors.

If nobody sees a stupid error in my layout or schematic, I'll post the Gerber files and probably place an order for some samples from OSHPark.

I started a new thread with the actual design, this will make it easier for folks to find the actual files.

Replacement MTH DCS Tach Sensor Board Design and Production Files